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  #1  
Old February 25th, 2014, 22:31
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yossarian19 yossarian19 is offline
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Fun with Wolfram Alpha and Leaf Center Pins

Right. So I'm building a bastard pack. OEM center pins have a 1/2" head & 5/16" body.
5/16" allen bolts, though, have a head from 0.457" to 0.469". This sounds like nothing, but I was concerned because, y'know, neurosis. I wanted to avoid thrust angle issues (drive wheels out of alignment, steering the car form the rear)
The worst case scenario is you have one center pin mashed all the way forward in the hole & the other all the way back with bottom-of-spec allen heads. So if I'm picturing this right, you can double the difference between that .50 center pin & the .457" allen head, getting .043", for a total of .086" (one screw back, one screw forward) misalignment over ~4 foot (actually 43.5"), serving up a maximum thrust angle of 0.11* - or .01* past the rule of thumb spec of 0* +- 0.1*
So... worst case scenario using 5/16 allen screws... you're still just fine. Maybe some accelerated tire wear. If your axle is moving enough to be worried about shear... your axle is moving too much.
Also... Wolfram Alpha. It's pretty cool. Like Google but nerdier.
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Old February 26th, 2014, 02:55
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Re: Fun with Wolfram Alpha and Leaf Center Pins

Drill them out for a bigger socket cap bolt.

Drill out perch for bigger head.

Problem solved with multiple benefits.
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Old February 26th, 2014, 13:35
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Re: Fun with Wolfram Alpha and Leaf Center Pins

Quote:
Originally Posted by MoparManiac View Post
Drill them out for a bigger socket cap bolt
Take Moparmaniac's advice and drill the leaves to 3/8" hole and drill the perch to fit the larger cap head. Then you will know it is done right.

A carbide concrete drill works well in opening up the center holes. A leaf spring's hardened steel can dull a HS steel drill quickly.
If you don't have the right allen-head cap screw, use the poor man's lathe.
Chuck a hex-head bolt up in a 1/2" battery drill and, using a bench grinder, grind the head to a round shape and fit to the perch hole. Spin the bolt in the opposite direction as the grinder's wheel rotation for best control and results.
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Old February 27th, 2014, 08:48
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Fun with Wolfram Alpha and Leaf Center Pins

0.043 is your head diameter difference. Starting from an assumed centered position, one will move forward by half that (radius difference) and one will move rearward by half. Total misalignment of 0.043.

Actual worst case scenario is breaking a center pin. We duct taped his axle in place after cranking down the ubolts. I'm pretty sure he made it home.
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Old February 27th, 2014, 12:31
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Re: Fun with Wolfram Alpha and Leaf Center Pins

Yep, sure enough I goofed.
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  #6  
Old February 27th, 2014, 12:33
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Re: Fun with Wolfram Alpha and Leaf Center Pins

I just carry spare center pins. end of story. Ive replaced center pins before on the trail. its not that bad.
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Old February 28th, 2014, 09:07
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Re: Fun with Wolfram Alpha and Leaf Center Pins

I drilled out my springs and perch for a larger Allen head bolt and used a grade 8 bolt. I used a carbide burr to "drill" out the springs.
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