Turbo speed sensor going to use optics instead ?

[nacelp]

I used to use a paint dab for spin balancing cranks (long time ago, ie early
70s), just as a reference.
Like using paint dab on the crank pulley when using a timing light.
Grumpy


> I have no idea, but I wonder what the response time is for your
> detector? Can is cycle on/ off at ~1/20 millisecond (assuming 10 blades
> at 120,000 rpm). Not trying to shoot holes in your plan, but it might be
> worth looking into. I have usually seen the tip of one blade painted
> white for an optical tach in compressor wheels.  That might mean a
> rebalance with the paint? I don't know.
>
> -Seth
>
> "Mike (Perth, Western Australia)" wrote:
> >
> > At 10:24 AM 9/03/2000 +0100, "Espen Hilde" <mwichstr at online.no> wrote:
> > >Take the compleate turbocharger and fix the wheel so it stands still.
> > >Drill trou the cower so you hit near the outer edge of the compressor
> > >wheel, turn the wheel 180 deg. drill trou the wheel once more to have
the
> > >balance fixed.Or offset the hole closer to senter if you dont want 2
pulses
> > >
> > >for each rpm.Glu the optical sensor in the back hole and your laser on
> > >front cower.Maybe you have to clean the sensor once in a while....
> >
> > OK - have given this some thought (and a short visit to my w/shop),
> > decided its not a good idea to mess around with the comp wheel which in
> > any way upsets balance or structural integrity - will also save me
> > doh in the event the balance does get upset.
> >
> > So,
> > This is what I've decided to do for the fist attempt:-
> >
> > a.      Cheap laser pointer
> >         positioned to glance off or reflect off the blades
> >         This could be axially mounted or better would be where the
> >         beam is interrupted by the blades directly.
> >         (Changing the batteries could be a pain ;-)
> > b.      Sensor mounted in comp cover but, behind a tube (1/4")
> >         so the surface is away from any dust/oil,
> >         ie. tube at r/angles to stream, sensor mounted at end of
> >         tube about 1" away from edge of comp cover.
> > c.      CPU to trigger counter or time between pulses, depends
> >         on number of reflections/edges detected. CPU can use
> >         time between pulses at low speed or count in gate time for
> >         high speed - with upper lower limits. Such as alarm if
> >         wheel stops and alarm/solenoid if wheel above preset rpm.
> > d.      Calibrate with infra-red optical tacho instrument
> >         and adjust laser/sensor position to suit multiple of
> >         sensed speed (given number of edges etc).
> >
> > The other way which came to mind was passing an AC field through the
> > comp wheel and using a variable reluctance pickup - that way I wouldn't
> > need to drill the comp wheel - I think the optical one looks best...
> >
> > I'm interested in any other suggestions,
> >
> > tah,
> >
> > :) mike
> > Perth, Western Australia
> >
>
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