Allis Chalmers B hydraulic pump

[RodNH]

You've said "the pulley locks up" and "the pump stalls out". I take this to mean the pump pulley actually stops turning in both cases. If that is true, your problem is related to the drive arrangement itself. The pump pulley should NEVER stop turning while the engine is running. If it does, one or more of the drive belts is too loose or one of the pulleys involved between crank and pump is too small a radius or there is insufficient wrap of the belt around a pulley to transmit the required power for the pump, even with a tight belt(s).

It seems you are using a double pulley on the alternator as the drive pulley for the pump. In other words, there is a crank to alt belt and a different alt to pump belt. Yes, of course both of these belts must be tight if that is the case. Even then, if you have insufficient wrap around any pulley, you still may not be able to properly drive the pump.

I'm assuming here that all the pulley grooves properly match with the belt cross sections that you are using. The crank pulley on an AC-B uses a "B" section belt, as does the original generator used on a B. A "5L" section belt would also work on a B. Automotive alternators as well as power steering pumps would not have pulleys that use either a "B" or "5L" section belt. Make sure all your belt cross sections and pulley groves match up correctly.

If the pump is capable of producing 1000 psig, and it should be, you should be able to get that with the proper drive arrangement.

 

[dcwatson84]

Yea that makes sense. If the belt slips then I should be able to correct that by moving the pullies. I.e. the tractor *should* always be able to produce the necessary torque to turn the pulley, as long as the tension on the belt can transfer it.

Im going to play around with the pump/alternator arrangement sometime tonight or tomorrow and see if I can get a higher PSI out of the pump.

Does anyone think that the RPMs of the engine will affect this at all? Ie the pump is probably designed to work in the rpm range of an automobile (> 2000 I would guess) And I doubt my tractor's engine is turning over that fast, even at full throttle. How will that affect the operation of the pump?

 

[J_J]

Rpm determines volume and does not affect pressure that much.

The resistance to the flow is what develops the pressure, and of course the pumps ability to develop potential pressure.

 

[dcwatson84]

Ah I see. So fewer RPMs may make the pump operate *slower* but shouldnt affect the amount of work it can do. That actually makes perfect sense. The power - ie torque translates into the pressure it can produce, and the speed ie RPMS translates into the flow it can produce. Im sure there are probably some other factors and complications, but in general that relationship seems to make perfect sense.

 

[olde man]

if you create more flow you create the need for more hp which will make your belt slip some more. rule of thumb is 1 hp per for each gpm at 1500 psi. I'm not saying your tractor doesn't have enough hp i'm saying (assuming this is an add on) that there is something up with the pulley diameters (driving the pump faster than the belts can handle) or maybe it's simply that using a remotely driven power source(the alternator) is giving you too much of an energy loss across the belts, you did make an improvement when you tightened the belt decreasing energy loss. lots of guessing but still some stuff to think about.