V8-60 Tube Axle and Split Wishbones: bad idea...or it'll be fine?

Starting a project that's using a V8-60 front axle, and the current plan is to use split Model A wishbones. But the more I think about it, the more I'm concerned about the V8-60 axle not being able to twist.

So I've been thinking more and more about building hairpin radius rods to use in place of the split wishbones....but I'm not sure if I'm overthinking the issue here. Will a V8-60 axle be fine with split bones, or is this a recipe for breakage?

This is going under a Model A Coupe, for what it's worth. I know that suspension questions tend to bring out everyone's opinion on here, so let's hear it.

Thanks...

 

In theory,

The perch pins would fatigue and brake with this set up in a situation where you were pulling into a driveway or hitting a bump where the one side of your axle was rebounding and the other side was compressing,.... the tube axle is resistant to twisting so the pins should fatigue or break,...... HOWEVER ! I have seen this configuration hundreds of times over the years in Hot Rods that were built before I was born, and these cars are still on the road without incident after unimaginable logged miles of use and abuse on the road.

Oh yeah,. and by the way, Hairpins would put you right back into the same geometric bind,..
(You could mount your wishbones to one pivot location (like stock)or very close together to reduce any bind)

 

What he said...

 

Depends on what you're putting it under. The tube axle will act like a sway bar and force the rear suspension to flex when a front wheel hits a bump, thus sparing it any twisting damage. This only applies to relatively light cars. If it's a heavy car, or a huge heavy engine/trans combo, it will reduce your pretty axle to twisted junk pretty quick. The four bar setup is what you need in that case.

 

Oh, by the way, hairpins are exactly the same as split wishbones as far as axle twist goes. Four bar allows the axle to move without twisting.

 

Back in the day, most of the nations highways and roads ,were a far cry from what we are use to today. You wouldn't want to put todays cars on them. Ford built those 20's ,30's & 40's cars to deal with those roads. Modern roads & highways are a piece of cake for Henry's old Fords . Build it the old way and have fun.

.......Jack

 

After what you said ^, I'm in the same boat. I am building a T "Tub" with a tube axle, hairpin radius rods, and a flathead. It'll be mainly a two passenger car and probably be around 2000 pounds; am I in in the weight range that this will work?

Denny

 

My 22 roadster was built in 62 and it has a V8-60 chrome axle and split bones without any problems....I just can't say that it won't have any problems. On another note I have never seen this damage before and in theory yes the axle should flex with bones, however the longer you make your bones the less flex and they should be at least to the firewall in length. $.02

 

Up to post 7 none of you are correct.In an axle set up with radius rods, any twisting elements are in the radius rods. Now before you all get your panties waded up just think about it. The axle doesn't twist, the rotational axis of the axle over a bump raises one(tire) side of the axle where the opposite tire becomes the center of the radius of rotation. Thus the axle creates an arch on that plane. The locating arms (radius rods) are tangent to that arc, there they cant turn in the same plane so that imparts a twist to the radius rods if they were mounted rigid. By mounting them with a urethane bushing, hiem joint or tie rod end the torsional twist is now minimized because the end is now movable and can rotate in an arch parallel to the axle. The axle does produce a minimum deviation as the arc created by the radius rod moves away from the lateral center line of the wheel base but this would not necessarily be a twist imparted to the axle travel more than likely it would cause the chassis to roll to configure to the movement . In most cases if you have a spring over axle the rotational forces are placed upon the main leaf of the spring rather than the axle.

Using a 37 tube axle with a Model A wish bone is perfectly fine provided that you choose an adequate rotary end for the radius rod.

 

...this is why we love Dick Spadaro...

 

I hope someone can clarify; is here any advantage of hairpins over split 'bones in this application?

 

My perception is that "typical" hairpins will twist and "give" more than split 'bones...that's "OK", up to the point that one of the hairpin bars buckles....

I suppose I'd say, that 'bones are stronger and less likely to be damaged by a pothole (etc) (assuming both have rotating ends at the frame).
.

 

The only advantage of hair pin radius rods vs split wishbones comes into play with a dropped axle set up. With the hair pin setup the stock steering arms do not have to be modified to allow the tie rod to clear the wishbone and there is less chance of screwing up the steering geometry by shortening or incorrectly angling the steering arms.

 

This is the roadster.

 

Adjustable Caster,..... ( or am I wrong again ?)

 

What Dick said............if it breaks I'll let you know

Terry

 

I understand what you are saying, and disagree.

I've never seen anyone use a mount for hairpins of bones that wouldn't allow the bones to twist along an axis parallel to the frame rails. I don't think the twisting of the bones is an issue.

If you have split bones or hairpins on an axle, during any time that the axle is not parallel to the frame, either the axle must twist, or the bones must bend. Its an over-constrained geometry.

The debate is to whether or not the strain caused by the twisting action is sufficient to cause mechanical failures of the parts involved. Time and testing indicates that this same setup on a rear end often results in failure. The smaller moment of inertia of the front axle and lower mass might alleviate the negative effects of the over-constrained geometry.

Some of this experience indicated here says that the strain is negligible and can be done without incident. You are placing strains and the accompanying stresses that weren't there before by using this configuration, and I certainly hope that those factors are involved in the decision.

 

arghh.
personally i would bring the bones back under the car as close together as possible, and mount them on tierod ends. (check photo)
next best would be hairpins to tierod ends,
then next best to that is split bones to tierod ends
and the really stupid option is split bones to bushed mounts.

 

Huh? Henry never built split wishbones.

 

Where's Bruce Lancaster when you need him - asleep?

 

Hi bass, don't know if it means much but it's been done before.

The Dynaliner has V8-60 axle and split bones and it got driven from Cincinnati to Vegas for SEMA last year.

 

Good stuff so far guys....

I wouldn't have an issue if I were able to use an unsplit wishbone or if keeping the split ends close together under the car was an option. The car is going to sit so low in front that the radius rods will have to mount to the outside of the frame rails. So I'm limited to a choice between hairpins and wishbones.

Here's a crazy notion that I haven't seen addressed yet...

How can we be absolutely certain that the V8-60 axle will not twist? I'm sure it will resist twisting a lot more than an I-beam, but how do we know that it can't twist at all? Has anyone here ever tested one or seen data from testing?

Isn't it possible that there has to be some flexibility somewhere in the axle or wishbones if cars like Royalshifters T have been able to hold up just fine for so many years on the road?

 

Both the Grabowski T and the Ivo T roadsters had V8-60 tube axles with springs mounted behind the axle off stock spring hangers reversed on the axle with the wishbones cut off. They both used four-bar setups made from tie rods mounted to welded brackets at axle and frame.
And these cars were used.

 

Any material with a finite modulus of elasticity deforms when a force is applied. In this case the material is in the form of a round tube, and the force is a torque, exerted by the wishbones. The force in the bones is a bending moment.

The short of it is that the rigidity of a shaft is dependent on the moment of inertia of the cross section of the shaft. An I-beam axle has a moment of inertia so low that you can twist it by hand and see the displacement. A round tube actually has the highest moment of inertia you can get, and is substantially higher than the I beam. As such, the rigidity of the I beam axle is so low that it can be ignored when you use it with split bones, not so much with the more rigid tube.

 

Here in Sweden you wouldn´t get past a tech inspection with that sort of setup. They say it just wont hold, has to be a four bar setup for one of those axels.

 

Help me out here four-thirteen...

My understanding is that torque is an external force applied TO an object. And that ALL materials have a finite modulus of elasticity, and they deform as and when that modulus is exceeded.

As Dick Spadaro said, the wheel lifting on one side causes an upwards force on the axle. This applies a torque TO the wishbone. Given the wishbone is fixed at the axle end, and in split form is allowed some movement at the other end, the torque causes the wishbone to twist along its axis. This twisting force decreases as you move further away from the axle end of the wishbone. In the original application, the wishbone actually rotated on Henry's ball-mount, around the longitudinal axis of the car.

How do you see the wishbone generating a torque on the axle?

There is certainly a component of resistance, from the material structure of the wishbone, which acts ON the axle, but it is in response to the torque generated ON the wishbones BY the lifting force of the axle/wheel.

Or is there something fundamental that i am missing here?

Bret

 

Hi Brian,
from my first hand experience with a Dodge tube axle and 46-48 split wishbones with tie rod ends (to the rails) in a T sedan flathead powered i tried the following, i placed a floor jack under the left hand side spring perch (to simulate one wheel over bump).
When the left wheel is one inch from the floor the right hand side wheel starts to move up from the floor , too.
That means if you drive over a bump with one wheel the other one is in the air!! i tried it!
Also the car doesn't lean to a side while driving , it handles like a go-kart, but in that
case it's not good.

Dick is wrong if he thinks a heimjoint helps. i tried it.no real big difference.
The (in my case) right hand side wishbone end wants to move up and not so much twist.Up and down movment (wishbone end) is allowed if you use an I-Beam , but
at the Beam side.
Really hard to explain in English....German would be easier )

The sedan has probably clocked 3000 miles on German roads and holds up fine.

I would build it with a tube axle and heimjoints or Model A draglik ends.

Michael

 

this may be untrue so take it as you will....

its been my understanding that because the V8-60 tube axle has an arc to it, that the torsional forces are actually bending forces

alot of the aftermarket tube axles are straight between the perch mount locations which does create a bind

but with the Ford 60 axle the bending of the axle within its elastic limit allows the set-up to work much like an I-beam axle although not as effortlessly

i took this such as how if your trying to bend a piece of tubing into a U but dont make it lay flat....if you stand on it...the leg thats not flat will flex and allow the shape to comform
the point of torsion is fighting, not allowing the tube to "twist" but the rest of the material is able to flex within its limits and allow the part to change shape
much like hitting a bump where the wishbone/hairpin will pull or push on the ends of the arc of the axle

my 2¢
Zach

 

Like the I-beam axle, the tube axle was never designed to twist in Henry's original application, the front suspension was mounted to the chassis at only two locations, the spring mount and the "ball joint" (the big ball at the end of a unsplit wishbone),....... This would effectively give almost full travel and motion to the suspension with very few bind points ( with the exception to the spring and shackles).

Like I said in my first point "In Theory" the tube axle and split wishbone mounted outboard on the frame shouldn't work without fatigue and or failure. I have had a friend that snapped a spring perch while turning into a steep driveway with this set up,........ But for that one incident there are hundreds of other examples that have never had a problem. I was a close friend of Frank Mack that had set up on his roadster,.. and it was never a issue, And Frank drove the daylights out of that car.

Here's a dumb little experiment for you, take a pen or a pencil and hold it between your index and middle finger in both hands, and hold the sides of your hands flat on your desk or table,... now rotate your right wrist up and keep your left hand/wrist flat on the table,....... the pencil wants to twist between your fingers,.. When you do the same thing with your arms on the table and bend your right arm up at the elbow,.... the twist on the pencil is still there but greatly reduced,...... this is how the "Theory" works.

So like I said, "In Theory" it should not work,.... however it usually does, probably because of the minimal arch of travel verses the slip fit of the parts and elasticity of the components,....... this is just my humble opinion, now I'll let all you experts fight it out,........

Here's Frank's car,....

 

also a v-8 60 axle is an oval tube not a round tube.it may be able to twist more than a round tube.

bass,i dont see a major problem.the problem i see is that with the prech width being so wide on that axle,you may have a problem with the tires rubbing the radius rods at full turn.

-danny