Pelican Parts Forums - RSR style cross brace welded in

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- - RSR style cross brace welded in (http://forums.pelicanparts.com/showthread.php?t=891404)

For those that don't wish to make a permanent modification to their cars by welding brackets onto the tub, can you comment on a second bar, say one that is run from the right hand strut area to a bracket on the tub floor, where the brake booster is located on the later cars?

Would that not eliminate most of the issues with the degree of freedom of the main bar attachment points at the strut tops?

JR

Quote:

Originally Posted by Geronimo '74 (Post 8883655)

7.5€? Typo I think, cheapest I can find are 27.5€

Their pricing is a tad confusing, one strutbar set is cheaper than the other for no obvious reason? I must be missing something.

If you still had them in stock, I'd know where to order. I'm still greatful for that featherweight starter I bought from you. Zero issues and awesome weightsaving!

I am sorry 27.5 Euros is correct - My poor typing late into the evening. :o

Frankly the price they are asking is sensible as if you have 20 pairs cut and folded there is a decent margin at this price.

I will have brackets in about 10 days and would be happy to sell them for the MH Teile price.

Quote:

Originally Posted by chris_seven (Post 8883354)

I don't understand why you couldn't align the car with the brace fitted as it shouldn't have any influence. I have been fitting strut braces to rally cars for more years than I will admit to and never had an issue with aligning the car.

It is important to fit the bars without preload as this will be a potential problem as the forces change and the bar then behaves as a spring and it an cause movement of the towers.

My objection isn't to making the bar adjust so it is easy to fit in a 'neutral' position it is the ability of the heim joint to misalign when the forces applied allow movement. The joint is designed to permit misalignment which is why it seems counter intuitive to use them for this application.

The ability of the bar to resist buckling is more to do with its second moment of area rather than clamping. Resistance to buckling is directly proportional to this property

If you weld a bar of the same diameter as the brace directly between the towers and then apply bending I am sure that the forces generated by the bolts will be great enough to allow the bar to flex in the same manner as if it were welded.

If you increase the diameter of the bar you will certainly reach a point where the bar is so stiff that the joint will fail or move.

I don't think you will see this level of force in any 'real' application but a 2" dia tube welded in place would be very stiff.

I believe the reason was that something was welded in with the car on a lift or with the bar not in place and the end result was that significant preload was necessary to fit the bar. I could not reinstall the bar with the car on the ground- too short I believe.

With all due respect (this wasn't my original point), it seems your post above is contradicting your earlier post? I agree that heim joints < bolts < welding but now you are saying that the bar's diameter is more important than the end condition.

I agree diameter makes a big difference in the second moment of area but the slenderness ratio is still quite high and if we go with the textbook Euler buckling formulas the critical load increases by a factor of 4 when going from a pin-pin connection to a fixed-fixed connection. I suppose this same change does only require a <50% increase in diameter so I can see why you say diameter is more important. Just seems like the end still count for something significant.

My original point was just that the bar's fixing is different in the transvers and horizontal planes. It is not that hard for the ends to rotate around the bolt axes just as a heim joint would. The bar will buckle in that direction even if it is totally restricted in the other planes.

Quote:

Originally Posted by javadog (Post 8883669)

Rennline's strut brace works this way.....

Todd