Sounds like cheap, poorly constructed hair pins to me. The '35 Plymouth coupe I posted the picture of above I built for a friend and has hair pins front and rear. If they were weak those 12" wide MT slicks and the 383 stroker motor would test them out pretty quickly.
4 bars, how about the Grabowski T-bucket, or Ivo's near clone. Both had 4 bar front suspension. Wasn't that the 50s? Just saying...
Dennis, that's a bit high off the ground! Limited travel in the cross spring? But the results speak for themselves. My first attempt to build a modified dirt car had a tube axle and a pair of F100 twin i-beam radius arms, those forged ones late 60s early 70's, and Watts linkage front to back in the rear suspension. Both ends suspended by Reese load leveling bars. On a flat track, that car hooked up off the corner so good, and looked just like your picture every corner. That left front was a foot off the ground. At our home track however, high bank, long straight, short tight corners, that thing headed straight to the wall on entry. It took a weird brake setup to start it to rotate, then big br*** ones to keep the pedal down. Lift, and straight to the wall! Jim had 13 years experience on that track by then. We changed to a 4 bar the next season, and that helped tremendously. But remember, I had just turned 20 by the 2nd year, and I knew better... Or so I thought!
Funny you should bring this up. Car buddy that lives nearby used hairpins with the urethane bushing style batwings on front of this 32 5W. Well built car with hidden style front disc brakes and little Firestone bias 560-15 tires. Told me a story one day of how he hammered on his brakes (highway speed) one time and had the hairpins on both sides bow drastically. Upper end bowed up and the lower end bowed down. Looked like a chicken wishbone on both sides. All kinds of bad ensued as he managed to get to side of road and stop safely. I always meant to snap a pic of the bent hairpins, as he hung them on his shop wall as decorations. Not sure how much the urethane bushing style batwings played a role in the incident, but helped confirm I’ll always use clevis style batwings/connectors to eliminate this pivot point. That and I like the look of the clevis versus bushing style batwings better anyway.
I guess there are always exceptions. The four bars make more sense for geometry sake. Just when I see four bars on a car it reminds me of the 80's stuff. I'm old what can I say.
Miller was using quarter-elliptic springs as a 4 bar for the front drive car in 1923. This stuff wasn't common for the average hot rod, but the inspiration was out there. Like Peugeot building a DOHC 4-valve per cylinder race engine in 1912, but it didn't become common in m*** produced cars until much later.
Regarding the last sentence, it beats the alternative! And the reality of the 4 bar is it needs to be adjusted so that all 4 bars are exactly the same length (well a little bit off won't be a problem, slop in the ***embly allows a little leeway). And both sides need to be parallel. If one end of the bars are spaced say 5 inches apart and the other end 4, so NOT parallel, the end results really look just like hairpins, only with a nonfixed rear pivot point. And if the bars are different lengths top to bottom, then there's a pivot point somewhere in space, again nonfixed, either above or below the bars, which with somewhat large travel will cause a bind. So what the racers did was 2 bars on one side, 1 bar on the opposite side. No problem with the setup as far as geometry is concerned. Handling might disagree, but no binds. And like Dennis (frames) has done, a hairpin on one side and a single bar on the opposite side works. His cars prove it and so does Bobby Unser's multi time Pikes Peak winning sprint car, which had that setup front and rear since the 50s. It had it on the rear because they didnt run an open tube axle in the car, probably to be able to run some type of limited slip differential. The car had to turn in both directions after all.
David, I'm not complaining! I just keep building Hot Rods. A bit more difficult to pick up nuts off the floor, but it is what keeps me moving. On the way back to the garage now. Just came in for a break. Merry Christmas.
Probably why they sometimes add a cross brace in the center of the hairpin. I have hairpins because I like the look, but am considering such braces, although I don't like the way they look.
There's way too much unknown stuff here to p*** any judgement. Was it cheap Hoffman/Helix junk? Was it someone's hair brain "this is good enough"? Was it actually caused by the crash? Did someone heat or weld on them sometime in their life? We'll never know now. My So-Cal hairpins are pretty heavy wall and seem more than sufficiently strong.
I've always liked the looks of most of the commercially available hairpins, especially when chrome plated, though some do look a bit spindly. I used aero tubing for reinforcements on my hairpins and ladder bars, then had them electroless nickel plated, I haven't seen any others quite like them, as a friend would say "they're hell for stout"!
Still have to add some bracing, haven't decided on the design yet. I'm an engineer who spent some time breaking stuff in unique ways, so I tend to overbuild and use materials that are beefy! This hairpin and its mate up front are made from dom, 7/8 od x 1/2 id. But in my defense, it's going to be the only thing absorbing all of the torque of the axles.
Dave, you could use a curved upright. The rest might be a little busy for your application, but mine is drag race. Tubes are .049 wall 4130.
I should send you dimensions and have you build me new, slightly lighter ones from chrome-molly. I do tend to oversize things. Partly because of my education and partly because of the years working on paper machinery. That stuff was built to last. But heavy!
I'd be very careful using hairpins with a tube axle. When you say hairpins can actually flex, are you sure you're not confusing them with a 4-bar setup? Hairpins are essentially the same as a split wishbone from a geometric perspective.
Have seen many many cars over the years with hairpins & don't recall ever hearing it was a problem , mine have over 50k miles , haven't been off roading though , most tbuckets have a front suspension travel of 2" up+down , not too much twisting going on there
I doubt that there is enough clamping force in a clevis to make it anything other than a pivot point. I don't think the bushing spec played any role at all. I'd suspect inadequate tubing dimensions and/or excessive slenderness in the upper and lower chords, due to excessive eccentricity and/or lack of bracing or gusseting. All four bars parallel in all planes will apply only as long as there is no roll motion, as in e.g. cornering or single-wheel bump. As soon as there is roll motion, none of the bars are parallel. Absent roll motion (and any elasticity aside) the four-bar linkage allows the axle both lateral and vertical degrees of freedom, and any combination of the two, plus a rotational degree of freedom about the longitudinal axis. However, any such rotational motion will eliminate both other degrees of freedom. A parallel four-bar needs a lateral locating device, and that makes it for all intents and purpose a five-bar linkage. That is one link too many. Conflicts are inevitable — if in practice resolvable through compliance in bushings etc..
Well, that may be. But what happened is that someone pulled out into an intersection so I don't think it would have been his fault anyway....
This is true, sorry I don't have any other info it has been years since I have talked to him and even longer since I saw the photos of the damage. Someone else chimed in about hard braking bending hairpins and the need for a brace, I don't even know it they had these braces. The truck was otherwise well built with a very high quality. But now we have two accounts of damage resulting from hard braking with disc brakes. I don't have a horse in this race, I'm running plain old split bones on my A.
Don't get me wrong, I'm not saying they are too weak or that all of them are too weak. Just p***ing on one person's encounter. I do think they look good, a lot better than what I have on my car.
There's been a lot of kits over many decades that were sold with tube axles with hairpins. What makes this combo wrong or dangerous?
99% of the time it works fine. The axle becomes a big sway bar. So long as you design with that in mind its not a problem. Put a cast iron front axle in and thats a different matter.
Sturdy hairpins on the Gemsa roadster, prolly because (I think) it had a dirt track rough-n-tumble heritage.
Like everything about me, even my computer files are snafu! I've been looking for a picture or two of the way I originally thought that I was going to run hairpins and a tube axle. Here's the picture: Yeah I know, it's changed a lot. Hey, that's why I call it the Whatever project. Side note, making a plan and sticking to it is a really good idea. Anyway, the hairpins are fastened to a set of brackets that bolt around the axle. The right side was the fixed side, and the left side was machined and honed to swivel on the axle. I didn't like the brackets that the hairpins actually fastened to on the swing sleeve and fixed sleeve, and also their weight. Then I saw pictures of the Unser Pikes Peak winning sprint car and its much simpler setup. But I digress as I often do... If you look at many of the Indy Roadsters, they had similar, but much more elegant, bracketry on the tube axles that they used. The ones that I have seen in pictures of Kurtis cars look to be cast or forged. I've never been close enough to one to get a good look at the brackets. One side was fastened to the axle with bolts thru the bracket into the axle tube to set the caster. Recently I have been reconsidering that setup, because I found pictures of different brackets from the roadster era to copy. And besides I also like the esthetic of hairpins... this discourse has gotten me thinking again. And that's probably not a good thing!
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