Tractor PTO driven generator ?

[Matchless]

Seen a tractor driven genny for sale, £200.00, I don't have a tractor, I want a genny for the power cuts just around the corner, I do have an old Thwaites dumper with a half decent petter / Lister twin cylinder diesel engine, looking at the data plate this looks adequate to me, what is the DOR of a PTO shaft, would a twin cylinder engine described above likely run this, The dumper is rusting away and getting in the way, am I stupid............

 

[carbon]

DOR of the pto on a tractor is clockwise when looking at the back of the tractor

Does this generator have a gearbox

 

[arther dailey]

@ that monies what have you got to loose ? if you cant get it to work re sell for a small loss .

 

[carbon]

Standard PTO speed was 540 rpm then 1000 rpm.

 

[Bornfree]

You would need to remove the gearbox from the generator and couple the engine direct.

 

[8ob]

That will make a dumper engine grunt, thats a big generator.

Bob

 

[brightspark]

whats the twin lister engine about 20 hp .its roughly 2 hp per 1kw

 

[oilcooled :)]

Want around 50hp at the shaft to run that at full draw

 

[minimutly]

It won’t, if you load the Genny up - but what are you hanging off it?

 

[Turbo]

The problem with tractor driven gennys is that there's normally no mechanical governer, you have to regulate the output with the hand throttle on the tractor. So if the load changes you have to mess around getting the revs set to get the right output voltage. If a big load is switched off it means anything else is getting too much voltage.

 

[GRW]

The 2-cyl Lister is probably more like 15HP I'd guess, but it might only be 10Hp.
The alternator is an old 3ph - quite probably a dedicated 3ph winding so it can't be reconfigured to a dedicated 1ph output like modern brushless multi-wire units.
It could well be uni-directional so your rotation needs to be suitable (brushless rotating diode alts don't care which way they rotate).
Your Lister might be good to sustain maybe 6 or 7kva if you were able to direct couple to the engine (& run at 1500rpm) far less via the gearbox as the motor will be ticking over.
As has been pointed out, you don't have a Governor (or probably don't) on the engine, so with such a small Hp you'd be constantly manually adjusting the throttle to compensate for load changes.
If you really want to use the dumper engine, then buying a twin-bearing modern alternator at say 10kva and buying /making a coupling would be better.... but in truth for a standby of just a few kva for essentials it's easier to buy a little Honda petrol set (convert it to lpg/propane if you're concerned about the fuel).
The PTO gen is cheap, but by the time you married it all up you'll have spent more to get a machine that works poorly with zero resale value.

 

[oilcooled :)]

To put into context how much power they need I have a 30 kva one coupled to a 100 hp tractor and it came with no drive shaft I bought a drive shaft of a fertiliser spreader thinking it be easy driven connected it up turned it on it wrung the drive shaft sheared it and threw it over the shed, ended up getting a heavy shaft of a topper

 

[Munkul]

The problem with tractor driven gennys is that there's normally no mechanical governer, you have to regulate the output with the hand throttle on the tractor. So if the load changes you have to mess around getting the revs set to get the right output voltage. If a big load is switched off it means anything else is getting too much voltage.

all tractor diesel engines have a governor, at least all the ones I've ever driven!
Yes the revs drop a bit under load but a man enough tractor will hold pretty steady within100rpm. How do you think any constant rpm work takes place otherwise?

We have a 40-odd kva 3phase tractor mounted alternator for backup on the farm, we swing a switchover switch and plug the genny straight into the distribution board. Works well on a 100hp tractor, it barely troubles it, runs our tank cooler and milking system and all the lights etc no bother, as well as the house. (it doesn't like running under-speed though... some really nasty power harmonics kick back to the tractor! My mistake one time)

regarding the 1500rpm rating, I assume that genny has a gearbox to step the speed up from 540rpm. I'd want a 60hp tractor on that, but you'd get away with less if you didn't load it up.

 

[minimutly]

Tortional vibration - seen it on my engine dyno. Could potentially snap the crank...

 

[Gareth J]

Unless you want to do something very basic and lightweight with the power, it's probably going to be overloaded or have such difficulty moderating revs at different loads, what you can end up running on it will end up being less than equivalent to £200's worth of used petrol genny.

Getting an old governor from a dumper engine to maintain a steady rpm at different loads, which will determine the stability of your Hz, will be tricky. Both because the engine is small and because, probably, everything on it is tired and worn. Maintaining perfectly steady 50Hz isn't so vital if you're running heaters, old motors or the like but some modern appliances can be really fussy.

 

[GRW]

As @Munkul says on his post - the very best way to run a PTO gen is
a) make sure its man enough for the loads you want to run
b) throw loads of Hp at it from the tractor, as the huge torque then compensates for a fixed hand throttle. There are calcs, but if you basically use double the tractor Hp of the kva of the set as a MINIMUM - you'll do ok, but more is better for no hassle performance.
There's plenty of stories where Farmers have tried to save fuel and save bringing a Field Working tractor on to run their PTO Gen by using the yard scraper old toy tractor - my fave is the guy who tried to run a 55kva fixed pro gen off a grey fergie using an old hefty shaft with no clutch. When he dumped the load on the fergie stalled-out.... but not before it had tipped itself on its side (It was less power to turn the tractor over than overcome the alternator demand) .
Running on 1000 speed with a big tractor is another.... and it's another bad idea. The tractor makes a lot less power/torque at much lower revs - so again it's a struggle to run the gen, plus you get a lot more shock loading impacts through the drivetrain.
People have to learn the hard way to stick to the 540 output speed (though most gearboxes are giving 50Hz at 430 or 500rpm anyway) and use a meaty enough tractor.

 

[Munkul]

This is what we used to do. Quite a sketchy setup relying on the alternator bolted to some pallets, the telehandler forks on top to stop it jumping around To be fair, we only used to run the thing around 20kw ish as the supply cable and plugs were only rated to 32 amps. We gauged it by the temp of the cable...




Then I made a frame for it lol, much safer and easier

 

[GRW]

This is what we used to do. Quite a sketchy setup relying on the alternator bolted to some pallets, the telehandler forks on top to stop it jumping around To be fair, we only used to run the thing around 20kw ish as the supply cable and plugs were only rated to 32 amps. We gauged it by the temp of the cable...

View attachment 318195


Then I made a frame for it lol, much safer and easier

View attachment 318194

I've seen a couple of PTO Gens, brand new- get smashed to bits.
Farmers bought them in a tearing hurry in a bad winter (cos they'd been gambling without one) - then finding they couldn't get a Sparky or Dairy Engineers to install on-the-spot.... so they cobbled together without understanding the power throughput.

People had just sat the gen in a link box, hooked a cable up & let rip.... and the insecure PTO gen promptly turned into a sort of Flail cum Catherine wheel flailing about on the end of a PTO shaft, smashing itself to smithereens.
Fortunately no-one was stood next to them at the time, cos that would have been ugly.

 

[Justme]

The problem with tractor driven gennys is that there's normally no mechanical governer, you have to regulate the output with the hand throttle on the tractor. So if the load changes you have to mess around getting the revs set to get the right output voltage. If a big load is switched off it means anything else is getting too much voltage.

I dont find that problem at all.

I set it to the right pto rpm / genny htz & it basically stays there with almost no droop.

But thats a 50+hp engine at full PTO speed & the max draw is prob about 10kw plus inrush current when I start to weld.

No cold starts. Trying to do that on a smaller genny results in cold starts.

 

[Justme]

PS

Running a PTO genny is not very fuel / energy produced efficient.

Ok like me for occasional work or remote work but not for long periods.