Function of Range and RPM on an HST

[npalen]

Thanks, npalen for the link. Very nice explanation. Worth spending the time to watch the moderatordevelop the hydraulic circuitry. The moderator doesn't think much of simple suction filtration and makes a good argument for low viscosity fluid - or other alternate low temperature flow.
rScotty

When one thinks about starting an engine in extremely cold weather and how difficult it is for the oil to start thinking, compare that to a hydrostat with its extremely close tolerances! Then consider a little bit of ice in the works from condensation and its a wonder the hydrostats survive as well as they do.

Yes it does make a case for filtration and viscosity. I believe he mentioned something about extra fine filtration and on the pressure side to force the fluid thru the filter.

 

[Vigo327]

Hydraulic pumps are not great at creating suction without experiencing nasty side-effects, so an inlet filter has to be pretty 'loose' and is just intended to prevent the pump from eating chunks. The oil pickup screen on an engine is that way as well, but even looser than the inlet screens you find in hydraulics. But, like a power steering pump, that pump has to be able to zing up to ~6000 rpm without cavitating, so they are VERY intolerant of inlet restrictions.

 

[PlasterProspector]

Really great thread. I feel like I have a much better understand now.