Re: Motor stick length

From: Bill Gowen <b.gowen_at_earthlink.net>
Date: Tue, 16 Oct 2007 12:17:06 -0400

I promise this will be my last opinion of the day! (maybe)

I think the most critical part of the flight envelope is the descent. Therefore I want to get the most kick out of the motor I can towards the latter parts of the flight. In an event that doesn't have a motor stick length limit, then I think the optimum length is the one that will produce the most torque in this phase. I used to use really long sticks because I thought that would be the ticket to higher torque. Then I noticed during motor tests that sometimes the torque would go up if I moved the winder in to shorten the motor.

So if these assumptions are true, it's fairly easy to figure out an answer. Just wind a motor, then unwind it until you're in the descent phase of the torque curve. Move the winder in and out until you see the highest reading on the meter. This is a good place to start with your hook to hook length in my opinion.

The Larry Coslick method of dealing with adverse twist at launch is to twist the crap out of the motor stick in the opposite direction right before launch. A lot of times it will get an unmanageable model into the air long enough for the torque to drop off a bit to where the model can handle it.

  ----- Original Message -----
  From: calgoddard
  To: Indoor_Construction_at_yahoogroups.com
  Sent: Tuesday, October 16, 2007 11:46 AM
  Subject: [Indoor_Construction] Motor stick length


  Assuming you can build under the minimum weight and still have good
  strength in the important parts of the plane, is is better to have a
  shorter motor stick or a longer motor stick?

  Which one is better at resisting the effects of motor stick twist at
  high iinitial torque that adversely takes out stab tilt?

  Does it make a difference if the motor stick is solid or rolled, in
  terms of making it shorter or longer?

  I understand that the length of the rubber should not exceed 2 1/2
  times the length of the motor stick so you first determine the optimum
  rubber length range, and work back from there to make sure your motor
  stick is not too long or too short.

  Given the same prop and the same motor size, winds and torque, would a
  solid motor stick that is X + 2 inches long resist twising more than a
  solid motor stick that is X inches long?

  Given the same prop and the same rubber motor size, winds and torque,
  would a rolled motor stick that is X + 2 inches long resist twisting
  more than a rolled motor stick that is X inches long?

  Thanks in advance everyone for your input.



   

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Received on Tue Oct 16 2007 - 09:17:08 CEST