One way to determine the horsepower of our engines for free and have a fun day at the same time is to attend one of the many steam shows or other vintage events where in addition to dozens of old stationary engines you will often see someone with a Prony engine brake. Many are home made and range from simple to very nice with electronic readouts. If you've never heard of one, it's a very simple design that probably any one can build using ordinary hand tools and a minimum investment. Rather than waste bandwidth here, check this link:
http://www.buckleyoldengineshow.org/Hor ... epower.htm
BTW Prony brakes at old engine events are usually set up to use a flat belt so it might take more than one visit - the first to get friendly with the owner and figure out how to direct couple to his brake (PTO shaft?) and the second to take your engine for a dyno run.
FYI
Avery
Measuring Horsepower
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