Wallowed spring perch holes

RatLabGuy

RatLabGuy

You look like a monkey and smell like one too
Joined
May 18, 2005
Location
Churchville, MD
So... aparently during the last ECORS race one of my u-bolts came prety loose, in the meantime the hold in the top of the perch got good and walowed out. A little on the other side too.

important lesson - always check your u-bolt tension!

now i know the *right* thing to do would be to cut off the perches ocmpletely and weld on some new ones, esp since I need to re-angle them for my pinion angle. But what a PITA for a backyyard guy like me.

What other options are there to fix this? I have a few ideas...
1 - weld in a bunch of new material, esenetially fill in the hole, then re-drill it out. I could see that re-drilling being a real pain though.
2 - get some 1/4" plate the szie of the perch, dril a hole it in, weld that on top of the perch. Essentially make a new "top" for the perch.
3 - Since I need to use shims anyway, just weld the shims to the perch, covering the old hole. Boy that woudl make lining up the axle/u-bolt/springs alot easier, but then the dergee of the shim is permanently in there. But, does that really matter?
 
Here's what I'd do.
I think the bolts on the spring pack are ~5/16 ish.. Id replace that with a similar grade 8 (find thread) bolt. I'd grind some of the hex edges off some.. This should produce a pin with a larger head than the stock style but still grade 8.
Drill the hole out the the larger size needed for the new pin/bolt.
If its to egged out. either fill it in and reweld or weld on a washer (temp) to keep your bit aligned properly.
 
side note - need new shims anyway, the shitty aluminum ones actualyy flattened out w/ the movemnt.
Takingrefs for a place to get 6 deg STEEL shims for Toy perches.
 
The flattening of the aluminum prob caused the u bolt to loosen. I would vote for new perches and eliminate the shims. I know you are prob a better fabricator than I am and I did my yj that way last summer.
 
New perches.

I am one to build everything and buy nothing, if at all possible. In this circumstance, even I would opt to buy some perches for $30 and weld them on. Fix your wallowed holes, and get rid of the band-aid shims which caused your problems in the first place.

my $0.02
 
Cost isn't the problem, in the end purchasing shims ~ = purchasing perches.
it's more the PITA of cutting off the old ones (no cutting torch), cleaning it up and then re-welding the new ones. Welding is no big deal, I'm just thinking of the pain of getting the new ones in just the right position/degree. Seems alot more room to introduce new errors.

after thinking about it - in the end, how is welding on shims on top of the original perches different from moving the current ones? Aside from the minor change in height of course, that's about 1/2".
 
RatLabGuy said:
it's more the PITA of cutting off the old ones (no cutting torch), cleaning it up and then re-welding the new ones. Welding is no big deal, I'm just thinking of the pain of getting the new ones in just the right position/degree. Seems alot more room to introduce new errors.
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Shouldn't take more than 20 minutes or so to get both perches off with a grinder and a BFH, it is what I use.

As far as setting the new ones

set full weight oftruck down on perches(not yet welded to axle tubes). use jack on pinion to set new pinion angle. measure from backing plates to make sure you're close to center, then weld away.
 
I got some steel shims for my axle years ago and never looked back. I heard too many bad stories about them. Might want to look into getting some of those.

As for the fix... I'd plate the top of them with 3/8" plate (that's plenty - most perches aren't that thick) and then put everything back together. I'd also get new U-bolts and nuts.
 
yep....I do all my cutting with a cut off wheel and a sawzaw...It's not that bad
 
So can anybody please explain how/why moving the perches (re-angling them) is different from welding shims to the top of the existing ones? Correct/matching size of course. Only difference I see is the very slight height and caster, which are fractions of an inch and irrelevant for the rear...?
 
It just seems counter productive to go through all the work to pull axle then do a half arse fix like welding shims on your perches. Yes it will work but it is not the corect fix.

For an extra $4 (the price of two 1/8" cutting wheels for a 4 1/2" grinder) and a an extra 10 minutes of work you can have new perches and set your pinion angle properly. I say if you are running your rig in races like ECORS then why would you want to cut corners?
 
RatLabGuy said:
So can anybody please explain how/why moving the perches (re-angling them) is different from welding shims to the top of the existing ones? Correct/matching size of course. Only difference I see is the very slight height and caster, which are fractions of an inch and irrelevant for the rear...?
Click to expand...

there is no difference. it's the same set up you have now. you're just welding them on instead of using pressure and a centering pin.
 
Just do it right - cut & turn the knuckles..
 
awspence said:
I am one to build everything and buy nothing, if at all possible. In this circumstance, even I would opt to buy some perches for $30 and weld them on.
Click to expand...

jds97Wrangler said:
It just seems counter productive to go through all the work to pull axle then do a half arse fix like welding shims on your perches. Yes it will work but it is not the corect fix.
Click to expand...
Rich said:
Just do it right - cut & turn the knuckles..
Click to expand...

OK so can somebody please explain why new perches are the "right' fix? I mean mechanically what is the difference?
Old perch with re-angled top ~= new perch at new angle... right? So what is so wrong with that solution? We are talking 6 deg here, small.
I'm not trying to be an ass, this has piqued my curiosity. I'm trying understand the logic.

awspence said:
As far as setting the new ones
set full weight oftruck down on perches(not yet welded to axle tubes). use jack on pinion to set new pinion angle. measure from backing plates to make sure you're close to center, then weld away.
Click to expand...

At the same time I'm rpelacing the springs (with the same ones I have - one is bent and they sag) and U-bolt flip kit.
Since the new springs (Pro Comp 33311) are notorious for being tall and stiff at first, (like 5-6" instead of the target 4) until broken in, it seems that the pinion angle when first setting up like this will be too steep for what it really needs to be later... yes? No?
Part of my inclination for the shim approach is that I know what angle works already.
 
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