Generator PTO generator feedback

[bucmeister]

Much has been posted questioning the long term durability of the Chinese Diesel gensets which I guess would also apply to typical backup units like my old 8hp Briggs powered Coleman Powermate though I am not sure why that has gotten so much attention. We are comparing air cooled engines to water cooled tractor engines, of course there is going to be a longevity difference between the two types of engines. These units are not being used as "prime power" units expected to run 24/7 for years under near max capacity. They are used for temporary power in cycles that may last for an hour, a few hours, a day, or maybe a week. In a worst case one might have to go for a couple of weeks. If my Chinese unit gives me 20 good years as the Coleman, which still runs well, has then I will be well pleased with the investment.

I do not envision going to the extreme that my neighbor did to have backup power after the Katrina/Rita episode. He bought a 40kW Cummins powered 1800 rpm prime power rated unit. Built a house for it etc. During our most recent extended outage he made power for just over 24 hours on 0.9 gallons per hour. Given his investment, I could run my tractor for many weeks even if it were to burn 3.0 gallons per hour doing so, and still have money left over. As long as I could get diesel anyway. One of the big issues we had after Katrina was even getting fuel and gasoline, which has been the driving force behind seeking low consumption alternatives. I now have a diesel unit that only burns half as many gallon per 24 hours as the gas unit I have to run the same basic load. In addition to that it has enough reserve capacity to run the water heater if necessary.

Maybe this summer I will get a chance to run the PTO and the Chinese unit for a few hours each tied to the 5kW test load I have and measure the respective fuel consumption. Rest assured, once done I will be glad to post the results to this thread.

 

[JB4310]

These Chinese diesel standalones are intriguing and maybe the wave of the future...

But talking about longevity, we know diesels outlast gassers in general due to their slower turning and HD construction required for the greater compression pressure.

These new diesels are turning 3600 rpm's, way hotter than any diesel we are accustomed to. Basically making them high pressure "whiz-bangers" made with CHI materials and engineering.
It will be interesting to see how they compare to gassers of the same output.

Not knocking them, even if they were just equal to the gasser in service life, and cost about the same. With them being diesel, for me just for the fuel stability issue they would be my first choice (between the standalones that is).

Here are the diesel standalones you really want. If you can afford them

Norpro | A Whole Lot More Than A Diesel Generator Manufacturer


JB.

 

[SPYDERLK]

Maybe this summer I will get a chance to run the PTO and the Chinese unit for a few hours each tied to the 5kW test load I have and measure the respective fuel consumption. Rest assured, once done I will be glad to post the results to this thread.

Points of info and curiosity ... Is that standalone diesel setup a direct 1:1 drive:driven rpm, or is there a gear reduction? What is the rpm they run at?
Thanks!,
larry

 

[bucmeister]

Points of info and curiosity ... Is that standalone diesel setup a direct 1:1 drive:driven rpm, or is there a gear reduction? What is the rpm they run at?
Thanks!,
larry

The ones this size are direct drive 3600 rpm units which I agree is right at the limit of diesel combustion speed.

 

[tsteahr]

The ones this size are direct drive 3600 rpm units which I agree is right at the limit of diesel combustion speed.

Interesting point. I wonder if there is a reduction in efficiency running diesel at this speed? I wonder if it is of similar magnitude to the gearbox losses of a pto unit? More? Less?

 

[Diamondpilot]

I have posted many times about this but here is what I ended up with. I have a $1000 Troy Build Genny that has a 13 HP engine. Starts 1st or send pull every time and puts out 8550Watts. I ran it for 8 days once 24/7 except to change the oil every other day. I even added fuel while it was running. I know call the safety police. It has also served many 3 day outages and a few 1 day outages. Probably ran for 20 full days since 2003 when I bought it.

Anyway it used 9 gallons per day. I had trouble getting gas so now keep 100 gallons on hand and just cycle it though my cars after 6 months or so.

My house has propane heat and hot water. It will run everything we need including the well pump, 2 fridges, 1 deep freezer, lights, tv's, micro, even the stove. We have also done wash but had to hang the stuff up to dry since our dryer is a electric unit. It will not run our AC but I have a old window unit I have moved up to the bedroom for a 3 day outage when we got hit by a tornado in 100 deg heat of august.

Would I like a PTO genny? Sure. I would only use it if needed to do the laundry or run the Central AC. The Troy Built has been top notch and if it dies I will buy another.

Chris

 

[Redneck in training]

Interesting point. I wonder if there is a reduction in efficiency running diesel at this speed? I wonder if it is of similar magnitude to the gearbox losses of a pto unit? More? Less?

My father used to be a diesel injection pump specialist for the army. He explained it to me. In the old days of diesels the limiting factor was minimum fuel metering to the engine (for idle speed). There were not machines able to manufacture small injection pump as later on. In example spark erosion manufacturing was invented and made practical much later. Therefore there was a smallest practical volume of the cylinder. I only vaguely remember that the minimum was more than 500 ccm (30 cin) or usual size closer to one liter (60 cin). So the reciprocating forces were large limiting the speed to about 1800 - 2500 rpm. Later on much smaller injection pumps were manufactured allowing for smaller volume of the cylinder and faster running engines that would last because of smaller cylinder with shorter stroke translates to lower median piston speed.
Today's high revving diesels are hard to tell apart from gassers. If you have driven one you would love them.

 

[SPYDERLK]

The ones this size are direct drive 3600 rpm units which I agree is right at the limit of diesel combustion speed.

Interesting point. I wonder if there is a reduction in efficiency running diesel at this speed? I wonder if it is of similar magnitude to the gearbox losses of a pto unit? More? Less?

Id say less. There are tricks to improve on it - injection timing, multi point injection, and higher injection pressure thru small nozzles for better atomization. Still, for best fuel economy I think yould want one designed around an 1800 rpm direct drive setup using the 4pole alternator. This would let you get nominal speed right at a long-stroke-engine torque peak so it would hold speed at full load extremely well.
larry

 

[tsteahr]

Id say less. There are tricks to improve on it - injection timing, multi point injection, and higher injection pressure thru small nozzles for better atomization. Still, for best fuel economy I think yould want one designed around an 1800 rpm direct drive setup using the 4pole alternator. This would let you get nominal speed right at a long-stroke-engine torque peak so it would hold speed at full load extremely well.
larry

True, those tricks all improve efficiency. However they all come at a cost. It seems unlikely they would be included in a budget portable CHI that is brought to market with extreme sensitivity to price/margin. I have to wonder if the budget diesel gens are designed to achieve the necessary 3600rpm at the lowest cost, with little thought to optimizing fuel efficiency. Just thinking about theoretical vs reality.

 

[Redneck in training]

Just checked some dyno test on internet. Two wheel drive cars deliver about 7% less power to the road than the engine produces. It includes all transmision and differential gears and tire deformation and friction to the road. It might give you some idea about losses of generators with gearboxes. My guess is that the gearbox makes very little difference in efficiency. Probably the cooling fan uses more power that the gear. Look at it this way. If the gear would lose (all loses are turned into heat) let say 10% of engine power to deliver 10kW it would run red hot.