- Joined
- May 1, 2017
- Messages
- 361
A BV ducted fan would be safe up to 30,000, providing a shroud was used. The photo shows the 3/8" thick aluminum shroud used on a typical torque cradle type test stand.Ducted fan props and shroud should work? But depending on your wallet? Cut down balanced larger props may also work? But like Lohring said if it goes bad? It goes bad in a hurry that kill switch finger better be your trigger finger and just as quick as a gunfighter or it may wreck the whole setup including the engine (I really hope not!) But hope for the best and prepare for the worst! Murphy was a prick!
Do it Terry!
There are many things you will discover with a good test stand. I wanted to determine the RPM limit of a typical AISI S-7 steel, "I" beam, roller connecting rod. The .80 cu in engine used was dyno tested at 38,000 rpm. After about 1 minute running time at WOT the rod failed completely! The carburetor used had a .750" bore. The exhaust timing was 198*; the transfer timing was 130* & the boosts 125*. The inverted drum opened 30* ABDC & closed 66* ATDC, for a total duration of 216*. The two stage pipes tuned length was 8.75 in & the fuel used was 65% nitro.
Jim Allen
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