I made a couple for testing our 29 hp half vw. Made from good quality pine, three laminations glued together with titebond 3.
On our first attempt, we used only two bolts. I don't know what I was thinking. The wood bar split into pieces and flew apart. We purposely did not stand in the plane of the prop, so no one got hurt. Some pieces flew over/past our cars, missing them too. We had a good laugh over it, but it could have been bad news.
On the second one, we bolted it properly, and it worked well.
I probably would use a stronger wood for higher horsepower engines.
You may already know, but the wood bar dyno shows valid max engine hp only when engine is at full throttle. One data point only. If you want more data points, maybe to draw a hp/rpm curve, more wood bars, of various sizes would have to be made and run to produce a hp point at a different full throttle rpm. Each size bar gives a hp data point at one rpm, full throttle. At reduced throttle settings, the bar and formulas will show the hp being used, but not much value for determining the engine capability.
