Bent rear anti roll bar
Discussion
I have at long last found out why my Griff breaks its rear ARB mounts. The two mounting points are not in line so when it rotates it applies all sorts of bad loads on the mounts.
Anyone have any bright ideas about replacement or straightening the thing? I see Clever Trevor has replacement mounts. Thanks.
Anyone have any bright ideas about replacement or straightening the thing? I see Clever Trevor has replacement mounts. Thanks.
It seems I may not have explained myself properly. The problem is not with the wishbone mounts or the droplinks (the rose jointed droplinks take up all sorts of errors without too much issue). The problem is the chassis mounts of the bar itself. My ARB looks like the exaggerated sketch below:
The ARB mounts are shown in red. You should be able to see that as the bar rotates in use, it will apply a twisting force to the mounts, eventually destroying them. The two mounting points on the bar should be parallel and in the same plane. The questions are how to straighten the bar with sufficient accuracy to fix it and have it stay fixed, and to ask if this is a normal Griff problem.
The ARB mounts are shown in red. You should be able to see that as the bar rotates in use, it will apply a twisting force to the mounts, eventually destroying them. The two mounting points on the bar should be parallel and in the same plane. The questions are how to straighten the bar with sufficient accuracy to fix it and have it stay fixed, and to ask if this is a normal Griff problem.
Straight is exactly how it's supposed to be, and exactly how mine isn't. The bar needs to be straightened somehow, but question is how to accurately get it to be like that... It's a non-standard ARB too - considerably thicker than normal Griffs for some reason, and this will make the fix much harder to implement. I think we know who my "local metal worker" might be 
I'll see what he says.
I'll see what he says.Pictures of what? The car has been in pieces for 13 months now so I have no pictures of it assembled. I remember there being an awful lot of washers to make the mounting plates line up properly but stupidly I didn't take pictures. It's always had a problem with breaking various parts of the ARB mounts on the back - even before I bought it.
You can see the bar is bent by eye (I'll try to capture this as a photo), and if you put a straight edge on it and use feeler gauges you can spot a greater than 1mm deviation in the length of the bush in the two orthogonal axes. If the bar mounts aren't at least approximately straight it can't work properly as designed, no matter how many washers are used, can it? You can't compensate for the twisting motion it imparts to the mounts...
I am wondering if I can fashion some form of spherical bearings to hold the bar on. These will deal with the twisting motion on the mounts. There's little chance of cold bending a 22mm ARB with any accuracy.
You can see the bar is bent by eye (I'll try to capture this as a photo), and if you put a straight edge on it and use feeler gauges you can spot a greater than 1mm deviation in the length of the bush in the two orthogonal axes. If the bar mounts aren't at least approximately straight it can't work properly as designed, no matter how many washers are used, can it? You can't compensate for the twisting motion it imparts to the mounts...
I am wondering if I can fashion some form of spherical bearings to hold the bar on. These will deal with the twisting motion on the mounts. There's little chance of cold bending a 22mm ARB with any accuracy.
You aren't a mechanical engineer are you? or I am not writing this well.
If the mount points of the bar were parallel as they are supposed to the forces would all act in the x-z plane using standard axis definitions of x forward y left z up. Because the bar is incorrectly made forces are applied as rotations around local z too. It is these forces that break mounts. the mounts are quite strong in the directions of correct operation.
or I am not writing this well.If the mount points of the bar were parallel as they are supposed to the forces would all act in the x-z plane using standard axis definitions of x forward y left z up. Because the bar is incorrectly made forces are applied as rotations around local z too. It is these forces that break mounts. the mounts are quite strong in the directions of correct operation.
It's in progress. Willow sports cars are making a replacement. It will be of slightly different design so I can simplify the brackets and make it miss the exhaust more easily.
Both they and I agree there was no way to straighten the original bar and can't see how it could have become bent in the first place unless it was made wrong.
Both they and I agree there was no way to straighten the original bar and can't see how it could have become bent in the first place unless it was made wrong.
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