Subject: RE: Toyota modifications
Date: Tue, 2 Mar 1999 08:10:26 -0600
From: "Gram, Marty" <Marty.Gram@mts.com>
To: "Larson, Rod" <Rod.Larson@mts.com>

Rod--
The Toyota poppet was built with a "nose" on the end which was intended
to turn the flow to balance flow forces.  The measured flow forces were
low -- < 1000 psi on a 16 sq in drive area.  Joe thought that the flow
forces might cause instability because the forces reverse direction, so
he had the nose cut off.  The flow forces went up to 3000 psi with a
curve that had a snaky shape but no force reversal.  The fixed mandrel
was added in a misguided attempt to reduce the flow force.

The Volvo poppets were built with no nose.  Hans will be building one
with a nose to try on the rear actuator tests should we have a flow
force problem.

I will mention to Joe that damping is crucial.
--Marty

> ----------
> From:         Rod Larson
> Sent:         Tuesday, March 2, 1999 6:25 AM
> To:   Gram, Marty
> Subject:      Re: Toyota modifications
>
> Marty,
> Dave Kusner mentioned to me just before I left that the poppet had
> much
> higher flow forces than expected.  Is this the mandrel thing ?
>
> Damping on the poppet control is crucial.  UCSD proved that.
> Rod
>
> Gram, Marty wrote:
>
> > This weekend, Joe was able to achieve a much improved waveform on
> sled
> > acceleration.  He made 2 changes:  added a mandrel to the poppet
> valve,
> > and increased decel pressure from 250 to 800 psi.
> >
> > The mandrel addition apparently did not change the drive force on
> the
> > poppet.
> >
> > The waveform was not checked with just the increase in decel
> pressure.
> >
> > The increased decel pressure eliminated some 5 kHz noise that was
> > thought to be caused by cavitation.
> >
> > At this point, we do not know whether the mandrel had any effect on
> the
> > waveform.  It may have added damping to the spool (there is no
> damping
> > provided by the servo loop at this point).
> >
> > I will continue to monitor the Toyota program to see what problems
> we
> > might have on Volvo.
> >
> > --Marty
>
