Anti roll bar clamps

[stutch]

I've got a 1990 1700XF. The front suspension consists of the anti roll bar which locates through the single top link via Y9 bushes.

 

In board of where the anti roll bar passes through the aluminium bushes are fastened two aluminium clamps (one just inboard of each clamp, each is machined in two halves and clamped using a single bolt - provision has been made for grease nipples but none are fitted and as they are clamped solid to the anti roll bar grease would serve no purpose), these are clamped to the anti roll bar and butted hard up against the Ali bushes. It looks as if they are "designed" to prevent transverse movement of the anti roll bar. Neither Caterham nor Redline could shed any light on what they were or where they had originated from. As a professional Engineer and experienced toolmaker I can say that they have been well made and not something that has been "knocked up". As I have no experience of racing I wondered whether that was where they had originated. Could anybody help? - should I refit them or leave them off? - if they do prevent transverse anti roll bar movement then this will be subjecting the anti roll bar to rapid cycling loads from compression to tension as hard cornering occurs.

[ECR]

I have a 1990 chassis which started life with a X Flow installed. The front anti roll bar on my car was originaly located transversley by jubilee clamps so what you have is a properly engineered solution. Re fit them and keep the abutting faces lightly greased.

[Graham Sewell]

My 1995 xflow only had the aluminium bushes (looked like clamps but allowed movement). There was nothing to prevent lateral movement other than the upper link to the upright.

[stutch]

Thanks lads, as I said the anti roll bar runs through the Ali. bushes which of course prevents the bar from deflecting under compressive loads but allows it to rotate as the top links move up and down. These additional clamps are clamped to the bar itself and prevent the bar from moving transvesely with respect to the axis of the vehicle, that is, they would prevent the bar from sliding through the Ali. bushes but do still allow it to rotate. I can't see any good engineering reason why they should be there - but things are normally done for a reason!. Thanks once again, I'll have a pint and think about it further!.

[Casbar]

I've a 1990 xlow. My roll bar only had the ali blocks fitted. I have now replaced the rollbar and fitted an adj double top wishbone.

[Paul Turner]

When I build my LC LA car in 88 I saw many race cars with jubilee clips on the AR bar to restrict the side to side movement. I asked someone at the factory about this and was told not to fit them as it induced stresses that were not part of the design. In 90 Caterham brought out the double wishbone top link mod that better located the top link and also minimised any sideways movement in the AR bar. Personally I would suggest that you look at fitting this, its an inexpensive but worthwhile mod.

 

Paul

[stutch]

Paul,

 

Thanks, you've confirmed my suspicions and I agree with caterham's comments, the tensile/compressive stresses being cycled through the bar will eventually cause it to fail. Anyone want to beautifully machined Al clamps!........

[John]

So the clamps dont twist with the bar then? Why should they cause it to fail? Nonsense in my opinion.

 

John

[stutch]

John,

 

The clamps do twist with the bar. But, because of their location the bar cannot slide TRANSVERSLY through the bushes hence, under hard cornering the nearside top link could be postioned high with respect to the road and the offside could be positioned low again with respect to the road. Under perfect road conditions there is no problem because each will lie diagonally opposite one another on the radius of the arc described by the movement of the top link. HOWEVER, if hard cornering occurs over rough ground or during hard braking then the two ends of the anti roll bar will no longer be diagonally opposite one another. When this occurs you will induce compressive forces at one end of the bar and tensile forces at the other. These would normally be prevented from building up due to the slight transverse movement of the roll bar through the Al. bushes and the movement available in the tapered Y9 bushes located in the top link. When these clamps are included the forces will build up with no where to go. Hence, the bar will be subjected to cyclic loading and eventually will fail through FATIGUE.

[R2D2]

I must admit I am struggling to see what you mean.

 

The anti-roll bar is basically a torsion spring and only has an influence on the roll stiffness of the car when the bar twists. If both front wheels move up and down together the bar should be free to rotate in the clamps and no stresses are generated.

 

When roll occurs the torque in the bar increases the roll stiffness and the effective spring rate increases.

 

The twist that occurs is generally well within the fatigue endurance limit of the anti-roll bar.

 

It is also true that the early Seven used the anti roll bar as a tie bar and this must produce some other stresses in the bar.

 

If I understand correctly you concern is that by constraining the bar and preventing any lateral slip the stress developed will cause fatigue failure.

 

I would think that the Y9 bush compliance is still quite significant in allowing some flexibility but even if the suspension were rose jointed I would be surprised if the forces generated were sufficient to cause fatigue problems even if the bar couldn't slip.

 

If a couple of Jubilee clamps could stop the side to side movement of the anti roll bar the forces being applied must be relatively small and any stresses developed as result would also be small.