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PTO Horsepower and Generator Question
Doc, I am just a humble retired civil servant.... I just marry well  Only kiddin'
I happen to like the PTO option, it is the best solution $ for $ but for the fact that I NEED to be home to operate it. It also doesn't do you a cent of good if you're skiing in Colorado and the power goes out and your pipes freeze or the T=storm floods your basement and there's no juice to power the sump. I think if a PTO gen is your choice it would be wise to have one dependable neighbor/relative who can set it up to run a couple of hours aday to avoid the problems I mentioned.
It doesn't really bother me THAT much about running the tractor. After all I use my 45K Diesel pickup to power an 800/1600 watt power inverter.
I have shown my wife how to hook up the inverter to her conversion van so that would power a light, tv, radio, fan or small sump pump until I suppose I could get home to start a PTO generator running. I left the inverter available with an extension cord and she knows where it is at.
Hmm, why does she need to do that when the van has ac, a bed, a tv/vcr, video game hookups? Just stay in the van
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PTO Horsepower and Generator Question
Chief, the formula that you have is good, but for PTO driven generators it is probably better to use 2 PTO horsepower for a KW of power produced. So, a 30HP tractor would be good for 15KW of power.
There are a few reasons for this but one of the biggest is that there is a drive train to go from 540 RPM to 3600 RPM for the generator. The efficiency varies depending on whether this drivetrain is belt or gear, but there are losses. All of these losses multiply together, so generator conversion efficiency, drivetrain efficiency, and so forth get you into the 60% neighborhood.
You also need some reserve engine capacity, or the system will crash faster than a NE power grid if a heavy load comes on line. If you exceed the tractor HP capacity, the generator will place an extraordinary load on the motor causing it to slow down. This causes the frequency to drop which in turn causes motors and transformers to draw more amperes and make more heat. All it takes is for a refrigerator to start or the well pump to kick in. In most cases, the high current load will kick out the generator circuit breaker or in some designs, the magnetic field in the generator collapses and it simply no longer generates power until the load is removed.
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PTO Horsepower and Generator Question
Murf's right on the power of a hydro. I haven't tried to have my dyno hooked to a tractor yet that is hydro with someone riding on it looking for more power loss. I like two horsepower per KW and I mean PTO not engine.
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PTO Horsepower and Generator Question
F-350, there were many people here doing just that. sleeping in their motor homes campers etc that had generators. Maybe I should order that pto option for the allison tanny on that over priced truck of mine. It outa drive enough Kw to power a few homes ! No joke the owners manual talks about that as an option !
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PTO Horsepower and Generator Question
Truck PTOs don't deliver anywhere near the engine HP. They are just intended to operate a few hydraulics, winches or lifts.
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PTO Horsepower and Generator Question
Me and the Chief were discussing that with the truck PTOs before the blackout. Someone wrote that they done't have too much output 15-25hp? Seems like a waste of a big motor
Do you know what the chevy one would be rated at? I am curious.
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PTO Horsepower and Generator Question
I had no idea that was the case. I was really just being facetious.
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PTO Horsepower and Generator Question
The link below is the best pic I have of an axial flow pump, which is a type I that think is commonly used for HST's. The swash plate is rotated by the input shaft and pulls pistons in the cylinder block in and out. The pump pictured has a fixed displacement. Variable displacement ones have a control that controls tilt of the swash plate. The plate spins all the time, but if the plate is perpendicular to the cylinder block then the pistons don't move and there will be no flow or pressure; that is unless there's something I haven't grasped yet. My impression is that the speed pedal controls tilt of the swash plate.
Here's where I am perplexed. If the pump works the way I've thought it does for quite awhile now I can't see any reason why it would develop circulation or pressure when in neutral. On the other hand, I also can't understand why a spinning swash plate would sop up much HP. The power loss from gears to HST would make more sense to me if the pump were doing something. Don't know! Another impression of mine is that the pto input shafts are pretty much separate from the pump.
Full of impressions today but then I'm just a gear head myself.
Link:
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PTO Horsepower and Generator Question
Tom, you were heading down the right track until you got to "My impression is that the speed pedal controls tilt of the swash plate.". This is where you made a wrong turn friend. As I mentioned earlier (maybe not clearly enough), and Mark H. re-iterated, the foot pedal on a hydrostatically driven unit is merely operating a valve which directs the flow of hydraulic fluid. It has nothing to do with swash plate dynamics, that is self-controlled based on input from sensors & valves, etc.
The variable rate pump, BTW, is only required so that you can have a wide range of functions served by one pump instead of several. For low motor speed applications, like loader work, you need maximum PSI, but not as much in the way of flow, as you do for high motor speed applications, like road speed travel, where you need an immense amount of flow, but not at as a high a pressure.
The best example I can think of to help visualize the need for a variable pump is in a log-splitter, you want the cylinder to travel as fast as possible 'unloaded' (on the return stroke and the down stroke before it contacts the wood) to mimimize the wait times, but then you want it to develop maximum power and reduce speed in order to actually split the wood.
Clear as mud, huh?
Best of luck.
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PTO Horsepower and Generator Question
Speaking of wood splitters I have the big bosses permission to buy a free standing log splitter next week end for a aniversary presant. Now I just gotta find one I like. Life is good
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08-18-2003, 10:28 
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