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Old Jan 27, 2003, 08:26 PM
Registered User
United States, FL, West Palm Beach
Joined Jun 2001
2,216 Posts
Motor for competition fun fly

Hello All

I was wondering, what motor would be the lightest(no more than 15 oz) motor/controller/pack setup to spin a 9x6 or 10x4(preferably this one) prop 18,000 RPM(has to be maintained). The total flight time will only be a max of 1 min long.

Here are the specs of the Plane.

I would like to use lithium batteries(Kokams), but what battery configuration and cell type would be ideal.

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Old Jan 28, 2003, 07:22 AM
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United States, MI, Commerce Charter Township
Joined Dec 2000
1,332 Posts
Well, I don't have a motor to recommend to you, but I can offer the following: High KV motor with lightest weight and a 3:1(ish) box. If you use an F5D motor, you should be about right.

I'd go with a 7 cell motor to save weight in batteries-if there are still any good 7 cell F5D motors made anymore.

One thing I can say with near certainty is that you won't be spinning a 9-6 or 10-4 at 18k with any kind of motor on LiPoly's. That is unless you ran a gazillion of them to spread the amp draw amongst them, but then you'd have a heavy pack. I know there are LiPoly's good to 30A or so now, but you'll be drawing more like 65 with an F5D motor.

The 'calc crowd can help you best here.

FWIW, Given that the Diamond Dust is meant for speed, you should try a square prop like an 8-8. It would still be vertical.


P.S. Search the web about DD's and radio failures-I hope you haven't bought the kit yet.
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Old Jan 28, 2003, 08:54 AM
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United States
Joined May 2000
5,174 Posts
Dave, he's talking about the diamond unlimited (competition funfly plane), not the diamond dust I answered in the sport planes forumn. You need, at most, 25~30 seconds of power, but as much power as you can get, so 100 or higher amps and the lowest cellcount (for weight reduction) that will still give you enough power, is probably the best route to take.

hint to eco8,.. you really shouldn't post the same thing in two forumns.
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Old Jan 28, 2003, 11:37 AM
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Canada, NS, Lunenburg
Joined Oct 1999
3,870 Posts
Thanks for the heads up Gary. I'll lock this thread as the other seems more important. If anyones looking for the other, it can be found here:
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