First off, I've done a search and have read several threads that touch on the topic, and most say don't do it, that a tube axle doesnt "twist" enough for it to work, etc. yet I swear I have seen it done... The reason i ask is because my car is finished, but was built with a chrome tube axle and polished stainless batwings and a 4 bar setup. I really don't want to change the axle, as I don't mind the chrome dropped tube, but I'd much prefer hairpins than the 4 bar I currently have, simply for a more traditional look. Now I know my car breaks several "Traditional Hot Rod Laws", including my rear suspension setup, but that's ok, its my first car, and I'm not concerned with achieving the look with 100% accuracy, I just prefer the look of hairpins up front to a 4 bar, as I'm sure most here do. So, can I remove/modify the frame brackets and swap the 4 bar for a pair of hairpins without doing anything else, or am I asking for horrific problems? Here's a pic of my current setup for reference/advice. Thanks!
I've seen it done, too. Supposedly, a radius rod setup places too much torsional twist on the tube axle when the wheels articulate up and down. I guess split bones would do the same? I have read an article (maybe on the SuperBell site?) where they tested their tube axle and a regular I-beam type axle and they found no problems with the setup. It seems to me that you would be fine as long as you used a tie rod end or something that is "twisty" like that to mount the end of the hairpin to the frame.Maybe someone else can chime in with a definitive answer, but I can tell you that I've seen it done.
See, I always heard that about split bones but not hairpins. I figure if the hairpins are long enough, they should flex.
Yeah, I would think that if your hairpins are at least a good two or three feet long that they'd twist to accommodate any flex.... which would be minimal if you had a good joint at your frame mount point that could also take up most of that twist. If you were in mockup, I'd say try clamping on the setup and move it around by hand to see if there was any binding. But you're not, so that's pretty useless... BTW, gorgeous car!
My last car had a chrome tube with stainless hairpins for 7years....no signs of fatigue....I say, just keep an eye on stuff for any signs of failure and you should be OK
I was always told that the problem was with the narrowed or fabricated tube axles, that the welds inboard of the perch pins would fail. If that's the only problem then I can't see why the hairpins wouldn't work. I haven't tried it myself, but i have seen it countless times at shows. No telling how many road miles they put on those though.
The problem is that a tube won't twist - at all. And when one wheel comes up the axle will try to twist causing the concern. Doesn't matter if you use a tie rod end or hiem joint the prroblem is at the axle itself. Best way to see the deal is turning into a driveway. However, that said, I've seen plenty of these setups over the years and I've only seen one failure. I think that was caused more by hydrogen imbrittlement than the hairpin. That car had been on the road for probably 20 years at the time the axle broke.
Folks have been using 4-bar suspensions for 50-60 years, isn't that traditionl enough for you? The Grabowski and Ivo T roadsters BOTH had 4-bar front suspensions in the mid-late 50s. And they weren't the first by a long shot. They used tie rod ends on the bars but, had they been commonly available, I can assure you they would have stepped up to bushed ends just like Pete & Jake's versions used in the 70s. Enjoy your car for what it is, half or more of the people yammering about traditional haven't even lived long enough for anything they've owned or even seen to be "traditional"!
Yes, I did discover the fact that a 4 bar setup IS indeed as traditional as anything else... I just honestly prefer the "look" of polished hairpins. I do enjoy my car for what it is, and have been driving the shit out of it all summer... it rides very well with the 4 bar, so maybe I'll just let it alone, was just curious if swapping hairpins onto it was a feasible idea or not... sounds like its been done successfully and unsuccessfully.. In PA the roads have plenty of bumps and uneven surfaces, so maybe its not such a good idea to consider... although that's what alot of people told me about switching to bias plies too, and I love them.
Hairpins/radius rods on tube axels has been the standard on T-bucket kits for years. Rode in several, know plenty that have been on the road for years with no problems. Don't have any pics handy, but that beautiful blue 32 ford rpu built by Roy Brizio a few years ago (Medium blue, red steelies, white walls, red and white "Greek" style striping, quick change, white top, did I mention I love this truck....) had a tube on radius rods, I remember Rodders Journal making a point that they had gone against the norm on that.
my advice: leave the car alone...and also make a mental note: next hot rod will have hairpins and i-beam axle
Been driving my "A" coupe with a tube axle and hairpins for 9 years...and aseveral others with the same setup for the last 35 years, no issues.
The type of connection from the radius arm to the frame will make no difference with axle twist. It will make the radius arm itself twist a little easier, but that isn't much of a problem with the small amount of articulation Rods get. The axle flex being talked about is like this... Take a yard stick in both hands and hold it out at arms length...wide and tight grip. Try to twist it like your working a cycle twist grip. Notice how it flexes? Now take a piece of steel conduit tubing and do the same thing. You can't twist it! THATS the issue with a tube axle VS an I beam. I beam will twist...tube won't. As you can imagine...things tend to bind up with a tube axle and control arms that don't keep the axle ends from twisting against each other. 4 bars allow up and down movement while keeping the batwing upper and lower control arm holes parallel...hairpin radius arms/split bones won't...so the axle itself must twist to accommodate the movement. Have people gotten away with it? Obviously. That doesn't mean its right or safe...just means people have and will continue to get away with it most times. The thing is...the lighter the car the easier it is to get away with! Drive a tube axle/hairpin equipped T bucket up on a service ramp with one wheel. See what happens... A tube axle will be stiff and in most cases will lift the other wheel off the ground. An I beam will flex more and a 4 link will allow complete flex...all things being equal of course and discounting REAR axle flex and any frame flex etc. Some things compound the problem, other things mask it. Thats why some people can get away with it forever while others have had issues. Anyway...its a dead horse...just build stuff strong and as safe as you can.
Agreed Hackerbill! If the car is built as though the driver's life (or his/her passenger) depended upon it, I don't think you'd see twisting tube axles built into the design. There really aren't too many places in the design of a rod where you can miss the boat. The length of "service" of this setup is dependent upon too many variables. Hard cornering, diagonal entrance ramp, speed bump taken other than straight on, pot holes, etc. I'll listen to Squirrel on this one. Or BrianAngus.
With urathane bushings in the front and a "smile" in the tube axle it seems to OK with hairpins. There are a fair amount of cars like that out there. How stiff it may be compared to your current four bar would be interesting to know. Go ahead and change so then we can learn on your dime. Haha... I saw a rear four bar setup that had the bottom (which can be seen)link bars covered with a piece of a ford wishbone and used a ford tie rod end on the front of it. From the side it looked like an old style split wishbone but was really a four link. It was somebody elses neat idea I'm just passin' it along. Have fun,Smokey
I ran hairpins with a tube axle on my coupe for about 8 years with no problems and no signs of fatigue. But more interesting is the fact that we track tested the setup on a slalom course, against the clock as well as against an IFS equipped street rod. Here is the story, check it out: http://hollywoodhotrods.com/PRESS-DOCS-PICS/Rod-and-Custom/RCAug2004.pdf Just some food for thought, hope it helps.
Thanks for all the advice guys, sounds like it "can" work, and often times does work...The scary stuff about broken axles and fatigue sorta scare me still, so I'm sure if I'm gonna change anything, but good to know that it's been done successfully. If the car didn't drive so damn nice the way it is I'd be more likely to overlook any of the negative things that have been said, but the fact is, i love the way it handles now, so maybe I should just let well enough alone and get the hairpins on my "next" car.
Why not install a beam axle in place of the tube axle? Overall costs shouldn't be too bad once you factor in money recovered by selling the old axle. Better yet, save the tube axle for your next project. Many a hot rod has been started with less. My 31 on 32 rails project got started during a bench racing session when a pal donated a front axle disc brake kit. Just brackets and some small stuff, but that's all it took to get started.
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