z bars

[Don]

Guys:

I am rebuilding a one off "special" from the 60s. The z bar and brackets are missing. So my question is what diameter and material should I use to make a new one? Based on the weight of the frame (and me!) it will be around 1125 pounds ready to race.

thanks, don

[problemchild]

Since nobody offered any help, I would suggest you find someone with a similiar period car with similiar shocks and springs, and copy that setup. Autodynamic and Zink would be the obvious ones to copy. Probably the key dimension is the spacing of the mounting blocks which must mount to your chassis.

I have a spare Zink bar that could be mounted as wide as 28" apart although it appears to have been mounted at about 22". It is 11/16 dia.

My Lynx is only mounted at 22" but that is the maximum allowed by the design of the bar which is 3/4" dia.

The math is really basic stuff, so a basic anti-roll bar formula will let you plug in values for lever arm lengths and make a custom bar with similiar performance to the one you are copying.
Here's a link to a formula that may help.
http://www.lumenique.com/Cars/mcoupe/mo ... llbars.htm

[Don]

thanks, can do the math, and will look for material that doesn't yield at psi calculated. Another interesting question, there are pictures of an early Beach cars with cables only limiting axle droop. I assume the z bar is a better choice because it conects both side in the up and down direction?

cheers, don

[Mark_Silverberg]

If you ask 10 vintage FV races about Z bar and cable limiters you will probably get 12 or 13 different opinions.

In general Z bar is preferred. The Zbar basically takes the roll resistance out of the rear suspension and also lowers the spring rate in two wheel rebound - it also increases the spring rate in on two wheel compression.

The cable does not lower roll resistance and makes the rear spring rate in rebound go to zero once the limit of the cable is reached. The advantage is that it does not increase the spring rate in compression.

There are several vintage cars still using a cable compensator and going quite fast. In some conditions (rain or slippery track they) can do quite well - but z bar is no doubt the preferred set up.

[Dietmar]

Don:

You have mail.

Dietmar