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Discussion Starter · #1 ·
Posting this mainly for my father.

Bought a gravel pup to haul dirt and stuff. Bought a PTO pump, tank, and valve assembly to have it run off a tractor PTO. It drains the tractor if you try to use it's hydraulics.

Anyway, how does the endgate release work? Is it air? Is it hydraulic? I haven't spent too much time on it but if anyone has an idea how it does what it does we'd appreciate it. If it's hydraulic he has a second valve for it all set up, just needs to be assembled.
 

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Discussion Starter · #4 ·
Ours is an elec over air cylinder to trip the lock. Hit an elec switch in the cab and it opens under pressure
When it's locked, is it under pressure? Or unlocked under pressure?

Do most gravel trucks have auxiliary power within the light plug? Is that where the wire would be? Would I apply power to unlock/lock or how would that work?

He did mention that when he hooked the light plug up to the tractor to test it he saw it was unlocked. Soon as he unplugged it, it locked again.
 

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No matter how it is tripped, the law is that it has to be setup in a fail safe manner that the gate is always locked unless it is purposely energized in one form or another manually to open it.

So if it is electric over air, it would then need power to apply pressure and open. Same with a direct air or hydraulic setup. Should be mechanical springs or something that holds it locked.

Most likely the power for the trip is wired on the center terminal or blue wire in the plug, but it is impossible to say for sure as there are many many variations in truck/trailer wiring involving the blue wire. Age and other factors dictate and one needs to investigate exactly what you have and how its wired.
 

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Most of them are connected to an auxiliary brake pod mounted under the box. Its connected to rods that then connect to the clamps on the endgate. Most setups have a spring attached to the linkage so that it will mechanically keep them closed. The brake pod is filled with air from the trailer system using an electric air valve. Most trailers have a separate 6 pin plug in addition to the 7 pin plug. The 6 pin would run the tailgate functions, could drop the air bags while dumping, or other functions. You can just get a glimpse of what i'm talking about in this picture
 

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Most of them are connected to an auxiliary brake pod mounted under the box. Its connected to rods that then connect to the clamps on the endgate. Most setups have a spring attached to the linkage so that it will mechanically keep them closed. The brake pod is filled with air from the trailer system using an electric air valve. Most trailers have a separate 6 pin plug in addition to the 7 pin plug. The 6 pin would run the tailgate functions, could drop the air bags while dumping, or other functions. You can just get a glimpse of what i'm talking about in this picture
Very good explanation , but if I read the OP post right it sounds like they are just going to pull it with a tractor. No use making it overly complex. They should be able to use a small double acting hydraulic cylinder run off the tractor remote to trip the gate. If it is a safety concern then a one way hydraulic cylinder with a spring return to closed should work.
 

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The hyd cylinder would work but if anything gets wedged in the tailgate clamps like small rock from gravel the hyd cylinder would bend stuff where the original air system wouldn't have that much power. I don't know what the best setup is but just be aware of some challenges. My personal opinion would be just pull the bolts off the clamps and let the tailgate free swing. The way the hinges are built to over centre and the weight of the tailgate itself will keep it closed in all the most extreme conditions. You won't be piling dirt at the very back of the trailer anyways, at least not enough to push the tailgate open.
 

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You would think they would install a little more positive fail safe, I've pulled several belly dumps and have often thought how easy it would be to dump by accident, myself and several others have never done it but there is a trucker in the area that accidentally graveled a half mile of the eastbound lanes of the Trans Canada just west of Brooks a few years back...
 

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The old gravel trucks just had a rope on the latch for the tailgate. I think that would work fine for the OP.
 
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