F1technical.net

I have been set an assignment which has a question about a “tie radius arm” on a f1 car but I have not been able to find any information on it.
Could some one please tell me what a tie radius arm it? (I know its part of the front suspension but that’s about it)

As im here as was I might as well ask if any one know of any websites (or other info) where I can find out about how to repair carbon fibre that has been slightly deformed and has a small chip?


Help would be appreciated .

I'll give you a clue, have a look at radius arms generally.

In a beam axle car, these will typically project forward and help to locate the beam axle.

Take a look at an older F1 car (say 1967 Lotus 49), you will see the radius arms projecting forward from the rear and back from the front. The radius arms effectively form part of the upper/lower wishbone in the suspension. One reason they were so visually obvious on these cars was to provide a wide base to feed the loads into the bulkhead of the chassis structure. Adjusment of the arms affects static & dynamic toe, castor and I suppose to some extent camber.

"tie radius arm" is not term often used in F1. I guess you mean what we call Wishbones, these are two V shaped links that connect the wheel assembly to the car. See Pic, is this what you mean.....?

Here's an article on repairing carbon fiber for bicycle frames. It may be of assistance
http://www.sheldonbrown.com/rinard/carbonqa.htm

thanks for the help guy.

Great photo Scarbs! But where are they on your site?

Manchild,
I have lots of pics that are not on my site, but I sometimes put a picture on my server to link to forums.
This one was from Renault...

BTW...

Why must double wishbone suspension have the push rod? Wouldn’t it be simpler, better for aero and less weight without the pushrod and rocker?

I’m thinking on upper wishbone slightly extended into chassis with shock absorber connected on that end and torsion spring longitudinally positioned on same axle as lower wishbone joints. Upper wishbone would transmit the motion/forces to shock absorber while lower wishbone would twist torsion spring...

A wishbone set up similar to this Manchild?

Second pic looks more like it...

This is a sketch of what I had in mind...

Like to Lotus 49? This has been tried before, and since no one currently uses it, there have to be disadvantages. Of course, the mechanical loads on that arm, especially at the fulcrum, have to be punishing.
I suspect that in engineering studies of mechanical failure versus improved aerodynamic efficiancy (and also weight comparisons), they don't want to risk breaking the suspension.

This sort of set up should give you fairly good geometry though, and help to aleviate some of the falling/rising rate issues that can crop up with an inclined pushrod and rocker.

manchild wrote:Second pic looks more like it...

This is a sketch of what I had in mind...

Not dissimilar to inboard rockers tried years ago (as said I think Lotus was an early exponent). As wheel rates rose, stiffness became an issue, the pushrod is structurally simpler. I have no doubt with current materials you can get plenty of stiffness, but the penalty has to be weight and it's all unsprung. Also, I can envisage that a certain amount of flex could occur (even a tiny amount could feel massive at the wheel), this flex would be undamped and creates a "spring" on uncontrolled rate.

Given how sensitive F1 cars are to ride height, I assume that absolute precision in controlling wheel movement is paramount (I have heard than suspension mounts are machined to positional tolerances of a couple of microns).

The pushrods let you place the springs dampers almost wherever you like and you can engineer almost any rising/falling/neutral rate your heart desires.

Interestingly it would seem that pullrods can be thinner and have the advantage of placing the suspension mass low down. I assume that these are not used due to packaging issues around the nose more than any other reason?

F1 teams don't use the lower pullrods because they need to assemble the front suspension higher since they started with high nose cars. Between better airflow management at the front and lower suspension mass, they preferred the aero advantages.

Using the upper wishbone to drive the damper/spring unit causes some really scary loading scenarios - the obvious bending, which is maximum at the hinge joint, and the less obvious torsion because the lines of action of the damper, hinge and the upright are all in different planes. These are additional loading to the normal loading of the wishbone which happens in its own plane. The nett result would be a very significant increase in the cross sectional area of the wishbone to withstand these loads. Increased area means increased drag and reduced aero efficiency, which was the motivation for the change.

A further issue would be the upper wishbone attachments becoming hinge joints rather than the current flexures. Hinge joints add a variable (albeit small) unkown damping factor due to friction in the joint - this complicates tuning the damping rate.