Tom Webber wrote:
Hi Paul, Here's my first shot at measuring the impeller to housing tolerance. I use a plastic
clay. Jewelers us it to make molds and models. I pressed the cartridge into the soft material
then used calipers to measure the thickness remaining. Kinda like plastic gage (sort of).
Anyway the measurement I got was Max of .060 and Min of .057. I did not torque it down so will be
some less. Although that's a pretty big gap. If you would like this done a different way let me
know. I'm always willing to assist.
Tom Webber
Thanks Tom. Good work. I'll see if I can machine the new water pump housing to a
smaller gap. That should pump more water at the same RPM. Or the same water
at lower RPM and HP consumption.
Paul Lamar
Paul,
It is not clear to me that a smaller gap will necessarily pump more water, mighten it just increase the viscous losses?
Also, what is the tolerances on the manufacture of the cartridge? That gap might be there for a reason.
Should be interesting to test the modified pump. You have my data on the "stock" pump (as modified to clear the cowl)
Bill Schertz.
I really appreciate the work you did measuring the flow of the stock pump Bill.
Don't destroy that set up. If you have the time I can send you a new pump
and you could get comparison data. We could also mount the new pump on
an engine along with the stock pump and test the new pump using the engine
itself as a power source. Would not that be fun? :)
It is well proven and well known the less the gap in centrifugal pumps the higher
the efficiency. Mazda themselves made a turbo charger compressor housing that was self
abrading to minimize the clearance. Many full sizes turbo fans use self abrading
material to improve the efficiency. William's is having trouble with the efficiency
of their small turbo fan for essentially the same reason. If I thought
it would live a would put some dry micro in the water pump. High speed
water is very abrasive and would probably eat it away.
Paul Lamar
---------------
Paul,
I have basically totally disassembled the pump testing setup and moved on in the construction process. I want to get something done so I can fly before I am too old.
A test of the pump (not pumping through the engine) cannot be directly compared to my curves, since my tests have the pressure drop through the engine included in the basic pump curve.
With the new pump you are making, the pump would have to be connected to the inlet/outlet of the engine in the circuit for direct comparison. That could allow a bit more data since you could get the pressure drop across the engine as a function of flow.
No problem. I'll just hook up another engine and pump the water through that:)
Paul Lamar
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