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Old Sep 03, 2012, 01:30 PM
Gravity always wins !!!
Photo Elevate's Avatar
UK, Essex, Tiptree
Joined Jan 2010
55 Posts
Question
Coaxial motor setup

Has anyone considered using different kv size motors ie. 710kv top and 770kv bottom.

Keeping the same size props all round, the bottom motors would spin faster to overcome the propwash.

I dont know if the HF board would throw a wobbly with this setup,

Would flight times or stability suffer?

Any thoughts?
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Old Sep 03, 2012, 02:00 PM
um.. yeah, I can make that fly
Carlos230023's Avatar
United Kingdom, Milton Keynes
Joined Jun 2007
3,695 Posts
I usually stick with the same motors and go with an inch bigger and one or two inches faster pitch on the bottom motor, the bottom motor will then go at a similar speed but move more air with the same effort (as the prop above is already haulin a$$)

CJ
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Last edited by Carlos230023; Sep 03, 2012 at 03:13 PM.
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Old Sep 03, 2012, 03:10 PM
Air Traffic Controller
United States, TN, Knoxville
Joined Aug 2011
250 Posts
I use 1" bigger on the bottom and more pitch as well.
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Old Sep 03, 2012, 03:13 PM
um.. yeah, I can make that fly
Carlos230023's Avatar
United Kingdom, Milton Keynes
Joined Jun 2007
3,695 Posts
Alot of echo in these hoverfly forums. :P.

CJ
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Old Sep 03, 2012, 06:15 PM
JZSlenker's Avatar
United States, PA, Harrisburg
Joined Aug 2011
377 Posts
Ditto 1" bigger slightly more bite on the bottoms of our X-8
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Old Sep 04, 2012, 11:02 AM
Registered User
Joined Sep 2004
135 Posts
In my current Y6, I have 1" larger props with more bite on the bottom and those motors are getting hotter than the top motors. I'm actually going to make them same props all around to see what happens.

-Mike
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Old Sep 04, 2012, 11:33 AM
A man with too many toys
United States
Joined Feb 2001
17,529 Posts
Quote:
Originally Posted by webgeek View Post
In my current Y6, I have 1" larger props with more bite on the bottom and those motors are getting hotter than the top motors. I'm actually going to make them same props all around to see what happens.

-Mike
Bottom motors tend to run a little hotter because of airflow there is nothing wrong with your setup. The important thing is to have the same load on all motors during a stable hover, If the power in unbalanced you loose efficiency and the board has to use compensate to keep it stable.

.
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Old Sep 05, 2012, 12:47 AM
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tahoelight's Avatar
North Lake Tahoe
Joined Nov 2009
596 Posts
Who has a prop suggestion for my X8. I have been running 14x4.7 SF top and bottom. I have never had good luck with the APC e props. How are you guys getting 1" larger props with higher pitch on the bottom? I just don't see any options for these larger props out there.
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Old Sep 05, 2012, 01:46 AM
um.. yeah, I can make that fly
Carlos230023's Avatar
United Kingdom, Milton Keynes
Joined Jun 2007
3,695 Posts
Quote:
Originally Posted by tahoelight View Post
Who has a prop suggestion for my X8. I have been running 14x4.7 SF top and bottom. I have never had good luck with the APC e props. How are you guys getting 1" larger props with higher pitch on the bottom? I just don't see any options for these larger props out there.
Try master airscrew, they have a good prop selection. They're pretty tough, they come quite well balanced (though I'd always balance them myself when they show up) and they do some good sizes too. They're a bit chunky but this helps with yaw speed.

CJ
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Old Sep 05, 2012, 08:33 PM
Air Traffic Controller
United States, TN, Knoxville
Joined Aug 2011
250 Posts
On my X8 I used 11x47 on top and 13x6 on bottom. I also have 14's also but I find I get a smoother flight with 12's. I'm flying 12x38 on top and 13x47 on bottom. I have flown 11x47 both top and bottom. It's actually a little easier to control with the 11's but less flight time.

I'm using BC 3536-11 750k with 4s. MTM distance is 38".
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