Picked up half a megawatt worth of Caterpillar power, think I'll make a PTO generator

[4570Man]

I’m betting this generator head powered with a 40 hp diesel will stomp all over the efficiency of a regular person grade pto generator. This head is a quality piece that is probably more efficient than the much smaller and cheaper head. There’s no parasitic loss to a gear box if it’s direct drive. There’s no parasitic loss to the tractor either. And retaining the use of the tractor counts as useful.

 

[ptsg]

And if the DPF light comes on, you can simply provide power to the neighborhood for a while just to load the tractor enough for a proper DPF cleaning action.

 

[radios1]

I am curious, though. it was never mentioned, but the second picture shows the proper diesels to mount the heads on, THAT would have been best.. and as far as efficiency goes, neither a gasoline nor a diesel gets more than a few percent efficiency!. but there are aircraft APU's that get 40% to 70% efficiency, the only problem is you'd need to remove the generators from them, since they are 400 cycle units, and mount your gen head to it, the other problem is, you'd have to make an interesting muffler, since the APU's are small Jet Engines..

 

[TheFarmerInAdell]

Speaking of diesels, you could look into a old box van with a 4BT Cummins in it. Or an old school bus with the 6BT (same as the Dodge cummins). Then you could turn 1800 RPM direct drive. And you would have a nice place to store it and keep it covered!

BTW, why did you say "Jeep" when it's only 2wd? At least you admitted that it wasn't a real Jeep. :laughing:

 

[KubotainNH]

It's not a "real" Jeep as it's only 2WD unfortunately. I'm not sure how the Jeep will react to having the weight of a small car sitting in the back seat, but I imagine it will at least squat a bit. The rated payload is 1488lbs, so I would be exceeding that by 300lbs if I just crammed in. But I would be removing seats, carpets, misc creature comforts which might bring it down to within its payload range.

2WD Jeep is blasphemy! That said, I've had 3 XJ's and none like too much weight in the back but that is easily fixed with some steel seeing this isn't a road beast anymore. The leaf springs on these are made for comfort not extra weight. The 4.0 has plenty of low RPM torque to run this setup, it would be great if you could gear it to run so the motor is at 1800 RPM or half the speed the gen head needs.

 

[BigBlue1]

2WD Jeep is blasphemy! That said, I've had 3 XJ's and none like too much weight in the back but that is easily fixed with some steel seeing this isn't a road beast anymore. The leaf springs on these are made for comfort not extra weight. The 4.0 has plenty of low RPM torque to run this setup, it would be great if you could gear it to run so the motor is at 1800 RPM or half the speed the gen head needs.

Doesn't sound like it is really THAT much extra weight that would be going back there anyway. I mean if a Ranger can carry this boulder then a Jeep can carry a generator...

 

[strantor]

I知 betting this generator head powered with a 40 hp diesel will stomp all over the efficiency of a regular person grade pto generator. This head is a quality piece that is probably more efficient than the much smaller and cheaper head. There痴 no parasitic loss to a gear box if it痴 direct drive. There痴 no parasitic loss to the tractor either. And retaining the use of the tractor counts as useful.

I cannot find published efficiency numbers for this head. Heads this "small" are apparently sold exclusively coupled to Cat engines, and the only efficiency-related data Cat publishes is the overall efficiency of the genset (engine + head), and fuel consumption data for various load from 25% load to 100% load. Caterpillar publishes much more detailed specs on their larger units, and they are typically 89% - 94% efficient at 25% load, and 95% - 97% efficient at 100% load.

The head is going to be less efficient at lower loads, as parasitic loss constants will occupy a bigger piece of the pie. I'm thinking that at any given percent of load, there will be the (more or less) fixed combined loss of generating the rotating field current, plus the load of spinning the fan, plus bearing losses, air drag of the spinning rotor, etc. I will be operating the head exclusively below 15% its rated load, usually 10% or less. So in order to estimate efficiency below 25% I've just taken the numbers from the larger generators and calculated the waste kW @25% load as a fixed parasitic loss, which looks like this:
...90% efficiency at 25% load, that's:
210kw * 0.25 = 52.5kw generated @ 25% load.
(1/0.9) * 58.33 kW mechanical
58.33kW - 52.5kW = 5.8kW (7.7HP) waste

So that's 7.7HP (conservative/worst case) just to spin the thing, with no electrical load.

If I were to utilize this thing at 10.5kW (5% rated load), powering my house, and there was 5.8kW tacked on top, that's only 64% efficiency. BUT...

I've done the math already on the field current generator and that's 1HP/746W.
Maybe another 1HP for the bearings, rotor drag, etc.
So I think it's reasonable to assume the big fan accounts for about 5HP. It's a pretty big fan.
That fan is designed to move the waste heat of a 210kW load. At 95% efficiency, that's 11kW of waste heat the fan is responsible for getting rid of. I won't be dissipating anywhere near that. I'll have the heat generated by field coil (746W) plus whatever inefficiency of generating 25kW max, so maybe 2kW.
I think I can ditch the fan, or at least shave the blades so that they don't throw nearly as much air.
I think I can this beast within the 95%-97% efficiency realm at my max load, with a single easy modification.

 

[strantor]

BTW, why did you say "Jeep" when it's only 2wd? At least you admitted that it wasn't a real Jeep. :laughing:

2WD Jeep is blasphemy! .

You think I would turn a REAL jeep into a home appliance? Come on!

 

[4570Man]

I cannot find published efficiency numbers for this head. Heads this "small" are apparently sold exclusively coupled to Cat engines, and the only efficiency-related data Cat publishes is the overall efficiency of the genset (engine + head), and fuel consumption data for various load from 25% load to 100% load. Caterpillar publishes much more detailed specs on their larger units, and they are typically 89% - 94% efficient at 25% load, and 95% - 97% efficient at 100% load.

The head is going to be less efficient at lower loads, as parasitic loss constants will occupy a bigger piece of the pie. I'm thinking that at any given percent of load, there will be the (more or less) fixed combined loss of generating the rotating field current, plus the load of spinning the fan, plus bearing losses, air drag of the spinning rotor, etc. I will be operating the head exclusively below 15% its rated load, usually 10% or less. So in order to estimate efficiency below 25% I've just taken the numbers from the larger generators and calculated the waste kW @25% load as a fixed parasitic loss, which looks like this:
...90% efficiency at 25% load, that's:
210kw * 0.25 = 52.5kw generated @ 25% load.
(1/0.9) * 58.33 kW mechanical
58.33kW - 52.5kW = 5.8kW (7.7HP) waste

So that's 7.7HP (conservative/worst case) just to spin the thing, with no electrical load.

If I were to utilize this thing at 10.5kW (5% rated load), powering my house, and there was 5.8kW tacked on top, that's only 64% efficiency. BUT...

I've done the math already on the field current generator and that's 1HP/746W.
Maybe another 1HP for the bearings, rotor drag, etc.
So I think it's reasonable to assume the big fan accounts for about 5HP. It's a pretty big fan.
That fan is designed to move the waste heat of a 210kW load. At 95% efficiency, that's 11kW of waste heat the fan is responsible for getting rid of. I won't be dissipating anywhere near that. I'll have the heat generated by field coil (746W) plus whatever inefficiency of generating 25kW max, so maybe 2kW.
I think I can ditch the fan, or at least shave the blades so that they don't throw nearly as much air.
I think I can this beast within the 95%-97% efficiency realm at my max load, with a single easy modification.

Maybe for the head itself. You’re taking a 2000 or more engine and gearing it down to 540 RPM and then putting it through another gear box to get it back to 1800 rpm plus any other loses that happens instead the tractor. Assuming the engine works at the same efficiency and the head works at the same efficiency a direct drive unit will be more efficient. Robs statement is blatantly wrong in an apple to apple comparison.

 

[strantor]

I got some bearings in the mail yesterday and I know I said I wasn't going to work on this for a while but seeing the bearings just sitting there is making me itchy. So I decided to get started machining the shaft adapter and bearing housing. For that I'm using this chunk of rusty steel which is a remnant of a project abandoned long ago. I was going to try to build a DIY lathe years ago, and this is what was supposed to be the spindle and chuck. It's a piece of 2" shaft that I turned down at the end and threaded 1.5"NPT and threaded this piece of 7.5" solid round stock onto it. I made it after hours on a lathe they had at a place I used to work (with permission, off the clock).

It's a good thing it has that shaft sticking out, because otherwise I wouldn't have had a way to chuck it up in my tiny lathe. It is requiring some creativity to machine it. I have arranged my tool holder in the most awkward and unorthodox way ever, and can just barely turn the OD.