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

Hey Bret.
While no expert on Henry's finest (Bass, unless You're putting an allison in it, I would imagine it will be fine. but I like Musclecars and Black Sabbath, so take that as You will.) I do know a few fundamental truths about I beams versus Round tubing.

An I beam, while incredibly strong from 1 angle ( with force applied to the top and bottom of the beam) is actually relatively weak from others (twisting, for example, is not it's strong point.) it actually bechaves more like square tubing. it can absorb and amazing amount of force- from 2 directions.

Tubing, however, can absorb an even larger amount of force from ANY direction. and what's more impressive is it's resistance to twisting forces.

Now, if a v8 60 axle is indeed an oval shape ( I can honestly say I have never held one in my hand.) than it's strenght would be impeded a bit...but only a very small amount. it would be slightly weaker on the plane where the tube was it's narrowest- but the "wide" side of the tube may actually end up stronger than when it was round!

How does this apply to the front end of an Early ford on either 'bones or Hairpins?

Beats the hell out of me. all of these arguments hold valid points on issues such as binding and load bearing stresses. but Honestly, I cannot see such a huge difference in it's behavior so long as everything has some room to move around. meaning that as long as it's not in an immediate bind once it's 3/4's of an inch off square. as far as having the bones split, I cannot imagine there being such a massive load difference thet the tube or I beam are going to behave terribly different to begin with.

I got it!

Put a Camaro clip on it.

 

I'm way ahead of you Lux! I bought a Pinto yesterday and I'm going to just bolt the whole front clip under the frame rails and call it done.

Seriously, it's not getting an Allison, but it is getting a stroked 424 inch '57 Chrysler Hemi with a 4 speed. Not the lightest engine combination, but it does have some aluminum goodies on it to lighten it up a bit.

And yes, a V8-60 axle is indeed an oval tube...with the narrow section of the oval facing front/back.


It constantly amazes me how much of a technical background some of you guys obviously have. It's cool to see so many different thoughts on Early Ford hot rod suspension, since it seems so simple at a glance.

So far it looks like the answer is something like, "It'll work just fine as long as you leave the wishbones as long as possible, mount them as far inward as possible with some sort of moveable mount at the end (like a tie-rod), and take into account that the turning radius is going to be reduced.

Also, be advised that there may be a problem with perch pin fatigue or breakage if one wheel rises or falls above the other to a point that there is undue stress placed upon either the axle or wishbones, such as encountering a steep incline one wheel at a time. Hairpin radius rods offer no real benefit over split wishbones in this case other than adjustability."

Sound about right?

 

That's kinda what I am taking from this lesson as well.

The only real difference I see is why would it be neccecary to get the bones under the bottom of the frame? (looking at how You did Your roadster, That situation seems ideal.) Why would it be neccecary to get the end point of the bones so close together if they are (ultimately) going to function independantly, as opposed to being one "unti" (if You will...does that make any damn sense at all? is this decaf?!?

Anyway. I though about this while in the "reading room"...if the adjustability and apparent flexibility of Hairpins is so vastly important, why is it commonplace to gusset the middle of them? (to stiffen them up? but I thought they were supposed to be all "noodly" and have an almost floppy charecteristic?

Here is where I think all of this is coming from- picture both of these set ups on an early circle track car.

a hairpin car would have the ability to adjust caster without using a hacksaw, torch, welder, and inherently have easier to replace peices. a split bone set up would be STIFF by comparison. (and considerably beefier, and by that logic, heavier.)

so You get into a situation where when in certian corners, The car lifts the inside front wheel (picture a sprint car) and shortly thereafter, it breaks some front end peices...whereas the I beam and hairpin doesn't because it is indeed MUCH more flexible under those forces. at that point, though, it's not a matter of binding, it's a matter of actually BENDING the hairpins/ Bones. add to that track width differences and it becomes logical that I beam can be used with Hairpins or bones, but the tube can "only" be used with hairpins....Mabey.

I do know that I haven't heard anyone say that the set up You are talking about broke and they crashed thier shit. unfortunately, though, we are babes in the woods, it would seem. everyone has an explination, but no one can set it in stone.

 

Ok girls, I don't know what you back yard rocket scientists are thinking but the torsional or shear stress on the axle to produce a bend or shear would require a force exceeding the elasticity of the axle. If you have such a force placed upon the axle , your in deep trouble, and a bent axle is going to be a minor issue.

This is a simple axis of rotation problem. The twisting force is a byproduct that effects the wishbone and is some what determined by the wishbone mounting angle both longitudinal or lateral. In most cases this torsional stress is minimal based upon the actual travel of the suspension 3" of deflection (up-down) and the torsional stress on the wishbone is further diminished by the addition of a rotary locating coupling allowing an axial movement in the wishbone.. Is the axle going to break or bend , NO, is the wishbone going to break or bend , NO, and unless this is vibrating like a guitar string or so misaligned its not going to produce a defect. If you look at a 4 bar the bars are mounted in a rigid urethane bushings and experience more torsional stress than a wishbone.

For those of you that have experienced or heard about defects in the perch pin relating to shear, this is more related to the misalignment and opposing force generated upon the perch pin by the shackle and spring main leaf resistance to rotation, than the axle rotation.

For those of you that have experienced rear radius rod failures this could be due to a mis alignment problem or more realistically the effect of rotational torque leverage during acceleration or braking exceeding the design or material strength of the wishbone. You cannot compare front end operation with rear axle operation when
comparing forces.

Mikey, Heim joint or not, if you can jack up the front of your car and the opposing side rises off the ground after 1" of lift you have that car sprung waaaay to stiff, that is why it drives like a rigid chassis go kart.

Will the axle deflect a couple .000ths torsionally, Yes, but it has to its not infinitely stiff.

 

That all makes good sense to me Dick....thanks for posting that.

Bear with me here, but I think that the real reason that we can get away with the V8-60 axle mounted on split wishbones is the lack of suspension travel experienced with an Early Ford hot rod type suspension. Since we are looking at an absolute maximum of around 3" or less of upward suspension travel and a similar downward travel, any twisting movement is afterall going to be pretty minimal. Under extreme circumstances something will have to give, but as you say you've got much bigger problems when that happens...and breakage would then not be the cause but rather the effect of a bigger problem.

Seems to me that even though the beam axle is much better at allowing twist, there's really not enough twisting going on to make the beam a necessity over the V8-60's oval tube.

Dick also makes a good point about being sprung to stiff...I would think that having the proper spring rate for the load of a front end set-up with a V8-60 axle would be a little more critical than the more flexible and/or forgiving I-beam axle set-up. In so far as ride quality is concerned.

 

Hi Dick,
no not stiff.rather soft.
Model A spring with 5 or six leaves, shackles at 45°s.
I did the test 8 months ago and I'm guessing right now, but even if it's 2 inches it was
not like 4 or six inches.

I sold my T otherwise i would have taken pics and do the test again.

If Brian decides to go that route , maybe he can test it ....??!!

I would go that route , because i think nothig will break if build properly and we all
now Brian is very good at fabrication and welding.

Michael

 

Too bad you're kidding Brian, I could use a Pinto body, but this is the wrong forum for that... hahahahaa


You experts are funny. I don't doubt your knowledge at all. Just, you guys are great at explaining, scientifically why 4 oranges fit in a paper sack but 5 are too many.

I know I'm being overly simplistic here (can't help it really, I'm just simple), but considering the average hotrod maybe has 5 or 6 inches of total travel, if that, and considering most control arm ends (hairpin or radius rod) are anchored with a rotating joint of some kind AND the axle is typically, located by a somewhat, torsionally flexible spring, AND if the rear of the car has any articulation at all, your V8-60 setup should be fine!
But I ain't know expert, just a banjo playin' crayon pusher.....

 

That's what I was looking for, also...I have never claimed to be teribly clever, but I couldn't see why the simple differences in Axle type would produce sunch a tremendous apparent no-no.

 

The modulus as you understand it is in actuality the "yield point". Typically, this is the point where plastic deformation occurs in a non-reversible fashion at 0.2% strain. http://en.wikipedia.org/wiki/Yield_strength

Torque is a force applied perpendicular to an axis of rotation, at a distance.

Something as small as a pencil laying on a desk deforms the surface, and you could measure that deformation with a laser interferometer or a number of other methods.

You could have a complete understanding of the problem with a fundamental understanding of the study of material science, deformable body mechanics and statics.

The reason Michael's car handles as it does is because his axle and bones work like a giant sway bar.

The simplest way I can think to explain this is to unbend a paper clip into a U shape on your desk. The two parallels are the bones and the straight midsection is the axle. Hold the two ends to the desk and lift up on one side of the axle. The other side of the axle lifts up too. The only way to have the other side of the axle remain on the table is for the axle to twist.

 

Well, enterining into the discusuuion, look at it this way.

there are two ends to the wishbone, One above the axle and the other below the axle.. As the axle rises the top end moves toward the back of the car and the bottom end moves toward the from of the car this twists the axle

Now a two bar does not have that problem as the radiuses are the same when the axle rises..

A little trigonometry will solve your problem.

the pressure might be low or high, but the stress is on the axle tube, and recurrent stress will cause fracture of the axle..

which is why people are saying to use long bones, so that the difference are minimized

Int the center mount wishbone the bone raises at an angle that minimizes the twist forces, and that was successful because of the i-beam axle will twist easily

But, of course, I am 86 years old now and might have it all wrong.

LOL

traderJack

 

Google Ackermann. Four bar beats bones or hairpins in Bass's case no ? And please don't mention 'the look'- yawn..

 

Split wishbones, you mean like in all of them late model Ford trucks?

 

I look at it this way: Springs are made to bend and flex. Joints are made to twist and turn and swivel. Axles and bones and bars are made to be rigid so the springs and joints can work. There is also suposed to be some workable geomerty in the mix too, to allow all this to happen.

Now if you're relying on axles and bars etc to do the flexing and compensation for wonky geometry, well you may be able get away with it for a short, or long time, as many have said.

 

This subject comes up frequently, and I find it endlessly fascinating, in a good way.

32Rules, you are correct that late model Ford trucks have "split wishbones", but you have to remember that they are also twin I-beam. Each beam end is mounted in a compliant bushing, and the radius rods are mounted in linear compliant bushings, which allow the end of the rod to rotate, as well as to facilitate the fore and aft movement that the deflection of the suspension induces. Not the same thing as a single beam, right?

Ironically, as durable as that modern design is, the (relative) shorter split I-beams induce a ton of camber change.

Anyway...I would agree that the tube axle/split wishbone/split hairpin design has "worked" for so long simply because of the (as previously stated) relatively minor suspension deflection that the design sees in application. Doesn't mean it's optimum. Doesn't mean it's "wrong", either, but we just know more these days, and so we have the advantage of dissecting these older methods.

When you consider a four bar, remember that it is a parallelogram, so when the suspension deflects,although there is some minor foreshortening of the wheelbase due to the arc of rotation, the axle remains parallel to it's opposite plane in the parallelogram...the frame mounting points.

The inverse is true with a hairpin/split wishbone. The front of a hairpin/split wishbone (let's think of that as the spring perch bosses, for the purposes of illustration) is a plane that is always perpendicular to the central (longitudinal) axis of the component...therefore, as the suspension deflects, that front mounting plane "rotates"...it describes an arc of rotation.

Consequently, when one wheel deflects, the associated link imparts it's arc of rotation into that side of the axle while at the same time inducing that minor wheelbase foreshortening that any link imparts.

An I beam, because of it's inherent torsional flexibility, allows for the resolution of those conflicting arcs. A tube does not (well, in this case, the tube we are talking about,right?).

It is also true that the wider the links are mounted (at the frame), the less axial rotation there is in the entire design, and the greater the roll stiffness...not good.

Optimally, you want the links to be as long, and the frame mounts to be as close together, as possible.

All THAT being said, and consistent with all the really great observations in this thread, I think the look is killer.

 

I recently replaced the front spring on my A Bone. It has a split/ stock front wishbone with FORD tierod ends mounted about 10" behind the firewall at the outside surface of the frame.

I set the frame on stands, removed the front wheels and set the axle on stands too.
Installed the spreader and removed the spring.

While it was out, I wanted to check for wear or play, so I moved the suspension around a little. When I would grab a hub and lift, the axle would move up and down easily for several inches with no binding or other indication of distress. In my opinion, it was far more than the spring would allow it to move during natural driving.

On my car, it would take a large (4" or more) one wheel bump to start binding. I hope this means that the stresses during normal driving are low. MIZ

 

Good discussion, guys, very erudite and informed arguments both ways. I notice no-one has mentioned actually seeing a twisted-off tube axle that had been mounted with split wishbones.
Well, I have. And it wasn't pretty. The tube split like a corkscrew, for about a foot stretch of axle, from one perch to the middle. The axle was chrome, so Hydrogen embrittlement may have been a factor, but a beam for sure would have survived. The car hit a curb at speed and down she went. No injuries, but shook up pretty good, and it ended his hotrodding career, he bought a VW!

 

Bass, I have a V-8 60 axle and hairpins and will use tierods at the ends for my 34. These will be mounted on the frame in the typical fashion. I'm gonna do it. My friend Squeak Bell is doing the same thing on his 29 roadster project. Go for it. It works.

 

This month's R&C features a cool 34 highboy with a mean chop, it's running a V860 axle, and bones, both drilled.

Take a look.

Rich

 

Not trying to copy what Dick Spadero said, but I was also going to say that everyone is WAY over thinking this. Then I saw that he replied.

With unsplit bones, stock configuration, each axle end can only rise and fall when the car goes over a bump. The radius arms as well as the spring work together to prevent the axle from turning.

As far as twist, there will be no more risk of twist if the radius arm is mounted in the center of the car, or more outboard. You're still working with the same strength radius arm, and the radius arm would have to buckle before twisting of the axle occured. The spring is also still assisting with the rise and fall, working to keep the left side of the axle moving with the right.

I would say that more force is being put on each radius arm once you split the axle because the energy is not shared with both side. However, I don't think it's going to be anything to worry about.


Don't forget your Motto Bass.... Drive it like you know how to fix it!

 

Correct on the point of rotation. On a single axle the point of rotation moves out to the wheel on the other end of the axle. The point being is that it works and will not bind throughout the suspension travel range as long as you have a pivot point on the frame end of the whishbone that can accomodate both arcs of travel.

 

Don't split the wishbones unless there is an issue with transmission clearance. If you can clear the trans, use a stock ball socket mated to a center section like the one pictured.

 

v8 60 axles and 40 bones Are my favorit . Here are some pics of the cars i have built with the 60 axles

 

Like Zach Suhr said.
I figured that most of the torsional twist deal is taken care of by the smile in the tube.
Smokey

 

Why don't you mock it up and see how it works ?

You would only need the axle, radius rods and a couple of temporary brackets to hold the radius rods clamped to the frame.

Lift one side of the axle, and see what happens to the other side. I think it will lift up as well, and you will need to put some weight onto it to hold it down - probably a serious amount of weight if you want to see any twist in the axle as they are a pretty stout piece.

But if you try it with the actual amount of travel you expect to use, you will know exactly how much it does bind up and you can decide which way to go based on real data, rather than just theory.

 

Sure it will work..................right up to the time it snaps !

 

I think a lot of people are missing this.

 

Any of you guys seen a tube axle on a old sprint car with wishbones that used a splined right side axle attachement and the splines were helical?
I wonder why they did that?

 

I have a Ford tube axle and hairpins,chrome plated to boot,on my roadster since 1961.Math tell me thats 47 years....No Break yet!!!!!!!!!!!!!Is everyone out there "Chicken Little"?the sky is falling,the sky is falling!!!!!!!!!!!!!!

 

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Instigator,,,,