Back in the day we built a brake dyno using 2.5" square steel tubing in a 2
by 3 by 6 foot frame. A big radiator was set into a tank under the engine,
with a cold-water fitting feeding the tank. On the flywheel end we had a
disk with a variety of bolt patterns connected to a short driveshaft that in
turn connected to a pair of 12" diameter steel wheels. The wheels were
braked using a couple of calipers mounted on a reaction arm, which was
connected to a hydraulic ram. Doing a dyno run entailed running the engine
up to a given RPM at wide open throttle while applying brake pressure (using
a handwheel) and then recording the fluid pressure in the ram. It was a
low-buck but very effective setup. It was most useful for aspirated engines
in the 200 to 300 hp range, and as the racing went on the group I was with
got more and more into turbocharging and high power levels, so the dyno
eventually got retired.
If you're not going to run the engine at high power levels you don't need
anything this elaborate, but I would recommend starting with something that
has at least a 3 x 4 foot perimeter frame. Engine stands (especially cheap
ones) are way too tippy. Doing the radiator in a submerged tank is great -
you can very effectively control the cooling by regulating the cold-water
flow into the tank.
Best regards,
Theo
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