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 some think 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,
Me too, on the demonstrator!

Paul,
1" mild steel on the axle OK!
Also thought a set of scales ( on edge, facing backwards might be OK instead
of the spring ?
George (down under)

One inch is marginal. I would stick with inch and a half. You can use pipe
if you wish but you will need sleeves for the pillow blocks. Make sure
that shaft is ground to the right size or you will play hell getting it
to fit the pillow blocks.

Bathroom scales are designed to work horizontally. Good luck on any other orientations.

You can use two or three smaller springs in parallel if you wish.
If it were me I would forget the static thrust feature. It is damn close to meaningless.
It only applies for a second or two on the takeoff roll or on air boats :)

Paul Lamar
 
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