An engine is placed onto a secure frame. This frame has a 1/8" steel plate attached to the front and the frame. The plate has two 1-1/8th” diameter holes cut 11” directly below one another into the plate to fit two shafts, one from the engine and one from the shaft that is connected to the dynamometer. The engine shaft is 1-1/8” while the dynamometer shaft is 1”. These pulleys were attached using two different quick-disconnect bushings to fit the specific shaft size. The belt is placed around the two pulleys. There is an idler pulley that needs to be attached to add tension to the belt. A custom bracket was made using the plasma cutter and welding and fixed to the steel plate with the idler pulley creating sufficient tension on the pulley. This piece is shown in figure 1. Two ½" holes are cut into the plate to attach the custom bracket.  

Once the dynamometer is hooked up to the engine pulley system, engine performance data is ready to collect.

The dyno will provide an output of engine speed and force. We will then determine the torque and power with two simple equations:

T = F x R P = T x n

• "T" is the torque produced by the engine (ft-lb).

• "R” in the torque equation refers to the length of the moment arm attached to the dynamometer (ft).

• “F” is the torsional force that is placed on the dynamometer by the engine (lb). 

• “n” is the symbol for angular speed of the engine’s shaft in revolution per minute (rpm).

Several points of values will be collected as the load on the engine is increased. Introducing more load onto the engine will result in a larger force and a smaller speed. A torque vs speed and power vs speed curve will be created in Excel to establish a visual representation of the engine performance. This will become important when calculating gear ratios and comparing efficiencies of different configurations.