Is hyraulic drive posible?

GeorgeB wrote in message . ..
On Thu, 08 Jul 2004 02:52:48 GMT, Andy Asberry
wrote:

I design and provide technical support for electrohydraulic systems
for a living, and this is not a place that I owuld recommend their
use.

George

Maybe you can answer a question I've had for sometime. What is the
relative efficiency of hydraulics, belts, gears and chain drive?
You've given the hydraulic answer. Care to take a stab at the others,
please?

STAB, yes ... feelings based on things I have seen and heard ... NO
HARD FACTS to back this up. (I looked and failed to find support)

hydraulics TOTAL ... ~80%
v belt, 90-95%
tooth belt, 92-97%
spur/bevel gear, 96-98%
worm gear, 25-80%
chain. 96-98%

lesser ratios (nearer 1:1) are more efficient.

Based on what I recall from my mechanical engineering days
spur gears will be the most efficient. This is because
spur gear teeth have a curvature called an involute which
permits rolling contact between the tooth surfaces. Still,
I think 95% is about the best you get with spur gears, I
wonder if I can still find my old texts...

Bevel gears have some sliding contact between the teeth and
so more friction less efficiency than spur gears. But they
have more surface in contact between meshing teath so they
can handle larger loads for their size. Typical worm drives
with a small worm and a large worm gear for a large speed
reduction and large torque gain will be the least efficient,
down around 5%, IIRC.

V-belts are probably the trickiest to optimize. Too little
tension and energy is lost in slippage, too much and energy
is lost in elastic deformation of the belt. Cog belts allow
you to reduce the tension on the belt without slippage.

The other drive mechanisms tend to have their highest efficiency
with a slightly 'sloppy fit' that minimizes elastic deformation
but also introduces other problems like backlash, vibration and
so on.

--

FF