+++ #85 Subject: Wood fatigue. From: Kevin Deutscher (bearhwk27-@aol.com) On the issue of wood fatigue. In general, for ductile metallic materials, fatigue failures result when the endurance strength of a material is exceeded for a number of defined loading cycles. The mode of failure is a breakdown of the material grain structure propagating from an area of localized stress caused by material flaw, surface condition or change of material section. The failure is visually indicated by a crack. After the formation of the crack complete section failure follows in a rather short number of cycles. Now for wood. Wood is organic. ( Natures composite and a lot better than epoxy and glass when used in the Bar-b-Que.) Wood has a cell structure (grain) that is composed of Cellulose material. (Not to be confused with cellulite which many of us are familiar with.) When the moisture content of wood is maintained within correct ranges, the mode of failure when endurance strength is exceeded is an increase in deflection. The material becomes more compliant. ( your wings flap more ) If moisture content is too low the material will shear with the grain.( Assuming we are talking spar here) Hence by definition, Fatigue Failure is when repeated application of a load will exceed the endurance strength of the material, and cause a change of material properties that result in an unsafe condition. Now how about all those who restore old wood, tube and fabric aircraft? All the articles go something like this......... After removing that old grade A cotton and cleaning out the rats nests both spars were replaced because of cracks at the root and compression attach points....... How did those cracks get there? Further reading: Fundamentals in Machine Design, Phelan Forest Products Laboratory Formulas and Reports National Forest Product Association +++ #321 Subject: wing ribs From: Russ Erb [ re: Al grain and bending ] We've discussed grain orientation before. It is preferable to bend across the grain (grain roughly perpindicular to bend line), but you can bend with the grain with sufficient bend radius. With the tip ribs, you can't avoid bending with the grain because they're longer than 4 feet and the sheet is only 4 feet wide. With 1/8" bend radius (not diameter) I had no problem. Point: By making the partial ribs, you can cut them out such that the flange bend goes across the grain, thus giving yourself better peace of mind. However you do it, doing it right will require time and effort. Probably more than you'd wish it would. Get used to it. This isn't a weekend project. +++ #676 Subject: 4130 sheet From: Bill Cox I just recieved some .190 4130 sheet for the strut fittings. I was surprised, the finish is very rough, about like a coarse sandblast finish and it is covered with the black preservative oil like tubing. All the 4130 I bought in the past had a very smooth finish. Aircraft Spruce sent a letter of certification, but I'm wondering is this normal for the heavier stock. What is your experience. +++ #683 Subject: Re: 4130 sheet From: Gary Danford I was down at Air-Parts this week and discussed the 4130 cost with them. When I compared the tubing list I downloaded the other day and figured the cost from Dillsburg, Wix, Aircraft Spruce etc. Air-Parts was within a few dollars. They also told me that if I bought the complete list from them they would allow an additional 10% discount???? If you are ordering Alum from them anyway the savings in Freight may workout. I also learned from my last project to buy 4130 sheet in strips. Wix has it in 6"X72" strips that can be UPS'ed. Unless you have a good steel cutting Vertical Bandsaw, the 6" strips can be cut off on a Horizonal Band Saw and shaped easier. Trying to cut parts from a large sheet with a Hack Saw is a nightmare. +++ #688 Subject: 4130 sheet From: Russ Erb >I just recieved some .190 4130 sheet for the strut fittings. I was >surprised, the finish is very rough... Quoting from the Aircraft Spruce catalog, "Furnished cold-rolled and ailed in sheet thicknesses of .025-.080 inch. Sheets of .090 inch and greater thickness are hot-rolled, pickled and oiled." Cold rolling leaves a smoother finish than hot rolling. Don't let the coarse finish bother you. Besides, you should eventually be sandblasting and priming the steel parts anyway. +++ #701 Subject: Re: 4130 sheet From: carolfaga- My .190 steel came in the same condition, lumpy. I thought it was odd at the time, but went ahead and cut it up anyway. I purchased all my steel, up to this point, from Dilsberg. I was not completely satisfied with the steel sheet I received from them. Most of the sheet pieces I recieved had a small arch/curl to them, some much worse than others. There was also some obvious corrosion and pitting on some pieces. Perhaps he didn't charge me for the sqft of material that was corroded, I don't know. I plan to go down to Spruce to get my fuselage tubing next week. I would have gone ahead and bought it from Dilsburg, but I can buy full size pieces in Corona, haul them home myself and save the trucking charges. +++ #985 Subject: Grain direction From: Tim Anderson - Is following the grain structure in cutting and forming Alum sheet critical? On one of the Bearhawk web sites, someone had done a sample Layout and had made note to pay attention to the grain direction. The end ribs (being 5.5 ft long) have to be cut with the grain (length-wise). I did see in Tony's book, he mentions that welding and grain direction is to be noted, but I didn't see anything about Aluminum grain structure being critical. +++ #986 Subject: Re: Grain direction From: T & E Yeomans Tim, I asked that question early on of Bob. He indicated that the design is fine in either direction.. I think the most important point it not to exceed the max bend allowance. I have played with pieces in both grain direction and exceeded the bend allowance and it still takes some work to break it..... I know the fatigue of the assembles will work on it though.... +++ #988 Subject: RE: [Bearhawk] Grain direction From: "Schutt, Barry C" barry.schut-@jsf.boeing.com For our application, the grain direction in not important for the thin material used in the ribs. This is not necessarily the case for other materials and useages in general. It is wise to be aware of the need to know what the grain direction is and why it is important though. As an example, the strut end fittings should not be made from a really thick plate material so the tension load would be taken in the grain short transverse direction. I don't know if they make plate material that thick or not so maybe this example is a poor one. The ribs have shear stresses in both the horizontal and vertical directions anyway and no loads in the thickness direction. In general aluminum material has the best strength and fatigue properties in the grain long direction, not quite as good in the transverse direction(90 deg inplane) and the lowest strength and fatigue in the short transverse direction(thru the thickness direction). Can give a more indepth explanation if anybody is really interested---let me know. +++ #1182 Subject: 6061-T6 vs 2024-T3 or T4 From: Lee H. Erb Just to add to Budd's comments. As a rule of thumb, 6061 is approximately 2/3 as strong as 2024. +++ #1185 Subject: Re: 6061-T6 vs 2024-T3 or T4 From: Bruce A. Frank True, but to be practical, most of the structure of the wings(not the Bearhawk's but all of the similar craft out there) could be and have been duplicated with wood. The difference in strength between 2024-T3 or T4 and 6061-T6 is of little consequence when considering the load factors and how these parts exceed necessary operational strengths by 500% to 1000%. +++ #1186 Subject: 2024/6061......2/3'rds as Strong From: Tim Cramb 2/3rds as Strong Good to know even if a rounded off figure. I'm going to give Bob a call and just ask for his take, on substituting 1.25> 2024 for 1.75> 6061....Realizing anything one changes structurally, makes the design a one of a kind..... +++ #1187 Subject: Re: 2024/6061......2/3'rds as Strong From: Bruce A. Frank The disadvantage to using 2024 is it corrodes much more easily than 6061 and is more prone to fatigue cracks. +++ #1188 Subject: Re: 6061-T6 vs 2024-T3 or T4 From: Lee H. Erb When you duplicate in wood you use larger dimensions, not the same size. +++ #1189 Subject: Re: 2024/6061......2/3'rds as Strong From: Lee H. Erb disagree on both counts. Check MIL-HNBK-5. +++ #1190 Subject: Re: 6061-T6 vs 2024-T3 or T4 From: budd davisson I was going to stay out of this one, but: Any structure can be made out of any material, if the proper allowables are used. You want a bubble gum structure, fine, crank in the load allowables for bubble gum and use enough of it to resist the loads. However, be consistent, or at least if you're going to change to spaghetti for some particular part, use spaghetti's allowables and make sure the spaghetti and the bubble gum interface in such a way they take into account all the material differences. If a part is made for 2024 (or any other material), the material was selected and sized to react-out the loads applied to it. The loads applied to it have a safety factor (it appears Bob used 6.0, but I can't confirm that). The materials also have safety factors included in the stress handbooks. For instance, 4130 tubing is reduced by 15% in the charts without ever telling anyone because they assume the welds will change the material. Then part of the charts assume the tubing is simply nailed together and the welds are incapable of transfering bending loads, which of course they can. Most bolted joints carry an additional fitting factor of 1.25 to 1.5 to allow for bad bolt fits. It goes on and on until, yes, there is a huge safety factor through out the structure, but I'd hesitate to say that the material allowables between two materials doesn't make any difference without calculating the equivalent sizes required and changing them accordingly. I'm a big believer in not screwing with a designers design unless A) you're a qualified engineer yourself AND B) unless the original designer buys off on it because he intuitively knows how things "work" in his design and knows what can and cannot afford to be messed with. I know I haven't cleared anything up, but at least I feel better. +++ #1229 Subject: Re: 2024/6061......2/3'rds as Strong From: Stephen Wolfe I just spent a considerable amount of time removing corrosion from my C150 at it's annual, a lot of it from the front of the wing ribs. What kind of aluminum does Cessna use in the wings? I know I saw 2024 in the fuselage. +++ #1235 Subject: Corrosion From: Tim Cramb Far as I know it's all 2024T3-4...........My buck and a half wasn't zinc chromated....Don't think Cessna was into that......My old C-150 (C-GIDO) also had cancer in the exact same place extending to the centre rib. It was bad so I used ACF-50...protects Alum, flushes out contaminates/water and stops electrolysis. My bird was parked about 3 miles from the ocean for around 10 yrs and gives meaning to the word 'Saltair'.....ACF-50 is in Spruces & Specialty Catalog and by the way, is a Canadian Product, it penetrates like a .50 cal slug....Deep, Dude! +++ #1307 Subject: Weight of Aluminum From: george velguth Can anyone tell me the weight, per thousandths thickness, of 2024 aluminum. What I'm after is a formula for determining the weight of any aluminum component, e.g., weight = sq.ft. * thickness in thousandths * X. If you don't know the weight per thousandth, how about the precise weight per sq. ft. of a known thickness? +++ #1309 Subject: Re: Weight of Aluminum From: Pierce Terry Civ 412 TW/TSI Aircraft Spruce shows .032" (2024T3)as .461 lbs/sq. ft. Even if you don't order from them, call and get one of their catalogs to use as a resource. They are free. Such a deal. +++ #1313 Subject: Re: Weight of Aluminum From: zippydog- The McDonnell Douglas (not a company any more) Design Handbood shows 2024-T3 to weigh 0.100 lbs per cubic inch. This would say that per thousanth of thickness, per square inch ( 1 inch x 1 inch X 0.001 inch) would weight .0001 lbs. This says that one square foot would weigh 0.0144 lbs (1 ft X 1 ft X 0.001 inch). The math then agrees with Terry's reference since .032 inch thick X .0144 lbs per square foot per thou equals .4608 lbs. A little confuseing, but the (1X1X.001=.0001 lbs) is easy to remember and should work for all dimensions of aluminum. This information will appear on the final exam ;-)> +++ #2005 From: Delton Savage Subject: [Bearhawk] Heat Treat Cycle of 6661-T6 Heat Treatment is a process in which metals are alternately heated and cooled according to a preset schedule of time and temperature to improve the characteristics of the metal. T6 Heat Treatment is a specific heat treatment process which may be applied to aluminum / copper / silicon alloys, such as hypereutectic, to increase the strength of the alloy by as much as 30%. In the case of T6 heat treatment, the process occurs in two phases. The First Phase of T6 heat treatment is called the Quench Phase. In this phase the alloy is heated to 985 degrees Fahrenheit for 8 to 10 hours causing the copper in the alloy to become dissolved in the aluminum and forming what is called a "Single Phase Alloy". If allowed to air cool naturally, the copper will tend to reconstitute, or reform itself within the alloy. However, when the heated alloy is cooled rapidly by glycol or water quenching the reformation of the copper is retarded and the aluminum, supersaturated with copper, is locked into the "Single Phase Alloy" state. In the Second Phase of the T6 heat treatment process, called the Aging Phase, the alloy is heated to 350 degrees Fahrenheit for 10 hours and then allowed to air cool. During this phase the copper combines with the aluminum in a process called "precipitation hardening" to form copper aluminum crystal, CuA12. It is the formation of these copper aluminum crystals which gives the alloy its strength. The key to maximizing alloy strength comes from controlling the size of the copper / aluminum crystals. Maximum strength is attained when the size of the crystals, or precipitated particles, if kept very small, forcing them to conform to the structure of the aluminum. T6 - means the temper was initially performed by the mill that produced the alloy. T62 - Means the product was heat treated by a "user" heat treater. AMS-H-6088 is the specification that you need to get all information required. There are a lot of quality requirements in the heat treating of aluminum, so take care if you intend on processing this yourself. Good Luck Guys. +++ #2059 Rod Smith Subject: Re: [Bearhawk] Materials Order List? > Thanks to Tim Anderson I found it on the Bearhawk FAQ. Duh. This comment is for everyone on the list. Glad you found the steel order list. I was the one that compiled it. What everyone needs to know is that it is the exact amount of material that you will use in the airplane. In other words it dosen't account for any mistakes or when you have a left over piece that is too short to use elsewhere, or where you need a longer piece to bend and then you cut off the ends. If ordering all at once, you might want to add 5-10%. I dont really know what a good number is but I have had to place some subsequent orders already and I am only through the tailfeathers and control parts. Maybe Bill Johnson could comment on how much extra material to figure for the fuselage. I used Dillsburg Aeroplane Works in PA for my steel order. Was very happy with the price and the service. If you have a fax machine, you can print out your order and fax it in, will save a lot of phone time. +++ #2541 From: budd davisson Subject: Scratches Re: Scratches A couple of thoughts about preventing scratches. The work bench should be carpeted with fairly deep pile carpet tht lets the chips (and rivets and drill bits and other small tools) sink into the pile where they can't cause scratches. Also, some of the aluminum from the UK has a thin, blue plastic coating on it, not unlike what comes on plexiglas. It looks like it might be sprayed on. If that could be found and applied to the raw sheets, it would work wonders to keep it from scratching. You just strip it off in the areas where you're riveting and leave it on until ready to start painting. Rule of thumb, No. 239: a scratch deep enough to catch your finger nail is about .003 deep and worth worrying about. Think about the cross sectional area reduction of a .003 scratch on a .025 sheet. Also, at the bottom of a pronounced "V" shaped scratch stress is increased approximately 15 times in the local area. +++ #2553 From: Subject: Re: Scratching Hi all, Much of the metal going through our sheet metal shop comes with plastic on it. It is an option most of out suppliers offer. Othertimes, when the product is not getting paint or is stainless steel and not getting bead blasted, we paper it ourselves if it is not already. How that's done, is with a 4ft wide roll of white plastic tape. The roll is attached to the wall a little higher than out carts. One guy pulls it out past the end of the material on the cart without letting it touch, while the other cuts it off. With both guys holding the sheet of tape by the ends, they eyeball it straight and one fellow touches his end down to the metal. The trick now is not to get any airpockets trapped, though they don't cause much of a problem. While the fellow, still holding up the other end, gently gives you slack, you can start to do the two handed breast stroke and get a fair job done. What works best is one of those dust pan brooms and just brush the tape down. +++ #2559 From: Subject: Re: [Bearhawk] Re: Protecting Sheets from Scratching Here is a quick simple fix. At an art supply store get a can of spray adheasive. High tack type, temporary, used to mount photos. Lightly spray the metal, place a sheet of kraft of butcher type paper on the surface. When done the paper peels off and most of the sticky is stuck to the paper. Makes an excellent surface to write on, unlike the plastic coatings. Glue stuck to the metal rubs off like rubber cement or wipes off with acetone. +++ #2560 From: Morrison, John Subject: RE: [Bearhawk] Re: Protecting Sheets from Scratching In the past I have used 'Saran Wrap' (plastic cling wrap) to protect aluminum sheeting, though never an entire 4x12 piece. If you lay it on flat, with no bubbles, you can't even see it and it stays put until you're ready to peel it off. It takes permanent marker, and doesn't lift off when you cut the metal. +++ #2561 From: Morrison, John Subject: RE: [Bearhawk] Re: Protecting Sheets from Scratching ...oops...forgot one thing...the aluminum can't be really cold or the wrap won't "cling"...though the expensive stuff is not bad.... +++ #2564 From: Subject: Re: Bearhawk>scratching Greetings Group On this sheet masking: I looked on the roll of tape today and found no clues as where it came. Our purchaser said Main Tape in Plymouth Tel: (800) 858-0481. Its 5mil thick and they have 3mil and 2 for sure. Works out to a dime a sq/ft on 60 sheets a roll, so budd, please send the wing kit with masking on the skins. +++ #2647 From: Bob Romanko Subject: Nose Ribs and Grain Direction Quick question AFTER I have all my nose ribs cut: Does grain direction REALLY matter on a nose rib? I don't think it does because a nose rib is not structural. Of course, EVERYTHING on the airframe is "structural", but more specifically, a nose rib isn't under much stress, and this is 2024-T3 after all. Regardless, my grain is parallel to my flanges and I'm not worrying much about it. Since I scared you all with the 8 vs. 9 rivet issue, I figure I'll open myself up to some live fire and give you a good chance to laugh at MY Bearhawk (grin). +++ #2648 From: budd davisson Subject: Cross grain ribs I would have thought that after going through all the trouble to grow the aluminum, you would have known to cut the rib blanks out of the log lenthwise, rather than across the tree. Oh, well, we'll all learn from your mistake. Cross grain ribs...some people just don't understand the way nature works. PS In the real world, as opposed to the Romanko world, it doesn't make any difference which way the grain runs. Most just prefer to run it parallel to the flange bend because it "feels" better. +++ #2649 From: Schutt, Barry C Subject: RE: [Bearhawk] Nose Ribs and Grain Direction OK for a somewhat serious answer. The most efficient (weight wise that is) would be to make the grain direction in the direction of the maximum tensile stress which most likely will be changing for every loading condition or situation. The material does not have a preferred direction for shear or at least it is not given in the Mil handbook 5. And then only if you plan on doing a weight minimization of the structure which is possible only on new design and then not very practical for this type of material and structural configuration. So the answer is No it don't make no difference. Take if from an old stress weenie Barry "old stress weenie"Schutt (036) +++ #2650 From: Bob Romanko Subject: RE: [Bearhawk] Cross grain ribs When I was a pup back at PIA (Pittsburgh Institute of Aeronautics) grain direction was an ongoing debate among the instructors. The "old school" guys all went by the book and said the grain had to be perpendicular to the bend. The younger instructors contended that the grain should be perpendicular to the stress. On a nose rib, I would think that any stress at all would come up from the bottom of the leading edge. Having said that, you'd think the grain should go perpendicular to the force, in this case, parallel with the bottom of the wing. Damn the bend. Those are my ribs, and I'm stickin' to 'em. +++ #2656 Russ Erb Subject: [Bearhawk] Nose Ribs and Grain Direction > Quick question AFTER I have all my nose ribs cut: > > Does grain direction REALLY matter on a nose rib? The only mention I've ever seen with respect to grain is that it should be perpindicular to the bend whenever possible. This is because bending at a very small radius parallel to the grain is more likely to crack (which is bad). If you bend with a normal radius it's not a problem. For instance, there is no way to cut a tip rib with the grain perpindicular to the bend on a 48" wide sheet. Bob Barrows has said before that no part in the Bearhawk is so tightly designed that grain orientation becomes an issue. See the archives below. Russ Erb From Bear-Tracks: Bob: Enclosed please find a check for the second half of the BEARHAWK plans. As for my progress, I do not plan on starting until June. I have however, spent considerable time studying the first half of the plans. This has naturally generated several questions which I would greatly appreciate getting your input on. 1.On aluminum sheets, how do I determine the grain orientation of the metal and what should that grain orientation be on the spar web, ribs and wing skins? 2.What welding technique do you use on the steel tube components, gas, heliarc, etc.? 3.A recent article in SPORT AVIATION concerning the merits of various types of welding rod has left me overwhelmed with concerns. I have been welding for over 10 years using classic gas welding techniques and mild steel rod- I have never had any problems with my welds. I would like to know your opinion on the issue raised in this article and what type of welding rod you use. Gordon Champion - Deep River - Ct. - serial #004 Gordon, Grain is determined by the direction of the printing on the sheet aluminum; however, grain orientation is not a problem while your aircraft is under construction. Stress levels are within limits for either direction. Be sure to use proper bend radii to insure crack free parts. As for my preferred welding technique I use gas welding (Oxy. - Acetylene), Tig should be OK as well. The article you mention has raised concern with other builders also. I am recommending that you stick with mild steel welding rod. Airplanes built with 4130 tubing have used mild steel welding rod for years with almost perfect results. Alloy rod can be a big problem with cracking and brittle failure. I hope that answers you questions. Let me know when you start construction. Bob From the archives (on the CD): April 1998 You mention on your web site that you are concerned with grain direction in the rib material. Bob Barrows says it is OK to disregard grain in order to get the best utilization of material. I'd like to hear some discussion of this. Archie Dunbar The consequence of indiscriminate grain orientation in parts relates mostly to the effects of bend radius. If you are trying to use the smallest possible bend radius on all flanges, you care about bend radius very much. If the designer used the minimum or larger bend radius specified for the thickness, temper and for bends parallel to the grain for all bends you will be OK. It is always OK to use a larger bend radius for a given thickness and temper of a material but the assembly may be impaired by fit-up issues including fastener clearance and edge distance. Refer to AC43.13-1A&2 (I think!) for the minimums. ...If you have the ability to form all your ribs in the annealed condition and then heat treat them (!), the issue of bend radius becomes much less important... David L. Downey To quote FAA AC 43.13-1A 98.a.: "Forming Sheet Metal Parts. Bend lines should preferably be made to lie at an angle to the grain of the metal (preferably 90°)..." Tony Bingelis says it too (Sportplane Construction Techniques, page 38. I think of it as the metal will stretch without cracking along the grain. Stretching it the other way (by bending) will cause the grains to separate (crack) from each other. The wood analogy works, but was mis-shapen: Watch a karate class breaking boards with "karate chops" They cut a wide board into strips with the grain running the "short" dimension, not the long dimension like you would buy lumber. The wood breaks because they are "bending" it with the grain--if they did it the other way they'd probably hurt themselves. Back to the original question. My interpretation of everything: if the part is less that 4 feet long, bend flanges across the grain (sheets only come 4 feet wide, with the grain running across the 4 foot dimension). If the part is longer than 4 feet (tip ribs, spar webs) then bend the direction you have to. Be sure to use at least the "normal" bend radius or larger. Erbman #164 Edwards CA I wouldn't sweat it too much, at least with the ribs. If you finish the flanges off the block like most of us have, it's hard to make the radius too small. Provided your forming block has the proper radius to start with. With the spars you don't have any choice, you have to bend along the grain. Again just watch your radius. I generally try to bend perpendicular to the grain, but that 2024-T3 gets more expensive every year so I really try to minimize waste. Rick Girouard #151 As has been mentioned before, AC 43.13 has everything you need to know about bend radiuses. If you don't have a copy of this book already, please do yourself a favor and get one, lots of common questions which come up are answered there. When the FAA inspects your airplane, his standard you'll have to measure up are the standard practices described in this document. The books are pretty cheap, about $16 or so (ASA reprint). It's been a few months since I read the bend radius section of the book (not many metal parts in my Cozy !) , but as I recall it lists a strength reduction of the metal at the bend for parallel-grain bends of about 20% (I don't remember the exact figure). Since you're not normally depending on the aluminum __at the bend__ for the strength of the part, this is not a problem in most cases. Something to keep in mind, though, as you bend in the future, for some parts this may be a critical difference... Darren March 1997 I have spoken to several aeronautical engineers, I work at the Cape and there are plenty of them to go around. Not one of which is very impressed with the bending with the grain, everyone advise (engineers) don't do it. Anybody out there have the right ansewer to this question. Bobby s/n 225 I've lost the thread of what this was in response to, but I'll address the question raised since nobody else has. The short answer: It all has to do with bend radius. The longer answer: Aluminum, similar to wood, has a grain structure. While I have not confirmed this, I believe the direction of the grain arises from the rolling process used to manufacture the sheets. Aluminum sheets, regardless of thickness, are created in the size of 4' x 12'. Why this size? I don't know. The grain and the lettering on the sheet both run along the long dimension (12'). If you have a piece of aluminum that has been cut off from the sheet, it is easy to determine the grain direction if it still has some of the labeling on it. If not, study closely a piece of aluminum that you know the grain direction, and you will probably be able to determine it on the mystery piece by inspection. Why is the grain direction important? Aluminum can be bent to a smaller radius (sharper bend) across the grain (i.e. bend line perpindicular to grain direction) than is possible with the grain WITHOUT TEARING. If you try to bend to too small of a radius (like none) you will tear the sheet regardless of the direction of bend. (Note that steel can be bent to a smaller radius than aluminum, and 6061-T6 can be bent to a smaller radius than 2024-T3.) Why is this? Perhaps an analogy is in order. Any time an object is bent, the inner edge is compressed and the outer edge is stretched. The material will separate under tension easier by separating grain lines than by breaking them. Consider a pine board--if you support it at the four corners and whack it with a hammer in the middle, which way will it break? It will split along the grain line. Ever watch a karate demonstration where 1x6 boards are easily broken? Look closely at those boards--the grain runs along the short dimension, NOT the long dimension! These boards are produced by cross-cutting a 12" plank into 6" long pieces. They are cut this way because they break easier in that direction, and are thus more entertaining. Hand them a 1x6 out of your wood pile (with the grain going the long way) and the karate kid might just hurt himself. What does this have to do with bending aluminum? If you bend with the grain TOO tightly, you stretch the outside too much and those grain fibers will separate. If not immediately, eventually. Bending across the grain stretches the grain lines rather than trying to separate them, and is thus more tolerant of smaller bends. So why don't we just make all of our bends across the grain? Two reasons. 1. If you bend a box or such from a flat piece, some of the bends are going to be with the grain. Geometry says so. 2. If you need a piece longer than 4', such as spar webs, your ONLY choice is to bend with the grain. There are a bunch of such pieces in the Bearhawk wing. So what do we do? Be sure you use sufficient BEND RADIUS (radius to the inside of the material). The FAA and thus Tony Bingelis say for NORMAL bends in 0.032 2024-T3 a bend radius of 4t, or 4 times the thickness should be used. This would be 0.128, or roughly 1/8". I have been using this so far with good results. While 0.025 could be bent tighter, I have found using 1/8" everywhere is working well and easier than constantly changing. It's really tough to bend the 2024-T4 sheets any tighter than this anyway. At some places on the plans a bend radius of .100 is called for. I think this is too tight and will use 1/8". If a part is shorter than 4 feet, such as all of the ribs, lay them out so that the primary bends will be across the grain. This means that the long dimension of the ribs (chord) will be across the 4' (short) dimension of the sheet. For pieces longer than 4' (spars, trailing edges, etc) the bends will be with the grain. Be sure to keep a generous radius, at least 1/8". Bob Barrows said in one of the early newsletters that none of the parts are designed so closely that grain orientation matters, as long as there are no tears in the bends. That's a long answer to a short question, but I think understanding what is going on will help you make better decisions than blindly following rules (always bend across the grain) that aren't always applicable. Now back to beating some ribs. +++ #2657 From: Bruce A. Frank Subject: RE: [Bearhawk] Cross grain ribs > When I was a pup back at PIA (Pittsburgh Institute of Aeronautics) > grain direction was an ongoing debate among the instructors. The > "old school" guys all went by the book and said the grain had to be > perpendicular to the bend. The younger instructors contended that > the grain should be perpendicular to the stress. > > On a nose rib, I would think that any stress at all would come up > from the bottom of the leading edge. Having said that, you'd think > the grain should go perpendicular to the force, in this case, > parallel with the bottom of the wing. Damn the bend. > > Those are my ribs, and I'm stickin' to 'em. In all the years of engineering classes I have sat through one point that was emphasized again and again was not to design on the ragged edge of material strength. Designs usually provide for a margin of 4 to 10 times expected highest load. If grain direction of materials must be considered for strength and durability then the cross sectional thickness must be spec'ed to that lowest common denominator. If a part were being stressed near its tensile or bending limits then either the part is changed or a note made as to its orientation. One of the things about an aluminum skinned wing, unlike a fabric covered wing, is that loads are distributed over a wide area of the structure. From what I have seen of it, the shape of the Bearhawk's leading edge is self bracing, able to handle the aerodynamic and structural loads with virtually no internal bracing -- a ridged "D" section. Bending on a very short radius is a very high stress process on the material. There is where grain direction is important. If the material survives the bending process without cracking then it is likely up to the job of supporting the loads intended for the finished part. Loads on a wings leading edge are very different from what "logic" would dictate. That bottom of the leading edge is likely in diagonal tensile loading with almost no loads perpendicular to its surface. Bob, quit worrying about it and just build the dang plane. 8^0 +++ #3003 Subject: Re: [Bearhawk] Prep Tank From: dmccarroll1 >> When I salvaged parts from both a Colt and TriPacer neither had >> any obvious preservation application to the aluminum parts in the >> wings. The youngest parts were from the 1963 vintage Colt. None >> of these parts, spars, ribs, or leading edges, showed any >> evidence of corrosion. > > Do you by any chance know what alloy the Piper parts are? The > 2024t3 used in the Bearhawk wings is fairly susceptible to > corrosion if unprotected, but other alloys (like 6061) don't > corrode as easily. The problem with 6061 is that it is too soft to have any stiffness or stregth in sheet form. We use 6061 here at Kenmore to form wing strut fairings and other non structural pieces, but never for anything structural. +++ #3016 Subject: Wing Strut Fittings From: Rod Smith Last evening I completed the wing strut fittings for the Bearhawk struts. I was careful to get the dimensions exact as shown on drawing 15A as there is only .01 inch clearance at the wing end when everything is nested together. When I went to test fit the four parts together (Al wing end fitting, steel link, two steel wing attach fittings) they wouldn't fit. I quickly determined that the .190 steel was actually .210. This is not a big problem I will mill or file the wing attach fittings back to .190 for about an inch on the strut end, being careful to fair it out so I dont leave a stress riser. If I had known the steel was thicker ahead of time I dont believe I would have done anything differently as I would not want to enlarge the size of the slot in the Al wing end strut fitting. +++ #3748 From: Russ Erb Subject: Thoughts on buying aluminum I just opened a shipment of aluminum from Airparts and had a few thoughts that some of you may benefit from. To finish skinning my right wing I needed two 6' sheets and one 10' sheet of 0.025 2024-T3, and one 8' sheet of 0.032 2024-T3. I looked at two options for purchasing, Aircraft Spruce and Airparts. I could have looked at Wicks or Dillsburg, but the result would have been the same. Let me say up front that I don't categorically discount any supplier for groundless reasons. There are those who have had a mistake made in an order and instantly come to the conclusion that that supplier is staffed by a bunch of incompetents, and then try to pontificate this to their friends. My experience has been any company can make a mistake, but every one of them has been quick to fix the error. Sometimes you may find that one supplier has better quality material, such as in wood, than another, but in aluminum this is pretty much a non player. Most of it seems to come from Kaiser or Alcoa anyway. Aircraft Spruce is close to me (2 hour drive), which for many things is convenient. I could drive down there, or can get shipments quickly, sometimes in 1 to 2 days. When it comes to aluminum, Spruce gets their supplies in 4x12 sheets. They'll sell it to you in lengths of 2', 4', 6' or 12'. Note that 10' and 8' are not options. For my requirements, I would have to buy two 12' sheets of 0.025 and have one sheared in half, plus a 12' sheet of 0.032. That's 2' extra of 0.025 and 4' extra of 0.032. This might be useful if I need extra for access panels and such, but I already have plenty of leftovers to use for this. So I would have to buy an extra 6' of aluminum to get what I needed. I looked at Airparts, which is the only supplier I know of who sells aluminum by the running foot. At Airparts I was able to order 22' of 0.025 and 8' of 0.032, which was exactly what I needed. Because I didn't buy an extra 6' of aluminum, the price was about $60 less than Spruce prior to shipping. If I had needed all of the aluminum that I would have to buy from Spruce, the prices would have been very close. The savings will vary depending on what you need. Other considerations: Spruce cuts their sheets on a shear, such that they all come with nice, straight, generally perpendicular edges. Airparts appears to cut their coiled aluminum with hand snips (maybe Planter Bob works there), so the short edge is not perfectly straight. Generally this is not a problem, but is something to consider if that is important to you. Airparts will also sell aluminum in cut sheets if that is what you desire. I have also noticed that aluminum sheets that start out flat tend to return to flat after unrolling. The coiled aluminum kept a little bit of a curl after unrolling. Practically, I don't see this as being a problem after forming into a part. Mostly much ado about nothing. Either supplier should be okay, but you may want to consider the coiled stuff if you need a whole bunch of aluminum. +++ #3790 From: Steve Eldredge Subject: RE: [Bearhawk] Metal Prices...Cdn Comparison I notice that you list 6061-T6 bar, I've been wanting to find out if this is an acceptable substitute for 2024-T3. being that to 6061 is so much cheaper I'm sure the question has been asked about substituting it. Can someone give me a pointer on this question? +++ #3791 From: Paul Foster Subject: RE: [Bearhawk] Metal Prices...Cdn Comparison The 6061 bar is used for spar straps. +++ #3792 From: Subject: RE: [Bearhawk] Metal Prices...Cdn Comparison Please note, 6061 is not the straps that run horizontally along the C-channel of the spar, but is OK for the little pieces that run vertically, under where the ribs attach to the spar. +++ #3793 From: Tim Subject: Re: [Bearhawk] Metal Prices...Cdn Comparison I've talked to Bob Barrows about this very issue and he has advised that 6061T6 is not a direct substitute. I mentioned going to a wider bar stock of 6061T6 to get the additional strength of 2024T3/4 but the down side of this is increased weight and the hole centers would also change due to the added width. 2024 Bar is mostly made in the USA, I've made several calls to producers up here in Canuck land and as the ole Military saying goes 'No Joy'. +++ #5088 From: Tim Subject: Rolled/Coiled Aluminum Good work....As for rolled Aluminum, I've moved 2024/6061 many times both flat and coiled/rolled....The rolled is easier to handle but if not taped or padded the inside end/edge usually causes some scuffing. A good tip is to bend/curve up the two inside sheet corners. You may want to check Airparts When talking to them about rolled alumimum for shipping, this is what they told me> UPS has a limit for weight of 70lbs...As the Alum is cut off large rolls, length is limited only by by weight and reason ;-)......Here's what I have, this info is 2yrs old and how they normally load a box based on 'Best Bang for Buck' (box included) .020 thou approx 50 ft...for 46 lbs......1-800-800-3229 (free catalog) .025 thou " " 40 ft @ 55lbs Cheers!! +++ #5092 From: Russ Erb Subject: [Bearhawk] Aluminum In the sizes you mentioned, sheet aluminum rolls well within the elastic range. When you open it up (watch out--it's a BIG spring!) it will lay out flat again. This is about your only choice for shipping unless you like paying for truck shipping or can pick it up yourself. +++ #5097 From: Benton Holzwarth Subject: Rolled Al > Good work....As for rolled Aluminum, I've moved 2024/6061 many > times both flat and coiled/rolled....The rolled is easier to > handle but if not taped or padded the inside end/edge usually > causes some scuffing. A good tip is to bend/curve up the two > inside sheet corners. A full sheet (4'x12') of 0.025 2024-T3 runs about 17 1/2 pounds I believe. When I bought mine (will call at Pacific Metal in Portland, OR) they rolled it up with a sheet of pasteboard (margarine box type paper) on the inside and a wrap of brown pulp-paper on the outside, and threw in a piece of twine to boot. Rolled to about a 3' diameter, it unrolled with no problems. I only wanted to work with a chunk at a time, so to keep it tidy, I'd lay out a couple boards (runners) on the floor, lay the roll over on it's side on the boards, clip on some of those big orange rubber covered spring-clamps at each edge a couple feet in, then pop the knot in the twine. With a couple feet exposed, I could mark and snip off a piece, throw the twine back around it, and pull the loose end back up. Then stand it back up in the corner. Kept rolled for a couple weeks at the 2 1/2 - 3' diameter it took a little curl, but nothing compared to the wave it had by the time I was done forming the rib, and with the protective paper I worried less about it getting marred. +++ #5098 From: Tim Subject: Re: [Bearhawk] Aluminum Especially .032 thou.....I've rolled about a dozen sheets of 32 by myself and now qualify to work in the Circus....Should have added to my previous post, you can ask for the protective plastic film when ordering, it cost more. Although on 2 occasions in the past 'due to 'Stock' on hand, I wasn't charged for this option.... +++ #6475 From: "Mark and Tina Lapierre" Subject: Re: [Bearhawk] Rib Material Did you have any problem with the memory effect of the rolled aluminum? The guy at Dillsburg didn't have anything good to say about the rolled stuff. I wouldn't think it to be that big of a problem myself. Mark +++ #6476 From: "Float-By Shooter" Subject: Re: [Bearhawk] Rib Material > Did you have any problem with the memory effect of the rolled > aluminum? The rolled aluminum from Airparts definitely has a memory. It wants to return to its flat state, and will do so forcefully if you let it. Fortunately it comes packed in a heavy cardboard box, which I slit down one corner and cut the tape on the roll, and only pulled out as much as I needed at any one time. You have to open one end of the box first to know which corner to slit down, be sure to tape that end up again before you cut the tape around the roll, which has a lot of stored energy from being rolled up. As for as the aluminum taking on a curved shape from having been rolled, not as far as I could tell. Del Rawlins +++ #6477 From: Russ and Penny Erb Subject: RE: [Bearhawk] Rib Material I was concerned about it too when I started out, to the point of driving 2 hours to Aircraft Spruce to pick up my spar material in a flat state. Later I would conclude that it's just not a problem. To put it in terms a materials or mechanical engineer would use, the aluminum is rolled to a large enough radius that all of the bending is elastic, like a spring which returns to its original shape, in this case flat. I have not seen any plastic deformation, which would be a spring that was pulled too hard and did not return to its original shape. If you've bent any aluminum (or steel) before, I'll say it this way: All of the bending on the roll is pure springback. Del is absolutely right, though--that coil of aluminum is a really big spring, and it will hurt you and/or itself if you do not very carefully control its unrolling. I've often wondered how hard it is to get rolled up like that. Russ Erb +++ #6478 From: "Donald Schindler" Subject: RE: [Bearhawk] Rib Material I remember after exposing my big coil of rolled aluminum I thought "Looks harmless enough" Then I cut the last restraining wrap and the whole coil started to jump and wiggle like a pot boiling and then I did the manly thing-I ran! Although in this case it was the most sensible. I was really surprised how long it continued to unwrap. Maybe Russ could do some engineering calculations on the stored energy in that bugger! Soldier on...Don 068 +++ #6480 From: Jim Ash Subject: RE: [Bearhawk] Rib Material I'm guessing that some engineer has given the aluminum folks a minimum diameter for rolling it up so it will bounce back. I think there's also a difference if it lives normally flat and rolled just for shipping, vs stored rolled up, but I'm guessing the time difference to be longer than any of us will remain alive and sane. Jim Ash +++ #6523 From: "doug" Subject: Re: What else do I need Here is a trick that I use when working alone with coiled aluminum. Get 4 medium Pony spring clamps, (the ones that look like oversived clothes pins) they are only about 4" long or so. Place two clamps on each side of the coil at 180 degrees, then clip the tape and uncoil the coil half a turn at a time, move clamps as nesessary. Reclamp and retape when through and will still fit back in the box. Doug #433 >>> 4sep02 #9154-11297 +++ #9227 From: "drennie540" "Don" Subject: 2024 alum. Bare with me ,not to smart yet. On the Barehawk C.D.under materials April /98 Some one said they had 2024-t3 .025 bare,could they use it? The ans. was that they could use it for skining doors,boot cowl,glove box,fairings etc. Isn't this what we're to use for the wing ribs? Also I see a list of material for tube, but not for the alum. I think I have it figured out but it would be nice to know how much others used for their,ribs , spars etc. Thanks in advance for your help. +++ #9228 From: Russ and Penny Erb Subject: RE: 2024 alum. Don--we normally use 2024-T3 Alclad (i.e. Aluminum Clad), not bare. Alclad has a very thin layer of pure aluminum (1100) on the outside. The pure aluminum reacts with the air forming aluminum oxide, which protects the aluminum from further corrosion to some degree. For real corrosion protection, you'll need further protection (conversion coating, primer, both, or whatever). +++ #9908 From: bearhwk272@... Subject: Re: Annealing Alclad Glad to see you are thinking about lots of little details before you do something. DO NOT MESS AROUND WITH ANNEALING MATERIALS IN YOUR SHOP ON SOMETHING THAT YOU MIGHT JUST HAVE TO TRUST YOUR LIFE ON. Use Correct Bend R and tools, with a little practice you will soon be making perfect parts. Send your Instructor to me here in Arizona, I can wrap him in aluminum foil and stand him in the parking lot to allow him to experience the full benefits of uncontrolled annealing and I am sure that I will not get him hot enough to drive out the copper ;)> +++ #10303 From: "Lee H. Erb" Subject: RE: Sub 6061T6 for 2024? >> I don't have Bearhawk plans, but I'm wondering if theres any reason >> one can't use 6061T6 in place of the 2024 folks have been mentioning >> for various parts? > Yes--the strengths and properties are different. Don't do it. I repeat, don't substitute ! Yield Ultimate Spec 2024-T3 42,000 psi 64,000 psi QQ-A-250/4 6061-T6 35,000 psi 42,000 psi QQ-A-250/11 Yield value is is an indicator of when the part starts to deform. 6061-T6 will start to deform earlier. Ultimate is where a part will break. 6061-T6 will break at about 2/3 the load of 2024-T3. Alclad values are lower for the same thickness in both cases. 6061-T6 is a real good material and has some advantges but, for a given structural design requirement, 6061-T6 will result in a heavier weight. +++ #10330 From: Russ and Penny Erb Subject: RE: FAT RIBS > Now as I cut with my trusty aviation snips I had a hard time keeping > the scratches off the aluminum. > > What's the best way to clean this up? Get yourself a box of maroon Scotchbrite pads. I get mine from Avery but I'm sure there are other sources. Any scratch that you can't catch a fingernail on isn't worth worrying about. If you can feel it with your fingernail, smooth it with the Scotchbrite until you can't. Unless you plan to polish your aluminum, you'll probably need to Scotchbrite it eventually either to clean it for alodining or rough it up for priming. If I had worried about superficial scratches I'd still be trying to get my first rib cut instead of wondering when I'll be ready to bring the wings back from storage. >>> 20may03 #11298-18250 +++ #12341 From: "Bruce A. Frank" Subject: Bearing? I am in the process of replacing the original Piper horizontal stabilizer jack screw trim mechanism with an electric setup. This is a piece of equipment from a company called Motion Industries. A really innovative screw with ball bearings held in a cage that could lift 500 lbs if needed, but stops without the use of electric limiting switches. One end of the 5/8" diameter screw is imbedded in the gear box. The outboard end has been turned down, at my request to the factory, to a 1/2" diameter that was going to be supported by a bronze bushing. In the process of assembling and disassembling and mounting the nut in a fabricated yoke I damaged the surface of the turned down section so that it will not work in the 1/2' ID bushing. The damage is slight but difficult to fix well enough to turn smoothly or wear free in the bushing. My alternative is to install an actual 1/2" ID ball or needle bearing set that will easily press onto the slightly damaged screw shank. While drawing up plans for a bracket to hold a bearing (of course I have already machined the part to hold the bronze bushing and it cannot be adapted to hold any other style bearing) it hit me that I had a 1/2" rod end (brand new, in the box, Mil surplus). The rod end bearing will press down onto the shank and provide an easy to put together mounting method by nutting the rod end's threaded shank through a bushed welded-on fitting welded right where the original Piper part mounted (Though horizontally rather than vertically as was the Piper design was). After all that, my question is will that rod end live long and prosper when subjected to intermittent axial rotation as I trim the plane? The original Piper jack screw ran steel against steel and lasted for decades. This rod end is a polished "ball" turning inside the housing that fits around it. There is provision for installing a zerk (grease fitting) on the rod end. My experience with rod end bearings is to use them to allow for misalignment movement as actuation moves parts through arcs and around pivots. Seldom have I seen the rod end bearing rotate more than 3/4 turn then back again. My application will rotate the bearing 30 revolutions if the stab were moved stop to stop....but in actuality it will likely see only two or three revolutions each time the trim is adjusted. Does anyone see any problem with this application of a rod end? Bruce A. Frank +++ #12342 From: Budd Davisson Subject: Re: Bearing? If I visualize this right, you've got a Heim type spherical rod-end bearing (no ball bearings around the ball like a Fafnir rod end) laying horizontally on top of the screw jack, with the screwjack feeding it's loads through the bearing hole vertically. If I have this thing pictured right, it looks as if the bearing housing will be loaded in bending (1/2" is pretty big so probably not a problem) but the loads are trying to push the "ball" sideways (vertically in this case) out of the housing. I may have this thing visualized all wrong, but if what I said above is the case, I'd worry about the load that's trying to push the ball out of the bearing housing more than I'd worry about the rotation. And I wouldn't worry about the rotation as long as it was periodically greased. Those bearings are hardened to something like 70 Rc and won't wear out in your life time. Is it impractical to send it back to the factory and have them either polish the surface of the turned part or turn it down a little further and go for a smaller bushing? The diameter of the ram on a screw jack is of little consequence because it sees practially no load. All it's doing is keeping the piece it's pushing centered. The loads are carried by the shoulder and by turning it down, you'd get a bigger shoulder anyway? As it is now, it sounds as if you have only a 1/16" shoulder which is a little small. bd +++ #12343 From: "Montee, Dan L." Subject: Bearing? Using rod ends in this manner is pretty common practice on custom roadrace cars and suspension. I ran a car for several seasons that used 1/2" rod ends as lower ball joints for the front suspension upright. Never a failure. The static and shock loads are off the chart in this application. I also used rod ends as a steering shaft bearings and even used one as rear engine mount in another application. You would want to turn a couple of heavy washers for protection in the event the bearing got pressed out of the rod end but I'd bet you'd screw the tail feathers off the airframe before the bearing ever failed. Rod ends are rated for the side loads on the bearing and there is quite a range. Being mil spec I'd guess that it is more than adequate but I'd compare the spec's just to be sure. I wouldn't hesitate to use the rod end in the application you describe, but then that's the red neck engineer in me talking. Dan Montee +++ #12344 From: "Bruce A. Frank" Subject: Re: Bearing? I left out some detail. The motor/gearbox end is solidly mounted so the only loading the Heim will see is rotational axial. There is no thrust or bending loads trying to push the ball out of the housing. As for sending it back to the manufacturer, it has gone back once because I had to remove the "nut" from the screw to press fit it into the yoke I fabricated. In the process 2 of the non-standard aprox. 3/32" diameter balls disappeared. They would not sent parts to me insisting I return the unit for "repair." "Repair" cost 3/4 of the original cost of the unit, add the cost of shipping and I have bought this thing twice. Diameter of the jack screw was selected primarily because I knew that I would have to do some adjustment of the travel stops which would require drilling the screw and inserting a roll pin. After I sent it back for repair they THEN informed me that there was an adjustable stop available (which I now have). Bruce A. Frank +++ #12346 From: "zipppydoggg" Subject: Re: Bearing? > After all that, my question is will that rod end live long and > prosper when subjected to intermittent axial rotation as I trim the > plane? At work we use rod end bearings all the time. We don't use them in the way you describe very often, but in a test rig that I'm running right now, I have two bearing running in a similiar manner. The bering doesn't turn a full 360 deg, but back and forth about 35 degrees (a worse case I would think). I suggest you use the zerk, just to remind yourself to check the bearing now and then. I would suggest that if possible, use two large washers on each side of the rod end ball, to contain the linkage in the unusual event that the ball would dislodge from the "lolly pop" portion of the rod end. This is done on flight controls when rod ends are used for the same reason, different loading. Our experience is that the rod end won't make its fatigue life and moderate to high loads (not your issue), and won't last when they get hot (also not your issue). Rob "$.03 worth" Gaddy +++ #12347 From: "Lee H. Erb" Subject: Re: Bearing? Motion Industries here in Arlington will not sell anything that is to go on an airplane. I've tried. Lee +++ #12348 From: "Bruce A. Frank" Subject: Bearing? Who said anything about building a plane? I am building an "adjustable suspension" off-road vehicle. Is that anything other than the truth? Bruce A. Frank +++ #12352 From: Russ and Penny Erb Subject: RE: Bearing? That's why you don't tell them what you're using it on. Popular ruses are 1) hot rod 2) go cart 3) tractor 4) a non-descript "project" The key is to walk in knowing the part number of the bearing you want. Erbman +++ #12403 From: "Bruce A. Frank" Subject: Motion Systems Jack Screw When I was asking the question a few days ago about using the rod end as a bearing for the top of my electric replacement jack screw I mis-identified it at Motion Industries. Sorry, it is a part from Motion Systems. In these pictures you can see the mechanism and the yoke that I fabricated. Bruce A. Frank +++ #12749 From: "Bruce A. Frank" Subject: Rod Ends A couple of weeks ago I asked about the feasibility and advisability of using a rod end bearing as a support for one end of my motorized jack screw trim. Funny then that just a few days later I received new catalogs from Aurora . My primary question had been as to whether the bearing could tolerate the rotational loading of trimming the horizontal stab all the time. Right in the front of the catalog is a short technical section stating that rotational loading should be no higher than 100 rpm.......right in my ballpark. The axial and radial loadings in this application are negligible, I was worried about rotational durability. The spec states that radial load should be limited to 10% of maximum radial static load limit when the bearing is doing full rotation service. Since the information on the bearing I intend to use states a radial static load of 6,600 pounds, I think I am safe. Bruce A. Frank +++ #13502 From: "Dan Shilling" Subject: Nuts and Bolts I confess to being a tight-fisted, penny-pinching till Lincoln screams, whiney kind of guy. But from some of the posts I've read, I think I am in good company. Asbestos suit is on. The question is, is there a viable alternative to the expensive AN nuts and bolts? Or just don't go there. Dan Shilling +++ #13509 From: "Bruce A. Frank" Subject: Re: Nuts and Bolts Well, just to stick my toe into a little bit of controversy, there are few reasons not to use alternative bolts in homebuilt applications. The specs on grade 5 and grade 8 are not the same as AN or MS bolts, but they are close. Those differences are not in areas that would cause us problems in applications we are using in most homebuilt projects. Yes AN bolts are more shear resistant, but we are not hanging a 4000 pound engine off a single bolt. I worked for several years fabricating and installing trailer hitches. I got to inspect hitches after the tow vehicles had been involved in accidents ranging from high-speed roll overs to having a tractor-trailer rig rear-end a 10,000 lb boat towed behind a 7000 lb pickup also carrying a bed mounted cab over camper. The stresses on the, usually no more than 4, bolts holding the hitches to the frames were off the scale. Sometimes whole sections of alloy vehicle frames were ripped out, but the bolts didn't break. We used grade 5 bolts for towing setups that were under 2000 lb capacity and grade 8 on everything else. Think about the highest loaded components on an airplane: engine mounts, strut and wing mounts, and most important the gear mounts. The engine weight is distributed through, usually, at least 4 bolts with 2 taking a combined higher load (tensile and shear) at times. In most cases, loads on the engine and mount never come close to the elastic limits or even close to using the elasticity of the bolts. On the wings; certainly we don't want the wings falling off. And after all, the entire weight of the plane is suspended on what appear to be ridiculously small bolts. Please don't let it bother you that those bolts are fastened into ALUMINUM and the bolt's strength exceeds that of the aluminum mount point shear-out strength by about a multiple of at least 4. (yes, there are exceptions, but I'm on a roll so let's not puncture my balloon yet). Now the gear is what I consider the most likely place of failure because the loading can be abrupt and again the full weight of the plane can be hanging on just 4 little 3/8" bolts ... think about that when you drop it in from 5 ft up on that mostly cobblestone "sand bar" in the boonies of Alaska. Man, the jolt can make you kidneys swap places with your gonads. After fixing that picture in your mine, forget about the bolts, think what tiny welded pieces of sheet and tube steel hold that bolt bracket to the longeron. Gives me the shivers. Anyway, inspections of heavily loaded and vibration punished equipment tell me that uniform quality grade 5 and 8 bolts will do everything we want them to do in our airplanes. (by the term "uniform quality" I mean brand name suppliers who go to the trouble to put their names on each bolt....not like you might ever get a bogus AN or MS bolt) Now the shortcomings of non-AN and MS bolts. The primary problem is the lack of spec on how long or short the threaded section of the bolt will be. It may be difficult to find a bolt with enough unthreaded shank to slip all the way through the fitting without having an inch and a half of threaded shank sticking out beyond the nut. Un-sightly at least and since the inspector is going to be checking to see if you followed accepted aircraft procedures you may get hassled (you can win the argument, it's your homebuilt). I have found bolt suppliers who have a very good product, Lawson for one, (the guys who come to your shop, give you a bin then come in to restock once a month) that produce standard grade 5s and 8s to suit my needs. But don't mention "airplane" to them, tends to send them screaming from the building. As for me, I use grade 5s and 8s on my project, at least until I can locate the right length AN or MS bolt. 8^O Bruce A. Frank +++ #14078 From: "Steve Eldredge" Subject: obscure AN hardware Question Ran across this during the stinson rebuild. I've heard of the regular AN3, and the close tolerance NAS 1103, but there also seems to be an AN173 which AS&S describes as a NON-corrosion resistant close tolerance bolt. My question is Why? BTW these are specified as the bolts that go through the control wheel to u-joint union. Steve E +++ #14089 From: bearhwk272@a... Subject: Re: obscure AN hardware ANSWER Typical AN hardware is constructed mostly with 4130 and 4340 steel. The parts are protected with some type of plating, cad, zinc, iridide, silver which gives the part some corrosion resistance. What AS&S and others mean when they say corrosion resistant is the parts are made from alloys of 321,304,316,A-286 which are truly corrosion resistant materials. Some of these materials have lower strength properties than standard hardware so stick with standard unless the application requires corrosion resistant materials. Examples,high temp, exhaust, salt exposure. Kevin +++ #14528 From: "Daryl Van Zee" Subject: Re: Question about Wing Changes > Yes, Bob is suggesting almost anything including laying down a heavy > bead of silicon before seating the tank. My first choice would be > something like a thick (1/8") rubber strip but it can be almost > anything. Aren't most silicones a No-No around aluminum? I think the Acetic acid given off during the cure will corrode the Al. D Van Zee +++ #14529 From: "Bruce A. Frank" Subject: Re: Re: Question about Wing Changes Many of the hardware store silicone glues, caulks and sealers give of Acetic acid during cure, but there are dozens which do not. BUT, and a big BUT here, I have used and have seen used silicone on aluminum and have never seen any corrosion. Once the silicone cures there appears to be nothing to cause corrosion and the short exposure during cure seems to cause no problems that I have ever seen. If you want to be careful go to McMaster-Carr and you will find many silicone glue products that emit no acetic acid. Bruce A. Frank +++ #14891 From: Benton Holzwarth Subject: re: Aluminum to start > I just went through this process a month ago. I ordered 2 shts of > .020, 7 shts of .025 and 5 shts of .032 plus all the other bits of > sheet stock required for the whole aircraft. Maybe this is a good point to chime in -- I found a list of *all* the metal and parts in the airframe, that I think Rod Smith had put together. I thought I got it off Del's webspace, but looking there now, I'm only seeing the 'fuselage steel list'. Anyway, I think it was in excel spread-sheet format. I found and fixed one or two minor errors and dumped it out as flat text, which I find much easier to manipulate. I also assigned each part a hierarchical part number. So how does this tie into the post I replied to? Part of the manipulation I've done is to sort out two copies of the list -- one by part number, so I can organize what needs to be built for, say, the aileron; the other sorted by material type/thickness, so when I go to order steel for the aileron hinge brackets, I can scan the adjacent line-items to see how much of that thickness steel I'm going to need, and consider buying all at once. I've also made some effort to figure ways to nest parts, and this list will show what I think is the rock bottom minimum material needed. For nesting, I've done things like cut my nose-rib blanks as trapezoidal pieces, and the list shows 46 req'd, 2 @ 11x14. (Something like that, I don't have the list in front of me now.) If you lay out for square blanks, you'll use a good bit more metal. I think I've said in the distant past that I'd post it when I had it cleaned up, but never followed through. (In part because I got the impression that Bob B thinks we learn more if we all have to "tough it out" ourselves.) I'll try to remember to get it moved up to my web-space and let you all know when it's there. Benton +++ #14907 From: Russ and Penny Erb Subject: RE: Rod's parts list > Originally, Rod made the parts list first, and later refined it into > the steel list, which was the actual order he placed with Dillsburg. > Russ Erb eventually converted it to html, at which time I placed it > on the FAQ page since it could be viewed directly with a web > browser. I've been meaning to write this for a long time--this is as good of a time as any. My hat is off to Rod for doing an excellent job on the steel list. Back in August 2001 I made my steel order from Dillsburg. I used Rod's list, subtracting out the parts for the tail feathers (which I had already built), and adding on a few feet extra here and there. I've built the entire fuselage from this stock with only an additional tube ordered here and there. I've even made several extra parts, such as the trim system, out of the excess. I still have a bunch up on the wall. Based on my experience, I can say that if you start with Rod's list, add a little extra as you see fit, you'll be in good shape. I won't say you'll never need an additional order, but I will say that you'll be building a long time before you get to that point. Russ Erb +++ #15852 From: "Montee, Dan L." Subject: Strut link material I have a piece of 7075 material on hand that from a size standpoint would be ideal to make the strut links. In this application is 7075 a suitable substitute for the 2024 material that was suggested? Thanks Dan Montee +++ #15858 From: "Vuxton, Christopher" Subject: Lubing those hinges Just the thought of shooting WD-40 into my Bearhawk sends chills up my spine. That stuff is just glorified kerosene. Now here is some MANLY GREASE!! Use Wurth HHS2000 This is expensive, about $20 (with postage) a large spray can. It comes out like that other stuff (WD-40) and then sets up into grease. The Germans use it for car door hinges, etc. Spray some on your fingers and as it gets warm it sets up. Really great stuff. I've used it for years. I get it locally but you can order it off from the people in the following: Lubricate Your Power Antenna by Bill Smyth, Northern New Jersey Region If your power antenna won't retract easily, the mast may need a proper lubricant. Mine would hang-up a segment or two when I tried to retract it. I tried several different oils on the antenna mast with no success. The oil attracted dirt and gummed up the works sending me back to the original problem. Then I obtained Wurth HHS2000 Spray Lube #11302 from Larry Reynolds at Car Care Specialties, Post Office Box 535, Saddle Brook, NJ 07663-0535. A big can goes for around $14. I cleaned my antenna and then sprayed on the Wurth lubricant letting it dry for an hour before retracting it. It's been a year now and my problem is solved. It retracts completely as Hirschman intended. The Wurth product dries and is not the least bit tacky, so it does not attract dirt. It works great. I also used it on my power sunroof. The roof slides back much faster and easier than before. It's like liquid ball bearings. I'm sure it will extend the life of the sunroof motor. Wurth is worth checking out Chris +++ #15870 From: bearhwk272@a... Subject: Re: Strut link material I think that I would stick with the 2024 material.7075 is stronger but much more notch sensitive and does not have as much percentage yield before failure.Do not have the charts in front of me now but I think the fatigue endurance of 2024 is also better. 7075 is great for limited life applications, (throw away missle) and light pressure containers. Beechcraft tried 7075 on landing gear actuators a number of years ago and ended up going back to 2024 and 6061. Kevin +++ #15872 From: "kb8rnu" Subject: Another welding question... Based on posts over the last couple monthes, I've gathered the following: 1) The Meco Midget is hard to beat for airframe welding. 2) It is not suitable for heavier jobs. I need to buy welding gear. I'm still making ribs, so I will not have to weld the fuse for a long time, but will have to do the wing iron at some point this year. Would it be reasonable to buy an inexpensive (ie, less than $100 on Ebay) gas welding kit to learn the basics on and practice, as well as to have on hand for the occasional larger project? I could then pick up the Meco later on once I get closer to building the fuse? I can't really justify buying the Meco/hoses/regulators now, but I could easily buy one of the knockoffs to start learning on. There's been a couple times in the last few weeks alone where having the ability to do simple welds and cutting would have been real handy. Any thoughts would be appreciated. Thanks! Jason +++ #15904 From: "Brian Cox" Subject: RE: Lubing those hinges Boy have I got a job for this stuff. I get a pretty steady "chirp chirp chirp" sound from my speedometer cable in my 1984 Silverado. To date, I've tried lubricating it three times with powdered graphite. Each time it fixes the problem, either at certain temperatures or certain speeds. If I go about 35 mph when the temp is about 40 deg. F, it sounds like I'm practicing turkey calls. Anyway, I'd like the chirping sound to go away completely, so have ordered the Wurth HHS 2000. I found it online at www.goodspeedmotoring.com. The cost was $13.49 plus $4.95 shipping FedEx ground. Their phone number is (209) 577-1133, and they are located in Modesto, CA. Note that they indicate that they can't ship it to Canada or Mexico due to NAFTA regulations on hazardous materials. Thanks for the tip, Brian Cox +++ #15920 From: Pat Fagan Subject: Re: Windows and skylights > A splash of gasoline can cause crazing and cracking on unprotected > Lexan (polycarbonate). It would be a good idea to use Plexiglass on the side(door) windows for just this reason. The tank drain plug sits above the open window and you can't help getting a drip or two on it after you sample the fuel. Pat Fagan +++ #16368 From: "Brian Cox" Subject: Wurth HHS 2000 Lube Just a little feedback. Earlier Chris Vuxton had recommended Wurth HHS 2000 for annoying sounds in cables and door hinges. I purchased a can and used it for the speedo cable on my 1984 Silverado. I've been trying to get rid of a chirping sound with powdered graphite, with inconsistent results. Well, I pulled the inner cable and squirted some of the Wurth HHS 2000 into the sleeve, then sprayed the length of the cable. After a week, not a peep at any temp or speed. I'm sold. Thanks for the tip. Brian Cox +++ #16532 From: "gmgdls" Subject: Re: Lower Flying wires > I always thought SS was harder than 4130......Had problems cutting > it before. In reality SS is softer, actually gummy/sticky. Big misunderstanding about toughness and actual hardness(Rockwell) SS has strange machining capabilities i.e. 303 likes to be turned into round objects, 304 likes the right angles/milling process. If I remember correctly due to SS gumminess (sp)there is some SS called free machining to aid in the cutting process. Also another concept in maching SS, alot of people use carbide,thinking its hard material but due to the gumminess all you are really doing is plowing/pushing material off. To get a excellent finish on SS use a properly sharpened tool steel bit, where you actually cutting the material. Mike C +++ $Id: 5.3-Ref-MatlsInfo,v 1.11 2003/05/22 04:15:54 bentonh Exp $