Will the BP Hobby ....H2217-4 3500 KV do this ? - RC Groups
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Dec 27, 2012, 05:41 PM
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Will the BP Hobby ....H2217-4 3500 KV do this ?

Never did a high speed pusher with a prop this small.......Are these numbers, prop speed & thrust, close to being real ?

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Dec 27, 2012, 06:03 PM
Wake up, feel pulse, be happy!
Piece's Avatar
The numbers don't look terribly off, but I would put the big red rubber "ABSOLUTELY NOT" stamp on this one since the poor GWS prop is liable to explode at those RPMs.

The Graupner CAMSpeed 3x3 would be a much better choice...

But still no.

You'll definitely want to run less RPMs and a bigger prop on that plane. You've cranked the RPMs and pitchspeed up real high, but in doing so you sacrificed so much thrust that the plane would most likely fly like a glider with a screaming noisemaker attached to it. Where are you mounting the prop and motor on a U2, and what sort of flying are you planning to do with it? If possible, I'd recommend a Suppo (BP) 2217/8 1100Kv motor swinging a 9x7 folder on 3S.

If you absolutely must run a small, fast prop on four cells, the 2217/6 1500Kv with a 5.5x4.5 would be a better choice. 3" props are firmly outside reality for most non-tiny planes.
Dec 27, 2012, 06:17 PM
Registered User
The motor & prop have a very flat efficiency curve as power is reduced.

This setup is strictly to get the slow U2 glider up high enough to find a thermal & glide down. Then back up again.
The 340 continous watts to use a EDF are out.

Will buy a GWS HD 3" X 3" & test it out on the test stand for scream of 39,000 rpms . Ok with a U2
Dec 28, 2012, 10:02 AM
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Dr Kiwi's Avatar
That GWS HD 3x3 will probably explode long before you get it to 39,000...to avoid injuring someone, use a carbon prop for such high RPM.
Dec 28, 2012, 10:08 AM
Registered User
Thank you Phil.

I am taking off my prop testing Flack Jacket.


I have wound up a APC E that high. I think it was a 5" for the GWS F-15 pusher.

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