2 stage Tractor PTO Pumps

[arboriculturist]

Just found the earlier post from Openspaceman, about 2 stage PTO pumps running at Tractor tickover speeds:

 

"Just Interesting little pumps but more for high revving little engines as they stand 3600rpm.

 

Most 2p series pumps which fit on the (typically) 1:3 step up PTO gearboxes are only good for 3000 rpm ( it's worth bearing in mind they need to run at over 1000rpm as they depend on some iternal pressure to maintain the sealing aluminium bushes in relation to the gear faces).

 

Also note the outputs for these two speed pumps quoted is the combined high flow at lower pressure."

 

So running a 2 stage at tickover revs - a no go. Any comments?

[openspaceman]

Just found the earlier post from Openspaceman, about 2 stage PTO pumps running at Tractor tickover speeds:

 

"Just Interesting little pumps but more for high revving little engines as they stand 3600rpm.

 

Most 2p series pumps which fit on the (typically) 1:3 step up PTO gearboxes are only good for 3000 rpm ( it's worth bearing in mind they need to run at over 1000rpm as they depend on some iternal pressure to maintain the sealing aluminium bushes in relation to the gear faces).

 

Also note the outputs for these two speed pumps quoted is the combined high flow at lower pressure."

 

So running a 2 stage at tickover revs - a no go. Any comments?

 

You are getting mixed up: Treequip provided the link to the small two stage pumps which I suggested are more suitable for small high revving engines. I expect these engines tick-over at near enough 1000rpm.

 

I had not seen these before although I have seen tandem pumps used to supply two independent loads and it would be simple to rig a power limiting arrangement for such a set up. However you have more than adequate shaft horsepower on the back of a 35x to not need worry about such stuff. Incidentally your 18litres a minute at 200bar is delivering only 6kW to the splitter.

 

The pumps I was referring to are standard throughout the industry, when I was young they were made by Dowty and I still tend to refer to them as Dowty gear pumps. They were made in at least 3 series (1P,2P and 3P) and each series had a common gear diameter, the capacity was changed by lengthening the gear and body. The 2P series were the ones common on a lot of these PTO gearboxes and I have them driven off the nose of the Counties but they are a fixed output per revolution so the only way of varying output is to change engine speed. 1P pumps were often engine mounted for power steering, driven off the timing gears and 3P were typically running flail hedge cutters.

 

 

As I said there are other means of doing things to get a quicker cycle time out of simple open centre set ups if you want to keep the price down.

 

These Dowty type pumps don't suffer abuse well, so get the oil too hot, over speed them of have a hard duty cycle and they will not last, they also cannot stand cavitation, so sucking cold viscous oil along a narrow pipe kills them in no time, I found that out one freezing day when we fired up the ruggerini power pack for the Trekkasaw.

 

I have a 9 gallon per minute one on an old 1124 that has worked for 30 years yet a similar slightly larger one on a different grapple loader seems to need replacing every 1500 hours or so and this must be to do with something subtly different in the two installations.

[arboriculturist]

You are getting mixed up: Treequip provided the link to the small two stage pumps which I suggested are more suitable for small high revving engines. I expect these engines tick-over at near enough 1000rpm.

 

I had not seen these before although I have seen tandem pumps used to supply two independent loads and it would be simple to rig a power limiting arrangement for such a set up. However you have more than adequate shaft horsepower on the back of a 35x to not need worry about such stuff. Incidentally your 18litres a minute at 200bar is delivering only 6kW to the splitter.

 

The pumps I was referring to are standard throughout the industry, when I was young they were made by Dowty and I still tend to refer to them as Dowty gear pumps. They were made in at least 3 series (1P,2P and 3P) and each series had a common gear diameter, the capacity was changed by lengthening the gear and body. The 2P series were the ones common on a lot of these PTO gearboxes and I have them driven off the nose of the Counties but they are a fixed output per revolution so the only way of varying output is to change engine speed. 1P pumps were often engine mounted for power steering, driven off the timing gears and 3P were typically running flail hedge cutters.

 

 

As I said there are other means of doing things to get a quicker cycle time out of simple open centre set ups if you want to keep the price down.

 

These Dowty type pumps don't suffer abuse well, so get the oil too hot, over speed them of have a hard duty cycle and they will not last, they also cannot stand cavitation, so sucking cold viscous oil along a narrow pipe kills them in no time, I found that out one freezing day when we fired up the ruggerini power pack for the Trekkasaw.

 

I have a 9 gallon per minute one on an old 1124 that has worked for 30 years yet a similar slightly larger one on a different grapple loader seems to need replacing every 1500 hours or so and this must be to do with something subtly different in the two installations.

 

Thanks for excellent feedback. I agree on the 35X the 11 tonne splitter is not good. Will consult a specialist about stage 2 pump.