Another question - Pull-rods?

Sorry guys for bothering you with so many questions, but I read that the CLK-GTR racer back in the day of the FIA GT1 class used PULL-rods instead of PUSH-rods in the suspension, and that was more suitable for a closed wheel car.

Now, I never heard of pull rods before, and there seems to be not much info on them around the web.

Is there a caring, knowlegeble soul out there that can wash away my ignorance? :)

Again thanks for any help;)

Just stick 'Suspension Pull Rods' into google. A wealth of info appears, including this Ten Tenths thread:

http://www.ten-tenths.com/forum/showthread.php?t=80510

At first glance the reasons are to do with the ability to use a thinner/lighter rod as the relevant materials are usually better in tension than compression, and by using the lower suspension pick-up points (the ones that are 'pulled' when the wheel 'bumps'), you inherently end up putting the main levering/springing/damper components lower in the car - lowering the CoG.

Apparently Gordon Murray used a design like this for a bit in F1, but it doesn't lend itself to modern 'high nose' F1 cars so its not used anymore. This maybe the reason Merc was referencing when it said that this method is more suitable for a closed wheel car in that they have points on the chassis suitable for it.

Pull rod as well as push rod, is a question of what sort of "packing" is the most suitable for the car in question. As for funktion, a direct working coilover is the best. Both push and pull rod include more moving parts that also add unsprung weight. The pullrod is working with the upper A-arm and the rocker is then down at the bottom of the frame, other than that it is almost the same idea. We could say that the pushrod is under constant pressure while the pull rod is under constant pull. I mention this becouse it is easely believed that the rod should be loaded in both directions.
Regards
Goran Malmberg

An advantage of Pullrods is that in some ways they are stronger , as they do not have to resist the bending loading that a pushrod system suffers , so therefore for bigger cars or a longer duration formula they offer better durability , but the suspension arms have to be stronger as these will suffer more compressive loading .

Draw a quick diagram and look at what happens when the suspension is put under load and you will see what I am getting at .

Pull rod as well as push rod, is a question of what sort of "packing" is the most suitable for the car in question. As for funktion, a direct working coilover is the best. Both push and pull rod include more moving parts that also add unsprung weight. The pullrod is working with the upper A-arm and the rocker is then down at the bottom of the frame, other than that it is almost the same idea. We could say that the pushrod is under constant pressure while the pull rod is under constant pull. I mention this becouse it is easely believed that the rod should be loaded in both directions.
Regards
Goran Malmberg

Broadly I agree with you on the unsprung mass issue.

However I'm not sure it's correct to say that a direct acting coil over is always best. If you have a decent level of suspension movement, then maybe.

However if you have small suspension movement - particularly formula cars, then moving enough oil inside the damper for it to provide a consistent damping force with minimal fade and stiction could be a problem. If a push or pull rod actuated rocker can double the damper travel for a given wheel displacement the damper will probably work better.

Also for packaging reasons a direct acting spring/damper limits what you can do with rising rate or falling rate. It's far easier to change these characteristics with a rocker than by changing the chassis mounting points.

Ben

Ben, agreed. I am just making a long story short.
By looking fare down at my site you will see I am using pushrods myself as it indeed is good for some aplications. In the pictures the reason speaks for itself, even on a non open wheeler. What I meant was only as a spring damper function, not taken in to account A-arm loading, aero, level ratio etc, as many believe that pushrod is better in general as it is used on F-1 cars.
Regards
Goran
Ben[/QUOTE]