>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
>--

Greg,

I would be interested to hear what the engineers have to say and more
importantly why.  Several years ago I was on an identical track as you
mentioned. Garrett turbo charger also explore it as a solution to
overcome turbo-lag but dropped it in favor of other methods.  Heat
generation = loss in efficiency. I was contemplating ways to lower line
resistance and finding a low viscosity compressible oil seemed be a
solution.  With the suggestion of one of this newsletter's contributors
I found the ROTREX supercharger planetary roller traction reduction
drive. At 98% efficient it is hard to beat.  The internal oil film does
the work of transferring power from the  direct connect, at turbine
speed revolving outer ring at the instant it compresses between the
rollers. At other moments it returns to its natural low energy state.

This doesn't`t get the torque to the e-shaft of course, but a multi-V
belt in this application should be at least 95% efficient.  95X98 =
93.1%

Doug in Japan

He, Doug in Japan:

Any thoughts on this variable speed planetary gearbox from Fallbrook
Technology?  Right now it's being used on bicycles, but their website
makes reference to auto, heavy machinery.  Could replace a torque
converter or fluid coupling.
A computer controller would be needed to adjust and match speeds to
maximize turbo rpm efficiencies.  Seems pretty simple with direct
gearing, high torque transfer efficiency.  As Paul said above, "hard to
beat gear"
http://www.fallbrooktech.com/NuVinci.asp

Greg