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Old 05-05-2011, 02:57 PM   #11
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I have never heard of an issue with a pin shear, even in crashes. I have seen instances where the 2" shank has sheared from an impact, trailer balls that have sheared, trailer tongues twisted and wrapped into a new shape, trailer axles pulled from underneath the trailer, but never a sheared pin.
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Old 05-13-2011, 09:57 AM   #12
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Quote:
Originally Posted by prof_fate View Post
1/2 dozen 9/16 grade 8 bolts to hold the hitch to the frame
4 more to hold the ball part of the trailer to the toungue
2 even larger bolts hold the two pieces together that make up the ball and receiver assembly, and mine came with shims to be sure there was no freeplay in there.
a 1" shank ball isn't strong enough, so you gotta get a 1 1/4" shank ball.
And then you gotta bolt this together at hundred of pounds of torque.

The only thing really keeping the trailer attached is a 1/2" pin that isn't torqued in at all, rattles in it's holes and weighs less than one of the bigger nuts.

If the pin is strong enough then everything else seems to be overkill.
The typical bent pin is such a stupid easy part to make, that it would be silly to make them at lower grades. So they probably make them for the largest pull-behind trailers (20,000 lbs?). To make the same geometry pin with a material grade only strong enough for a 10,000 lbs trailer, would drive up inventory costs, probably be a grade with imperfections, and likely only save us $0.25. Of course there is a smaller pin, for use in the 1¼" Class 2 hitches.

As far as the other fasteners in the system being overkill, I disagree.

That bent pin is placed in pure shear. There is no tension or compression loading on that pin. Conversely, the other fasteners you mentioned are threaded joints, place in tention, to produce clamping load. Any steel fastener or pin can take far more shear force than tension.

I remember an axle joint I was working on (at my job), where you had four (4) 3/8" threaded studs holding the brake assy to the axle flange. During some extreme powertrain durability tests (forward/reverse transmission cycling), the drivers could hear the brake slipping thru the axle joint, and "clunking" against the fasteners. The 4-bolt joint was not strong enough to prevent the slippage...tightening the bolts further would break the bolts. But the impact from the holes banging the bolts in shear wasn't even close to damaging them. The noise was the complaint, not damaged bolts. The solution was to increase the bolt size and bolt pattern diameter. Not to protect the bolts from shear, but to allow the bolts to take a higher torque, and prevent the slippage in the first place.
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Old 05-13-2011, 11:42 PM   #13
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This is what happens when you try to pull start a semi :P (NO, IT WAS NOT ME)


So that shows how much strength that the pins have! I cant find the pin picture but it was just slightly bent.

ALSO stay away from the pins that have the little swivel part at the end that is supposed to hold it in. well they dont and we lost a sled trailer once..
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