RCU Forums - Safe thrust testing, BP Hobbies thrust stand.

I purchased this test stand a couple of years ago so that I could finally tell how much thrust various setups I was experimenting with were actually producing. Prior to that I had been using some online calculators or relying on other peoples data. The design is basic, but has produced results very close to others data which makes me belive its decently accurate. I have used it with setups that made up to 1.5lbs of thrust, but its sturdy enough that it can likely handle much larger stuff without problem, assuming that the base is properly secured to the table.</p>

I use this rig in conjunction with Astroflight wattmeter and a hobbico mini tachto get the big 4 data pieces, amps, watts, rpm and thrust. These info pieces have allowed me to play with different props, gearing and cell counts to find setups that make good power without overloading any components. I have found for instance that in one particular example, that going to a slightly lower gear ratio with no otherchanges gave nearly the same rpm but dropped ampsnearly 15%. In that case, the motor was beingoverloaded, causing its efficiency to drop off fast. Changing the ratio slightly took fixed that so I got almost the same rpms even though amps were back in the safe zone.</p>

In testing, I use an old reciever with my transmitter to control the motor, keeping the transmitter and wattmeterbehind the prop line for safety. The only time I have to cross to the front of theprop line is to take thrust readings from the scale. Its nice to have solid data to work with when setting up power systems for our parkflyer sized planes, and considering this rigs lowcost, I think its a good investment.</p>

Dean</p>