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n001pa
12-04-2005, 11:47 AM
What size prop can I spin DD with this motor? I just won one and I am trying to decide what plane to put it on. I know what prop to use if I gear it but am having trouble finding out what prop if I go direct drive. This is only my third brushless motor so I am still in a learning curve here. Any help would be greatly appreciated.

n001pa
12-04-2005, 10:06 PM
Ok I got a response from Great Planes saying that I can run a 7.5 to 8.4 electric prop on this motor. However, over on rcgroups they are saying that 2.5 prop might work. You got to hate smart-alecks.:mad: But which is correct?:confused:

zappedalaskan
12-04-2005, 11:39 PM
Ok I got a response from Great Planes saying that I can run a 7.5 to 8.4 electric prop on this motor. However, over on rcgroups they are saying that 2.5 prop might work. You got to hate smart-alecks.:mad: But which is correct?:confused:
Carl...
All this stress over this new motor of yours.. It is not healthy, so in the better interest of your health and piece of mind. I would be happy to take it off your hands. Kidding aside I would try a 7.5 and see what that does for you. I run a simular set up in a wattage crazy8 with a 3cell LiPo. Hope this helps :)
Sorry for the smart-aleck comment :p
Take care and have a great evening,
Jay

n001pa
12-05-2005, 12:05 AM
Thanks Jay
I'm not really that upset.:D The plane that it will go in hasn't even left the drawing board yet.

I did get another response from Great Planes. He thought I was talking about the 3600kv motor. He now agrees with what they are telling me over at rcgroups. He suggested that I try to trade mine with someone that has the lower kv motor.

I am also thinking of posting in the for sale thread to see if anyone has a good motor for spinning around a 7 to 8.5 prop DD that they might be willing to trade for mine.

Carl

zappedalaskan
12-05-2005, 12:57 AM
Or you can run a cobri gear box.. I went and looked, my crazy8 has a gear box.
Jay

Dr Kiwi
12-05-2005, 03:50 AM
I wasn't being a smart aleck - I guessed at 2.5" 'cos an ARC 20-134-130 (which is only 4600Kv) draws >17A at only 6.5v with a 4.2x4. Your Ammo would draw a heck of a lot more - even on just 2s I doubt that a 3x2 would work..

An ARC 20-34-110 (3100Kv) can certainly run a 3x3 on 3s (8A) and you might get away with a 4.2x4 (14.5A). On 2s you can run as much as a 5x5 (13.2A), but nothing any bigger.

If you want to run a bigger prop DD on a 20mm inrunner you need <3000Kv (Himaxx 2015-2800 or 2025-2700?), or else go to an outrunner.

n001pa
12-05-2005, 09:30 AM
Sorry about that. I'm just so use to getting and seeing smart-aleck responses on rcgroups I guess I just jumped the gun. Thanks for the info. As I said I am still learning about brushlesses.

zappedalaskan
12-05-2005, 03:46 PM
Hi Carl,
An exellent source of info and figuring props and gear boxes is the motor/gear calc. It is a very neat program that will show you exactly what you can do with your motor, using and direct drive or gear box set-up. Here is a link. http://www.wattflyer.com/forums/showthread.php?t=2070
Hope this helps.. Have a great day :)
Jay

n001pa
12-05-2005, 07:57 PM
Thanks for the suggestion. I'll try that tonight after I fet home from work.