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Lets see those custom parts v.2017

 
Old Mar 15, 2017, 03:02 PM
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I'm guessing the spring itself as it is compressed has a non-uniform loading on the end faces with peaks around where the coil starts contacting. So the hydraulic perches may accommodate those non-uniform loads.

That is a higher level of uniformity than what I'm fixing though. First step, and the big bending load correction will be keeping the end faces from being forced to non parallel where the hydraulic perch allows the spring to go where its lowest energy state is.
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Old Mar 15, 2017, 04:28 PM
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Originally Posted by kaj View Post
RE says those are just basic spring perches and recommend the hydraulic perches to avoid binding. Am I missing the advantage? Just curious.
It's not really an either/or situation. you would need the regular spring perches to put the hydraulic perches onto. without modification the rear springs on an evo just rest on the body (basically).

I've done the hydraulic perches on an evo. They are very high maintenance, needing rebuilds way too often (the oil will leak out). Wasn't worth the return for me.
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Old Mar 15, 2017, 04:57 PM
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Subscribing to this thread. Yet to make anything for the car (just got it last week) but work in a CNC shop so have some good tools at my disposal.
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Old Mar 15, 2017, 05:21 PM
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Subscribing as well, always looking for more project ideas I'll never get around to doing anyways
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Old Mar 15, 2017, 09:28 PM
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So here's what I'm making to get the spring coaxial with the shaft. Ignore the location of the two silver spacers. I'm going to make the perch basically replace the bigger spacer and do the spherical centering.

Hopefully you can see the purpose here. Also, hopefully you understand the chassis isn't perpendicular with the shock shaft.

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Old Mar 16, 2017, 05:50 AM
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just make sure the rear spherical in the top mount can take that load..
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Old Mar 16, 2017, 06:53 AM
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Yep, I was just thinking the same thing. I also want to model the top plate to run FEA on it to make sure it can exceed worst case loads before I make it. Just looking at compared to other things around, the front spherical is similar in size but carrying around 2X the load. Also the top hat is similar to what I had made for the front of my DSM (Dennis Grant style).
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Old Mar 16, 2017, 08:19 AM
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That top hat wouldn't be hard to make out of steel if you had too.
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Old Mar 16, 2017, 08:33 AM
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I just checked my AST's and rears use a large 18 mm ID spherical to hold the shaft and carry spring loads.
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I would speculate that your bending force doesnt come from top mount but rather from bottom mount as on the 8/9 it is solid rubber bush, and not a spherical as other two bushes in the rear arm.. just a speculation though..
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Old Mar 16, 2017, 09:09 AM
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The DFVs also have an 18mm spherical in the top hat. Maybe the old R/Ts didn't though? But you can see my top hat tilted above, there's definitely a spherical in there. One part you don't see is the is I removed the spring centering pieces that also clamps the bearings and made a flat piece to sit flush with the bottom face.
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Old Mar 16, 2017, 09:30 AM
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yes, I remember ohlins having the spherical in there.. just wasnt sure of its size..

you will be ok for sure.. I would take a bit of care and tighten the lower shock mount when the car is on the ground.. might lessen the bending on the shock that is exerted by the relatively solid bottom bush..
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Old Mar 16, 2017, 09:33 AM
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I thought about that load too, I've always tightened with the car in the air and wondered through the full range of stroke, how much extra load is put on it or does it eventually slip. I think that stiction is something I'm going to add to my list of next projects.

I can probably just pull my stock arms and add the spherical via probably an insert rather than cutting material from the stock arms. Though I wouldn't mind just getting or making something more adjustable than the stock eccentric setup.
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Old Mar 16, 2017, 09:42 AM
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Making an adjustable lower arm would be pretty easy. Uniball/Spherical bearings at the outer pivot and shock mount, and a double sided adjuster on the inside.
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Old Mar 16, 2017, 10:10 AM
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I would need to go to the workshop and measure to be sure but I think you can just push out the stock bushing and make a sleeve for the stock end spherical and use that, as the shock bushing is larger dia. ... those end sphericals are nice and sealed and I am always shocked when I see people changing them with poly bushes..

My car is in pieces right now and I have all the new Ralliart bushes on the table so can check quickly...

I did make my own rear track arms, but I think the lower arm is the last on the list that should be done, we never had trouble adjusting that one.. Upper one is interesting for development as it also has firm bushes.. Also, rally R4 specification has different upper arm..

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Old Mar 16, 2017, 12:29 PM
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Now I get it. Gimme some!
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