Run a PTO with a Diesel engine - PTO w Donkey Engine

[Renze]

Why did the MB chopper have to relieve the engine?

because the MB-trac doesnt have a powershift (modified 16 speed truck transmission), and crop varies in height within the length of the field. There is a delay in crop thickness and engine lugging because it takes a few seconds for the crop that gets grabbed by the header, to reach the chopping disk. So when you hit a good spot of crop and the engine dropped below 1600rpm, the torque curve fell down so quickly that the seconds that the heavy crop flow endured, were enough to stall the engine.

Automotive engines are usually tuned for peak hp at high rpm, not for lugging... however the OM617 was used in commercial vehicles too, and has about the same displacement as 60hp industrial engines.. With the OM617 you'll be o.k. because the torque curve is quite flat for an automotive diesel. It has no turbo, so it doesnt have any lag when it has to take up an intermittent power peak.
http://wiki.mercedes-benz-classic.com/index.php/W123-300D-Getriebe/en

Oh, and if you worry about it being able to get the momentum going: why not use an automatic transmission behind it ? I would just put an oil cooler on the transmission and it will be fine.

 

[muddstopper]

I am not familar with mixers so I can only guess at requirements. As for 60 hp tractor to run one, I suspect that the tractor is rated at 60hp at the PTO. At least that is how my last tractor hp was rated. The would lead me to suspect that with proper gearing, you could get by with a less hp rated engine to accomplish the same thing. Dont take my word for it tho because I am just guessing and could be guessing very wrongly. I would think that 240hp would run a very big mixer.

Your requirements of 60hp and 500rpms suggest a torque requirement of 630ftlbs of torque. Meet this requirement with what ever engine combination, hp, and rpm and gearing mix you can comeup with and it should work. A 15hp gas engine turning 3600rpms geared at 7:1 would only give you 153ftlbs of torque and, because of gearing, it would be similar to a 105hp, and the correct rpms, the torque would be on a fraction of what you actually need.
Horsepower Design Equations Formulas Calculator - Torque Rotating

 

[CNC Dan]

The gearing will result in multiplying the torque and hp at the ptoshaft...

Torque will multiply up, and speed divide down, but not the horsepower, that will remain the same less losses to friction.

 

[muddstopper]

Torque will multiply up, and speed divide down, but not the horsepower, that will remain the same less losses to friction.

Thanks for clarifying, I wasnt sure on that.

 

[CNC Dan]

Thanks for clarifying, I wasnt sure on that.

It can be easy to get lost in the numbers sometimes.
I try to remember that power is RPM x torque. So you can have the same power with a wide range of speeds, or torques.

 

[Sysop]

I had considered finding a tractor that was in bad shape but that had a running pto. Looking for a 60hp tractor though means I'm looking at spending about $5000

It should be mentioned with a tractor that isn't moving it's own weight will be able to supply the full amount of PTO power to the PTO shaft, and many horsepower requirements provided by large implement manufacturers are simply to ensure you have a large enough tractor to handle their machine safely (many don't require the horsepower as much as they do the average size & weight of a given horsepower class). Was the fact this will be a stationary setup part of their consideration when they said you needed 60HP? Being a stationary setup that is only used for mixing you may be able to get away with a 40 horse and reduce the cost.

 

[BHD]

Had another thought,

take a truck or pick up with a working cruse control, lock up the differential, and make a bolt on PTO shaft to the wheel hub,

If I am figuring correctly, a 33 inch tall tire. 33 tall tire x 3.14= 103.62 inches, or 8.63 feet, 5280 (mile) / 8.63, 611 rpm at 60 mph 540 RPM that would be approximately 53 mph on a trucks speed-o-meter, the cruse control would act like a governor,

About the only modification would be to lock up the differential. and make the adapter.

 

[hophornbeam]

Andrew,
I liked to jerry rig machinery as much as the next guy, but I can't help but think all your effort to eliminate a second tractor is going to cost more than an older tractor. JMHO

 

[Sysop]

Andrew,
I liked to jerry rig machinery as much as the next guy, but I can't help but think all your effort to eliminate a second tractor is going to cost more than an older tractor. JMHO

At least if you count the value of your time in making it work. Some folk view their time as "free to them", in which case I'm interested to watch and provide sideline idea assists on whatever OP chooses to do.

 

[hophornbeam]

Sysop, I understand that in the farm community, or even anyone, we usually value our time extremely low in an effort to make gains, sweat equity I call it. However, unless the donkey engine(s), transmissions, reduction gearing, etc, etc, are sitting in the back shed waiting to brought to light there is a cost. Hey, I wish the guy luck on his endeavour and look forward to seeing the creation too. I just wanted to suggest that before the blinders get too restricted, consider the option that at first seems less favourable. For all I know, one day he may find himself stuck with his one tractor and wouldn't a second tractor look good then.