Subject: RE: Volvo poppet forces
Date: Mon, 17 May 1999 15:31:41 -0500
From: "Gram, Marty" <Marty.Gram@mts.com>
To: "Albright, Joe" <Joe.Albright@mts.com>
CC: "Lorenz, Josh" <Josh.Lorenz@mts.com>, "Chen, Hans" <Hans.Chen@mts.com>,
     "Saari, Byron" <Byron.Saari@mts.com>, "Kusner, Dave"
     <Dave.Kusner@mts.com>, "Larson, Rod" <Rod.Larson@mts.com>

Joe--
The oscillations on the poppet drive force are mass times acceleration
on the poppet.  With feedback, the oscillations can be damped out.
Another problem with the data, that I sent you, is that the actuator is
in the cushion as it starts up.

We ran a new set of tests last Friday and have better data -- flow
forces still low.  By going to a smoother startup, most of the
oscillations were eliminated.  The forces measured by these tests are as
follows:
-- valve friction                +- 7500 lbf,   300 psi
-- acceleration force         15000 lbf   600 psi
-- flow force  return valve         6000 lbf,  240 psi
-- flow force pressure valve   -4000 lbf   160 psi

Flow direction on the return valve is same as on Toyota.

If you would like to discuss the data, I suggest you drop by my office
where we can look at it in mathcad.

I am sending you a copy of the data  in mathcad format.

--Marty

> ----------
> From:         Albright, Joe
> Sent:         Sunday, May 16, 1999 9:10 AM
> To:   Gram, Marty
> Cc:   Lorenz, Josh; Chen, Hans; Saari, Byron; Kusner, Dave; Larson,
> Rod
> Subject:      RE: Volvo poppet forces
>
> Hi Marty,
>
> Thanks for the flow force plots.  After looking at them, a variety of
> other questions came to mind.  The most important question I believe
> is why are there oscillations in the flow force/spool position, and
> how much will they grow with larger poppet delta P.  That was my
> largest concern when we started Toyota.  Thus far, we have only seen
> small amplitude oscillations, at a relatively high frequency (>200
> Hz).  So far, so good.
>
> The 990506 Volvo data shows cyclic delta P of more than 400 psi
> (10,000 lbs) on the return poppet.  The frequency is relatively low at
> 20 Hz.  The pressure poppet seems to be much lower in amplitude,
> although the initial spike is similar in magnitude.  The basic
> frequency is similar to the return poppet.  The return poppet also
> shows measurable poppet position oscillation.  It has been our
> experience on Toyota that if you can see the motion (when we had the
> LVDT), then you will definitely see acceleration distortion.
>
> My other questions relate just to better understanding the data, and
> what it might indicate.  Would discussing them be worthwhile for you?
> If so, I suggest that we meet and discuss, since I am sure there would
> be real benefit in being able to look at the plots while we talk.  I
> encourage the cc's to add any insights they may have on this issue.
>
> Joe
>
>
>
>
>
>       -----Original Message-----
>       From:   Gram, Marty
>       Sent:   Tuesday, May 11, 1999 2:46 PM
>       To:     Albright, Joe
>       Cc:     Lorenz, Josh; Chen, Hans; Saari, Byron
>       Subject:        RE: Volvo poppet forces
>
>       Joe --
>
>       I think you are right about the 9 fold force increase with
> pressure versus the 3 fold that I suggested.  Forces should still be
> ok.
>
>       Regarding the differences between the valves that could account
> for differences in flow forces; the width of the ends may be
> significant -- leading to the conclusion:  Wider is better!     I
> don't know how the flow distribution might change at higher pressures,
> but it did not seem to be a problem with UCSD and Watervleit.
>
>       I will send you a copy of the plots by mail.
>
>       --Marty
>
>               ----------
>               From:   Albright, Joe
>               Sent:   Tuesday, May 11, 1999 1:15 PM
>               To:     Gram, Marty
>               Cc:     Lorenz, Josh; Chen, Hans; Saari, Byron
>               Subject:        RE: Volvo poppet forces
>
>               Hi Marty,
>
>               Thanks for the update.  That sounds promising.  I would
> like to see some of the plots if practical.
>
>               Regarding what to expect at higher pressures, I just
> double checked in Merritt.  According to that reference, flow force is
> proportional to the pressure drop.  If that analysis is appropriate
> for your poppet, that would mean a 9 fold increase in flow force with
> a 9 fold increase in pressure drop.  Even at that increase you would
> still only be at about 36000 to 45000 lbs of flow force, which is less
> that 2000 psi delta P on you poppet.  Would that still work out OK for
> you?
>
>               Regarding possible errors in our measurement, I have
> thought about that many times, and don't see the error if there is
> one.  My conclusion at this time is that the flow force you measure
> will be very dependent on the end geometry of the poppet, and which
> pressure you feed to the back of the poppet.  One major difference
> between the Volvo poppet and the Toyota poppet is the large poppet end
> area that is on yours.  This presumably creates a larger surface area
> upon which the pressures will act.  My suspicion is that for your
> current tests the pressure has distributed favorably giving a low flow
> force.  Any thoughts on how it will distribute at higher pressure
> drops?
>
>               Joe
>
>                       -----Original Message-----
>                       From:   Gram, Marty
>                       Sent:   Friday, May 07, 1999 4:17 PM
>                       To:     Albright, Joe; Lorenz, Josh; Strand,
> Dick; Chen, Hans; Melander, Dan; Kusner, Dave; Gallagher, Steve;
> Saari, Byron; Larson, Rod; Hessburg, Thomas; Fullen, Mark
>                       Cc:     Beduhn, Bill; Cohoon, Steve
>                       Subject:        Volvo poppet forces
>
>                       Poppet valve test results.  Good news.
>
>                       On May 6, we ran a series of tests on the Volvo
> rear actuator.  In these test we kept the main pressure below 600 psi
> to avoid lifting the actuator off the floor.  We were able to flow
> 22000 gpm through the valves in each direction and measure flow forces
> (we reached 28000 gpm when we opened the valves fast).  The valves
> have a 12" diameter poppet with a 25 sq in drive area --they are about
> 25% larger than the Toyota valve.  The Volvo valves were built without
> a flow deflecting "nose", and there is no insert in the center hole.
> We use an LVDT to control valve position.
>
>                       Flow force measurements were consistent with the
> flow forces measured on Watervliet and UCSD -- very low.  Flow force
> on the return valve was about 5000 lbf (flow in the same direction as
> Toyota).  Flow force on the pressure valve was about 4000 lbf.  The
> flow forces did not vary noticeably with valve opening.
>
>                       When we run at full system pressure of 5000 psi,
> we expect the flows to increase by a factor of 3 and expect the flow
> forces to increase by the same factor.
>
>                       Joe:  It may be worthwhile to revisit the Toyota
> valve flow force measurements.  Could the very high forces that you
> measured on the poppet be due to something other than flow force? --
> acceleration?  --effect of a loose LVDT?  --vibrations on the
> transducer?  --pressure taps seeing a venturi effect?
>
>                       --Marty
>
>
