Twin & Multi Engine RC Aircraft Discuss the ins & outs of building & flying multi engine rc aircraft here.

Counter rotating or not

Reply

Old 03-16-2019, 08:15 AM
  #1  
Skyhawk940
Thread Starter
 
Join Date: Nov 2005
Location: sandusky, OH
Posts: 129
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default Counter rotating or not

I'm building an OV-10 electric and don't know if I should use counter rotating motors or not. First of all will a brushless motor run backwards as well as forward (same power)? I know if you reverse two of the three wires it will run the other way. Counter rotating; I've saw were some people say it doesn't make much difference. What do you think??? I'm new to twins and have plans for more.
Skyhawk
Sandusky, OH
Skyhawk940 is offline  
Reply With Quote
Old 03-16-2019, 02:19 PM
  #2  
BarracudaHockey
My Feedback: (11)
 
BarracudaHockey's Avatar
 
Join Date: Jul 2003
Location: Jacksonville, FL
Posts: 23,141
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

If you can get the prop then yes, its worth doing. If it's not a common prop size then I wouldn't worry about it.

There is no running backwards or forwards, however you hook it up it runs, it doesn't know or care which way its spinning.
BarracudaHockey is online now  
Reply With Quote
Old 03-17-2019, 05:15 AM
  #3  
Skyhawk940
Thread Starter
 
Join Date: Nov 2005
Location: sandusky, OH
Posts: 129
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

I know some of the motors, to reverse the motor, the shaft needs to slide through the motor and come out the other side. Doesn't make sense to me.
What's a good source of electric props?

Skyhawk

Last edited by Skyhawk940; 03-17-2019 at 05:31 AM.
Skyhawk940 is offline  
Reply With Quote
Old 03-17-2019, 05:32 AM
  #4  
Skyhawk940
Thread Starter
 
Join Date: Nov 2005
Location: sandusky, OH
Posts: 129
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default


Skyhawk940 is offline  
Reply With Quote
Old 03-17-2019, 01:07 PM
  #5  
BarracudaHockey
My Feedback: (11)
 
BarracudaHockey's Avatar
 
Join Date: Jul 2003
Location: Jacksonville, FL
Posts: 23,141
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Originally Posted by Skyhawk940 View Post
I know some of the motors, to reverse the motor, the shaft needs to slide through the motor and come out the other side. Doesn't make sense to me.
What's a good source of electric props?

Skyhawk
The only time I've seen this required is when the X mount needed to be on the front with the motor recessed into the fuselage or firewall as opposed to having the mount on the back of the motor. Not to reverse the rotation, again, there is no reverse rotation on a brushless motor, its merely a factor of how you have to mount it and what prop you're using, if you need to spin it the other way, as you already said, you reverse two wires.
BarracudaHockey is online now  
Reply With Quote
Old 03-19-2019, 07:00 AM
  #6  
Appowner
Senior Member
 
Join Date: Nov 2017
Posts: 876
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

First, whose kit/plans are those?

Second, memory doesn't allow me to provide details but, do some research on the Lockheed P-38. It started with the props spinning the same direction. Then they reversed one. Then they reversed the direction of both. Which way they settled on I don't know (but you could probably figure it out from a picture. But I know running them opposite does improve things. And one combo is better than the other.

Also, I've been told that for electric you pick your prop first. Determine the speed range of the model to get max prop RPM. Then find a motor capable of spinning that prop at that RPM. And nothing says you can't use a prop for a nitro motor on an electric.

Last edited by Appowner; 03-19-2019 at 07:03 AM.
Appowner is offline  
Reply With Quote
Old 03-19-2019, 08:06 AM
  #7  
speedracerntrixie
My Feedback: (29)
 
speedracerntrixie's Avatar
 
Join Date: Jun 2010
Location: Sacramento, CA
Posts: 6,587
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

The electrics can be a bit confusing. We all got accustomed to glow engine displacement and the very narrow range of props they are able to use for a certain displacement. Current brushless electrics are far more flexible. First thing is that the motor does not care which direction it is spinning. Back in the days of brushed motors, the timing of the motor was determined with the contact location of the brushes on the armature. With brushless motors the timing is purely a function of the speed controller. In some cases with the larger setups the timing is user adjustable. Faster spinning inrunner motors require low timing, 0 to 5 degrees while the lower rpm outrunner motors such as what the OP has requires high timing, 20 to 25 degrees. Most of the lower cost, smaller stuff will be plug and play but you do loose a little bit of efficiency. In order to select the correct size prop you need to know the KV of the motor, what voltage you will be running, the motor diameter and the motor length. For example one of my electrics has a 63mm diameter with a 55mm length. The KV is 230 and I run a voltage of 38v. Multiplying the KV x V we get 8,740 rpm. The prop selected is a 21.5x13.5 delivering around 2,700 watts at about 65 amps. If I was to lower the voltage ( thus rpm ) I could fit a larger prop and if I upped the voltage I would have to go with a smaller prop to keep amperage draw the same. I am going to assume that the batteries selected by the OP are going to be 3S or 11.1V, knowing the diameter of the motor and the KV would allow a prop size recommendation. I suggest looking at the APC web site to select props. Robert has in the past few years introduced a number of multi Rotor prop sets in various sizes that may work very well and are quite inexpensive. They come in sets of 4 with two being CW and two CCW rotation. As far as how to set up rotation, I would do some experimenting but I suspect you will notice little or no difference. Good luck with the project, the OV-10 is one of the airplanes that I always liked, Cal Fire has a few flying close to my home often.
speedracerntrixie is offline  
Reply With Quote
Old 03-19-2019, 08:09 AM
  #8  
BarracudaHockey
My Feedback: (11)
 
BarracudaHockey's Avatar
 
Join Date: Jul 2003
Location: Jacksonville, FL
Posts: 23,141
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Patty Wagstaff flew OV-10's for Cal Fire for a while.....
BarracudaHockey is online now  
Reply With Quote
Old 03-21-2019, 05:35 AM
  #9  
ps2727
 
Join Date: Feb 2003
Location: ft worth, TX
Posts: 470
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

I would run them the same direction to keep it simple. After a few twins I haven’t seen any problems with this setup. The only time I would consider counter rotating props is if it was a taildragger to prevent it swinging on takeoff.
Just my opinion.
paul


MU-2
ps2727 is offline  
Reply With Quote
Old 03-24-2019, 02:08 PM
  #10  
Appowner
Senior Member
 
Join Date: Nov 2017
Posts: 876
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Why stick with the same old thing when a simple change, especially with electrics, could possibly make a noticeable performance improvement?

Time to experiment and have fun doing it I say!
Appowner is offline  
Reply With Quote
Old 03-24-2019, 03:54 PM
  #11  
speedracerntrixie
My Feedback: (29)
 
speedracerntrixie's Avatar
 
Join Date: Jun 2010
Location: Sacramento, CA
Posts: 6,587
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Limited prop selection when it comes to finding clockwise rotating props for one.
speedracerntrixie is offline  
Reply With Quote
Old 04-01-2019, 08:05 AM
  #12  
Appowner
Senior Member
 
Join Date: Nov 2017
Posts: 876
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

So I contacted some vendors and guess what? XOAR offers precision matched tractor and pusher props. Only trick is you have to special order them.

So the selection is out there but one has to step up and ASK.
Appowner is offline  
Reply With Quote
Old 04-01-2019, 08:50 AM
  #13  
speedracerntrixie
My Feedback: (29)
 
speedracerntrixie's Avatar
 
Join Date: Jun 2010
Location: Sacramento, CA
Posts: 6,587
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Good to know, are these electric only props?
speedracerntrixie is offline  
Reply With Quote

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Thread Tools
Search this Thread

Contact Us Archive Advertising Cookie Policy Privacy Statement Terms of Service