Generator PTO generator feedback

[Soundguy]

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What seems more relevant is the loss of power between the net engine output and the PTO output. The only info I have on hand for this comparison are the specs for the Massey GC2400/2600. Looking at the MF GC2400, the net engine power is 16.1 kW @2600 rpm. The PTO power is speced at 13.9 kW @ 2600 rpm (555 PTO rpm). So the power transmission loss from the engine output shaft to the PTO output shaft is 13.9/16.1 = 0.8634 or a loss of 13.66% (1-0.8634).

Therefore total transmission efficiency loss of this PTO driven setup is approximately 15.66% (13.66 + 2).

So if we look at a MF GC2400 running a 10KW PTO generator vs a 10KW standalone, the question becomes is the MF motor running at 2600 rpm 15.66% more fuel efficient than a standalone diesel running at 3600 rpm?

Well, the MF motor is clearly a "higher quality", higher cost motor running 1000 rpm slower. Does that make it 15% more fuel efficient? Unfortunately I don't have fuel consumption curves for any of these motors.

Can anyone add to this?

Edit: The MF numbers come from the '09 MF GC series Owner's Manual.

That's an incredibly high loss between net engine and pto... 13%.. etc.

looking at the spec sheet on my ford 5000 diesel 8spd, the net engin hp is 70, and pto is 67.2 that a loss of 2.8hp.. or 4%..

here's a link to the spec sheet in case anythinks I'm fudging the numbers..

http://www.springfieldbiz.com/oaktree/images/5000front.pdf

Looking at another unit I have, a ford 3000 diesel, it's net hp is 41.4, and pto is 39.2 for the 8spd trans.. that's a difference of 2.2 hp, or 5.3%

http://www.springfieldbiz.com/oaktree/images/3000front.pdf

I can live with 4% and 5.3%.. and not worry about having to pull start my backup generator..

soundguy

 

[tsteahr]

Yes. Ill have to subtract from it some tho. 1st bigger engines have more parasitic losses - more friction and pumping losses both in the cylinders and crankcase. Its a factor, but only a contributing one, as you say, less important than the power transfer losses
- Your gearset info is correct as far as it goes. What isnt said in your references is all the contributing parameters that are considered. To see only 2% loss in a gearset while seeing over 13% loss in a straight shot out the pto is fodder for quizzicality.

The MF example I am citing is a HST tractor, not a gear tractor. Power transfer from engine to PTO is not a "straight shot out" as you state. As you suggested in your earlier post, engine to PTO losses are significant in a HST tranny. I am not making up the loss data. It is FACT based on published data. Not my data. Not my gut feeling. Published data from the manufacturer I take to be factual. Nothing quizzical about FACTUAL data.

I believe we would find that the 2% figure is possible only in a gearset in the 1:1 to 1:2 ratio range and that the gearset is being supplied perfect lubrication for it and its bearings.

Please refer to my cited references. Reduction ratio is irrelevant to efficiency. Gearset efficiency is determined foremost on tooth interaction. Tooth interaction is based on tooth design. While all gear teeth make look similar, there is a large variation in design, efficiency and cost of manufacture. I'm speaking to differences in tooth design (profile) of straight cut gears. (Not between one gear types and another) Lubrication also is vital. Hardness is also important. If you refer to the references, the efficiency numbers assume gearset operating in a 90W gear oil bath.

Please understand, these references are not some theoretical calculation from some math professor. The references are engineering design handbooks.

A light spray of oil is what is needed -too much and you add to losses.

This statement is irrelevant. The cited efficiencies are based on gearset in oil bath.

I can tell you from experience that my 12kW Northstar pto gen runs a very hot gearbox at just medium output - - the whole area in contact with the gearbox runs hot [front of gen and pto coupling] ... even after I broke it in and then switched to Mobil 1 gearoil. The issue?... 1:6 speed increase and more oil than needed..

On what basis do you conclude this heat results from a 1:6 speed increase and excess oil? On what basis have you quantified this heat dissipation? It would be interesting to see as we can then invalidate the accepted engineering design basis published in every mechanical design handbook I have ever encountered.

My experience in testing heat input vs delta T in turbulent open air tells me this isnt a 2 or even 5% loss when I cant hold my hand on the gearbox of a gen outputting 4 or 5KW. Thats why I throw 10% in as a ballpark figure.
larry

You have some objective basis for quantifying 10% vs 5%? Other that what it seems like to you?

The facts remain. 13% loss to PTO on the Massey GC2400. 2% gearbox loss based on engineering design reference unless you can produce a reference to refute this.

 

[tsteahr]

That's an incredibly high loss between net engine and pto... 13%.. etc.

looking at the spec sheet on my ford 5000 diesel 8spd, the net engin hp is 70, and pto is 67.2 that a loss of 2.8hp.. or 4%..

here's a link to the spec sheet in case anythinks I'm fudging the numbers..

http://www.springfieldbiz.com/oaktree/images/5000front.pdf

Looking at another unit I have, a ford 3000 diesel, it's net hp is 41.4, and pto is 39.2 for the 8spd trans.. that's a difference of 2.2 hp, or 5.3%

http://www.springfieldbiz.com/oaktree/images/3000front.pdf

I can live with 4% and 5.3%.. and not worry about having to pull start my backup generator..

soundguy

Soundguy, I believe the difference you are seeing is gear vs HST. I believe both your examples are gear.

The gross hp and PTO hp specs for the MF GC are here. Unfortunately I have only seen the net power number in the owners manual. I would be happy to scan and post the relevant page if some would like to see the numbers verified.

Take a look at Kubota B3200HST as another rough example of power loss. The Kubota spec sheet lists gross engine hp at 32.0 and pto hp at 23.0 This is a gross efficiency of 0.72. Kubota does not list net hp on the web site. Perhaps a Kubota HST owner could post this data if it is available. I think you will find this typical of the smaller HST CUT tractors. I would agree gear tractors have more of the engine hp available, just as your examples show.

Edit: What is interesting to note is you have a 4-5% loss in a gear transmission . I'm guessing there are 2 or 3 gear interfaces in power path from the tranny input to the PTO output? This supports the nominal 2% loss at each gear interface that is cited in the references.

 

[IXLR8]

I have been doing the PTO vs standalone Generator debate for a while now. We lost power last night and my decision was made. Power out, winds blowing at 45-55mph, raining 1.5"/hr. I decided that there was no way I would want to go out in those conditions to; remove the attachment on the tractor, attach the PTO generator then move it to the house and hook it up. Differences in fuel burn be damned... I would rather do what DiamondPilot did, pull generator out of corner of garage, hook it up, plug it in, fire it up. No dealing with wind/rain/cold. I am also out of town about 50% of the time, no way would wife be able to hook up PTO generator, but she would have no problem hooking up a standalone generator.
Now to solve the diesel vs gas power generator debate.

 

[JB4310]

Now to solve the diesel vs gas power generator debate.

DIESEL, hands down IMO.

That was my first criteria before stand alone vs pto.

JB.

 

[Diamondpilot]

I have been doing the PTO vs standalone Generator debate for a while now. We lost power last night and my decision was made. Power out, winds blowing at 45-55mph, raining 1.5"/hr. I decided that there was no way I would want to go out in those conditions to; remove the attachment on the tractor, attach the PTO generator then move it to the house and hook it up. Differences in fuel burn be damned... I would rather do what DiamondPilot did, pull generator out of corner of garage, hook it up, plug it in, fire it up. No dealing with wind/rain/cold. I am also out of town about 50% of the time, no way would wife be able to hook up PTO generator, but she would have no problem hooking up a standalone generator.
Now to solve the diesel vs gas power generator debate.

Just what you said weighed my decision. My wife is pretty handy but at 120# and 5'2" with a baby at home and me on the road being a pilot 5-6 nights a month I worried also.

I typed up a instruction sheet for her and gave a 10 minute course to both her and my neighbor who I think highly of. It is zip tied to the transfer switch with 6 easy steps all including pictures. A 13 year old boy could do it if needed.

Diesel is nice but Gas is cheap, even for a quality unit like my Troy Built. Just be safe with what ever you do. Also I would spring for a whole house transfer switch. I looked at the little 30 amp jobs that run 6 circuits but for $100 more I was able to get a full 200 amp manual switch that powers the entire panel and I am smart enough to pick and choose what I run. It will also be in place if and when i ever decide to upgrade to a larger genny. Harbor Freight has Cultler Hammer 200 amp switches for $300 or less.

Chris

 

[JB4310]

The 200 amp switches are nice, but these things are interesting, and very simple/cheap.

Generator InterLock Kit

J.

 

[IXLR8]

The 200 amp switches are nice, but these things are interesting, and very simple/cheap.

Generator InterLock Kit

J.

I am leaning towards a diesel generator as I am converting my home from all electric heat to solar with oil fired backup. Since I will have a tank of diesel fuel... I will always have a supply of fuel for a diesel generator.
The Generator Interlock Kit looks interesting... thanks. The breakers in my panel are already in the proper position for it to work on my panel. That will save some expense and hassle of installing the transfer panel, which I don't really have room for.
Looks like small diesel generator w/GI kit is the way I am going to go. Now to decide on what size generator.. only items that will be 208 after conversion will be the well pump and wall oven. Don't need wall oven during power outage, so that leaves the 1/3hp well pump. So I am thinking a 4kw generator would be plenty.

 

[JoelD]

Personally I would never run my tractor to power a generator. Last power outage for me was three days. I paid $300 for a brand new 6K, 13HP generator. I change the oil every 25 hours and I'm good to go. It blows up, I buy another, my neighbor ran his for 8 days straight with no issues what so ever. I could not imagine putting that kind of hours on my tractor when there are inexpensive alternative purpose built machines.

A couple hundred dollar generator motor is a lot easier to replace than a $3K tractor motor.

In the end, my purpose built generator was less money than a 3 point would cost.

Joel

 

[Soundguy]

Yes, both gear examples in my post.

Yep.. it's hard to compair net to gross numbers. I wish all manufacturers would post gross, net, and pto numbers.. it would help people like us that are trying to make a factual and objective comparison.

On the 5000 it is independent pto, and the other is live via a dual stage clutch... both obviously have some gear interaction since they are dropping crankshaft speed to pto speed.. I believe we are pretty close at hashing those numbers down between the data we have posted. vs the subjective data collectionmethods of how long one can hold thier hands on a gear box and mist lube vs spalsh lube vs oil bath thoughts.

soundguy

Soundguy, I believe the difference you are seeing is gear vs HST. I believe both your examples are gear.

The gross hp and PTO hp specs for the MF GC are here. Unfortunately I have only seen the net power number in the owners manual. I would be happy to scan and post the relevant page if some would like to see the numbers verified.

Take a look at Kubota B3200HST as another rough example of power loss. The Kubota spec sheet lists gross engine hp at 32.0 and pto hp at 23.0 This is a gross efficiency of 0.72. Kubota does not list net hp on the web site. Perhaps a Kubota HST owner could post this data if it is available. I think you will find this typical of the smaller HST CUT tractors. I would agree gear tractors have more of the engine hp available, just as your examples show.

Edit: What is interesting to note is you have a 4-5% loss in a gear transmission . I'm guessing there are 2 or 3 gear interfaces in power path from the tranny input to the PTO output? This supports the nominal 2% loss at each gear interface that is cited in the references.