Tube axle and hairpins.

I would think the longer the hairpins, the better; less "arc" as they swing up and down. Axle probably won't really twist much anyway, as most hot rods don't have much suspension travel.

 

I am putting as curtis styled hairpin on the A with a tube axle. I agree, I think if the hairpin has a little flexability, it would probably make a difference.

 

http://www.jalopyjournal.com/forum/showthread.php?t=5861&highlight=tube+axle+wishbones+hairpins

http://www.jalopyjournal.com/forum/showthread.php?t=219600&highlight=tube+axle+wishbones+hairpins

http://www.jalopyjournal.com/forum/showthread.php?t=115769&highlight=tube+axle+wishbones+hairpins

 

my thoughts are (without experience) that if the axle is a ford type with a long curve, then you are no longer twisting it tortionally you are actually bending it
and if the bending is within its elastic limit then there should be no problem at all

where i would be concerned is with some of the T-bucket axles shaped like this
\_,______,_/ where the haipins attach at the (,) leaving a perfectly straight flat section between them

good luck in any case!
Zach

 

I'm so sick of hearing all the bullshit put out by the people who claim they "invented" the 4 bar front end. All that is a sales gimmick. Frank Kurtis built over 500 midgets with tube axles, and hairpins, and all his indy cars had hairpins until he came up with leading/trailing link torsion arms that located the axle. Henry Ford built the 37 V8-60 passenger cars with wishbone located tube axles. My first roadster was built at Kurtis' shop with a tube axle from a 58 Indy car with hairpins. Raced and drove the shit out of it, and as far as I know the axle that is now in England is not broken. My current roadster has a tube axle and hairpins. It's worked fine for almost 14 years. A tube axle and hairpins is pure race car history. If you want to build it that way, do it. There are different schools of thought on radius rod length. When I bought my current roadster, it had the tube axle with long split wish bones. It bump steered pretty bad. I talked with Arlen Kurtis, and Jerry Kugel. They both agreed that the long wishbones (almost a foot longer that the drag link) were in a conflicting arc with the drag link. I switched to hairpins that are only a couple inches longer than the drag link and no more bump steer. Look at some of the midgets and sprint cars on the Vintage Sprint Car thread. They wern't built with tube axles and hairpins just because they looked cool.

And FYI: The big time hot rod shop that claims to have invented the 4 bar front end, didn't. Next time you see Ivo's T bucket, built in the early 50's, check out the front end.

 

I believe the big controversy about the tube axle with hairpins or bones is more about the new dropped tube axle than the original tube strait axles. From what I've gathered from many discussions and experience I've been through is that the problem is the new axles are not one piece.

Currect me if I'm wrong but the old chassis builders who used tube axles used a one piece tube with the king pin bosses welded to the ends. This in theory shouldn't produce any problems when run with bones/hairpins.

The new dropped tube axles from the aftermarket manufacturers are only tubes in the center. The outter parts from the perch bosses out are forged steel, press fitted into the tube and WELDED. Every broken tube axe I've heard about has broken at the welds because of the little bit of torsion that the axle experiences.

Now heres the key issue, and pleeeeaaase note this... All axles I've heard of breaking were first generation after market dropped axles. The new generation axles are pinned through the overlap of the tube over the forged ends and then end of the pin is welded into the tube. With the pin, the axle end can't pull apart even it the welds fail.

My dad still runs an unpinned first gen 4om dropped tubr axle to this day under his duece. The key was the 4bar. A friend of ours (not mentioning any names) who has run a rod shop for over 30yrs purchased one of these axles from the same manufacturer around the same time (mid 70's) my dad bought his and ran it with split bones... It broke, right at the welds...

Take it for what it's worth... This is just the info I've collected

 

The Ford tube axle, used on the Ivo and Grabowsky T's and many circle track cars, had forged ends and tube center. Ford welding was automated and very high tech for the day.
On the Ivo and Kookie T's, does anyone have good pictures of the four-bar construction?? I've got many pictures in old magazines, but all are shot from bad angles and/or very grainy.
Twist has to happen in a simple split front end, I suspect real issues are distribution of said twist through the parts and of course quality of the metal...no Chinese rebar, please.
I think in a good build, forces will distribute twist through most of the structure, with axle doing the least twisting. In a poor design, one part, typically the frame bracket, will be weak enough to absorb most of the twisting and eventually fail. Actual twist is limited greatly by length of the links and by the short total movement of the Ford frontend. Worst setup I suspect would be something like Ford tube with split Ford bones, giving a great deal of resistance to twist and dumping forces into rod ends and brackets.
I think the hairpins probably serve as torsioin bars to some extent...replicate wishbone geometry by breaking off two tines of your fork, bite down on survivors, and twist handle...twist will distrbute through that structure unless your teeth are weak...

 

Try it. Jack your car up and disconnect one rear end of one hairpin and see just how much effort it takes to move it up and down the couple of inches it will be distorted in the real world when your wheel goes over a bump.

If it takes a great sweaty heave off a strongman to move it 2 inches then I'd be worried, but if you can flex it up and down several inches with one hand I'd not worry that stuff is being distorted and abused too much. Afterall, an I beam is expected to flex happily.

 

Just ran into a picture of a circa 1955 Kuzma chassis Indy car...hairpins at both ends. Indy cars back then had to work hard all year, not just last 500 miles!

 

You guys can believe anything you want but the fact is that, if you are serious about proper handling, "tubes and bones" don't mix. As long as you are going in a straight line and bobbing straight up and down you are probably alright but, when you enter a corner, the tube becomes an unyielding anti roll bar and one of two things is gonna happen. Either fasteners, rod ends, mounts and brackets start bending and breaking, or, if the size and strength of your fasteners, rod ends, mounts and brackets exceed the amount of applied stress, the front end will go, instantly, into infinite roll stiffness and apply maximum lateral load to the front tires.
The parallel, equal length four link setup is far superior and allows the chassis to roll properly, applying vertical load on the front tires for maximum tire capability. Tires like to be loaded vertically , not shoved laterally.
As for the observation about how great Kurtis midgets were with "tubes and bones", I can assure the Kurtis midgets would have been a whole lot better with a proper four link suspension.
As far as the wishbones on the live rear axle of an Indy car, it is irrelevant because each wishbone is attached to an independently rotating "birdcage" bearing mount.
Some Indy cars with front wishbones had one of the wishbone mounts attached in such a way that it could rotate freely around the axle, eliminating torsion bind. Others had a wishbone on the right side only with a single link on the left.
The best current suspension linkage setup is parallel, equal length four link with lateral panhard links front and rear.

 

Mac speaks the TRUTH !!!

 

I'm no chassis engineer, I've never even played one on TV.

But I do agree with Dean Lowe when he talks about all the midgets and sprint cars that ran with tube axles and hairpins for years. The last thing any of those guys wanted was a suspension failure when steaming into turn 3 at Ascot!

I also don't doubt that what Mac Miller says is correct also.

I've been running this set-up on the street for four years now with no ill effects. At least none that I can tell.









However, this ain't no sports car and I don't drive it like one. I have hit a couple of railroad grade crossings and freeway bridge transitions harder than I'd intended to and everything survived okay. But for the most part I take it easy turning corners and freeway on-ramps and off-ramps.

I see no point in putting any unecessary stress on things.

At least that's what I tell myself!

 

Correct!!!!

 

FIRST HAND EXPERIENCE!!!!!

I drive a T Sedan with split 46-48 wishbones and a Plymouth/Dodge 1935 TUBE axle.
MacMiller got it right.

if you jack one side(wheel) up the other one has to stay on the ground on a proper
working suspension.

Mine doesn't stay on the ground .It lifts BOTH weels.

Not good for a street driven car.

Jus because the T-bucket guys build them , that doesn't mean it is right!!!!

A lot of mags feature wrong setups VERY often.
When editors build their own cars ......Rizzo in R&C for example........


USE YOUR BRAIN!!!!!!and don't follow everybody.
That is what is Hot Rodding is all about.

Michael

 

With these COUNTLESS axles snapping all over the place,,,,,,,, does anyone have pictures of a bunch? Seems to me with as many tube axles/hair pin set ups that are actually out there, I should see 100 pictures of them posted by tomorrow. What about the rear ends? Hair pins on a rearare the same. Anytime I see a bracket snapped its either a really crappy weld from someone who shouldn't have been welding,,,,,, or torn from horsepower and really sticky tires. Look forward to the pics.

 

He asked for 1st hand experience ......not for pics.

It's not only about breaking...it's about handling and how the suspension works.

 

Our current straight axle car has a stock "A" axle with split bones and a panhard bar. It isn't a race car and it doesn't ride like a limo but the thing has gone 15,000 rough miles in three years without so much as a loose bolt. We would have used a tube axle if one was out in the shed.....but only the "A" axle was "in stock". I think that proper engineering and geometry with carefully chosen hardware is the key to this whole mess. You can have the best tube axle, the strongest four bar setup available but if the geometry is NOT right and junk heim joints/bushings (or whatever you use to secure the ends) are used.........breakage will be a problem. We use hairpins in the rear and I heard all of the horror stories about how they were going to fail and that we should have use four bars or something else. The same holds true here......get the geometry right, use good hardware and do it right.

 

Good question Kevin.

Some great answers as well.

Fwiw, the 4-bar setup in my 32 roadster works great, runs twisty mountain roads and has no trouble keeping up with the sporty cars.
Granted, neither of us are getting crazy cuz some of the penalties - like running over the cliff - are harsh.

It seems like the 4-bars with their Polyurethane bushings - with said bushings being very hard - are operating much like a split wishbone setup during extreme corner loading such as entering a driveway at an angle.

With that in mind and desiring a look that's a little more 'trad' I built radius rods for the 31 A on 32 rails roadster project.
A beam axle was used and the bushings at all three corners are adjustable which makes life easy for length and/or caster changes.

The 4-bar type bushing at the back.


At the front.


There shouldn't be any more twisting up front than there is on the 4-bar and it looks like the hard Polyurethane bushings will work fine.

If there was a problem it looks like it could be cured with a softer bushing.

Somewhere in the early 60's, a lot of guys were utilizing the GM rubber suspension bushing that had a steel outer, bonded rubber and then a steel inner bushing.
It worked quite well I understand and I would guess that this same bushing is available from the aftermarket that supplies parts for the Tri-5 Chevys and similar cars.
If not, there's probably a similar bushing available from cars other than GM.

I do remember a couple of guys in the car club setting up a 29 roadster for the drags although it did run on the street.
They built a set of radius rods similar to the rounded end ones you see from the aftermarket as well as ran a dropped beam axle.
It was a nice looking setup, but it kept breaking.
Even after adding some gussets.

Clevises at the front and Ford tie rod end at the rear.

I always thought the breakage could be attributed to poor quality arc welds and maybe even the quality of tubing.
I would not be surpised to learn that it was something on the order of schedule 40 pipe.
I did hear some talk about using genuine tubing and after a professional welder rebuilt it there were no more problems.
So I don't really know what the cure was.

Mainly posted to see what some thought about my use of Polyurethane bushings on the 31.

Fwiw, rear suspension is a Chris Alston Chassisworks 4-link with parallel 1 1/4" OD bars inside the frame rails and panhards both ends.
Along with a very stiff frame incorporating a couple of extra crossmembers over what 32 frame builders usually do.

Fwiw, the 32 roadster runs parallel 4-bars outside the frame, panhards both ends and the abovementioned front 4-bars.
It has an extra crossmember as well and you don't get the dreaded 'roadster pinch' between door and rear quarter panel when transiting driveways at an angle.

Since the 31's 4-link setup has multiple mounting holes for tunability it will end up with the bottom bar up one hole from level and the upper bar down 1-2 holes from level.
The differing arc swing won't be a big deal here, there's not enough of a difference to create problems vis a vis pinion angle etc.

I fact, when you swing arcs with trammel or pencil and string the differing arc swing doesn't amount to much at all.
The differing arc bit was started by a magazine writer who seemed to be more interested in math than an actual suspension on an actual car.
The actual arcs swung by suspension components that were built with a little common sense, real world engineering experience and the like seem to work just fine when driving the car on the street.

Granted, running Indy or other tracks, minor deviations in suspension arc may be completely unacceptable or the little fact that they don't have much suspension travel may not be problematic.

I love Indy cars, but it ticks me off whenever someone sneezes in the stands, the cars aerodynamically unload, get sideways and seldom if ever come back to where they should be.

When the best drivers in the world can't get a barely out of line and sliding car back to straight it's time to toss the aero stuff and get back to racing or . . . stick some wings on em, put a rudder and elevator on em and fly them in ground effect....

 

One thing I’ve notice with my T bucket that has a tube axle and hairpins is the torsion bar effect. If one wheel hits a bump, it can send the front axle into an oscillation where the front tires alternately bounce like basket balls. Not fun at 70 mph.

The friction shocks help, but set too tight and it made the suspension stiff, too loose and you got basket balls. I switched to hydraulic shocks and that helped a lot.

 

I had a 39 Ford convert with a superbell tube axle and split wishbones,,,,they were not pulled out to the side of the frame but they were pulled out about 12" from the original wishbone pivot location,,,

The car had a 350 chevy engine and a 350 turbo transmission.

I drove the car for over 30,000 miles without any problem,,,until one day I hit a big ass pot hole and the spring perch snapped on the passanger side of the car,,,

Rollback time,,,

I replaced both perches and drove the car another 5 or 6 thousand miles without anymore problems. HRP

 

If Henry Ford had not been a cheapass and tried to nickel and dime everything, he would have used what most other car companies of the era used - parallel leaf semi elliptic suspension. It doesn't care if you use a beam axle or a tube axle. Simple, effective, easy and cheap.

 

My 32 Mordoor has a 4" dropped superbell tube axle and Pete & Jake 4 bar setup,,the car has seen a ton of miles with never a problem,but if I was to build the car today I would use a forged axle,,,,personal preference,,,I just like them better. HRP

 

On paper it does not work. I brought a 34 sedan that had hair pins and a super bell 4" drop tube and on two occations when i went through a small dip on the side of the road like comming out of a parking lot onto a street with a drain alone side of the road I heard a loud pop and get out to see what it was I had broken or sheard off the bottom of the right spring perch , the threads where the shock bracket is. Here at the shop don't know how manny total perf. T-Bucket kit cars I have welded up the rear hair pins brackets on the rear end where they have ripped out of the axle housing, same theory as the front axle. Tube Axle and hair pins need to be in a triangle just like Henry did it. He had it right.


Bruce

 

4-bar and tube are ok on geometry.

Bruce is right with the t-bucket stuff.

 

Sheared off almost flush with the top of the axle the spring hanger was still attached to the spring. HRP