Radius rods on the rear, open drive conversion ..Lets argue

I read something that I found interesting in this months Street Rodder magazine.

Now I could care less what you think about the magazine, what a Rat Rod is or your interpretation thereof. I just found this article intriguing and want to make sure if what he is preaching is valid.

In the Shop Manual section, Ron Ceridono states that running rear 36 radius rods on an open driveline as a primary means of locating the rearend is unsafe.

Now, he says that some reinforcing and additional links are needed to be safe. Just wondering what your take is on this? I had thought about this very conversion on my 36.
Engineers? Rocket Scientist, Hamb Metallurgist?????

Just in case ya wanna read it....Aug 2004, pg 203-204.

 

If the bones are split to the outside of the frame rails,
what is the difference between split bones and ladder bars?
You can get away with it with an I-beam,but not on the rear.

If they still taper in towards the center,like the P&J set up,they should be ok.

The further apart the attatching points at the front,the more they will work like ladder bars.

There was a guy here a few months ago,with a set of Yellow '36 split bones.
Very broken. Luckily for him,he found it before it found him.

 

I am going to split my 40 bones,are the much different than 36's?? Is there much difference in just opening them up a little or all the way out to the frame??

 

Keep in mind guys this is the rear...not the front bones.
The 36 bones are sought after because the "unbolt" and have the transverse leaf that retains the traditional look but on an open drive.

Here's what he says in his article:

"Truth is, those rear radius rods were actually rather flimsy and only served to stabilize the outer ends of the of the axle housing; it was the torque tube that located the rear end and took all the abuse of traction and braking forces. So, even though it has been done, I don't trust early Ford wihbones as the only means oflocating a rear end."

 

you can split the bones on an i-beam axle without problems, because an i-beam will twist without breaking. you can split the bones on a rear end, but you WILL break stuff.

take a paperclip, unbend two of the legs so it looks like a U shape. lay it on a table. hold the two ends down to the table, like they were mounted to the frame. now pick up one corner of the U. the other cprner comes up with it. if you want that corner to stay flat on the table, something has to bend or break.

crawl under a car with a poorly set up rear suspenion like split bones or ladder bars. a good number of them have parts that have been rewelded because they broke. and you can bet they ride like a lawn tractor, because the rear end can't act indendently. David

 

[ QUOTE ]
Keep in mind guys this is the rear...not the front bones.
The 36 bones are sought after because the "unbolt" and have the transverse leaf that retains the traditional look but on an open drive.

Here's what he says in his article:

"Truth is, those rear radius rods were actually rather flimsy and only served to stabilize the outer ends of the of the axle housing; it was the torque tube that located the rear end and took all the abuse of traction and braking forces. So, even though it has been done, I don't trust early Ford wihbones as the only means oflocating a rear end."

[/ QUOTE ]

Henry Ford was a stingy,cheap SOB.
If he thought he could get away with building a '36 Ford without the torque tube and just run them cheap-ass little radius rod/wishbones, don't ya think he would have done it in the first place?

Ron is right, and if you don't know of him or trust his credentials, then read all the stuff he wrote in the pages Tex Smith's Hot Rod Mechanix magazines.

 

Ill let ya know......

 

Hey Guys,

I'm running 42 bones on the rear of mine - unsplit with an open drive diff. what do you need to do to stop the mounts from cracking or fix the radius rods with wishbone issue?

Someone suggested running a rod above the drive shaft to a mounting point above the wishbone mounting point... explaining that this will stop the back/forward motion of the diff under braking and acceleration which in turn stops the mounts from cracking.

What do you think?

Danny

 

[/ QUOTE ]Henry Ford was a stingy,cheap SOB.
If he thought he could get away with building a '36 Ford without the torque tube and just run them cheap-ass little radius rod/wishbones, don't ya think he would have done it in the first place?

Ron is right, and if you don't know of him or trust his credentials, then read all the stuff he wrote in the pages Tex Smith's Hot Rod Mechanix magazines.

[/ QUOTE ]

I don't know Ron or even care how wonderful he may be.
I just want to know if this is true? Are we setting ourselves up for failure? I don't want to put my ride at stake...but I do like the looks of rear bones. I just want to be safe.

 

If I was running them on an open axle and anyy kind of torque motor at all I'd also run a 80's Camaro style torque arm to take the place of the missing torque tube.

 

[ QUOTE ]
If I was running them on an open axle and anyy kind of torque motor at all I'd also run a 80's Camaro style torque arm to take the place of the missing torque tube.

[/ QUOTE ]

And change the mounts,on the rear of the bones,so they act as trailing arms.
You only need one torque arm,not 3.

 

So would that be a 4 link?
Or would that be 2 triangulated 2 links inside of one another?

What if you have a set of bones, split but not all the way to the framerails.....and a panhard bar? The tranverse leaf and factory crossmember will handle some of the torque, won't they?

 

l have also been informed of this type of failure as l am installing 36 bones in my car.
l have also been told that to get around it you run a torque to compensate for the missing drive shaft as said before, also to install a plate where the casting meets the tube to make that area stronger, thats where the weekness is.

 

I may be in error- but I feel like my set up will work.
It will however have very little torsion capability I know.
I hate the way an early ford set up rocks side to side so excessively.
Mine only has 1-1/2" total travel in the vertical mode.
I ,like Roothawg think the rear spring heavy Truck gas shocks etc will behave better by NOT allowing much 'twist" right to left before bottoming the housing to the frame.
I am adding snubbers there.
a common form of ladder bar failure occours as a result of the rod ends having a small diam threaded end and running a JAM NUT there to totally prohibit the ladder from pivoting the limited amout it could -THEREFORE allowing the bar to twist itself into failure at that joint area.
Mine have coarse threads 1-1/4" diam and are not locked where they thread into radius rod allowing that small additional amount of give as well as the forged 3/4" bore heims joint coupling the frame to the radius rod ends.

 

If you had one trailing arm easch side,a torque arm like on the latemodel Camaros('84 up),
with a panhard bar,that all you need.The trailing arms locate the axle front to back,and the torque arm handles the reactions in acceleration and braking.Aside from the spring(s)and sway bar,the rear suspension is free to move in roll.There is no bind.

If you wanted to get away from the panhard,you could go with a pair of triangulated upper trailing arms,to creat a triangulated 4 bar.Again,no binding.



[ QUOTE ]
The tranverse leaf and factory crossmember will handle some of the torque, won't they?




[/ QUOTE ]

Probably a negligable amount,the spring can actually twist a little

 

I am not totally sold on the setup. I just want to weigh out all my options up front, before I spend a bunch of money only to fail. I have a set of 36 bones but should I use em?

 

All the torque that makes cars with enough torque want to do wheel stands is transferred to the weight of the car through that lever, the torque tube/lever/arm. Is that '36 radius rod strong enough to hang the whole car on the end of? I doubt it..
Is that picture clear enough?..
(just trying to help, not feeling argumentive at all tonight, it's too hot and humid...)

All the radius rods were designed to do was triangulate the axle tubes into an unflexing structure to keep the rear axle perpendicular to the torque tube and reduce the possibility of stress fractures.
Ya see, the banjo,being round in the side view is strong enough to take the torque wraping up of the engines power, but as one wheel pushes forward, as it does, it's torque would be pulling on just the bolts that hold the axle housings onto the banjo but the wishbone, as installed originaly keep the tension and compression forces on the torque tube instead of the Banjo housing bolts and bolt holes.

A torque arm would work just like a T-tube, in that it would swing the rear endthrough an arc like the Torque tube does, definitely different from what 4 bars do.
or
What Ian sid too if you're not running a Ford Banjo.

 

I guess you are right about the banjo being designed differently........I hadn't thought about that.
I may stick with what I know, even if it is "cookie cutter".

 

I went through the whole 36 vs 41 (in my case) radius arm idea. The radius arms, pivoted at both ends, with a torque arm parralell to the driveshaft was the only situation that I would take my kids along with. Since I am going too damn low, have the driveshaft way above the floor level, which is welded to the bottom of my rails, the torque arm would hit no part of my chassis, but slam into me occasoinally. Then I looked at some more of Harry Miller's wonderful creations. Now I'm going with four 1/4 eliptic springs set up as a 4 link on the rear. Henry's bones just weren't designed for how we rodders use them. Enough of my rambling on the subject.

 

Bones dont have the strength w/o the TorqueTube. I did the bushed ends and Tork-arm.

 

Choprods, something about that doesn't seem right to me. If you put your heavy duty rod end in a big vise and had a couple of your extra-large buddies reef on the other end of the radius rod, would it hold?
I don't get how leaving off the jam nut would affect the strength of the joint, either.
How do you figure?

 

One of the Texas? HAMBers folded a couple sets of split bones on a coupe a few years back if I remember?

 

DrJ covered it well in my opinion.

You have to remember we are dealing with TWO potential failure issues here.
(1) Failure caused by binding as fully split bones try to flex while the car leans in a turn or enters an angled driveway etc.
(2) Failure caused by the bones being unable to absorb the rotational twist caused by torque loading as the car accelerates OR brakes hard on LEVEL ground.

BOTH issues can be addressed individually so make sure your setup prevents BOTH problems!!!

I REALLY like 36 style bones...I'd run them, but I'd do like the Dr says and add something to absorb torque AND run them as close together as possible at the forward pivot point as well.

The bones that bolt to the axle end with the backing plate bolts are NOT acceptable as the ONLY axle location device no matter how you configure them IMHO. The outer forged end is just too weak and the tube thickness just isn't there either. I'd only use them if I cut the forging off and added a bushing to the rear so they could be used as lower links in a multi-link suspension.
I did see an added upper link somewhere that joined the center of the axle housing to the front of the narrowly split bones to form a ladder bar like truss...seems workable in a lower power situation. Both failure problems are addressed...but I still don't like the questionable forged ends on the later bones!

IF something breaks, I want it to be a total surprise! If I expected it might break and built it anyway...?

Well, that means I FAILED doesn't it?

4-1/4 elliptics would ride and work nice but could have some lower spring wrap problems under acceleration with a strong motor. I'd bias the leafs to favor the lower packs slightly...maybe even do a "Military Wrap" on all the mains.
The idea seems very workable. Seems unsprung weight would be very low as well.

Double cantilever suspensions (uses FULL 1/2 elliptic springs but mounted in a 1/4 elliptic fashion) are similar and were used on several large 1920's luxury automobiles and were even on 30's race cars like John Cobb's W12 aircraft engined Napier-Railton!
In other words...I think torque issues CAN be addressed!

Bill

 

Some guys have gotten away with it but I wouldn't trust the bones to handle much torque in a very heavy car for very long.
T-man is right about one of our Texas bros folding up a very nice pair of ford Bones at the strip one day. He even posted photos of it. I was because of that particular occurance I was planning a torque arm for the Rocky 33 before I put the new, improved flathead in place. The 33 went to T-man and the new flatmotor went to av8 before any torque arms were fab'd up. I was planning on using a length of 2"X3" box tubing and mounting it solidly to the rear axle and bolting the other end to a frame-crossmember with a big squishy bushing from a early 70's chevy pickup traililng arm. A big spherical rod end would also work in place of the squishy rubber bushing.

 

[ QUOTE ]
I am going to split my 40 bones,are the much different than 36's?? Is there much difference in just opening them up a little or all the way out to the frame??

[/ QUOTE ]yes and yes 36s are more substantial than the 40s and do not use that little forgeing to mount the radiusrods unless its a 35-6 end if you split them to the frame it turns the axle into a giant sway bar if you bring them in like pete and jakes bars they are able to piviot, better yet do as samiyam and weld them together unsplit then they can pivot and borrow strength from each other i work on a 40 pick-up done this way that had been a rod since the 60s and pulled a 5th wheel 100k miles on it they still worked fine!

 

Thanks for all the input.As much as I hate to say it....I think I may just bail on the whole idea. I can fabricate something that will be a little safer and easier as well.

 

Why not do what some of the modern rod builders do?
Build a triangulated 4 bar setup.
Similar to the ones with the lower bar directly under the frame.

In your case use the split bones as the lower link, bush it both ends, maybe a nifty bracket/tab setup at the rear to disguise somewhat the fact that it does pivot.

Then a pair of upper bars triangulated so as to locate the rear end or - better yet in my opinion - run the upper bars parallel to the 'split' bones, but on the inside of the frame.
Add a panhard to the mix.
Most times a panhard can be hidden away from the casual observer if you don't like them.
I use em, don't mind their looks and they're hard to see anyway.

What you've gained here is using the split bones loaded in column.
Push-pull in other words and no bending stresses from torque.

With the bones and upper bars parallel, both vertically and horizontally and a panhard in place you'll find it handles pretty well on the street.

Use a transverse spring as well.
It's gonna ride better due to more capability for tuning as well as more travel available than the coilovers.

What will really help here is a sway bar.
There are some nice ones in the aftermarket, but a good one can be found at the wrecking yards.
Don't overlook the foreign cars either, a lot of their stuff is sized just right for our hot rods.

Some trad guys may poo-poo this approach, but to my way of thinking you can have your cake and eat it too.
At least as far as good handling and trad looks go....

 

T-Man,

That pic makes me wonder if everything moves in the same arc - if not, it'll bind & may break.

Of course, it could just be the angle of the pic that makes the arms look different lengths...

 

I think there are many good points here. I have actually been going through this exact question for my 27 coupe project with 394 Olds power. Was going to use 36 rear bones, but I think it needs an additional upper link or torque arm like mentioned by several previous posts. So instead of using the 36 rear bones, I am going to use a ladder bar set-up I think. Maybe not the most traditional, but then neither is the Olds rearend in place of the traditional banjo.

Here is the engineering reason that the unsplit bones are not sufficient. Several factors are involved.
1. The bones do not have sufficient stiffness to hold the bending forces of a high torque engine. The stock radius rod is designed to hold the rearend in place as stated, not subject to bending forces. Reason that many rods get away with it is because the skinny bias ply tires spin before any real serious torque bends the radius rods. Get enough traction and a healthy engine and the bones will permanently deform or break.
2. By splitting the bones you create a very stiff sway (really anti-roll) bar with the rearend housing. That is why it is best to leave the bones pointing in towards the center as much as possible. Rubber bushings can be used to take up the distortion so it is not transferred to the welds and mounts.
3. If you use the 36 rods mounted solid to the rearend and split to be parallel with the frame, the upper mount has to be able to change length. It must be exactly the same length as the lowers or it has to be able to change length, due to the different arcs. That is why it was suggested to mount the lower rod using a pivot-able design. The stock 36 rod uses a solid mount. In stock configuration there is not change in arc length of the rod, so it does not require a pivot.

An alternative to the torque arm is the triangulated four link, or even a triangulated upper wishbone that mounts with a single point on the rearend. This would keep from requiring a panhard bar if set up correctly.

The metallurgy of the rods has nothing to do with the problems of splitting them and running open drive. It is a problem of stiffness, and to some extent yield strength. Stock radius rods are low strength and will bend (and potentially break after bending too far). As evidenced by the examples cited.

A stock 36 radius rod would make a fine lower bar as long as it has some additional upper bar or torque arm to handle the rotational forces due to torque.

 

One of the factors I have to consider is the fact that mine is a 36 pickup. Very little weight over the rear end and it tends to ride like a buckboard if the springs are too heavy.

I had looked into running 2 small airbags over the rear end, (up out of sight) and using a parallel leaf setup with 1-2 leaves only. Maybe throw in a couple of trailing arms to help keep it all in line.

Does this sound like something that would be reliable. I am more concerned with ride and adjustibility more so than the typical lowering aspects.