OP
stoyan79
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4.5 ratio PTO generator gear box
- Thread starter stoyan79
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Raspy
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stoyan,
I wish you'd expand on where the fuel savings come from. I can't see how a "$350. gearbox will pay for itself in no time". Running the engine a little slower will reduce internal friction, but may or may not be a more efficient RPM. Also, you are introducing an additional gearbox with its parasitic losses that could match the lower RPM internal engine friction.
The work being done by the engine, at a given kilowatt load, is equal whether the engine is running slow or fast. Equal horsepower means equal fuel used unless the engine doesn't run as well at one of the two speeds. The ratio of the engine RPM difference does not equal the ratio of the fuel savings, in other words, RPM is not equal to horsepower or savings.
So, what does a large savings mean and where does it come from? Do you have any way of actually measuring the savings from one engine speed to the other with an equal load on the generator?
I wish you'd expand on where the fuel savings come from. I can't see how a "$350. gearbox will pay for itself in no time". Running the engine a little slower will reduce internal friction, but may or may not be a more efficient RPM. Also, you are introducing an additional gearbox with its parasitic losses that could match the lower RPM internal engine friction.
The work being done by the engine, at a given kilowatt load, is equal whether the engine is running slow or fast. Equal horsepower means equal fuel used unless the engine doesn't run as well at one of the two speeds. The ratio of the engine RPM difference does not equal the ratio of the fuel savings, in other words, RPM is not equal to horsepower or savings.
So, what does a large savings mean and where does it come from? Do you have any way of actually measuring the savings from one engine speed to the other with an equal load on the generator?
CalG
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I need some deep pocket to sponsor this study!
I use the 1000 rpm PTO option to drive the chipper shredder instead of the 540 speed option, mostly because the Mistubishi K4F 4 cylinder sounds so much happier at 2000 rpm than it does at 2500. (I still wear hearing protection ;-)
When the load is intermittent, as is the case with a chipper or a gen set. When the load is light, It just "seems" that lower revs would be more economical.
A graph of efficiency verses HP output would be good information for any tractor owner. Seldom do we tax our machines to the maximum for hours on end as is the case with field work.
I think the OP should just purchase a tractor with a selection of PTO output speeds and call it good ;-)
I use the 1000 rpm PTO option to drive the chipper shredder instead of the 540 speed option, mostly because the Mistubishi K4F 4 cylinder sounds so much happier at 2000 rpm than it does at 2500. (I still wear hearing protection ;-)
When the load is intermittent, as is the case with a chipper or a gen set. When the load is light, It just "seems" that lower revs would be more economical.
A graph of efficiency verses HP output would be good information for any tractor owner. Seldom do we tax our machines to the maximum for hours on end as is the case with field work.
I think the OP should just purchase a tractor with a selection of PTO output speeds and call it good ;-)
Raspy
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Or look for some kind of variable speed, constant cycle, inverter generator. Like the modern Honda and Yamaha portable generators are. Then just use the existing PTO output, forget the additional gearbox, and slow the tractor engine to as slow as would still carry the load. Case closed.
