Hot Rods broken radius rods?? why??help!!!

No.


the set up shown is OK for a Billy Cart, you will need a full redesign on that rear end for that car, even to be drivable let alone safe. Don't take any ones word, not even mine, do some true research from various sources regarding ch***is dynamics and set ups. Your life depends on it

 

Thanks...
We appreciate it!

 

Here's some you guys might appreciate.
These were on a project I bought and here's how that went. Go to look at the car, 15 min walk around then a ride around town. Guy tells me he drives this car almost everyday, and we finish the ride with a burnout and a sprited jaunt down the straight away, back into the garage. We then put the car up in stands and scope out the underside. I see somethings that make my skin crawl and the hair stand up on the back of my head because I just went 80+ mph in this thing. I did buy it after renegotiating, and this is one of the things I saw while under there.
Split 35/36 rear bones, front mounts moved to the inside edge of the stock 34 center x bracing, with nothing for a torque arm. After getting them back home and on the bench it's easy to see its been this way for a while and compromised much worse that I originally thought. Both sides were nearly identical.

 

Cracked from white line here to white line in previous pic around the bottom of the bones.

 

I thought this was a pretty good fix for the old bones, but a redesign of the mounts is needed.

 

Just put some duct tape over that yellow tape and you'll be G-2-G.

 

Not trying to hijack this thread I have a question though. Is the consensus that "split wishbones with an open drive line and buggy spring" does not work correctly and is prone to breakage. I have an A-V8 done that way years ago and would change it if this is an inherent problem. Seems like Speedway and other rod shop sell all the stuff to do just this type of suspension. Thats where I got all the parts. I really am interested in this now.

Pat

 

It's been almost a year since this was posted,I would think the repairs have been made. HRP

 

Yeah, it could cause a problem. Triangulate the bones and install a torque arm to alleviate the problem. Read post #3 and #23 for more details.

 

Yeah probably for the original poster, but everyday Someone building a hot rod contemplates this. Good reminders for those not well seasoned.

 

That's super high tack yellow tape, not the cheap stuff.

Do I really need to show that's a pattern for a steel patch ?
I suppose so incase some numb-nut thinks otherwise.

 

looks like the rear of my 34 was set up like this by the previous owner...I have not driven it yet, but before I do I am going to thoroughly investigate how it is set up

 

I was kidding, hence the goofy smiley face. Of course I knew it was a pattern!

 

I knew you knew, but who knows about them lurkers


But the tape alone was a far shot better that without. That's some scary ****.
80 on those things. Damn

 

Yeah, that's scary. Looks like there was some rot going on there too. I had very similar scary issues to deal with on my '33 truck. Some people just don't belong building these things!

 

Thanks for sharing your knowledge, guys. Suspension talk is pretty hard for me to visualize, but this thread helped.

 

I'm using 40 ford rods on mine full length, the longer the rod less stress at the mounting point.

 

That's what she said !

I'd like to hear your theory on that.

 

I can tell a few first hand obsevations of split bones and tube axles,either front or rear. Some were really exciting. I have posted most at one time or another. Put a P&J or a triangulated 4 bar under it and get rid of ALL that junk.

 

^^^^^^^^^^^^^^^^^
Listen to this advise. I love the old way but do it with knowledge of how the suspension works or use the current technology and be real safe.

 

I just stopped on this post to see what was up , its about a year old so I,m sure the issue has been resolved. The issue is the fracture of the radius rod at the axle mount and from my perspective can be attributed to the installation of a tie rod end on the frame side of the locating arm. Tie rod ends only have an axial offset of about 5-8* so as the body rolls and the suspension goes into bump mode the rotation of the frame exceeds the limits of the tie rod end and this turns into a rigid mount. The ridgid mount now produces a torque in the radius rod to compensate for the additional body or axle rotation on the lateral axis . Since the rotation angle is greater than allowed by the tie rod end operating angle the torque is displaced to the radius rod where the torque stress is induced into the component until the torque fatigues the metal and it cracks because it cannot twist to the angle of operation required.

This is a good example of why your radius rods should not be parallel to the frame rail and should be skewed to the central axis of the vehicle. They should have a higher angle of operation end to allow a wider range of motion. I know some will ask why you can do a parallel frame mount with a 4 bar setup and you can have good results, the rotational torque is divided between two bars not one. Under limited travel you can have rather rigid bushing with some compliance but if you notice severe defection 4 bars use axial ball ends on the mount points to limit the induced torque effect.

 

what do u think theres 2 ft. of suspension travel or what?

 

Take a look at Rod & Custom magazine, October, 2013. Kiwi Steve solved the problem on a model A roadster pickup in that issue.

 

You don't need much suspension travel to break bones that aren't installed appropriately. Just look at the OP.

 

Says the guy running 40 rear bones...

Which buy the way ...unless you triangulate them they are going to bend and break... That little forging is paper thin more than likely a crack starts in a bolt hole and works out or the fusion weld.. I have seen it a dozen times .. I always give the warning.. For some reason everyone is smarter than I ..then it happens.. If you decide not to fix it right at least keep an eye on it.. You may save a life besides your own..

Radius rods were never meant to be location devises ... They are only a diagonal stabilizer for a torque tube rear... The only reason 35-36 bones work is because for some reason ford waay over built them... Even then the need strengthening in a few key areas... And 400horse clutch drops are going to tear them up also... Unless people have some basic engineering and fabrication skills stick with store bought..


If your lucky you may get 4,000 miles like this car did after I warned the builders... This one let go on the fella who bought it from them.... On the autobahn!... Lucky for all people involved

 

35-36 rods are heavier because the spring is mounted to them not the axle.JW

 

If you run the tie rod style in the front and run then inward as close to the drive shaft as possible it will help eliminate some bind. I've seen people using a pivot ball and hooking them to that just under the u joint for the drive shaft that's the route I'm going to be taking called a super pivot ball I got from suicidedoors.com there used in 4 links and stuff extremely heavy duty and well made. I've never seen a way to run them outward that I like it puts to much twist on the tubing.

 

http://www.jalopyjournal.com/forum/showthread.php?t=659939 check this out good ideas

 

well this has all been sorted now, and i must say how great it all works. i have removed the radius rods all together and installed a ladder bar system from rodtech, fabbed up a cross member and attached the radius rods to them the legal 300mm apart,
the suspension works so much better now. lush plush ride and amazing handling for a car of this age.
it runs through corners like its on train tacks with no body roll.
ive also corrected the front suspension.
4 inch drop beam axle, stock height spring and new stubs steering arms to suit this set up

 

Walking home is traditional.