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Old Apr 05, 2012, 12:39 PM
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Can I use small prop on Megajet motor?

I should have thought about this before building it, but I am almost done building a foamy Learjet and now have a issue with prop clearance..
I was planning on using two "grayson hobby" Megajet brushless motors, 2550Kv, but the recommended prop is 6x5 and I only have 3 inch prop clearance.. will the motor have any thrust with that prop? or will it just scream and not move the plane?
If anyone has any motor/prop combos that will work for me I would also appreciate that info.
The plane should weigh around 15-20oz (in just foam) and I would like to use 2 motors, not looking for going vertical just a nice cruise speed.

Thanks in advance everyone)
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Old Apr 05, 2012, 12:46 PM
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United States, NE, Bennet
Joined Mar 2011
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That motor is too slow for a 3 inch prop, you will be at full throttle and get very little thrust.
If you want to run a three inch prop you need this motor and a cutdown prop: http://www.aeromicro.com/Catalog/meg..._2_4934110.htm
I use it with a 3.5x4.1 prop and it gets my 15 ounce plane going 150 mph. I am sure it would be better for the motor to run it with a 3 inch prop.
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Old Apr 05, 2012, 01:12 PM
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An ARC 20-34-130 (~4500Kv) might work (only 41g)... with a 4.2x4 it draws ~17A @ 6.5v ... so it might do okay with 3" on 2s.

I remember I tested an ARC 2008-3900 (32g, ~4050Kv) and see that with a 3x3 Graupner CAM on 3s I got 11.65oz @ 100mph from 14.50A/155W
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Old Apr 05, 2012, 01:13 PM
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Quote:
Originally Posted by 100mph View Post
That motor is too slow for a 3 inch prop, you will be at full throttle and get very little thrust.
If you want to run a three inch prop you need this motor and a cutdown prop: http://www.aeromicro.com/Catalog/meg..._2_4934110.htm
I use it with a 3.5x4.1 prop and it gets my 15 ounce plane going 150 mph. I am sure it would be better for the motor to run it with a 3 inch prop.
damn that thing is expensive and doesn't come with esc... I need two of them.
is says to use nimh battery can I use lipo if I do use that one?

Any other suggestions?
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Old Apr 05, 2012, 01:35 PM
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Originally Posted by Dr Kiwi View Post
An ARC 20-34-130 (~4500Kv) might work (only 41g)... with a 4.2x4 it draws ~17A @ 6.5v ... so it might do okay with 3" on 2s.

I remember I tested an ARC 2008-3900 (32g, ~4050Kv) and see that with a 3x3 Graupner CAM on 3s I got 11.65oz @ 100mph from 14.50A/155W
The chart I found for this motor only listed big props (10inches) and needs a gearbox..
http://www.lightflightrc.com/HTML/pr...0-34-130-I.htm
Do you need a gearbox for this motor?
Are you saying I can use this motor without gearbox and use a 3inch prop for 11.65oz thrust?
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Old Apr 05, 2012, 04:23 PM
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Yes, you can use lipo, that is what I'm running. I am running a three cell.
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Old Apr 05, 2012, 06:01 PM
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Chattanooga, Tennessee, United States
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Quote:
Originally Posted by Sendmedem View Post
The chart I found for this motor only listed big props (10inches) and needs a gearbox..
http://www.lightflightrc.com/HTML/pr...0-34-130-I.htm
Do you need a gearbox for this motor?
Are you saying I can use this motor without gearbox and use a 3inch prop for 11.65oz thrust?
I said that the 20-34-130 might manage a 3" prop on 2s...3" on 3s might be too much..... then I found figures for a completely different lower Kv motor (2008-3900) and found that it could do okay with a 3" prop on 3s
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