Author Topic: Spring perch sag correction  (Read 4087 times)

Offline chicomecha

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Spring perch sag correction
« on: March 17, 2008, 09:13:24 AM »
When I put new springs on my straight axle Toyota, I found the front driver's perch to be fatigued and sagging due to a weak perch design with no gusseting combined with flat springs that reverse arch when old.  I put on the new springs on the old perch, and the new spring reverse arched the bottom leaf.  Must correct somehow.  I guess most people cut off the old perch and weld on a new one, but that sounded like a lot of work.  Some just say to heat it up and wail on it with a BFH, but I didn't like that idea, as you could not tell what other damage might happen in that process.  So I made a tool/perch puller out of an old perch, and it puts no stress on the existing axle tube or perch weld, and just straightens the perch.

It is a two piece tool, and you can just use the old set of U-bolts.  I figured if U-bolts were strong enough to bend it downwards, they were plenty strong to bend it back up.

That goes together like this

And is used like this:

Notice that there are two shorter u-bolts used as spacers to make sure the puller is pulling out on the ends of the perch, as well as a 1"x1" tube with some spacers to keep the channel iron from collapsing under the stress.  You also need the bottom leaf out of your old spring pack (or any thick steel spacer) to get the right fit.

My experience was that you need to pull it just past flat, and then when you weld in the gussets, the heat from welding will cause it to pull back slightly, making it dead flat.  Don't forget to weld in some gussets, or you will be right back sagging again.

If you are around Chico and want to try this, you can borrow the tool.
« Last Edit: March 17, 2008, 09:31:40 AM by chicomecha »
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Offline Wilson

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Re: Spring perch sag correction
« Reply #1 on: April 29, 2008, 04:28:56 AM »
Interesting, although i can't say i've ever noticed the stock perch being crushed on the handful of those I've done.  Did you gusset it to keep from happening again?  Seems like the metal would already be fatigued and would just bend again if not remedied.

Offline chicomecha

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Re: Spring perch sag correction
« Reply #2 on: April 29, 2008, 06:03:56 AM »
Did you gusset it to keep from happening again?
Yep.
The internet is full of sagging spring perch woes, but not too many solutions.  Old Man Emu hd told me to watch for it, and I thought, nah, not me.  then I looked at the spring after I installed it on the unreinforced perch.  Yikes!
"If you're lucky enough to be in the mountains, you're lucky enough."
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Offline Onkover

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Re: Spring perch sag correction
« Reply #3 on: March 26, 2009, 05:20:30 PM »
Interesting fix. Very inventive. I hope you get the longevity your looking for. If not then cuting and putting on a new perch isn't that big of a job.
In the effort for world peace I have given up killing people.