Can any rear radius rod handle SBC/open drive line combo?

I'm semi-following the Bishop/Tardel book for my first A build, and was wondering if there's any type of rear radius rod that can handle an SBC/open drive line combo? I've heard from some that there aren't any that can handle the torque/twist resulting from the open drive line, but haven't really heard if that's for all radius rods. I think I'd like to see them on the outer perimeter of the rear axle, and mounting to the outside of the frame, if possible.

 

I have 40 ford rear wishbone set up on a Banjo 283/3 speed combo. They seem pretty stout. But I do not have them parallel to the frame...they are split but mounted to the inside of the frame with tie rods.

I added some bracing like the Rolling Bones guys set up their rear ends.

 

Hmmm....for now, I'd be running a 305/PG combo...possibly swapping out to a 283 that I've got if I get around to rebuilding it...but the 305 is what I'm going to roll with for now. It's lower end torque is what concerns me more.

 

Just by looking at them Id say the model A's are pretty weak.
I rebuilt a late '40's T (flathead and C4) for a friend using 1940 era bones and it worked quite well until they decided to put a softer rear spring in the car. The added amount of articulation caused cracks to form in the forged portion (ahead of the rear mounting points). See picture.
Ive always heard that the 1936's are the strongest, so thats what I running behind the Cad/hydro my A coupe. It will be a while before I get it on the road and test this theory.

 

Chop32 nailed it. The rear suspension needs to articulate. If it can't then you will be bending something and eventually it will break. So you use 'stronger' parts and then the problem moves somewhere else. Design it such that the forward ends are as close together as possible, and use front bushings that can truly articulate. Henry's design used a perfect triangle, and that can articulate all day with no problems. As soon as you split the bones you begin to introduce geometry with an interference motion. So your bushings need to be able to twist as good as Chubby Checker.

 

I think you will need to add something for torque. The radius rods mounting to the bottom of the rear end would not be enough...in my opinion. I have seen some people add a third link from the top of the rear to the center cross member that seemed pretty easy and effective.

 

Completely agree. It's really the same issue that keeps coming up on other threads where a builder/owner is ripping control arms loose from the rear axle or breaking the control arms themselves. In most of the cases I've seen pics of, we are talking arms rigidly mounted to the axle housing, like the Ford bones in question, but they ARE ALSO anchored to the frame widely spread apart at their forward ends. That induces a twisting force any time the body rolls in a turn that stresses the parts the more the roll increases. If the bones (or contol arms) are mounted near center with ample rubber bushings, those stresses are eliminated, or at least reduced, dramatically.

I think because people have been "splitting bones" on Ford front ends for decades, and it didn't usually cause any identifiable problems, it was just assumed by many builders that it's okay to do that in the rear as well. The difference of course, is that the vast majority of Ford axles are "I" beam and they twist along their length and absorb/dissipate the twisting forces induced. Not so tubular front axles or rear axles.

Ray

 

So, does this mean that a rear pan hard bar will eliminate this issue and still allow for wider mounting of the radius rods?

 

No, you need to make at the very least a torque arm from the top of the pinion to the front mount of the wishbones to stop the twist from the torque. But a four link/ladder bar set-up will save you alot of grief. Or parralell leafs is a cheap alternative to this is your car will accept this, but they look bad on anything other than a fendered car.


Tim

 

Tim, If you are ONLY addressing the upward rotational torque of the rear axle housing upon accerlation, you suggestion would add additional strength to that offered by the "bones".......but that IS NOT the forces my comments above were addressing.

If a builder attaches control arms rigidly to the axle housing and aims them, roughly, straight ahead and anchors them to the frame rails, ANY rolling motion of the chassis in relation to the axle will try to twist the axle housing along it's length, whether the engine is running or shut off. This has NOTHING to do with the rotational forces of acceleration.

Take a pencil, attach "control arms" to it with glue or tape, then hold the forward ends of the 'arms' in one hand while twisting the 'axle' (pencil) in the manner that body roll would cause with the other hand and see what happens to your control arm attachments.

If, on the other hand, the 'bones', 'control arms', whatever they are called, are angled to the center, just like they were in the original Ford driveline design, they pivot at the center of the chassis and DO NOT try to detach themselves from the housing in the roll mode.

The Panhard Bar merely locates the axle side to side, keeping it centered in the chassis when the springs, shackles etc are doin' their thing.

Ray

 

That is why I mounted mine in a triangular fashion sim to how Ford made them.

 

POBOYROSS the answer to your question is NONE. The strongest and heaviest radius rods are 1935/6 style but because of the pickup location point on the axle housing they are still subject to bending or bowing. Some modified 35/6 bone designs add a triangulated the rod to help prevent the potential to bow but this still subject to deflection. The most effective design is a pair of hair pin style or ladder bar rear radius rods located triangularly.

 

fixed it for ya!

 

Here's what I have gathered so far.
Your question is really which rods are strong enough, the answer to that is none.
the question that needs answered is can you put a more powerful motor and eliminate the torque tube. The short answer is no,

The long answer is the function of the torque tube need to replaced by a different method.
how you do that depends on the rest of the build but there at least a few ways that you can utilize the old radius rods in doing so.

 

If you want the bones mounted to the outside of the rails for that look (not sure what that look is about) then you would be best to modify them to pivot at the axle like a 4 bar set up and then add two upper links concealed under the body or maybe even just a third link.

 

This is the biggest reason why my A is not on the road.
My bones are mounted to the outside of the frame rails and I know they are going to snap something probably sooner than later.
Ive looked at it all sorts of ways, but cant come up with a decent way to "soft mount" the '36 wishbones to the axle.
Even if I could kick them in towards the center of the car (frame kick-up says no) there would still be a bind. Henrys setup attached them solidly to the torque tube which could, in turn, pivot at the bell coupler to the trans.
The T I mentioned earlier had a very heavy rear spring with almost no suspension travel and I think that this is what kept the bones in tact.
Im about to cut off the '36 bones where the tube meets the forged mount and go with a Pete and Jakes style ladder bar, just using the rest of the bones for spring mounting only, but if I remember correctly, the P&J ladder bars use clevises at the rear and a urethane bushing up front so Im still anticipating a bind.
Arent hot rods fun??

 

Ladder bars or 'hairpins' that attach to the housing in a rigid fashion are functionally no different than the 'bones' under discussion here. As has been said by others, the only satisfactory way to use bars roughly parallel to the vehicle centerline is to have them on bushings that permit movement between the bar and axle housing. That does require a third (or optionally, a fourth) link to keep the axle in place.
Unfortunately, the Laws of Physics and Geometry aren't going to be repealed anytime soon

Ray

 

Ladder bars will control the torque movement.
Mounting them out side of the rails or anyway without triangulation just don't make sense on anything used on the street. Show rod trailer queens, drag cars go for it.

And one single Ford style radius rod on each end ( without torque control ) will eventually fail.

 

Ray
Maybe if we had a senate committee convene on the subject we could get the laws of physics repealed.

Ray is correct, ladder bars are not very forgiving. They will either need a diagonal link or a panhard bar or perhaps a watts link.

The Raven runs his open drive with 40 split wishbone parallel to the frame. he uses an old trick to stifen them that amounts to a piece pf round stock welded at an angle from the axle mount bracket to the radius rod.

SBC, 200R4 and 9" ford on a buggy spring. He did have trouble with the brackets breaking and found the old timey solution. It has held fine ever since.

 

Just wondering why a kick up would prevent bringing the front of the 35/6 arms inwards?

Mine is a 32 stock frame, but with an X made from 35 frame. I turned the center part of the X around, and made my 35/36 arms into a true wishbone with a ball. The arms go inwards of the back legs of the X, so there is room on my frame for the arms to travel without hitting.


If you could put up some pics, someone will figure out how best to do something on your style frame.

 

I've often wondered about building a triangulated 4-link (so you don't need a panhard bar) with bones for the lower bars. The uppers would be heavy bar stock, triangulated to the frame and somewhat hidden in-board of the framerails and connected with heim joints. They would effectively replace your torque tube by helping eliminate torque twist, and also locate the rear by stopping lateral movement.

The lowers would be your bones setup parallel to the frame, using heim joints to allow a bone to rotate slightly as the rear articulates (if one tire goes over a big curb, etc).

The truck guys do these all the time, except this would use Ford wishbones on the bottom for the right 'look'.

Thoughts?

 

Here ia how I did my rear copying how the Rolling Bones set up theirs.

 

Man, this is getting bonkers...

If I have to go with ladder bars, I guess I have to go with ladder bars. I just think they're so damned ugly XP

Is there a way to solve this via shocks in the rear, etc and still use the radius rods?

 

My frame is a combination of Model A front rails and 2x4 square tubing that is stepped 4" in front and 8" out back and the bottoms of the wishbones are even with the bottom of the frame. In hindsight, if I had placed the rear kick-up 4" further forward Id have the needed clearance for the wishbones, but at the time the plan was to run them parallel with the frame. I might be able to notch the kick-up portion and shorten the rear legs on the X-member. The only chassis pics I have/had are on another computer that has "problems".
I remember a picture on the HAMB of someone using a front wishbone ball and yoke as a center pivot on their rear bones, was that you?

Ive thought of this also...The problem isnt the rotation at the heim joint (or tie rod end) of the the bones...its that when they are run outside the frame rails and attached rigidly (stock) to the axle housing there is no flex when one tire goes over a big curb or you go into a driveway at an angle... This forces one side of the axle down and the other up placing stress on the brackets. Like Plym49 basically said earlier, you tear the bracket off of the housing, so you go to a stronger bracket (or better welder!), then you twist the wishbone tube, so you reinforce that, then something else gives...As Hnstray so elloquently stated, "Unfortunately, the Laws of Physics and Geometry aren't going to be repealed anytime soon".
The truck guys triangulated 4 links have a single pivot point at the end of each bar...the only way I could do that is to cut the bones loose from the spring mounts and then mount the bones seperately, along with an additional set of bars up top, which might not be a bad idea!

 

Okay, but you'd STILL have to mount the 'bones' to the axle housing with a pivot point, NOT rigidly!!

Gentlemen, this really shouldn't be so hard to grasp. Make a simple model from pencils or straws or popsicle sticks and you will soon see what happens when the suspension tries to articulate in a turn and body roll is brought into play.

Ray

 

This is how I did mine, kinda'.
So far so good.




Sent from my iPhone using TJJ sucka!

 

I've got a triangulated 4-link on the road in my F1 and like it so much I'm doing it on my coupe. The geometry on that one is a copy of the rear suspension in my 67 GTO because I loved the way that car handled under hard acceleration.

Like you said, my design for the coupe will use bones top and bottom with sealed bearings pressed in at the axle mounts, and threaded tie rod ends in front. The angled uppers will be inside, and the lowers parallel to the frame and just outside.

 

this is how i did it.

-danny

 

Yes, like I said, just like a triangulated 4-link. Each end of all bars are pivot points. This isn't an issue when splitting the bones on a front end because the i-beam will twist when the suspension articulates. That's why you can't use a tube front end with split wishbones, it has to be an I-beam that will twist a little.

And yes, I realize that the original bracketry wouldn't look the same at the rear of the bones if you're making it a pivot point, but that's mostly hidden.

 

Hot Rod Pro,
Very nice work