Hydrostatic Drive Efficiency

He is wrong, efficiencies can be higher it depends on the type and on the used controls. He thought, I presume of not piloted systems which will not work at optimal point in all load combinations. Look at the the catalogues of Bosch, Vickers, Rexroth, Parker, Sauer and other to see that efficiencies can be a lot higher.

I think your friend might be right. Hydrostatic drives have a transfer rates that are quite low, compared to gear boxes. Depending on the set up, quite a bit is lost to friction. The fluid running through pipes, pumps and motors. Most pumps and motors have internal bypass, so you get a loss of transfer. You also lose with the elbows and internal friction of the piping. Adding all these losses, it could amount to 40% loss of efficiency.

Instead of simple gearbox + cardanshaft transmisson hydrostatic transmission efficienty may vary more significantly depending on speed (or transmission ratio). Maximun efficiency of variable pump may be up to 0.91 (at specific flow), variable motor may have up to 0.88 (also at specific flow or speed), if you need change speed (transmission ratio) efficiency of motor or pump may lower up to 0.5 or even more. So, best possiable ratio of hydrostatic trans. (without loss on valves and tubes) =0.91*0.88=80%. So, your friend have right notion.

WE here offer Fluid Drives that can trnsfer their power at about 1:1 ratio with only 2% loss at the highest. Please contact us for further info at 248-328-8130 or E-mail us at suttonsofholly@sbcglobal.net.

I tried too contact you but no successs. Is it a joke since your efficiency simply is not possible with real fluid drives ?

Your address is not found on the net!

We have always used 20-30% loss of horsepower with hydrostatics compared to an equivalent gearbox system. But, there are advantages with hydrostatics as compared to gearbox systems, that we like better. This is mostly with snow grooming equipment.

Not a bad rule of thumb for a cheap system on a lawn tractor, for example (although even there a bit conservative). However, if a system is carefully engineered for efficiency (rather than, for instance, cost) efficiency can be higher. This subject came up in a thread about hydraulic vs electric hybrids.

Wow!! I wish I could call $200k equipment cheap!

My response was actually to the original post. 60% is at the very low end of the scale. Your equipment, at 70-80%, is much better. I wish I could call $200,000 equipment cheap too.