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Not enough power to stay airborne!

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Not enough power to stay airborne!

Old 11-04-2002, 02:03 PM
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rahtware
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Default Not enough power to stay airborne!

Guys,

I went out to drain (what I thought would be) the little bit left in
the DDs' battery and it ran for 5+ minutes! So, it didn't have a low
battery on the first flight, just one that couldn't deliver enough
amps. On that flight, the takeoff was great with a good climb out,
but within a minute the DD didn't have enough power to stay airborne.

On the advice of "Radical RC" I had bought a 7 cell 300mah NiMh
battery. This is supposed to be the perfect match for the IPS motor
that comes with the GWS Sticks. Also, they advise against going with
an 8-cell battery for "draggy" (Desert Duster) designs.

There are some differences between the drive that comes with the GWS
sticks and the one I bought. The sticks come with the IPS Dx2 AXCS, I
bought the ------2XCS. See below.

AXC on 7.2 volts - 10 x 4.7 prop, thrust = 129g @ 1.67A

2XC on 7.2 volts - 7 x 6 prop, thrust = 115g @ 2.01A
2XC on 7.2 volts - 8 x 4.3 prop, thrust = 123g @ 1.93A

I flew it on the 7060 prop. I do have an 8043 prop that I can try.
On a bench test (7060) the amps quickly dropped below 2A and most of
the run was closer to 1.6A. I know that changing the prop will change
the amps, but if the 8043 still doesn't have enough power, what should
I try next?

As this is a different drive, should I try an extra cell? At the
price of these motors, I don't mind burning one up, but I would like
to find a reliable drive for the DD. How about going to the AXC? It
looks like it produces more power on fewer amps, but I don't think the
DD would ROG with that larger prop. Or should I try Nicads? The same
physical size Nicad would be in the 110 to 150 mah range. I have read
that Nicads dump their amps at a higher rate then NiMhs. Radical RC
claimed that these were high rate NiMh, and were similar to a Nicad in
that respect.

I know this is a lot to ask, but any thoughts would be helpful.

Thanks,
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Old 11-04-2002, 04:46 PM
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Matt Kirsch
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Default Not enough power to stay airborne!

The amp dumping capability of NiMH is nearly the same as NiCds of the same physical size these days.

I run the "S2" drive (same ratio as your 2XC) on a Birdworks Tilde with a 7060 prop and 8 cells. 12-15 minute flights on 300mAh NiMH cells, and the amps are only about 2.25 static. On 6 cells, this plane would fall flat on its face.
Old 11-04-2002, 11:17 PM
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LESLIEx317537
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Default Not enough power to stay airborne!

That DD looks neat.

I was wondering how do I test my amps with a regular multitester?

Thanks.

Is it better to draw the least amps?
Old 11-05-2002, 03:08 AM
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rahtware
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Default Not enough power to stay airborne!

Thanks

Through another site, I was told to cycle the battery again and slow charge it once. Also, to charge it just before flying. With this and the prop change, she flew great! I am now down to the tedious part of trim and balance.

Leslie,

I use mine all the time. To do this though, your meter must have a way handling the amount of amps you are going to test, or it will smoke.

When testing amps, your meter has to be in series with (in-between) the battery and the motor on one leg (wire). During a bench test I use two meters, one to measure voltage, and one to measure amps.

Amps x volts = watts. Watts = power. MAH is a way of telling the total storage capacity of a battery. So, to answer your question, less is better as it means longer flights. But, if you use too little you won't get off the ground.

I know, I know, an oversimplification.
Old 11-05-2002, 03:15 AM
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Default Not enough power to stay airborne!

Aight sounds easy enough.

I have the Radio Shack Pen Multi tester.

It has a 2 amp fuse on it I think.

Is that a bad sign???
Can I still use this multitester?
Old 11-05-2002, 04:31 PM
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rahtware
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Default Not enough power to stay airborne!

Leslie

Read the specifications that came with it, they should tell you the max amps it can handle.

A cheap and semi-reliable MM can be bought through any local hardware store that carries the cheap tools in bins. They carry a digital one for under $9 that can handle 10 watts.

The picture is of the $9 MM (yellow) next to my well-used RShack MM. In the picture I have them set up as a "Watt" meter, to test volts and amps.
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Old 11-05-2002, 06:05 PM
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Default Not enough power to stay airborne!

OK thanks.

I got to definetly test my 3 setups.

I just 3 GWS setups.

A 2amp ESC, 5amp ESC, and a 15amp ESC with brake.

Thanks.

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