[sfsouter]

I am considering the idea of running a 540 rpm pto generator on the 1000 rpm shaft at 1134 engine rpm for extended periods of time. JD manual suggests minimum operating rpm as 1500. Does anyone have experience related to this? Perhaps those older engines don't lubricate properly at lower rpm? I'd love to hear of positive and negative experiences with similar setups.

 

[hosspuller]

According to the Nebraska test, Std power at full RPM is 60 hp, you'll get about 25 to 30 hp at that rpm. Is that enough for your needs.?

link to test: https://digitalcommons.unl.edu/cgi/...redir=1&article=1403&context=tractormuseumlit

An engine torque curve would be helpful to you.

 

[Herminator]

I suspect it is going to load up with fuel or possibly overheat if is hot out at those rpm's. It is also going to be a bit slower to react to load changes.

Are you looking to save fuel or for less noise? I am sure you know it can be switched between 540 and 1000 with the standard stub shaft provided so those were my guess.

 

[sfsouter]

Thank you Hosspuller.

My 3020 is the latest 1972 Syncro-Range so I believe my PTO hp on the 1000 rpm shaft at standard engine rpm of 2072 is ~65 hp. That should correlate to ~165 ft-lb of torque. Assuming constant torque and adjusting pto rpm from 1000 down to 540 which reduces engine rpm from 2072 to 1119 that reduces the 1000 rpm pto shaft hp to ~35hp I believe?

My question is can that gas engine and the hydraulic system handle the lower 1119 rpm without lubrication concerns or other issues? In reality I'd only operate the generator/tractor this way for short periods to run 15A (1500W) tools mostly, so in the order of ~3hp at the PTO. I just wanted to use the mid mount 1000 rpm shaft for the generator at the front of the tractor when I have my log processor 3 point hitch unit running off the rear PTO. This way I can run electric saws off the tractor at the same time.

When I need full site backup, I'd connect it to the proper 540 shaft and ramp up the engine to specs.

https://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1418&context=tractormuseumlit

 

[Herminator]

That makes it a bit different. I don't think lubrication will be a problem. Short answer is I have run mine in parades under 1500 rpms for an hour or more and for short periods at 1,100rpm but 1,100 is slow. I think I would let the tractor sit and idle at that rpm for the time you think it will need it to do in the field and see if the plugs foul. I would give it a 25% chance of not fouling them.

Then you just have to make sure you unhook the generator before you wind up the wood processing equipment.

 

[Longhorn_007]

Have you thought about just picking up a 2000W inverter and running it off the tractor's electrical via the battery? I'm guessing the alternator should be able to keep up with your use case and you could run it at the proper rpm per JD's recommendation.

edit: upon further research, I realize that my suggestion only works if you've done the 12V conversion as I believe your 3020 is a 6v system when stock, right?

 

[Tx Jim]

When 3020/4020's were sold new JD advertised the engines to be variable speed(1500-2200 rpm) under load engines. I think 1119 rpm's under load is too slow engine rpm's

 

[Tx Jim]

edit: upon further research, I realize that my suggestion only works if you've done the 12V conversion as I believe your 3020 is a 6v system when stock, right?

JD 3020 with gasoline engine will have 12 volt electrical system from the factory

 

[Longhorn_007]

JD 3020 with gasoline engine will have 12 volt electrical system from the factory

ah ok..if that's the case then I'm doubling down on the inverter solution

I found a bunch of threads on the interwebs discussing the conversion of 3020's to 12V but if they were talking about something else, all the better

 

[Herminator]

Some came with 24v so the conversion was to 12v. I also think some came with Positive ground as well so there are threads on switching to Negative ground.

 

[Longhorn_007]

Some came with 24v so the conversion was to 12v. I also think some came with Positive ground as well so there are threads on switching to Negative ground.

Gotcha. I just skimmed the threads as I was poking around for particulars on how I would implement a solution if it was me. There were some discussions related to 6v ignition coils, but I also saw some 24V things too. If OP's tractor is already 12V then he'd be good to go should he choose that route. Thanks for the clarification!

 

[Tx Jim]

Some came with 24v so the conversion was to 12v. I also think some came with Positive ground as well so there are threads on switching to Negative ground.

JD new generation tractors(10 & 20 series) with gasoline or LPG powered engines had 12 volt electrical systems. Early('61-'68) diesel powered had 24 volt electrical systems. All gasoline/LPG tractors('61-'68) came positive ground except for the very few that had option of alternator.All '69-'72 tractors came with 12 volt negative ground electrical systems. Technically 24 volt systems had both positive & negative for accessories & no ground for starter,generator & voltage regulator as these components were insulated from the tractor frame

 

[hosspuller]

Thank you Hosspuller.

In reality I'd only operate the generator/tractor this way for short periods to run 15A (1500W) tools mostly, so in the order of ~3hp at the PTO. I just wanted to use the mid mount 1000 rpm shaft for the generator at the front of the tractor when I have my log processor 3 point hitch unit running off the rear PTO. This way I can run electric saws off the tractor at the same time.

When I need full site backup, I'd connect it to the proper 540 shaft and ramp up the engine to specs.

In this case, I'd go the inverter route previously posted. Perhaps another battery in parallel to original battery. Seems to be less hassle than connecting and disconnecting the generator when switching from 120 volt power and wood processor

 

[mo1]

I am considering the idea of running a 540 rpm pto generator on the 1000 rpm shaft at 1134 engine rpm for extended periods of time. JD manual suggests minimum operating rpm as 1500. Does anyone have experience related to this? Perhaps those older engines don't lubricate properly at lower rpm? I'd love to hear of positive and negative experiences with similar setups.

Generally that is not recommended unless you are putting almost no load on the engine. Your engine is making little power at that low of an RPM. If it makes 65 PTO HP at 2075 engine RPM, it's making well under half of that at 1100 RPM as the engine is making much less torque at 1100 RPM than 2075 RPM. You would have to make the same torque at the lower RPM than the higher RPM in order to have the power decrease in a linear fashion as HP is the product of torque and RPM. If you overload the engine, particularly at a low RPM, it would be likely to overheat. Since it is a carbureted gas engine, it will probably also run rich as the carb is trying to dump a bunch of fuel into the engine due to it seeing little vacuum as it is under quite a bit of load, and you'll likely foul plugs and cause a lot of carbon buildup inside of the engine.

The other risk you run with running such a low RPM on your engine in driving a generator specifically is that generators are very picky about the speed they are driven at. Drive it too fast and you end up with too high of voltage and line frequency, and drive it too slow and you end up with the opposite. Both can ruin whatever you plug into the generator, although I suspect you are using universal motor saws, which really are only sensitive to the voltage changes and not the frequency changes. Running an engine so far out of its powerband makes it much more difficult for the carb to regulate the engine speed very well with changing loads than if you run it in the meat of the powerband where the engine can much more easily keep the engine RPM in a narrow range with changing loads.

A 2kW inverter would be a pretty big load and you would need to use this pretty sparingly. Drawing 1500 watts through the inverter will draw 125 amps from the battery, which is going to be well above what the alternator itself can supply. I looked in the manual for the 3020 for the alternator size and it wasn't listed, but it did list the battery as an 85 amp-hour unit. A new open station utility tractor of about the same power as the 3020, such as my 5075E, has a 70 amp alternator feeding an 85 Ah battery, so yours is probably a bit smaller.

 

[Longhorn_007]

A 2kW inverter would be a pretty big load and you would need to use this pretty sparingly. Drawing 1500 watts through the inverter will draw 125 amps from the battery, which is going to be well above what the alternator itself can supply. I looked in the manual for the 3020 for the alternator size and it wasn't listed, but it did list the battery as an 85 amp-hour unit. A new open station utility tractor of about the same power as the 3020, such as my 5075E, has a 70 amp alternator feeding an 85 Ah battery, so yours is probably a bit smaller.

Agreed, though the OP's use case is for "short periods to run 15A (1500W) tools mostly " which, to me, says intermittent loads with a possible peak of 1500W and the average draw a lot less than that when you look at the course of the day. But yeah, if it was going to be a saw mill setup running for hours at a time...that wouldn't be a good application for the tractor-fed inverter. But all that is just conjecture on my part given what I've read in the thread...only the OP would know for sure what the intended use case would actually be in regards to duty cycle etc and whether the average draw over the course of a work day would be too much for the alternator to keep up with.