Ok, they are pleasant to look at. With only one pivot point, they function just the same as split wishbones. Four bars with parallel rods function better. Were they developed to make routing of the steering links easier? To look like the drag racers?
One major difference in function from a split wishbone. Hair pins can actually flex meaning less suspension bind. I plan on running hairpins with a tube axle myself for that very reason
Someone with a Hank Hill avatar, I would expect them to know everything. Unless you're a Dale Gribble. (I'm kidding around).
Like all things we emulate on our hot rods, it seems that hairpins were first used on racecars. The oldest picture that I've seen dates back to the 30s and racecars built for dirt track racing, using mostly Ford suspension components. I would bet that the design predates that, and was used because they are lighter, and flex compared to split wishbones. And they .ook so good!
I love the 4 bar selling point. No axle twist throughout the travel. How much travel does the average street rod have? Maybe 3" total?
The tube axle will effectively be a very rigid anti-roll bar that will transfer m***ive loads to the hairpin mounting points. Be very careful that they don't fail....... I-beam axles twist a lot more, which makes them more suitable for hairpins.
Microflex bushings to allow a little movement. What a bunch of B S that is. They are rock hard. If I remember right I clearenced them just a little instead of press in.
the wishbone have a fixed connection in the axle, but the hair-pinns have radius rods connected to the axle, which I believe give the axle a better vertical travel flex possibility? but that's just my thoughts.
do not know that it has been mentioned, no one was probably even thinking about it when they first built them but they also lend a degree or two of adjustability on castor angle. For me it has always been a looks thing. They work and look good doin it.
The comments regarding hairpins on tube axles acting like a really stiff antirollbar is accurate. More so with split wishbones. It's probably why most if not all racecars before 4 bars with tube axles cornered with the inside front wheel a foot off the track... Just saying
Ease of steering component locating, providing adjustment of axle caster, they look good (even better when chromed!)...what's not to like.
Hairpins and split wishbones single pivot point work with the pre-'35 side steering box and drag link location having coincident pivot points. Changing to 4-bar likely requires altering the steering to give parallel travel to prevent bump steer.
I am using hairpin radius rods on my roadster with a dropped I beam axle. The hair pins are mounted fore and aft in poly bushings and uses a bat wing mount to the axle. Not one problem in 15 plus years of driving the snot out of it everywhere. I believe that the poly bushings allow flex that tie rod ends and clevis' do not.
Light weight, packaging advantages e.g. for tie rod etc., adjustability, and, importantly, ease of fabrication using the range of tools available to small constructors. As regards "flexing a little", I don't see it. Hairpins are pretty much triangulated but for what is needed to accommodate the various frame pivot details which have been used, which I submit arose mainly out of practicalities of fabrication. If I were to design a suspension arm to "flex a little" it wouldn't end up looking like a hairpin.
How strong are they? A guy at work (when I worked) had a Model A truck with hair pins and in a panic stop they collapsed. I don't think they were home made hair pins, I'm sure he bought them from somewhere, don't know what brand. This truck has disc brakes and larger than what I would use radial tires so this may have something to do with it. But they collapsed letting the axle move rearward breaking the brake hoses, this let him crash into the car that pulled out in front of him. Anyone else hear of something like this?
When I started my ch***is business in the early 80's it was all about 4 bar suspension. Gradually thru the 90's my customers starting asking about hairpins and by 2000 that was just about all I was doing. I don't think I did a 4 bar after about 2005? Pete & Jake's made me a custom length and design hairpin that was a little different from their production unit. They simply called it Cornhusker style. Thru the years I moved toward more tie rod end rear adjusters over the urethane bushed adjusters. Tie rod ends allow for a little more flexibility as the front end motions twist the back adjuster.
Hairpin on the right. Single rod on the left. I built this car with parts from a 5 year old race car. Owner/driver had a very tight budget. Cross torsion rear suspension. Torsion bars were junk. The very first race and the first time driver ever made the feature. WON after starting dead last.
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