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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.


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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  #81  
Old 05-16-2014, 10:09 AM
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Will there be wear material/rings/bearings between the spherical part and the inside of the bore/snap ring parts you made? Like a Johnny Joint?



If not, what are the contact surfaces between the spherical and the housing you made? Is it two line contacts, one on either side with one being machined into the housing and one being the c-clip? What is the material of the spherical?
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  #82  
Old 05-16-2014, 10:14 AM
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The bearing is one of these (actually Aurora COM12T's but this is the picture I found quickly):



So it's just a light (0.001") press fit in the bore. No rubbing/sliding involved...I hope.



On edit: This was part of the decision making process on going this route. It moves the weld away from the bore so there shouldn't be any distortion of the bore due to welding, which eliminates a tricky (for me anyway) post-weld machining operation to get the press fit right.

Last edited by Graham08; 05-16-2014 at 10:18 AM.
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  #83  
Old 05-16-2014, 10:18 AM
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Aaaah. I didn't realize you had a complete bearing to go inside of this. I though it was going to form the outer "race".

Carry on with the awesome work!
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  #84  
Old 05-19-2014, 07:49 AM
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Here is the link all finished up:



I need to repeat the process to make a spare. The plan is to have two of everything that bolts to the car so if something happens in hot laps or a heat race we can fix it at the track.

And a mock up on the car:



It's a good thing I did the mock up before I made the bracket that attaches this to the rear end. My original design would have had a big interference problem with the lower crossmember at the main hoop of the cage that would have severely limited droop travel. I got it redesigned last night and ordered steel this morning to make a fixture to build the bracket, which is the only way I can think of to get it right. The mounting point for the Watt's linkage sort of floats out in space relative to the rear end, and it's important to have it accurately located relative to the through bolts that hold the rear end together.
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  #85  
Old 05-19-2014, 09:46 AM
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Why is it two piece with respect to the tubing? Is that due to the redesign or was there something that made it easier to do this way?
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  #86  
Old 05-19-2014, 10:21 AM
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Originally Posted by TheBandit View Post
Why is it two piece with respect to the tubing? Is that due to the redesign or was there something that made it easier to do this way?
You mean the bung in the right side where the rod end is screwed in? If so, it was to get the shank of the rod end aligned with the centerline of the two bearings, so there isn't a bending load on the shank of the rod end. If the link were longer, there would be enough room to have an "S" bend with that section of the tube pointing the right way with a small bung slid into the end of it. Since the link is so short, I made a long bung and cut a notch in the tube to weld it in. I cut as much off the bung as I could to save weight, so the ID is opened up after the required amount of thread, and it's cut at the same angle as the tube.
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  #87  
Old 05-19-2014, 12:51 PM
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Okay I understand. I don't think a bending load on the rod end would hurt anything though since it surely must be stronger in bending than the mating tube (which now open-ended; you may want to consider capping it) and the bending moment reduces as you get closer to the joint. Also the side loads on this are ~half for each link in the Watts compared to a panhard where they all go through one link, so I would think the overall design would be plenty strong with a bent link having the rod end at an angle. Of course I have zero experience with this stuff - just bouncing my thoughts around.
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Last edited by TheBandit; 05-19-2014 at 12:55 PM.
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  #88  
Old 05-19-2014, 12:55 PM
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I'm blown away that you made your own rod end. I like making my own parts, but that is even too much for me.

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  #89  
Old 05-19-2014, 01:06 PM
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I'm blown away that you made your own rod end. I like making my own parts, but that is even too much for me.
Thanks! Not rod end, per se...just an adapter to use a uniball/spherical. I would have gladly bought the piece if Armada made them in the size I wanted.

Bandit,

I think I have a complex about using rod ends in bending from doing Formula SAE when Carroll Smith was a judge. The practice was grounds for public shaming in design competition. Although, I had a pair of rod ends at a slight angle on the one supermodified suspension I did, and it was surprising how easily the stupid things bent. Granted, they weren't the best quality pieces that we were using, but it seemed like they bent if you looked at them funny.

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  #90  
Old 05-19-2014, 02:39 PM
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Originally Posted by Graham08 View Post
Thanks! Not rod end, per se...just an adapter to use a uniball/spherical. I would have gladly bought the piece if Armada made them in the size I wanted.

Bandit,

I think I have a complex about using rod ends in bending from doing Formula SAE when Carroll Smith was a judge. The practice was grounds for public shaming in design competition. Although, I had a pair of rod ends at a slight angle on the one supermodified suspension I did, and it was surprising how easily the stupid things bent. Granted, they weren't the best quality pieces that we were using, but it seemed like they bent if you looked at them funny.

We didn't have a formula team at my school when I was there, but we did have Mini Baja. I did that for three years. I remember seeing some really bad stuff at competitions, like rod ends at 90 degree angles to how they should have been. We hosted one race while I was on the team and I worked in the shop helping make repairs to cars that didn't pass tech. Some of it was awful.

FWIW I have some front control arms on my car where the rod ends are slightly loaded in bending. These are labeled as drag only items and typically used with skinny front tires so they aren't ever expected to take severe side loading.

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  #91  
Old 05-19-2014, 03:12 PM
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The inner pivots on the uppers, right? Those aren't terrible, but you're right that it's best they don't see big lateral loads.

The one the FSAE judges used to love was the lower ball joint as a rod end with the pushrod or spring right next to it, like this one here:



(Bonus points if the LBJ is a the end of its adjustment in an attempt to get negative camber)

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  #92  
Old 05-19-2014, 04:49 PM
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Thanks for the smile Graham! I am traveling this week in Europe for technical design reviews and I have seen one too many avoidable failure for the day. If I see another missed tolerance analysis, stress analysis, requirement or molding failure, I think I am going to pop like MeanMike's GIF above. I spend my days developing electromechanical drug delivery devices, not fabricated suspension parts, so pretty much any time I have a comment, take it as a question because I am just probing so I can learn more. Performance suspension is way more fun to think through that my daily duties.

I guess looking at your link, it doesn't seem like the rod end would be under all that much bending, but admittedly I haven't got a damn clue about the system you're working with and now that I look at it closer, the rod end shank diameter looks like it could be as little as half the diameter of the larger link tube, which could be good reason for keeping it out of bending.
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Last edited by TheBandit; 05-19-2014 at 05:56 PM.
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  #93  
Old 05-19-2014, 08:38 PM
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No worries, Clint. The bent tube part of the link is way oversized for stiffness. It's 1-3/8" OD, the bung is 1" OD, and it's got a 1/2" shank by 7/16" bore rod end screwed into it. Part of the problem is the testing I get involved with at my day job that makes me all too aware of suspension compliance which means I am pretty fanatical about making stiff components.

By comparison, the upper links are 1" x 0.065" wall, but they're straight.

Is your trip to Europe for work?
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  #94  
Old 05-20-2014, 06:24 AM
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Watt's linkage is finished! After I make a spare lower link I'm going to make the stuff it attaches to...
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  #95  
Old 05-21-2014, 01:04 PM
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Thanks for the explanation. Now can you come over and build one of these for my Nova please? :)

Yes I am here for work. Nothing better than a good long technical design review with Italians. Fortunately I had some time over the weekend to play tourist and visit Bologna, Firenze ("Florence"), Pisa and Genova ("Genoa"). I also spent some time in southwestern Austria and the northeastern part of Italy earlier in the trip - driving through the Alps in that area was spectacular. I think this is my fourth trip out here for work, but every trip is something new. I can't wait to get home to my wife and kids though.
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  #96  
Old 05-21-2014, 03:23 PM
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Thanks for the explanation. Now can you come over and build one of these for my Nova please? :)
If it doesn't work for me, I'll have a pair to sell you at a bargain basement price...

I just had a package show up here at the office that's about 12" x 5" x 2" and weighs 33 lb. I have steel to make the fixture for the rear end bracket!
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  #97  
Old 05-27-2014, 06:53 PM
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Originally Posted by Graham08 View Post
The one the FSAE judges used to love was the lower ball joint as a rod end with the pushrod or spring right next to it
I just came across a suspension design like this recently where the LBJ is a rod end, mounted almost exactly as shown. See this post What alternative joint would you recommend for the LBJ? What are you using for your sprint car?
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  #98  
Old 05-28-2014, 07:45 AM
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Originally Posted by TheBandit View Post
I just came across a suspension design like this recently where the LBJ is a rod end, mounted almost exactly as shown. See this post What alternative joint would you recommend for the LBJ? What are you using for your sprint car?
What was always recommended in FSAE was to use a spherical bearing with the housing built into the LCA, which I agree with. Actually, for a road going application, it's hard to beat automotive ball joints, especially with all the low friction options available now from Howe and other suppliers. You lose adjustment at the outboard end with this configuration, but gain stiffness, strength, and reliability.

I hope the pictures in your link are just mockup. It looks like the UCA needs to be longer...the rod end is stuck out a long ways. I use 1.5 diameters as the min engagement for rod ends, and unless that one is unusually long, I don't think there is that much thread into the UCA.

On the sprint car there are no control arms or ball joints because there are two solid axles. On the rear axle I do have a set of "wishbones" that locate the axle longitudinally...and I have rod ends at the front pivot in bending, but the loads are really low because the drive/brake torque is reacted by the torque tube.
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  #99  
Old 05-28-2014, 09:58 AM
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Originally Posted by Graham08 View Post

I hope the pictures in your link are just mockup. It looks like the UCA needs to be longer...the rod end is stuck out a long ways. I use 1.5 diameters as the min engagement for rod ends, and unless that one is unusually long, I don't think there is that much thread into the UCA.
Minor Hijack:
Now that it has been said... the suspension pictured in the above link is poorly designed and executed! Even the welds look like...
End of Hijack.
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  #100  
Old 06-09-2014, 07:58 AM
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I finally got the fixture built for the Watts linkage bracket. The purpose of this is to get all the points in the right relation to each other, so the end of the link is in the right place relative to the center section of the rear end.

Nothing too fancy, just a substantial block of steel with holes drilled and tapped in the right places, with a chunk of flat bar bolted to it that has another strategically placed hole.



The drilled and tapped holes in the block are in the same location as two of the through bolts that hold the center section of the quick change rear end together. The block is about 0.030" wider than the assembled center section to account for weld shrinkage, so hopefully it all fits right when it's done.

Now to actually make the bracket...
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