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Race Car Fabrication There is a lot of cool fabriaction going on the race car industry, show us what you got.

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  #1  
Old 03-04-2014, 02:47 PM
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Spherical bearings

I'm designing an upper mount for a coil over which has a 0.5" threaded rod on the top of the shock. My thought is to use a spherical bearing at the top of the shock tower, and found some interesting candidates, including this one from QA1:



Here's my question: According to the manufacturer I just cut a hole in the top plate of the shock tower and weld in the housing, and then install the bearing. Any suggestions how to not warp the housing during welding, yet still get a strong weld, since the suspension is going to be banging on this connection all the time?
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Old 03-04-2014, 03:02 PM
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What kind of shock tower are we taking about? Tube or sheet metal? Do you have a photo? Was this previously a strut mount?
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Old 03-04-2014, 03:06 PM
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The shock tower is a 4.5" diameter tube of .120 wall steel that I am fabricating and will be tied in to my cage. The car originally came with shocks and separate springs in the rear, and I'm converting it to coilovers.

Or is there a better bolt-on application? I can't find any bolt-on versions for less than $200, so thought I'd take a swing at making my own since the bearings are only $10-30.
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Old 03-04-2014, 03:26 PM
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You might try pressing a brass or aluminum puck into the housing to try to help hold its shape while you're welding, but I suspect it's still going to shrink when you weld.

I would be concerned about the details of the design so you're not putting the weld in tension. Welds in tension are generally not a good thing. Depending on how thick your top plate is (hopefully 1/4" or so), I would suggest making the through hole the same as the ID of your spherical bearing housing, and press the housing into a shallow counterbore (about half the plate thickness) on the bottom of the plate so there is a mechanical hold on the housing in addition to your weld.

Then you could use 3-4 short welds (preferably with a TIG to minimize heat input) to retain the spherical housing.

I'm fighting the same sort of issue with a fabricated assembly on my sprint car project and have resigned myself to boring the parts undersize to start and final boring after all the welding is completed.

On edit: Another thing to keep in mind is the thrust rating of your spherical. In a lot of cases, the allowable thrust load on a spherical is pretty low compared to the radial load.
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Old 03-04-2014, 03:29 PM
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Very good points. I don't suppose you've come across a monoball housing with flanges for bolting on to the top plate?
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Old 03-04-2014, 03:45 PM
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I haven't ever seen such a creature. If you were going to that kind of trouble, would it make sense just to machine a top plate with a bore for the spherical as an integral part?
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Old 03-04-2014, 03:50 PM
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Why not use a female threaded rod end on your coilover and put a simple set of flanges on the chassis?

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Old 03-04-2014, 04:01 PM
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Quote:
Originally Posted by TheBandit View Post
Why not use a female threaded rod end on your coilover and put a simple set of flanges on the chassis?

THIS!
However take into account that you are building an overhung-lever that the stud may not be rated for.
Next question would be to mount it as it was designed but replace the typical Poly or rubber bush with a Delrin puck?
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Old 03-04-2014, 04:10 PM
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Quote:
Originally Posted by TheBandit View Post
Why not use a female threaded rod end on your coilover and put a simple set of flanges on the chassis?

There you go. Simplest (and best IMO) solution yet. At that point, couldn't you do away with the pocket altogether?

Last edited by Graham08; 03-04-2014 at 04:13 PM.
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Old 03-04-2014, 04:13 PM
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I feel like I'm going in circles . That is what I have, a shock with a rod-end at the top. I was originally going to attach the shock to a mount directly to my cage, but did not want water coming in through the gaping hole in the rear wheel well. Here is what a friend did:


He built a can out of 4.5" x .120 wall tube on top of the rear wheel well, tied the can in to the cage, and mounted a spherical bearing on the top plate of the can. I know an adapter is available to convert my rod-end to a threaded rod, and I was thinking of copying my friend's idea. I should mention that this is for a front-engine, rear-drive car that only weighs about 2300 lb.

I'd love to use the rod end directly to my cage, but can't figure an easy way to keep it water-tight.
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Old 03-04-2014, 04:25 PM
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Quote:
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Will your shock project through the Wheel Well that far?
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Old 03-04-2014, 04:32 PM
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If water is the concern, could you use a cover to go over the top of the shock/rod end? Or if the top of the rod end can be positioned below the top of the 4.5" tube end, perhaps you canmake a simple plate.

Basic concepts in attached MS Paint design. The one on the left is similar to how my Nova's shocks are mounted except there is no access from the top at all.
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Last edited by TheBandit; 03-04-2014 at 04:37 PM.
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  #13  
Old 03-04-2014, 04:48 PM
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The coilovers do project above the wheel well, and I was originally thinking of mounting them cage something like this:


The problem is keeping water out with this setup. If I mounted to the cage directly I'd delete the heavy can entirely, and maybe make some surround out of aluminum. Or, is there some kind of neoprene rubber grommet thingy I that could surround the shock body and keep water out right at the base of hole where the shock protrudes?

Last edited by idickers; 03-04-2014 at 04:51 PM.
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Old 03-04-2014, 04:54 PM
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I would mount the shock the best way which would be on two tabs off the cage.
I would then form 1/16"-Thick flanges that I would weld to the cage tube to mount an enclosure to.
I would form Alum sheet so that it can be attached to the wheel well and the flanges using Sillycone sealer and pop rivets (if the shock bolt can be removed).
If the shock can't be removed then I would do the above with an access panel or two...
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Last edited by entropy; 03-04-2014 at 05:58 PM. Reason: phatphinkerzd
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  #15  
Old 03-04-2014, 05:04 PM
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You know, this is what I was originally thinking about, but I got side-tracked into thinking the spherical bearing would be easier. I think you've convinced me to take another look at attaching the coilover to the cage again!

In science, this would be called "successive approximation". I'll just call it what it is, "waffling". What a great site this is, thanks for all the suggestions!
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Old 03-04-2014, 05:10 PM
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Successive approximation, that is funny right there.
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Old 03-04-2014, 05:24 PM
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My first question would be..do you have machining capabilities?

I had the part your talking about on my 67 nova strut front end 20 yrs ago.

Weld the bung to a plate, re-machine the bung,(like Graham suggested) bolt the plate on so you can adjust camber ,etc.(or not if its the rear)
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Old 03-04-2014, 06:00 PM
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I've got friends with machining capability that will do me favors
Or, I could use this mount, which I already have.
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Old 03-04-2014, 06:03 PM
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Pics would help.

I thought you already had the tube/tower type of thing.
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Old 03-04-2014, 06:09 PM
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Sorry about that. Look up in post #10, which shows my friend's race car with similar rear wheel wells. To get more shock travel for better suspension compliance, he raised the upper mounting point about 5" in those steel cans he welded to the top of his wheel wells. This is about the same space that the back end of my cage will be occupying, so I thought I'd mount direct to the cage. Which then led to the concern about water and exhaust getting into the trunk, which led to the waffling about using the spherical bearing in an enclosed structure. But I think Graham and Entropy have convinced me to revisit the cage mount, since that would make the suspension independent of the rear wheel well, and thus avoid those heavy cans.
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