RSR style cross brace welded in

[tdw28210]

Anyone have any experience with the factory style RSR strut tower braces that weld into the car? I am considering one for my street oriented RSR backdate car. I like the period correct look, but wondering if it is practical for a street car. Thanks.

[Bergo]

most I've seen bolt in solid:

[1ricardo]

Hello,

Where do you found the bracket to buy? Or this is just a photo? I would like to install it on mine as well but I´m having a hard time to find the parts

Thanks

[KTL]

Rennline makes one that has vertical dimple-died brackets welded to the tower and the bar itself is bolt-in removable. Nice piece, just like most everything Rennline makes.

[irl]

I think I got one from Dave at TRE but there are templates on here to make them if you do a search.

[RichardNew]

Are the templates any good?

I've used a brace for a few years and while it worked on the track I'm not sure if it did anything on the street.

I like the RSR look but I also like the look of carpeting. Especially since I'm turning my car back into a street car.

Richard Newton

[bpu699]

These things are always on ebay from germany for $100 plus 20$ shipping...

Thought about installing one too, but wondered if it would be frowned upon at resale time...

[chris_seven]

mh teile on Ebay.de has the brackets for €7.5 for the pair and better than the $100 you sometimes see.

Tangerine 911sells them with a tube that doesn't have the correct end details so looks a bit odd.

We made them for years but are out of stock at the moment.

[javadog]

MKL Domstreben Konsolen Set passend für Porsche 911 RS RSR ST | eBay

Also has a complete kit with the bar included. Search under mh-teile.

[Trackrash]

Here is one I fabbed myself.

I would recommend an adjustable crossbrace.

[chris_seven]

Originally Posted by Trackrash

Here is one I fabbed myself.

I would recommend an adjustable crossbrace.

We keep on having this debate as I don't believe adding a degree of freedom when there is compression or bending applied to the bar works.

The factory used a small diameter tube welded through the main tube but at 90 degrees and bolted the whole thing up solid which is the best way.

The heim joint only works in tension and if you check on hard driven cars the towers generally move inwards.

I agree that the use of adjusters makes them easier to fit but the best way is this type of connection.



I am resigned to the fact that no-one will agree with me but I just have to keep trying.

[Quicksilver]

Originally Posted by chris_seven

. . .

The heim joint only works in tension and if you check on hard driven cars the towers generally move inwards.

. . .

Not sure why you would say that heim joints only work in tension. Like most things they are stronger in compression then tension. Heim joints are rather limited in side loads. (not applicable here) The allowable side loads are listed in the spec sheet for the joint.

Note that all rod end bearing makers will rate the strength of their bearings in an "axial load" which is both compression and tension.

[chris_seven]

The strength of the joint has nothing to do with the issue it is the degree of freedom that limits the ability of the towers to share load.

The side loads you refer to are the loads needed to make the joint fail and they are irrelevant to the argument.

When you apply a compressive load to a long thin strut it will simply buckle (as defined by Euler) and this will allow movement.

If you hinge the ends the column (which is the degree of freedom provided by the heim joint) it will be much less stable than with the ends pinned.

By pinning the ends you effectively halve the effective length of the column and make it much stiffer and capable of transferring more load between the two strut towers.

The compressive loads occur when the car drives over bumps and both wheels load differently.

The presence of the heim joint will allow movement and the compressive load that causes the strut to buckle will allow movement.

If you draw the free body diagrams it becomes obvious.



During cornering on a flat road the bar sees tension and this means that the bar is more stable and the presence of the heim joint has no impact on load transfer.

Pinning the ends of a strut makes it more effective in compression which is the point I was making.

[Charles Freeborn]

I'm having no luck searching for a DIY template. Can anyone share a link?
Thx.

[rwrink]

I used Daves from TRE. Fits well.
Rob

[tdw28210]

So what is the best approach to getting the bar installed and bolted up after the brackets are welded in? A farm jack pushing on both towers? ; )

[Flieger]

Originally Posted by chris_seven

The strength of the joint has nothing to do with the issue it is the degree of freedom that limits the ability of the towers to share load.

The side loads you refer to are the loads needed to make the joint fail and they are irrelevant to the argument.

When you apply a compressive load to a long thin strut it will simply buckle (as defined by Euler) and this will allow movement.

If you hinge the ends the column (which is the degree of freedom provided by the heim joint) it will be much less stable than with the ends pinned.

By pinning the ends you effectively halve the effective length of the column and make it much stiffer and capable of transferring more load between the two strut towers.

The compressive loads occur when the car drives over bumps and both wheels load differently.

The presence of the heim joint will allow movement and the compressive load that causes the strut to buckle will allow movement.

If you draw the free body diagrams it becomes obvious.



During cornering on a flat road the bar sees tension and this means that the bar is more stable and the presence of the heim joint has no impact on load transfer.

Pinning the ends of a strut makes it more effective in compression which is the point I was making.

I had a fixed bar but somehow it came to be that the car couldn't be aligned with the bar in place so I went adjustable.

However, I am not so sure that the factory style will prevent buckling. Certainly in the horizontal plane it will be better, but in the vertical plane I think it is not going to resist buckling much.

The most rigid solution is a large diameter tube welded straight between the towers, as you'd see on full race cars.

[Flieger]

Originally Posted by tdw28210

So what is the best approach to getting the bar installed and bolted up after the brackets are welded in? A farm jack pushing on both towers? ; )

You put the car on the ground, put the brackets on the bar, and weld the brackets on with the bar in place. Then hope that the metal doesn't shrink too much.

[chris_seven]

Originally Posted by Flieger

I had a fixed bar but somehow it came to be that the car couldn't be aligned with the bar in place so I went adjustable.

However, I am not so sure that the factory style will prevent buckling. Certainly in the horizontal plane it will be better, but in the vertical plane I think it is not going to resist buckling much.

The most rigid solution is a large diameter tube welded straight between the towers, as you'd see on full race cars.

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.

[Geronimo '74]

Originally Posted by chris_seven

mh teile on Ebay.de has the brackets for €7.5 for the pair and better than the $100 you sometimes see.



We made them for years but are out of stock at the moment.

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!