PTO Generator

[California]

... The problem using one of these is you'll need to build the drive yourself so you can turn them at 1800 rpm at a reasonable speed from the tractor.

How about direct drive from the front of the crankshaft? You wouldn't have the power loss or maintenance that step-up gearing (PTO) entails. And looking at the power curves for a similar Yanmar diesel, 1800 is approximately the torque peak and lowest fuel/bhp. What rpm do the Yanmar-powered generator sets run?

 

[Underwaterdog]

I think what Underwaterdog had in mind for the 1800 rpm genhead is the ST design made and imported from China. These are large, heavy and intended to be run 24/7 for long periods. They do have a lot of rotating mass that helps with handling transient loads. The problem using one of these is you'll need to build the drive yourself so you can turn them at 1800 rpm at a resonable speed from the tractor.

My Generac 40 KW was complete with a 540 to 1800 RPM Gearbox and a standard PTO driveshaft with the shaft guard. Actually it says 40KW/80KW, with 40 being continuous duty and 80 being surge. It has a needle type voltage and frequency guage. I think I had to run about 2600 engine rpm. I just watched the frequency guage and set the throttle to give 60 HZ. It was a bit dusty, but still in the crate when I got it. I have a spec sheet somewhere on it. I not sure if they make them anymore, I looked at the Generac.com site and don't see them listed. You can do a search on e*ay for PTO Generator, there are several of them on there right now.
Mickey, are you telling me my Generac was made in China? It is big and heavy. Grainger used to have the exact same one, it was red and was being sold as the Dayton brand, and their price was out of sight. The ones Grainger sells now aren't the same.

 

[Mickey_Fx]

... Mickey, are you telling me my Generac was made in China? It is big and heavy. ...

No, I think I specifically mentioned the ST design gennys that come from China. You can find them on E-bay. A 7.5Kw model weighs about 250 lbs and is direct drive @ 1800 rpm. The armiture weighs about 75# by itself.

California, it may be possible to drive on of these gennys directly from the engine but depending upon the tractor design, it might be more difficult and costly than making a platform and drive system to run off the pto. More losses that way but still likely more easily done.

Here is a link showing an example. 7.5KW ST Generator Head 1 Phase for Diesel & Gas Engine - eBay (item 330202134615 end time Jan-12-08 17:00:21 PST)

 

[RonMar]

California
The problems with front drive could be many, such as radiator, front frame, battery front end loader, ect. You would also loose the ability to add spinning mass that a PTO type generator with reduction gear would and should have. The governor on your tractor may or may not have a lot of lag and overshoot. This isn't a problem running a brushhog or tiller, but leads to possibly wild frequency and in some generators, voltage variations as the engine RPM hunts all over the place after the load changes.

If I was building a PTO type, and I may, I would make the primary reduction pully(the one coupled to the PTO shaft) as heavy as possible to add some flywheel inertia to the mechanical drive. This spinning mass will resist RPM change and buy time for the goveror to react and settle after load changes. I have a 24" 150# cast iron flywheel that I am saveing for this type project with perhaps a 10KW head. Spun at a little over 600 RPM(I have a 540/1000 RPM PTO), an 8" pully on the generator driven by a single 8 groove micro"V" belt will yield 1800 generator RPM. This is how my slow speed generator is driven and it works great. With the engine running at a reduced RPM to give me 600 PTO RPM in the 1000 RPM gear, I should get enough HP to sustain a 7-8KW load with an excellent surge capacity from the 10KW windings and the large spinning mass. And the tractor engine won't be setting there screaming away at full song...

 

[tmar04]

Hi. got any pics of this setup?? thx

 

[brin]

My sentiments exactly. I knew I always keep the tractor ready to go, but its easy to forget about something you are not using.
Look for one that has a generator rpm of 1800. Not the gearbox, which will be 540, but the actual rpm of the generator rotor. It should be in the spec sheet. The 3600 rpm generators are cheaper, because they have less copper in them. But I have noticed they tend to cause a noticeable flickering in lights, even fluorescent. The 1800 has twice as many poles and windings in it, I think its 2 poles vs. 4, and give a stable power output. Also, the rotor will be heavier thus have more inertia to compensate for peak loads such as starting motors (air conditioner ). I have a Generac, but I'm sure there are others that are of good quality also. When my wife and I first met, she couldn't understand why I had stockpiles of food and supplies, barrels of fuel and a big generator. Then Katrina hit. We are about 60 miles north of New Orleans, and outside the mandatory evacuation zone, so we stayed put. We had about 2 weeks of 100 degree plus days. We were one of the few in the whole parish that had A/C . My 40 KW generator that I picked up on 3bay for less than the cost of a 25KW, has a 150 amp breaker and plug and a 50 amp breaker and plug. I used the 50 amp since it would take a 80hp tractor to get the full 150 amps. It was enough to run the 4 ton A/C, lights, satellite TV, refrigerator, freezer, water well, and an Oxygen concentrator (about 6 amps on 120v) for a neighbor. If you want to run the oven, or the washing machine, you have to turn other stuff off accordingly. They soon learned if they pulled too much power the breaker would trip and they would be in the dark. If I wanted to run the hot water heater I would have to turn off the A/C, but most of the time we had enough hot water from the A/C's hot water recovery unit for everyone (family refugee's totaled 7) to be able to take a quick shower. I ran this on a YM2500, 24/7 for 12 days, only stopping for fuel and oil changes. I changed the oil and filter every 3rd day. I ran it with the hood up and the engine ran cooler, especially during the middle of the day. As best as I can estimate, I was averaging about 14 gallons of diesel a day. I do remember that we had a cool night toward the end of the ordeal, and fuel usage dropped dramatically with the A/C not running as much. Sorry for the long post, just trying to fill you in on what to expect.
BTY; Stabil is in all my fuel barrels. There website says if you double the recommended amount, it will keep fuel fresh for up to 2 years instead of 1. And since no one was at my house for more than 60 days, I didn't get no check from FEMA.

Underwaterdog....I am looking at buying a 40KW Generac PTO generator from a lady whose husband had a chicken farm and he has passed away the generator in 10 yrs. old and been kept in the barn all this time ..it was only used twice since they bought it new 10 yrs. ago. My question is - Should I be concerned about it only being used twice in 10 yrs. since it has been sitting in the barn ? She has the manual and the receipt from her original purchase..Thanks for any advice you can give..Brin