Roger Enns wrote:

Paul,

Have you considered Garrett/Allied Signal's method of
monitoring turbine speed?  They simply mill a flat on the
shaft, and drill and tap the center section casting to
accept an inductive prox sensor.  The prox sensor aims at
the shaft centerline, and is threaded down to provide
suitable voltage output as the flat on the shaft passes
during rotation. Counting pulses gives you rpm.  I've seen a
simple Fluke meter with frequency capability used to display
speed if the budget prevents a more elaborate method.  The
turbine/shaft must be rebalanced after milling the flat.
Consider replacing turbine/shaft once testing is complete.

Roger Enns

BTW I am in the process of researching a fiber optic tach

for

the turbo RPM. I will feed the fiber optic cable down the

exhaust

pipe of the compressor to look at the compressor blades

and count

them as they go by with a high speed photo diode I hope.

Paul Lamar

Roger Enns wrote:

Paul,

Have you considered Garrett/Allied Signal's method of
monitoring turbine speed?  They simply mill a flat on the
shaft, and drill and tap the center section casting to
accept an inductive prox sensor.  The prox sensor aims at
the shaft centerline, and is threaded down to provide
suitable voltage output as the flat on the shaft passes
during rotation. Counting pulses gives you rpm.  I've seen a
simple Fluke meter with frequency capability used to display
speed if the budget prevents a more elaborate method.  The
turbine/shaft must be rebalanced after milling the flat.
Consider replacing turbine/shaft once testing is complete.

Roger Enns

I was wondering how they did it. I guess the shaft is more
than strong enough to tolerate the milled flat. It seems every time 
I asked Turbonetics about getting that option they said we will get back 
to you. I would like to apply this to the stock turbo. The mag pickup is 
going to run real hot threaded into the turbo bearing housing. Any idea 
what brand of mag pickup Garret is using? I am thinking of keeping it
on the instrument panel as a read out.

Paul Lamar
 
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