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rear knuckle upper spherical discussion

 
Old 01-20-2019, 01:23 PM
  #401  
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Just a question here ... I am finally getting around to installing the spherical bearing kit in my rear uprights. Earlier in this thread, one post mentions that the bushing is an easy slip fit into the upright, and that the OD of the bushing is 1.495". My bushing is 1.501", and the ID of my rear upright seems to be around 1.498", maybe as low as 1.496" (I measure one side slightly smaller than the other).

Was the design of the bushing changed at some point to be a press fit?

Should I be worried about a possibly .004"-.005" interference fit on a 1.5" OD, steel into cast iron? It seems high to me, what I read on the internets is roughly .001" per inch of diameter...
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Old 01-20-2019, 01:38 PM
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When I do interface fits on bearings at work I typically run .001-.002. Yours should still work but will be tight. I would definitely use heat to get it together
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Old 01-20-2019, 03:01 PM
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.005" is not intereference fit on steel, it's "does not fit". I would take the upright to a machinist and have it reamed to size.
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Originally Posted by codrus View Post
Basically I've come over to the camp of "If something is a reliability problem on the track, just ask Andrew and do what he says".
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Old 01-20-2019, 03:31 PM
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Originally Posted by Savington View Post
.005" is not intereference fit on steel, it's "does not fit". I would take the upright to a machinist and have it reamed to size.
Well, I'm hoping Sean chimes in, I'm curious if he intentionally made a design change that would require a press.

I agree, .005 is no press fit. I'm going to try and hone out the bore of the upright a bit more, I would think it'd be more like 1.498" like the other side.

If it comes to machining stuff, I have a lathe in my garage ... I'm no pro, but I'm sure I can turn a couple thou off the bushing if required.

Thanks for the input,

Mike

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Old 01-20-2019, 11:41 PM
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Speaking straight from my ***, my money is on dimensional variance at the upright. Remember that the OEM is sticking a rubber bushing in there which will easily absorb a 0.005" variance in ID.
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Originally Posted by codrus View Post
Basically I've come over to the camp of "If something is a reliability problem on the track, just ask Andrew and do what he says".
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Old 01-21-2019, 12:15 PM
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Originally Posted by Savington View Post
Speaking straight from my ***, my money is on dimensional variance at the upright. Remember that the OEM is sticking a rubber bushing in there which will easily absorb a 0.005" variance in ID.
You speaking straight from your *** is more reliable than many other sources. :-)

Dimensional variation in the upright is probably some of it. I went back yesterday after zeroing my calipers properly and the upright varies between 1.495" and 1.500" ... it's not round. The bushing is a perfect 1.500".

Earlier in the thread, the bushing was described as being 1.495" ... so I think that changed at some point.

I turned a piece of round stock to 1.492" yesterday and it's a touch too loose. I think 1.495" will be perfect. I'm going to turn a test piece and see before I touch the bushings.

Mike
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Old 01-21-2019, 04:32 PM
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I got this done this morning out in the garage. Turning them down to 1.495" made them a stiff fit partway through by hand, and easy with the vise. I didn't worry about the finish on the OD, I figured it would help the Locktite grab better.

I'm happy with these results.

Thanks for the advice!





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