View Single Post
Old 09-03-2012, 12:29 AM
Farmhand Farmhand is offline
Platinum Member
Join Date: Jun 2010
Location: Australia
Posts: 3,389
I'm dubious about the home done dyno tests. I don't see how if a belt that has a
much lower friction value could give the same result as one that has a higher
friction value. ie if the belt used is slippery a lot more force could be applied to
the belt before the same effective drag is placed on the motor shaft.

eg a belt made from greased leather compared to one with tar applied or two
leather belts but just with different friction values would show different results I
think. As a belt is used it will probably get more and more smooth and slippery.

I don't think any old strap or belt could be used to give an actual HP value, I
think all that could be determined would be a relative value for comparison.
And with a belt that becomes smoother and shinier as it is used the friction
value would change and so skew the results.

To come up with an actual "horse power" value from a home made dyno using
a strap and some scales is dodgey to say the least in my opinion.

It doesn't make any sense to me that two people can use different straps
with different friction values and both get an accurate power value.

Any thoughts on that ?

Bottom line is these type of tests can be easily faked I think. Maybe that is a
good project fro me to do next, see if I can show two different readings from
the same motor using belts with different friction values, or the same belt
modified to have a lower friction value. Sounds like fun to me.


P.S. And the reflective tape for the RPM meters is a doozy, if the meter
comes with reflective strips they are meant to be used I imagine. The
question is if the reflective strips are there why not use them to be more
accurate ?


Last edited by Farmhand; 09-03-2012 at 12:38 AM.
Reply With Quote