Torsion bar suspension

Shocks, Springs, Brakes, Frame, Body Work, etc

Moderator: Team

Post Reply
lada ok
Guru
Guru
Posts: 1089
Joined: Fri May 10, 2013 9:20 pm
Location: te puke, bay of plenty, new zealand

Torsion bar suspension

Post by lada ok » Fri Sep 12, 2014 8:55 pm

The more I think about T/Bar suspension system, the more I like it.
This came about while figuring out a simple adjustable anti sway bar for a small auto x car

the T/Bar can be kept at a low level ... C of G
The T/Bar probably doesn't weigh much more than a coil
Ride height can be altered easily
The spring rate can be altered by adjusting the radius of motion on the T/Bar arm
Unsprung weight would be better
The shock can be actuated off the sprung T/Bar arm ... even better unsprung weight

Or am I looking through rose tinted glasses ?

Brian P
Guru
Guru
Posts: 1202
Joined: Wed Jan 02, 2008 7:35 pm
Location: Toronto, Ontario, Canada

Re: Torsion bar suspension

Post by Brian P » Fri Sep 12, 2014 10:08 pm

Plenty of vehicles have done it, from air-cooled VWs to traditional rear drive Chryslers for a couple of decades to Renaults to Toyota pickups and others. (Notably, I believe every one of these has gone away from it ...)

The length of the torsion bar can be something of a packaging issue. Normally the torsion bar has to be in line with one of the suspension arm pivot axes (usually the lower one). You can go straight back from that location if it projects back under the floor of the vehicle. That's possible in many trucks. But in practically all modern cars, the lower control arm pivot axis is above the level of the floor of the car so you can't have the torsion bar extending back, and as often as not nowadays,there is a transverse powertrain ahead of the control arm axis so you can't extend forward. So then where do you put it?

Renaults for a long time used transverse torsion bars in the rear suspension, in conjunction with a pure-trailing-arm rear suspension design. You wouldn't want to use pure trailing arms nowadays. More modern multilink systems have better toe and camber control. I suppose you could do it with a twist-beam axle, and plenty of front-drives use that - but a lot of the time, the fuel tank is in between the front ends of the trailing arms and ahead of the beam axle. If you use a twist-beam, the trailing arm pivots no longer pivot purely in rotation, they are dependent a little bit on what the wheel on the other side is doing.

There are lots of ways to design suspensions, and what we think of as conventional nowadays is by no means the only way to get the job done - but a lot of the designs of the past have been relegated to the past for good reason ...

Brian P
Guru
Guru
Posts: 1202
Joined: Wed Jan 02, 2008 7:35 pm
Location: Toronto, Ontario, Canada

Re: Torsion bar suspension

Post by Brian P » Fri Sep 12, 2014 10:12 pm

I should add that the Simca 1100/1204 used a transverse front-drive powertrain in conjunction with a front suspension design using torsion bars. That car morphed into the Talbot/Simca Horizon which then became the Dodge Omni / Plymouth Horizon ... but in the process of crossing the atlantic, the front suspension became MacPherson with coils. It might be of interest to you to find out why they did that. Probably front foot-room because they wanted to make the front floorpan lower to get more space inside the car.

lada ok
Guru
Guru
Posts: 1089
Joined: Fri May 10, 2013 9:20 pm
Location: te puke, bay of plenty, new zealand

Re: Torsion bar suspension

Post by lada ok » Fri Sep 12, 2014 10:18 pm

Brian P wrote:Plenty of vehicles have done it, from air-cooled VWs to traditional rear drive Chryslers for a couple of decades to Renaults to Toyota pickups and others. (Notably, I believe every one of these has gone away from it ...)

The length of the torsion bar can be something of a packaging issue. Normally the torsion bar has to be in line with one of the suspension arm pivot axes (usually the lower one). You can go straight back from that location if it projects back under the floor of the vehicle. That's possible in many trucks. But in practically all modern cars, the lower control arm pivot axis is above the level of the floor of the car so you can't have the torsion bar extending back, and as often as not nowadays,there is a transverse powertrain ahead of the control arm axis so you can't extend forward. So then where do you put it?

Renaults for a long time used transverse torsion bars in the rear suspension, in conjunction with a pure-trailing-arm rear suspension design. You wouldn't want to use pure trailing arms nowadays. More modern multilink systems have better toe and camber control. I suppose you could do it with a twist-beam axle, and plenty of front-drives use that - but a lot of the time, the fuel tank is in between the front ends of the trailing arms and ahead of the beam axle. If you use a twist-beam, the trailing arm pivots no longer pivot purely in rotation, they are dependent a little bit on what the wheel on the other side is doing.

There are lots of ways to design suspensions, and what we think of as conventional nowadays is by no means the only way to get the job done - but a lot of the designs of the past have been relegated to the past for good reason ...
I was thinking more along the lines of an easily adjustable / low cost system for a race car

Brian P
Guru
Guru
Posts: 1202
Joined: Wed Jan 02, 2008 7:35 pm
Location: Toronto, Ontario, Canada

Re: Torsion bar suspension

Post by Brian P » Sun Sep 14, 2014 3:35 pm

Most autocross cars that I've seen are built out of a standard car, and then the rules for the various classes are going to have something to say about it.

If you want to build something like a KTM Crossbow or an Ariel Atom then you are on your own. Most of those are using coil-over-shock assemblies.

lada ok
Guru
Guru
Posts: 1089
Joined: Fri May 10, 2013 9:20 pm
Location: te puke, bay of plenty, new zealand

Re: Torsion bar suspension

Post by lada ok » Sun Sep 14, 2014 7:05 pm

Brian P wrote:Most autocross cars that I've seen are built out of a standard car, and then the rules for the various classes are going to have something to say about it.

If you want to build something like a KTM Crossbow or an Ariel Atom then you are on your own. Most of those are using coil-over-shock assemblies.
Yes, luckily the sort of competition class i'm looking at is open to all ideas & there's plenty of ways to skin a cat, things come and go, mmmm ... maybe carbon fiber as a torsion bar material may make the system advantages, pretty hard to make a coil spring out of the stuff

jed
Pro
Pro
Posts: 460
Joined: Tue Nov 18, 2008 4:18 pm
Location: Dallas

Re: Torsion bar suspension

Post by jed » Sun Sep 21, 2014 10:00 am

I used to build engines for a guy that used torsion bars in his chevelle dirt track car.
All the drivers I talked to said the cars handled very well.
The cars were much smother on rough dry slick tracks.
Several other car owners tried the torsion bars but could not get them to work.

I also think sprint cars use cross torsion bars.

lada ok
Guru
Guru
Posts: 1089
Joined: Fri May 10, 2013 9:20 pm
Location: te puke, bay of plenty, new zealand

Re: Torsion bar suspension

Post by lada ok » Wed Sep 24, 2014 3:56 pm

jed wrote:I used to build engines for a guy that used torsion bars in his chevelle dirt track car.
All the drivers I talked to said the cars handled very well.
The cars were much smother on rough dry slick tracks.
Several other car owners tried the torsion bars but could not get them to work.

I also think sprint cars use cross torsion bars.
Ta Jed, we actually ran t/b in our midget, and they worked great, but your right t/b is just a springing system, you have to get the whole combo right for it to work no matter what you use

Post Reply