Hi everybody...

I've been flying RC for a few years now and want to get into the electric sailplanes. I've bought a GWS tiger moth - that's the limit of my knowledge.

I went to the London, Ontario swap meet this past weekend to pick up an electric glider, I could not find a ready to fly one so I bought the glider, motor and speed controller together. Then went and got a battery pack.

I made the purchases based on the information shared by the people at the swap meet, however being that they were sellers and maybe more interest in selling than selling the right thing, when I got home I realised I needed some help.

I bought a 2 meter sailplane with 700 motor. The sailplane looks like a scale model glider not like say a 'gentle lady'. It's fiberglass or plastic body. The speed controller is a 'graupner 25A' . The batteries I bought were a 7 cell NiMh GWS 1600Ma pack, that's what the guy who sold me the plane and motor said to get a 7 cell 1400-1600Ma pack.

When I got the plane home and started to put the pieces together I realized the connections from the spped controller did not fit the motor in the plane, plus the batter pack connection does not fit the GWS battery, plus the other connection, which looks like it might go into a reciever is of an unknown type to me - rather than the connections encased in plastic they just protrude out. Only one I ever saw like that was an old futaba radio I once saw.

Questions:

1. Is a NiMh 1600Ma battery ok for a 700 motor and 25A speed controller? (I just want to be sure it works - doesn't have to be the best just functional - I can't return them after all)

2. What do I do about all the incapatible connections? Should I just go to radio shack and buy some similar male/female connectors?

3. Center of gravity, how do I know where to balance the plane? (I never asked that quesion)

Looking back I just didn't know the right questions to ask.

Any help would be appreciated.

RD

RD,

I don't have a Speed 700 motor but you can find information on it [link=http://www.hobby-lobby.com/speed700.htm]here[/link] at Hobby Lobby. Perhaps you can give them a call or e-mail L.A. Johnston there for some answers.

It would appear that this motor is happy up to 30amps. The Graupner 25-amp ESC is probably ok since it is a continuous rating and can take more current short term.

I couldn't find any information on your 7-cell GWS 1600mAh NiMH pack.

Good luck!

For that sort of current you could use Deans Ultra or Sermos connectors all around. Personally I am a devotee of Gold Connectors (from www.aircraftworld.com) - Dave stocks MP Jet 2.5mm (50A) and Jeti 3.5mm (80A) at about $1.50 a pair.

Try your 1600 pack but I THINK in the long run you may need a larger battery pack - 1600mAh @ 25A will give less tha 4 minutes run time. I'd go for an 8-cell KAN 1800 NiMh High Rate at only 33g [1.1oz]/cell or Sanyo HR-4/5AUP 1900 at 32g, or Sanyo HR-4/5AU 2150 at 35g. These should all be able to supply 20-25A or so without trouble.

Cheers, Phil

I agree with Dr. Kiwi. Pick one connector type and stick with it. Always a good thing. My vote goes for Deans Ultra. Man, if I could eat 'em for breakfast, I would... That's how much I like 'em.

With cheap can motors like the Speed 700, I usually solder the speed control wires directly to the motor. Saves a connector, and is slightly more efficient.

Get yourself a AA alkaline battery out of the TV remote and compare it to the individual cells in that 1600mAh NiMH pack. If they're the same size, the pack won't hold up to 25 Amps, I'm afraid. AA NiMH cells generally have a very high internal resistance, and can't produce lots of current. That GWS pack would work great in a GWS warbird or GWS E-Starter where you'd see at most 10 Amps on a bad day. BTW, has it got a tiny red connector on it? Any of the cells mentioned above will work great.

Any idea what size prop you're going to use? That'll be the big determining factor in how many Amps the motor will draw.