Is a prony brake a fairly accurate way to test HP. I built a prony brake just with wood to fit on a rotating shaft with a 1 foot arm. I get .75 of 1 HP if the shaft is rotating about 180 rpm and the arm lifts and holds 22 lbs. The diameter of the shaft is 2" - does that matter? And is a prony brake very accurate? thanks from a tinkerer.