Gasoline air compressor. Need ideas.

[Tony Hanna]

I've got an old Craftsman horizontal air compressor sitting here with a bad electric motor. I'm seriously considering mounting a 5hp briggs gas engine on it, but I need some ideas on how to design a rig to disengage the belt and throttle the engine down at around 120 psi. For now, I think I'm just going to extend the wire from the points to the coil and run it through the compressor's pressure switch to shut the engine down once the max pressure is reached. I dont see this being a good permanent solution though. Ideally I'd like to do something that will manage the pressure automatically without having to restart the engine each time.
Any ideas would be appreciated.
Tony

[Jasmeleg08]

What about instead of shutting the motor off you would have some kind of bypass valve so when you reach 120psi or so it would open thus diverting the air from the pump to the atmosphere? You could just run the motor at part throttle all the time but when you wanted crank it up.

[Tony Hanna]

Hmm. I think it may already have a popoff valve on it. I wonder what it's rated at?

[mboyek]

centrifugal clutch + throttle governor rigged to run off air pressure, tuned to throttle down at certain psi slow enough to disengage clutch.

maybe for the governor use swingvalve type actuators to cut throttle/give at certain psi?

the pop-off safety valves don't tend to reset themselves until the pressure drops allot. (put ear plugs in, get 100 psi in the tank and pull the valve, the spring will not seat the valve again until the tank is almost empty, unless you manually re-set the valve. I think its a bad way to regulate the pressure.)

I'm sure in the long run it will be cheaper to buy a new/ used electronic motor, but its still fun to piddle around!

[cordes]

With the current cost of gas, you would pay for the electric motor in no time.

[mboyek]

Thinking about this: performance diesel wastegate/swing valve actuator with a bleed of some sort rigged to cut throttle (push closed) at high psi (regular ones seem to work at 30 some psi with stock springs, a after market can may hold allot of pressure).

when the pressure drops, the spring takes over and pulls the actuator arm back in, increasing throttle, theoretically engaging the centrifugal clutch and upping the air pressure.

if you balance it right, it sounds like it would work (in my mind).

[phaxtris]

you would use what is called an unloader valve, basicly a bypass when tank pressure is reached

[Tony Hanna]

Thanks for the tips guys. I think alot of the pre built gasoline compressors are using an air pressure regulated throttle. Maybe I can just source the replacement parts for one of those and go from there. The trick is going to be finding some sort of cintrifugal clutch with the right pulley on it. The pulley on the compressor head takes a ribbed belt that looks alot like a TM alternator belt...

Along another line of thought, TSC sells pressure regulator valves that work along the same lines as our G-valve boost controllers but are quite a bit larger. I'll have to look into one of those as a possibility. While not the most efficient way to go, I bet it's gong to be the cheapest and easiest to work with.