i've run hairpins more than once on tube axles. Never had a problem. In theory if you weld the batwing to the axle you create a shear point along the weld. I've run 'em that way without a problem. But to some it is a concern. I usually try to make my pivoting suspension components fairly long to swing wider smoother arcs, but its probably overkill. I have a tube axle now that was made by a pretty smart fella in the '60s. Its got bungs welded in it where you would normally mount a pair of radius rods on a stock axle. I'm building my batwings off an old set of radius rod ends. They will bolt right up with the pivot bolt/spring perch. If you're really worried about shear where you weld the batwings on that is an option. I don't worry about it but my axle already has the bungs in it so I might as well use 'em.
I don't know if this helps....but, my uncle does chrome, and he always used to talk about "hydrogen embrittlement" as something adverse that took place during chroming. So, he was against chroming suspension parts, or things that were beyond ornamental.
As asked for, first had knowledge here; My 27 had a Tube Axle and Hairpins with a 455 olds hanging over it. If I went into a steep driveway at an angle it would lift one wheel off the ground and NO it wasn't running out of shock travel. It just wouldn't twist that far! It never broke the axle but it did hammer the hairpin bushings, changed to tie rods ends and hard on them too. Eventually it did bend the hairpins. I guess the axle was built plenty strong so the next weakest link took the pounding. No theories or guesses, just real life experience.
It all has to do with suspension travel... The Pierson car and the other race cars mentioned were designed to run on the Lakes... Which at the time was a fairly virgin flat surface. A couple inches of travel would have probably been enough. A tube with hairpins was probably fine for that. And on a race car, you're alwayse taking things apart and reworking them so they had ample oportunity to inspect and fix any cracks should they hit a dip or whatever. I don't know how many failed but if you think about it, why do we run tubular driveshafts? Because torsionally, they're pretty rigid and strong. I think if you plan on running a tube axle on anything that goes up and down driveways at an angle, you might want to think about a triangulated wishbone or 4 bar setup... Otherwise a beam is a better choice... If anything, just looking at a comparison of material thickness and shape between a tube axle and a beam axle, you know the tube is going to be more rigid. It's roughly the same ammount of metal just shaped as a tube vs a beam, and a beam is more flexible tortionally than a tube if all things are equal. Add weld joints to the mix on the tube and it just makes it a worse combination. Why tempt fate?
One thing that is being missed is that we are NOT comparing correct geometry with incorrect, we are largely trying to find best wrong solution. Splitting the wishbone is done out of necessity at a certain point in lowering...no one would consider it geometrically right, and if more anti-roll is desired, this would be the worst untuneable way you could achieve that... 4 bars divide and spread out the bind...streetrod ones try to lose some of the bind in rubber bushing distortion. Perhaps the 4 tie-rod end sort would eliminate the bind? The sleeve around axle setup does eliminate the problem...but pretty much requires an axle made for the required sleeve, essentially a sprint car part. I think the hairpins themselves (and here I am thinking of real tubing/certified welder, not Chinese pig iron ones) are inherently twistable in the open section and so would absorb most of the twist away from axle, perch forgings, and brackets, assuming reasonable strength there. This certainly requires good material and good welding...and no streetrod cast perches. Another big point is that a normal early Ford front end does not have much span of movement. I would not know how to begin to calculate twist over the resulting arcs of motion, but the actual dimensions would have to be small. Me, I like my real wishbones with their rigidity and free movement. And...Ford did not use the system to avoid the cost of a second spring...the truck type parallel leaf front end has severe deficits over a henry front end on cars of relatively light weight...greatly reduced unsprung weight, much better anti roll for a couple. Braking did not enter the picture in 1908, but ability to handle high braking torque is another issue... Colin Chapman was once a speaker at an east coast Corsa (racing Corvair) meeting. He was asked what type of suspension he would choose to develop for roadracing if restricted to only one...his answer was "Model T", because it perfectly answered the needs of keeping the tires in the right places, and all other problems were easier to figure out than that!
Best wrong solution, definitely. I wonder how much suspension travel the average hot rod has? And I wonder how much the average hot rodder thinks his has? I don't think my roadster had more than a couple of inches travel at each wheel. (in front) Maybe three total if also including initial sag. The coupe is set up the same way and I truly think it will be fine.
Materials, materials, materials. Note the '34 with perch broken a lower end...massive triple jeopardy: Cast streetrod perch, maybe even stainless. Probably cut threads at bottom. Shock mount forming a lever stressing the extended thread length. Add in the stress of the geometrical bind. Bang. Oh. Quadruple, yes. Bad geometry must at least be resisted with good forged parts... I'm going home to visit my nice unsplit wishbones.
Just because it hasn't had a problem - YET - does not mean it won't in future either. Just because you haven't had a problem, it doesn't mean you won't. An aircraft had never hit the World Trade Center on or before 9/10/2001 and they had never had a major Tsunami in S.E. Asia on or before 12/25/2004 either. The fact is that manufacturers and racers made many mistakes, and still do. There is a reason why certain practices are no longer advocated - usually on the basis of real life catastrophic failure. Think of all the manufacturer's safety recalls. When in doubt, don't do it. This really should be a no brainer.
Great thread! THIS is the kind of stuff I'm on here for. Thanks. I really love the look of a chromed tube axle, but I will definately will go with a beam and hairpins (can't do the 4-bar look). Question: Running a 40 rear leaf spring - does this mean P&J type ladder bars are gonna crack the flange on the axle due to twist too?
My only advise, take it or leave it, is don't build something that you think will look cool, but then be afraid to drive the hell out of it after it's done. It's one thing to think about the tube and hairpins in your mind when you're building it, it's another thing to have to constantly think about them when you're driving down the freeway because you're scared of a failure. You want to be able to put the car togeather and drive it with as little worry as possible. You don't want to feel like a test pilot everytime you want to go for a spin!
kevin i think i sold you a v8-60 axle if it's the white one it came out of a 28-9 rpu that had split bones and had been that way since the late 50'-early 60's, the truck had well over 100k miles maybe closer to 200k when it was taken apart last year to build a streetrod out of it. the truck had a nailhead with a stick and was raced in the 60's and abused pretty hard it's whole life from what i understand and nothing had ever broken/cracked. the wishbones off that truck are on the front of my model a and they aren't twisted either.
No Chrome The spring perch shearded between the bottom of batwing and the super bell shock mount and no the shocks were not bottom out and the parts were painted and both times it happen it was on the right side went to four bar set up and never had any more problems. I have one customer that has 5 or 6 cars with tube and hairpins with chrome front ends and never a problem. But something has to twist to shear a spring perch. Bruce
One thing to remember is that there is a difference between hairpins and split wishbones in the amount of flex they have. Hairpins have quite a bit of flex built into them, so if they are long, they will definately take up the torsional movement on a real world street car. Split wishbones on the other hand, will not flex as much. On the BFD, you can jack one of the sides of the front end up 8-10" before the other end even begins to come off the ground (with the tie rod removed for clerance and no spindles... I actually tested this) You can actually see the hairpins twist tortionally. The spherical rod ends on the aft end help too.... but it has a double sheer/poly bushings up front. I can remember a front suspension Dustin bought from Speedway. It had somewhat short wishbones, and I can remember putting one on a block of wood and standing on the other end and it flexed a bit. But the extra 10" on the BFD's hairpins put quite a bit more flex into the system. As far as rear suspensions and the P&J ladder bars Fritz Town Ford mentioned... again, the ladder bars construction along with the ANGLE that they are mounted, reduce the amount of compliance put on the bars. Add to that their forward mounting points are relatively closer together as compared to mounting them to the sides of the frame, and the system can rotate tortionally quite easily. Also, that tube axle you are going to use, Kevin... is oval... so it has more torsional ability that an aftermarket round tube axle... so, you're good to go.... just make the hairpins long, don't put a brace in them... and have at it! Sam.
Kevin I know there is a lot of controversy over this topic, so I'm just going to provide some personal info. My first build was a 31 Ford Roadster. Because it was a project when I first purchased it, it had many parts that I used. I installed a Super Bell front tube axle and hairpins. I believe that the hairpins are about 27 inches long without clevises and heim ends (to facilitate a full fendered build). It has clevises on the front hairpin brackets and heim ends on the rear. I logged almost 6,000 miles, and the car proved a very stable ride. No problems encountered. The car is still on the road without any stress or premature wear on the heim ends or clevises. I hope that I never experience any of the problems described by other rodders here. I'll keep you posted. A local friend has a 32 Ford Tudor (one of my all-time favorites). He used 32 front split wishbones with a Super Bell front tube axle for probably 20 years. If I remember correctly, he had over 80,000 or 90,000 miles logged on that car. Even thoug there are a lot of questions over that setup, he did not experience any of the problems mentioned in this or other threads. His car is still on the road today. I hope this serves as information and food for thought. RGV
How long are your radius rods Sam? The ones on my 31 on 32 rails roadster are 34 1/2" long eye to eye center. The ones you show look way longer. I do plan to add a small gusset at the rear where the lower bar curves up, but the main run will remain un-gussetted. In a way, similar to your multi-tubes welded together arrangement.
i can tell you first hand go for it! my austin is street driven and raced does bigggg wheel stands and never had a problem with anything other than i bent the axle when the back bumper hit the ground and slamed down .i would say make sure your front cross member is at 5 degree's or so just so your not on a bind to start with.
C-9, the car is over at Tim's house, I'll see if I can't get over there today to measure them. I don't think I would put a gusset in yours. You want to be able to grab one end of the hairpin and be able to hold the other (not my hand ;D ) and twist them. If you are looking at forces applied during that tortional exercise, on your current set up, it is being applied at the welded joint (which would never break with only 3/4-1" inch of movement). What looks to be an almost 90 degree bend on the lower bar will take up the flex, as well as the length of tube (upper and lower). If you weld a gusset in there, you are then asking the "flex" during torsion to happen at the cross section of the tube nearest the gusset and along the tubes... I'd just leave it as is... which ultimately will flex even more than the ones I did for the BFD. Sam
No shit!,,,I am not in the habit of keeping old broken parts nor lying,,,Had I known 20 something years later I would have to prove something I said with photographic I might have kept it. C9's right! HRP
Here are some pics of the hairpins I am making. Never liked the Curtis style, not a fan of anything I'd seen in a catalog, but did like the use of early tie rod ends I'd spotted in some old photos, and really really liked a design I saw on a little dark blue modified. (I think Jim Stroupe's?) So this is what I've come up with. Now looking at Sam's and hearing how they flex... I think I have effectively put a giant gusset back by the rod end with the way I have tied all of my tubes together. I think I will be fine though. Haven't put a tape on them but they are pretty long attach to the frame about mid cowl and the front end is spring behind so they are hanging out a bit further than they normally would. Plenty of length to flex there, but I will have a pretty long weld back by the rod end. So we'll see what happens with that when I finish them and jack a wheel up. 1) Started with a Model A wishbone, tie rod, spring perches, and some DOM tubing. The rod end bungs were pirated from various V8 spindles. 2) Plenty of measuring, plotting angles, and flat out guessing followed by some time on the band saw. Set up a fence to get the straight cuts. 3) Finished them out on the belt sander making some flats where the two pieces of DOM meet. 4) Made sure everything fit well before clamping and tack welding. 5) Weld and wait. What am I waiting for? Planning to take a day to set up the front end. Caster and spring and whatnot. The idea is to cut off the last four inches or so of the wishbone. With a bit of grinding this fits right between the DOM tubing. I will then drill through to give a solid place for the spring perch to mount. So set caster, tack wishbone stubs in place, slide spring perches through holes, align spring, tack, then pull apart for final welding.
Small stumbling block. One of my spring perches failed the hang by a wire and tap with a hammer test. "Thud"... cast repop junk. Have another that is passable (the bore is worn) but the way I'm using them I'd like something better than just passable.
Here is a link to pictures of my rear engined dragster with a 37 V8-60 tube axle and hairpins.http://www.jalopyjournal.com/forum/showthread.php?t=236103 If you need more info let me know! Dan Marvin, Owner Exeter Auto Supply
I wish there was a better consensus about if it works safely or not, as I'd really like to swap my 4 bars for hairpins, strictly for appearance sake, but don't want to replace the tube axle... Personally, I THINK it would work fine, but I KNOW the 4 bars work well, and with my luck, I'd be the first one posting pics of broken parts... My axle is chrome, as is my spring, and its also a monoleaf (2 more topics of debate as far as safety goes) so I figure I should probably let well enough alone as to add one more element of potential faliure into the mix. For what it's worth, i DO think hairpins would be ok, but as mentioned above, i think I'd kinda always feel like a "test pilot" every time i hammered on the car.
Just because some of you have gotten away with it, doesn't make you smart and it doesn't make it correct and safe engineering practice either - it makes you lucky - so far ....
Don't make a special trip - just a curiosity thing. The gusset would be at the extreme rear and not too big. About the width of a four-bit coin. Thought I'd make it somewhat race-o looking with a genuine lightening hole within. The bend on the lower bar is about 40 degrees fwiw. Somebody wanted a pic of a broken part. Here ya go. The tack welds broke on the 400 mile trip from Central California to Arizona. The rope made an entirely adequate repair. I gotta admit though, the 31 was in a car trailer when it let go. One of those jobs I gotta finish when I get the Heliarc out . . . which I seldom do and then when I do I forget....
Here is a better look at my setup. It was good for 200 mph at Bonneville in 1954. Dan Marvin, Owner Exeter Auto Supply
Never said you directly, but with as MANY rods out there running this setup from hell,,,, there SHOULD be countless EASILLY obtainable pictures.
Since the digital camera age started, it's been pretty much common thinking that hairpins and tube axles don't mix... So there might not be that many pictures of failures on the internet. Most people don't know from scanners... The thing I keep coming back to is that if the guys who manufacture tube axles tell you it's not a good idea, then it's probably not a good idea... They may just be legally covering their ass but they might have seen a few failures too. I like beam axles better frankly so it doesn't matter to me. I can see the desire to run an undropped FORD tuber though... Run it... But check it often and don't be afraid to post pics if it starts to take a powder...
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