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

That joint is pretty slick...I wonder if it's just a straight swap with my Heims? Probably not :/

UPDATE: Checked, naw, they don't have them in 5/8" 18 thread...only as small as 3/4". D'oh.

Yeah, I wish I had some 36 hangers at the time, but as I mentioned, what's the difference between milling tough ass replacements for these if they do break, since I've already got hangers off the back, ya know?

 

Since the pot is being stirred, is the ball and socket from the converted front wishbone assembly strong enough to take the hit/forward motion of constant forward push? On the front, it has to take the force of braking. Turned around, every time you accelerate you are pushing the whole car (2000 lbs or so) plus (I think) the added force required to get that mass in motion. So under heavy acceleration isn't that ball socket being subjected to 5, 10 who knows how many thousands of pounds of force?

 

I did a quick paint thing to see where the problem lies. The upper pic is split bones/radius rods and separate (although close) mounts. The twisting of the bones comes in when one wheel goes up and the other down. On the lower pic, you can see that the pivot point does not stay static, one bone tries to go up, and the other down. A small amount, but movement none the less.
The rod end/tie rod/bushing is only doing it's job because the bones are twisting. And I guess that's where the breakage occurs over time. If you think about the bones and rear being made out of something massively strong and inflexible, there would be no way to twist the rear end. I guess that is why the single pivot point of the original design has no flaws. I didn't add a third link because that is a separate issue unrelated (more or less) to the twisting bones/fatigue issue.

 

Pretty high-speed graphics there, badshifter. Just kidding, your drawing illustrates the problem pretty well.

It actually shows the point that several people here have been making and many have been missing. It took me a while to get it (about 1 and a half times through this thread). That the concern is not the hiem/tie-rod joint rotation. Those joints will rotate more than enough. The concern is the combination of a rigid mounting at the axle housing and a lack of vertical articulation at the front of the radius rods. The ball joint/full triangle (ala F&J and Hot Rod Pro) method is the best, but it seems to me the situation can be solved with either an articulated joint at the axle (ala 8flat) or by using a material that is resilient enough to resist the stress cracking resulting from fatigue caused by binding at the limits of suspension travel.

This is such a useful thread. I've learned a lot about something that seemed so simple at first glance. Or I could be all screwed up.

 

okay so the Jonnie Joint is looking pretty good to me with 36 rear wishbones, so I got that part, still think I am missing the best way to attach the wish bones to the rear?

if I just bolt them on like stock will there be an issue?

further more is making a torque arm that goes from where the bells bolt to the banjo to a mount underneath the Jonnie Joints okay?

this thread is really helpful but damn there is soo much to take in!!!

thank god for the hamb or I would have just split my rears and mounted them to the outside of the frame!

 

Poboyross,

Somebody said that your set up was just like ours. That is not correct.

Our torque arm front mount is attached to the front of the radius rod so that the torque arm pivots with the radius rods. Your front torque arm mount is not in line with the radius rod mounts. The torque arm will not pivot on the same axis as the radius rods (this has been explained by others).

I just wanted to point out the difference.

 

While it's not attached to the same pivots as the radius rods, the front torque arm mount has since been moved to be parallel to the radius rod mounts.

For what it's worth, while I enjoy (mostly) reading the science and replies, I'm signing out on this thread, barring anything terribly interesting coming up that hasn't been beaten into the ground already. I'm going to run it as it sits, move on with the build, and get back to having some fun.

 

i was told by a good friend (chassie builder +) , to attach 2 rods from the rear axle to my radius rods . all work together . im using moly tubing with heim's at the radius rods to trans , & on both ends of the torque arms (anti-roll) . looks good to me .. steve

 

^ that's exactly what I'm doing......all connected to a common Model A front yoke/ball (spun around 180 degrees of course), so it all rotates/swivels as a common unit. I'm using two 1-inch diameter, .120-wall DOM tubing, trussed together like a bridge as the torque arm. That's my upcoming weekend project.

 

Holy snappin' arseholes!

 

WOW, good stuff!!! The work of (racemad55) link on the previous page.

 

If you really want to see how your suspension set up works, try this: remove the rear spring(s), support the frame at ride height on jack stands, support the axle at ride height on a floor jack in the center. Lift one side until it binds or the frame is lifted
off the jack stands, repeat on the other side. Or if you already have a lot of weight on the chassis support the the axle at ride height at the ends on jack stands, then using a floor jack or cherry picker, first lift then lower one side at a time until it binds or the frame lifts off the stands.

If your anticipated suspension travel is within the range of free travel you just determined, it should be good to go if the components are also strong enough to hold up to engine and brake torque.

 

That just makes to much sense! Lol

 

Read some of this. Thought I'd show what I did. It has no bind whatsoever and the fork set up deals with the torque. That's my Torque Fork.

It has worked OK for 2 years behind a 401 with a 4 sp. Admittedly I have been looking after it because I didn't want to break axles or the banjo.

Now I'm putting a QC with splined axles in and I expect to start giving it a harder time. I'm looking at swapping the '48 rear radius rods for a '48 front wishbone for a bit more strength.





Pete

 

Would there be a problem with running the original torque tube to a frame cross member with a short coupler/driveshaft between it and a newer transmission. I know this would only adress banjo style and would not help with later rear differential. Was just an idea and curious if it would work safely.
<!-- / message -->

 

I have used 35-36 rear wishbones on my 5 window and my roadster with pretty hot 327 in them and have had no problems at all... I never ran slicks so I never put them under any serious strain either. I wouldnt use anything else.Good luck.

 

You would need to mount the torque tube with some kind of universal joint or flexible mount to allow not only up and down movement of the rear end but also 'rocking' of the rear end. (one wheel up, one down). You would also need to seal the front end of the torque tube. I suppose if you really wanted to you could make something like that work. I think there are easier proven ways to skin that cat.

 

I,ve seen it done on a 39 Buick, which has a short drive shaft after the trans, and that shaft was was removed and a open drive shaft was installed. It had the torq tube contained by a mount in the X memeber. You basically have the right idea on the setup you have. What I would do is makeup a torq arm with heavier tubing running alongside from the differential, taking the place of the original tube driveshaft.

 

Check out Hot Rod Works, they have a setup up for this..............

 

Here's how I designed my rear suspension for my 26 RPU. A sort of modified triangular 4 bar system.

 

Nicely done. My only concern with your setup is the shallow horizontal angle of the upper bars. I think you will get too much lateral movement, unless you also use a panhard bar. This is similar to GM mid-size (Chevelles, etc.) rear suspension. In the original application the horizontal angle of the upper arms is right around 45d to the center line of the chassis.

 

I am thinking that I won't need the panhard. I am sure that the coil overs will help some in that regard howerver it seems to be pretty solidly located side to side in the tests I have done so far.

With the urethane bushings I used there is nowhere near the flex encountered in the big rubber bushings that GM used.

 

Great thread I have the same rear radius rods I would like to use to adapt to this rear end is there someone that makes the brackets for this set up.

Thanks
Frenchy

 

What about hooking the front mount for the rear radius rods (I'm thinking ball mount) to the existing trans mount?. I have a tube style mount that just goes from frame rail to frame rail and is bolted to either side on an un boxed stock A frame. Mind you this is a low HP 4 cyl in there now, I just want to ditch the rear that it has now. So all the suspension movement (for and aft) will be subjected to 8 bolts of the trans mount, seems the same as the brackets bolted to the frame now for the A split bones to me???.

 

bump

 

My T has '35 radius rods that I split to the frame and a not-very-stiff "A" spring. It lasted about two weeks before the radius rods broke off their forged ends.

Sooooooooooo... I made the rear suspension into a "4-bar" using the radius rods as the lower links and fabricated the upper links from 3/4" black pipe. I used 3/4 ton Chevy tie rod ends on the rear of the radius rods and on either end of the upper arms. The upper arms tuck neatly up inside the frame so you can't see them unless you lay on the ground. I filled the stock radius rod forged bracket and drilled then reamed the hole with a 7 degree tapper ream to properly mount the tie rod ends.

It was great! It was like going from riding a buckboard to a cadillac! amazing what happens when the suspension can articulate the way it's suppose to

As far as power is concerened: Once we go to an open drive line, under hard acceleration (well, any acceleration including braking) the axle tries to rotate the radius rod upwards (or downwards), and therefore try to bend it into an upsided down "U". This is not what Ford designed them for. But by going to a 4-bar set up, now the radius rods are only under compressive forces and the upper bars are only under tensile forces during acceleration. Any rod / bar can handle ALOT more compressive and tensile forces than it can handle bending forces.

I'm running a flat 6 (80 HP) so obviously I'm not as concerned as you are about power breaking things. If I where up around 400 HP and tires that could hook up I would run a 3/4" pipe down the center of the radius rod, weld the tie rod ends, pipe, and radius rods all together at each end. That would be stronger than four links on a drag car. The weak point then becomes the tie rod ends, one could upgrade to 1 ton truck tie rod ends, they are massive! More importantly though is to taper the holes where they mount to the frame and axle.

Hope that helps.
Kipp