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PTO Horsepower and Generator Question
Chief-Seems no one knows the answer for sure, so I am going to throw in my 2 cents. Like you I am guessing the hydraulic pump is always running and always pumping and always maintaining a given pressure. If the tractor is not moving, the oil is simply moving thru a bypass. When you move the pedal, the oil is diverted thru a different path to turn the wheels forward or backward. Since the pump is maintaining a given pressure, the engine load would be the same with the tractor moving or sitting still. ????
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PTO Horsepower and Generator Question
Gosh Harvey, I have a 45k truck just like several of the other guys here. The last I checked Thats regrettably what a HD diesel costs theese days. I too like to save a buck on a filter and $ on gas. Heck I even use that synthetic stuff only the rich folks use.  . I hope that doesn't make me a whiner, If it does someone send me a hanky please. I think maybe we all need to realize there is simply NO definative right or wrong. Its just not that simple. Whos to say F-350 is wrong, Heck I bet the last time he checked his wallet it was his name on the pay check ! And whos to say Harveys wrong even with the side tracked venting ? I would like to learn more about the PTO generators as I THINK they MIGHT just suit my needs right down to the ground. But then I'll have to add a flame retardent suit to the cost to get the info I need here  NT has a stand alone Diesel Genset at around $2800 for a yanmar Diesel. The JD PTO is about 1/2 that cost and I already have the tractor. I have a 7500 Kw Generac with 25 Hours on it if anyone wants a deal on a gas one. I am switching to diesel. PTO or stand alone. That is the Question.
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PTO Horsepower and Generator Question
Good response and it does point to an assumption I made. We might get to a more general understanding of HST's here if that's interesting. I think most HST's use variable displacement axial flow pumps or motors. They can be of swash-plate or other design.
My assumption is that most HST's use a variable displacement pump rather and a fixed displacement motor but it is an assumption. A swash-plate type axial flow pump doesn't move oil or develop pressure in neutral because the pistons don't move. Of course, that wouldn't be true if it's the motor that's variable. There are other types of variable displacement pumps often used in closed center hydraulic systems that do maintain pressure.
I think I've heard of some HST's that use variable displacement designs for both the pump and motor. In that case one of them becomes the range selector.
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PTO Horsepower and Generator Question
Tom, I just want to make sure I understand your point completely. Are you saying that with a variable hydro pump the trans would be working the entire time a pto driven implement was run ? If so I want to understand that just for my own info. If that is the case I would think for many that would be a very large point against a hydro that I have never seen mentioned before and it is something I for one would take in to serious consideration on my next purchase.
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PTO Horsepower and Generator Question
Historically I have only really run gear units, for technical reasons, but have recently added a HST unit to my 'personal use' department.
Based on what I know of them the way it works is remarkably like the way your vehicles power steering system, the pump is creating full pressure constantly, whether or not it is required. However the pressure relief valve opens and shuts constantly maintaining that pressure level.
This though is nothing to do with the amount of WORK the pump is required to do, which is a LOAD on the system. If the PTO is running and the tractor is stationary then the only thing the pump is doing is is maintaining the pressure set by the relief valve. There is some intrinsic power loss by even just this amount of work being done, but not nearly as much as pushing the tractor along.
My overall caution is that tractors are not overly efficient at rated output, nor do they like to produce at 100% for very long. Generally when we are spec.'ing equipment we like to use 75% as a rule of thumb. In other words if your machine puts out 28.5hp at the PTO, consider it to be about 21 hp and it will perform well without beating up the equipment.
Best of luck.
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PTO Horsepower and Generator Question
There is a basic premise I question.
The front drive shaft, the mid PTO, the rear drive axles and the rear PTO all emanate from the same "box" under the tractor seat.
Seems to me that all those functions must be powered through the same hydrostatic "link" that separates the engine from the drive train.
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PTO Horsepower and Generator Question
Murf and I were pontificating at the same time. I like his explanation. It makes sense.
The power is always instantly available. We just use all those levers and controls to direct it.
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PTO Horsepower and Generator Question
So is the consensus that my 2210 with 17 pto hp will not be over burdened powering the JD genset at an average of 8 hours a year ? Even in a big outage I would not run 24/7. I see the point of haveing the tractor available for other tasks semi moot. Just uhook the genset take care of buisiness then hook it back up. Personally I try use use black outs as an excuse to do less work around the house so I dont think I'd be mowing or tilling with the power down.
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PTO Horsepower and Generator Question
Doc, I think that is right, but from a different angle.
That generator is pre-engineered to match up to a 20-24 horse gas or diesel tractor with 26-12x12 tires on the back.
Sounds like your tractor to me.
I'll weigh in on the other issue too..... my tractor and my pick-up were purchased with work in mind. I don't care if the hours or the miles pile up as long as they both do their jobs.
If one of the tractor's jobs is to keep the water running and the food from spoiling during a crisis, the total on the hour meter become irrelevant.
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PTO Horsepower and Generator Question
My thoughts have always been the more hours on the meter the beter. After all thats exactly what I bought it for !
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Gas Generator Weather Protecti
08-18-2003, 07:01 
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