X-Mozilla-Keys:                                                                                 
Charlie and Lynda Rosenzweig wrote:

Paul,

I would be interested if you could send me more
informtion on how to build a home made engine
dyno. I see the drawing for the Dyno and Thrust
stand on your website, but quite frankly I am not
sure what to do with the scale readings once I
get them. Nor how to calibrate the garage door
spring or to what weight? i.e. 200 lbs or 2000 lbs?

Well you get HP from measureing the torque and the
RPM. The formula, if memory serves me correctly,
is HP = Torque X RPM / 5252.

The bathroom scale reads out half the torque.
You must multiply the bathroom scale reading
by two to get tha actual torque, The RPM is that
of the prop. This dyno works best if you have
a ground ajustable prop so you can change the 
pitch. That will allow the engine to run at 
different RPM's at WOT(wide open throttle).
>From this info you can then plot a HP curve.

The garage door spring is calibrated by hanging it
from the limb of a tree. Tie a garbage can on it
and add water while measuring the length of the spring.
Water weighs eight pounds per gallon. See my article in
Kitplanes a few months back.

What you wind up with is a giant fish scale.

In a nutshell it appears that the contraption only
measures spring tension and differential (not total)
weight from static to WOT? Correct? (Minus the friction
from the resistence of the contraption to roll).

P.S. do you know of a reasonalby priced (<$100.00)
scale that measures up to $500 lbs?

Thats is a tough one. I have been looking for something like
that for the past 30 years. Best use the garage door spring.

Charlie Rosenzweig.
9070 Ocean Beach Hwy.
Loongview, Wa.  98632
360 577-6407.

 
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