Mike E.

I recently decided to resurrect my Clancy Stagger Bee (the one with the wingerons!) and I have installed a Magnetic Mayhem motor with a 3:1 Master Airscrew gearbox and an Astro Flight 215D speed control. All-up weight is 38oz.

Using a 12x6 APC Slo-Flyer prop and a 3 cell TP 2100 LiPo pack my Whatt Meter shows 62 watts and 5.9 amps. With the same prop on a 2 cell 2500 mAh Flight Power Evo 20 it reads 32 watts at 4.1 amps.

I obviously need more power. Is it possible to just up the size of the prop on either of these batteries to make the power system workable and if so what size would you recommend?

Thanks for your help.

Dr Kiwi

There is something seriously amiss here: you should be getting a lot higher amp draw than that;

Motor: Kyosho Magnetic Mayhem; 2260rpm/V; 1.37A no-load; 0.0667 Ohms.
Battery: Thunder Power TP2100 (ProLite) (15C); 3 cells; 2100mAh @ 3.7V; 0.018 Ohms/cell.
Speed Control: Castle Creations Pegasus 35P; 0.0015 Ohms; High rate.
Drive System: Direct Drive Propellers; 12x6 (Pconst=1.69; Tconst=1) geared 3:1 (Eff=95%).
Airframe: Anything you want.

Motor Amps = 23.3
Motor Volts = 9.8
Input (W) = 228.9
Loss (W) = 64.0
Motor RPM = 17844
Prop RPM = 5948
Thrust (oz) = 48.6
PSpd (mph) = 33.8

Mike E.

You're right, the figures you give suggest that I have a real problem! The motor and gearbox are NIB, just gathered dust in a drawer for a few years. The speed control has been used a few times but I have no reason to suspect it is the cause of the problem.

I ran a Master Airscrew 05 at first but changed to the Magnetic Mayhem because of the low power. I guess this means the speed control could be the culprit.

Is there any way of testing the speed control or do I just have to replace it?

Thanks again.

Mike E.

Well, I have to plead brain fade! It occurred to me this morning that I hadn't checked the end point adjustment for high throttle and that solved the problem. I draw 20amps at 123 watts on the 2 cell Flight Power pack and the thrust feels like more than enough to fly the plane. The TP 3 cell is an older pack and it cannot sustain 20 amps without a severe voltage drop. Time to replace it.

Thanks a lot for your figures, Phil. They give me a benchmark for a new 3 cell pack.

Dr Kiwi

The 2s FlightPower pack doesn't look too good either if it drops to 6.15v at 20A!

Mike E.

Good point! I'll have to give it a fresh charge and re-check. It's a brand new pack.