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Unusual rear suspension

Old Guy

Member
My T-Bucket has a torsion bar rear suspension.....sort of. It took a lot of digging to find out what I have, but I did find out. It's part of a VW bug front suspension. It's a single 2" dia. tube that is mounted across the rear of the frame. Inside the tube are 8 leaf "springs". The leaves are secured in the center of the tube. At each end of the tube, attached to the leaves, there are arms with links to the rear axle. Looks good, however it doesn't work. It's not strong enough to support the rear of the car.

That's the way I got it. I added a couple of air shocks to get at least some sort of suspension. Has anybody else got anything like this?

I posted this in the wrong place first. This is where it should be. I cannot yet post any pics. I think that might help but a few more messages and pics will be allowed.
 
I think I would.....no I know I would replace that! Call Ron @ RPM and get new stuff on the way.
I agree. I've been doing a lot of searching here and I am wondering why I don't hear about guys using torsion bar rear suspension. I get the impression that they are popular on sprint cars.......why not T-Buckets?
 
I agree. I've been doing a lot of searching here and I am wondering why I don't hear about guys using torsion bar rear suspension. I get the impression that they are popular on sprint cars.......why not T-Buckets?

Old Guy... I think there are several reasons T-Bucket guys don't use torsion bar suspension. Most people don't really understand how they work as compared to a conventional coil or leaf spring. A spring is a spring no matter what configuration. The second reason is packaging. A coilover shock is very compact and easy to adjust or tune to the application unlike a torsion bar and levers with linkage. There are a number of ways and directions to mount a torsion bar but it can get crowded in small cars. I have used them in drag race cars and road racing cars several times over the years and always liked them. With a coilover setup you can change the calculated spring rate for a different spring rate very easily. But with a torsion bar you have to have one machined to a different diameter to get that change as the overall length can not change without major fabrication re-work. The lever link usually is not adjustable in length due to another major fabrication project. Coil prings can be made with the same overall length and diameter by changing the wire diameter. And for the most part coil springs are available off the shelf from a number of people overnight. They are usually much cheaper then custom built torsion bars. But if you like them then move forward as they do give a very good ride. Hope this gives you some insight to your question. Good luck with your project.

George
 
Thanks for the input George. I guess what got me going on torsion bars is the fact that there is a torsion bar set-up on the car. I don't know why anybody would think that half of the torsion bar system used on the front of a VW beetle would do the job. One of the posts I turned up said that a Nissan pickup truck had 36" long torsion bars. I could maybe make that work. I would need a lot more info besides the fact that a Nissan Pickup has 36" long bars. Like, what year truck, model, front or rear bars, for a start. In order to afford it, I would need to be finding my parts in a salvage yard. I do have a machine shop and lots of room to work.
 
The stock VW front axle had TWO of those torsion bars (early models had 8 leaves per bar, later had 10). The mid 60's beetle had a curb weight of 1,629 lbs with approximate weight distribution front to rear of 35/65. So, the TWO front torsion bars were designed to support about 570 lbs, leaving your ONE bar with a capacity of 285 lbs. All of these numbers are variable, as a driver and full tank of fuel changes the weight of VW by 15% + . But, the end result is still the same.
If you like that design, look at the rear VW bar. It is a single bar designed for the the 1,059 lbs on the rear. Would take a little fabrication to mount and attention must be paid to lever arm length.
 
The stock VW front axle had TWO of those torsion bars (early models had 8 leaves per bar, later had 10). The mid 60's beetle had a curb weight of 1,629 lbs with approximate weight distribution front to rear of 35/65. So, the TWO front torsion bars were designed to support about 570 lbs, leaving your ONE bar with a capacity of 285 lbs. All of these numbers are variable, as a driver and full tank of fuel changes the weight of VW by 15% + . But, the end result is still the same.
If you like that design, look at the rear VW bar. It is a single bar designed for the the 1,059 lbs on the rear. Would take a little fabrication to mount and attention must be paid to lever arm length.
Thanks for the reply. Maybe whoever built my car had a reasonable concept......just used the wrong parts. I will get more info on this. Perhaps it's not a dead end after all. The biggest limitation is the width of the rear of my T. Having a machine shop makes most fabrication possible.
Thanks again
 
the vw rear bar 1 right , 1 left were in the same housing , end to end..if you're able to machine internal splines , they could be used running parallel to the frame , otherwise a crossbar would be in the way of the driveshaft/rear axle..
 
Thanks for the input George. I guess what got me going on torsion bars is the fact that there is a torsion bar set-up on the car. I don't know why anybody would think that half of the torsion bar system used on the front of a VW beetle would do the job. One of the posts I turned up said that a Nissan pickup truck had 36" long torsion bars. I could maybe make that work. I would need a lot more info besides the fact that a Nissan Pickup has 36" long bars. Like, what year truck, model, front or rear bars, for a start. In order to afford it, I would need to be finding my parts in a salvage yard. I do have a machine shop and lots of room to work.

Old Man...
Just a word on machining torsion bars. By reducing the diameter the spring rate will decrease. Most custom bars are heat treated high strength steels. If they are trough hardened you need to be careful as any nicks, turn marks or chatter become stress risers. Torsion bars are notch sensitive and need to have a very fine smooth surface, Bars out of OEM systems such as older Chryslers, Nissan trucks, Jaguars etc are usually forges to size, straightener with the splines last. There are plenty of torsion bar calculators and design information on the internet. Google is your friend!
George
 
There are a number of variations of torsion suspension intended for trailers. More than once I've pondered potential simple uses for the components...but the ideas have quickly gotten complex.
 
I can't imagine anything more simple than the way mine was done. I think that using a "rear" VW bug torsion bar might fix my problem. Soon, I will know.
9ie4uo.jpg

It's right there under the frame.
 
By shorting the arms increase weight load
The vertical movement of the car is limited to the length of the shocks. As the car goes up and down, the torsion bars rotate. The information I have, tells me to limit the rotation of the torsion "bars" (a stack of 8 flat leaves) or they will be permanently deformed. I put marks on the parts that rotate so that as I shorten the levers, I can see how much rotation I have. If I shorten them more (there are holes on 1" centers to provide adjustment) , I will have gone to the point of deformation. When it became clear exactly what there was to work with, it was also clear that the installed components could never do the job.
2igydd5.jpg

There are a number of things that convinced me that, whoever built the car, when confronted with several things that made the vehicle nearly impossible to drive,,,,,,,they just quit. Never finished the build. I have corrected several, still have a few to do. It's been fun.
 
Not sure what's happening here. I put a 216ci Buick V8 on the back of a kit car with the standard VDub suspension. Added a couple of coil overs and it was good to go. When you figure that I had a small V8 cantilevered way back from that torsion bar, I'm not aware of the problem you have.

The original 'plates' that go between the end of the torsion bars and the swinging arm are part of the suspension, and in your case these are eliminated. They provide a spring resistance to twist, add some 'bounce' between the unsprung weight and allow for roll.

I lowered the whole back end on the splines that fit between the torsion bar and the plates, until I got the correct ride height, then added the coil over to take up the slack.

If its a front end V Dub bar then you can get a kit the allow adjustment of the ride heigh by a simple screw...

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