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Old Mar 02, 2014, 08:08 PM
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Dr Kiwi's Avatar
Chattanooga, Tennessee, United States
Joined May 2003
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Mini-Review
The Dr Kiwi Test Stand- consistency

Excuse the self-indulgence, but today I was testing a 5x3 E-MAX Professional CF prop against the venerable orange 5x3 GWS HD and I had occasion to run both props head-to-head on an ELERC C20 2500Kv motor (19g, ~2121Kv). It so happens that I previously (8yrs ago in fact) I had run the same 5x3 GWS HD on the very same motor. I looked at my results from 8yrs ago and from today, and I think you will agree that [within the limits of experimental error on hobby-grade equipment] they are essentially the same.

I have always liked to think that for my "Dr Kiwi Mk III Pusher Stand" I could vouch for the "consistency" of results.. I've never made a claim of absolute "accuracy" since I've had no way to determine exactly how "accurate" my results are.

But I like the "consistency" of these results from 2006 versus 2014!

Cheers, Phil
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Old Mar 04, 2014, 07:27 AM
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Blacksburg, VA 24060 USA
Joined Feb 2000
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Shock Absorber

Dr.,

I wonder if steadier, more consistent readings could be achieved by means of a dashpot, snubber, or shock absorber somewhere in the system. Something with a short stroke. Possibly a flexible pad.This would steady the various readings and make it easier to record data, either pencil-and-paper or digital.

Dimensions permitting, one end would be anchored to the base of the test stand, the other would be attached under the horizontal arm to the scale, but not onto the digital scale.

The shocks in the picture are Dromidas, $6.99 US the pair from Tower Hobbies. Short shocks should be fine, because we aren't dealing with much movement on the test stand. Experimenting with different grades of shock oil could be fun.

Jim R.
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Old Mar 04, 2014, 08:46 AM
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Chattanooga, Tennessee, United States
Joined May 2003
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I don't think I have any problem with steady readings.. once the motor is running at WOT, over the succeeding few seconds while I write down the numbers, the readings remain essentially the same. For hobby grade equipment I reckon it does pretty well.
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Old Mar 04, 2014, 01:33 PM
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Blacksburg, VA 24060 USA
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Dr.,

I agree that we hobbyists don't need engineering-grade results. Enough is known about most motors that most of us are interested in, so choosing a motor is no shot in the dark. But as long as we are, indeed, playing junior engineer when we put together and use a thrust stand, it might also be a fun thing to try to improve results.

As soon as I need to put together a Tower Hobbies order for other stuff, I'll order a pair of shocks while I'm at it.

Jim R.
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