I'm exploring the idea of turbo-compounding thru hydraulics instead of
direct mechanical drive.  Here's the basics:

Have the turbo unit drive a hydraulic pump and also drive an electric
generator, both on the same output shaft.  Free hydraulic and electrical
power, right??.  Suppose the generator was also a starter/generator that
could be engaged on a static engine to produce limited hydraulic power
for any reason without need for the engine to be started.

Then I thought a hydraulic starter (hydrotor) would be a good idea since
the starter/generator could be engaged to power the hydraulic pump which
in turn would power the hydraulic starter.  Once the engine started, the
turbo exhaust would power the hydraulic pump and allow the
starter/generator to convert to generator mode for electrical power.
There would be no loss of hp from the engine since all the work is being
done by the exhaust turbo.

Then I thought that maybe the hydraulic pump could continue to power the
hydrotor all the way thru the operating range of the geared output shaft
that the starter was connected to.  (2500 rpm max).  This would satisfy
the objective of the turbo-compound assisting the final drive by
providing torque to the final drive shaft.

My question to a supplier this morning:  "Can you design a hydrotor to
run continuously at near max rpm (2500 rpm) delivering about 50 hp to
the final drive shaft?  There would be no need for a Bendix system since
the hydrotor would be engaged all the time to the flywheel.  System
pressure would be 3,000 psi, hydraulic oil to be air/water cooled. In
otherwords, the hydrotor's main purpose would be to provide continuous
power to the drive system, and secondary role would be to start the engine."

I received a reply just now that they are interested in the concept and
are taking it to their engineering department.  Maybe they'll all have a
good laugh at my idea but I think it has some merit.  I hate having
single purpose components, especially a Bendix starter that is used for
5 seconds, and then just tags along for the ride doing nothing but
adding 10 lbs.  Starter generators, which can weigh more, at least have
a dual purpose.

Greg Fleming


The down side is the relatively low efficiency of the hydraulic motors
and pumps in common with electricity approaches.
Eff1. times eff2. = lower overall eff.
Hard to beat gears.

Paul Lamar