Go Back  RCU Forums > Electric Aircraft Universe > Electric General Discussion
Motor, propeller gyroscopic effects avoid rotating at takeoff. >

Motor, propeller gyroscopic effects avoid rotating at takeoff.

Community
Search
Notices
Electric General Discussion General Discussion forum about rc electric related aircraft, accessories, flight, tips, etc.

Motor, propeller gyroscopic effects avoid rotating at takeoff.

Thread Tools
 
Search this Thread
 
Old 05-18-2014 | 05:01 PM
  #1  
Thread Starter
Junior Member
 
Joined: Apr 2014
Posts: 17
Likes: 0
Received 0 Likes on 0 Posts
From: Sao Jose, BRAZIL
Default Motor, propeller gyroscopic effects avoid rotating at takeoff.


I constructed this pusher RC, and i'm having problems to get into the air.
Fisrt, the main landing gear was too far from CG and elevator had not enough power to rotate.
Moved the landing gear fwd to 40% of MAC. CG is at 25% of MAC.
Now, I realized that, the more power i set on accelerator, the more hard it become to rotate.
That makes me wander if there are gyroscopic affects from motor and/or propeller.
The plane weights 0,8kg, motor is 1100Kv and propeller is 8 in diameter.
Does anyone faced something like this?
Attached Thumbnails Click image for larger version

Name:	image.jpg
Views:	312
Size:	831.5 KB
ID:	1996434  
Old 05-19-2014 | 01:39 PM
  #2  
Thread Starter
Junior Member
 
Joined: Apr 2014
Posts: 17
Likes: 0
Received 0 Likes on 0 Posts
From: Sao Jose, BRAZIL
Default

I spent the day thinking about this issue and concluded that:
1 by the time I discovered the pitch-down moment, the wheels were blocked, as if they had brakes.
2 in such case, there will be a pitch-down moment caused by the thrust vector multiplied by the distance between ground and the thrust vector.

I hang the plane by its center of gravity and applied power. The elevator responded well, for pitch up and down, at various leves of power.
Let's go for another tentative flight and see what happens.
Old 05-29-2014 | 09:34 AM
  #3  
Senior Member
 
Joined: Nov 2003
Posts: 229
Likes: 0
Received 0 Likes on 0 Posts
From: Uxbridge, UNITED KINGDOM
Default

It's difficult to see the angle the wing is at when the model is sat on its wheels, but I'd suggest it needs a bit more wing incidence to get airborne. Easiest way is to lengthen the nose undercarriage leg a bit and try again. If you think it's the motor thrustline preventing it from getting airborne, try a takeoff run and when it's at full speed, kill the throttle. If it leaps into the air, be prepared to open the throttle again quickly!
Old 05-29-2014 | 01:48 PM
  #4  
Thread Starter
Junior Member
 
Joined: Apr 2014
Posts: 17
Likes: 0
Received 0 Likes on 0 Posts
From: Sao Jose, BRAZIL
Default

Gtarling, thank you for the contribution.
One thing I did, was to move the main landing gear forward, closer to the CG.
This gave more authority to the elevator at the rotation.
I could not try another flight, because of rain last week.
Next saturday i will try again, and will publish the results here.
I believe it will take off this time. I will keep in mind your advice.
Old 06-03-2014 | 04:52 PM
  #5  
Thread Starter
Junior Member
 
Joined: Apr 2014
Posts: 17
Likes: 0
Received 0 Likes on 0 Posts
From: Sao Jose, BRAZIL
Default

This plane flew well last sunday. Takeoff was easy. No problens on rotating.

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
Trackbacks are Off
Pingbacks are Off
Refbacks are On



Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

Copyright © 2026 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.