Ed Klepeis wrote:

Dear Paul
      Looking at your eng dyno I have some questions. !. how is the long
shaft connected to the eng flexcoupling,bolted flange,etc 2. On the other
end what is mounted to take the reading
gauge,meter,etc and where can you get it. I was thinking of making
something like this to take to air shows to show people whats on the
market and who's making it. Any ideas or offers vendors out
there let's hear it.

Regards

Ed

techwelding@comcast.net

Flex coupling? We don't need no stinking flex coupling!!!

I don't follow you Ed. Are you talking about a large garage door spring to
measure
static thrust?  If so the dyno needs to be mounted on wheels. You
calibrate
the spring by hanging it from the ceiling and using weights to measure the
deflection.
It comes out to something like 100 pounds per inch of deflection. Then
all you need
to do is measure the spring with the engine off and again when it is
generating
max static thrust. Don't optimize the prop or the engine for static thrust
as that
can be dangerous. Some guy did that with a Suzuki engine and killed him
self.
Maybe you are worried about the shaft twisting the spring. Does not
happen.
The shaft only moves several degrees and that's it.

That is a small part of the dyno. The other part is the bathroom scale
to measure the torque. You might think a bathroom scale a bit crude but
the fact of the matter it makes an excellent torque sensor with high
resolution
and sensitivity. Does this answer your question? Perhaps a little sketch
would make it more clear for me.

Here is another drawing off the web site. You need one of these Ed. Would
help
with your Soob work. You could charge those Soob wienees for dyno time :)

BTW don't forget to use a pick up truck  steering damper opposite the
bathroom scale
beam to damp out the torsional vibrations. You will find that out right
away when you start to use it.

Paul Lamar

Ed Klepeis wrote:

Dear Paul
    Some questions what range should the scale have 0-200, 0-300lbs etc.
Also the hurricane strap could i use something better like a heim end with a
bolt thru it. If I understand it right the eng floats on the main shaft
which pulls against the spring for a reading and also rotates with the
torque of the eng for a reading on the scale. correct me if I'am wrong.
                                                                Regards
                                                                    Ed

A NA rotary has on the order of 160 foot pounds of torque so with a 2.85:1
gear box that becomes 456 foot pounds of prop torque. If the lever arm is two 
feet long the bathroom scale will see half of the force or about 228 pounds.

Yes, any low friction joint will work fine.

Correct on your assumptions. You might also use a safety cable if you use
a spring. Don't want the dyno heading out across the farm :)

Paul Lamar
 
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