REFLECTOR: Bearing AD (Duane Swing)

["Brian K. Michalk" <michalk@awpi.com>]

Duane has email working now.  I'll add him to the reflector
list so his email won't bounce anymore.

Forwarded message:
> -----Original Message-----
> From:	Duane Swing
> Sent:	Monday, January 11, 1999 11:36 AM
> To:	'Michalk@awpi.com'
> Subject:	FW: front bearing questions
> 
> 
> 
> -----Original Message-----
> From:	Duane Swing
> Sent:	Friday, January 08, 1999 9:56 AM
> To:	'reflector@awpi.com'
> Subject:	front bearing questions
> 
> To all Reflectorites:
>    Scott and I have been looking at the front bearing support and are 
> working on a solution.  One of the problems that any wide area washer type 
> retainer or the reversal of the bearing in the holder, or even the 
> replacement of the countersink screws with standard flat head screws, is 
> that unless the control stick is restricted from being pulled back further 
> than the full down elevator will allow (26 degrees) the possibility of a 
> total bearing failure or the attach aluminum bracket breaking as a result 
> of constant flexing is still an issue.  It would be my initial thought that 
> the control stick full aft movement should be restricted by placing an 
> aluminum stop on the keel where the control stick would normally contact 
> the aft end of the control stick hole when fully deflected.  On all the 
> airplanes we have built, the total available movement of the control stick 
> was always determined by the control stick contacting the fiberglass keel 
>   once the 26 degree down elevator was reached. This does not eliminate all 
> the loads on the bearing but does prevent "excessive" loads as a result of 
> the elevator reaching it's maximum 26 degrees with still another 5 degrees 
> or so of stick travel available to the pilot.  This added pressure is what 
> can cause the bearing, attach bracket or screws to fail in time.
>    This is at this time just some thoughts on the subject.  We will 
> continue to monitor the Reflector for answers and solutions to this 
> problem.
>    Sincerely,  Duane Swing  Velocity Inc.
> [Duane Swing]    This message was originally sent on January 11th. My 
> computer e-mail server was holding all my e-mail for some reason and 
> nothing has been going out since December.  Sorry for all the delays in 
> answering those of you who have been asking about the AD on the front 
> bearing.  Everyone should also be aware that no standard ball bearing is 
> designed for heavy for/aft thrust loads that we have all been talking 
> about.  Adding wide area washers and other means of bearing retention is 
> NOT the total answer.  We tested the round head screw (AD note) and found 
> it takes at least 800 lbs. of load before anything happens and then the 
> flange ring around the bearing failed leaving the screws intact and 
> virtually destroyed the attach bracket. Reversing the bearing in the 
> bracket is certainly a good idea if the airplane is not already built but 
> is not necessary assuming some other means of restricting the aft load on 
> the control stick is made.
> Sincerely,  Duane Swing
> 


-- 
Brian Michalk  <http://www.awpi.com/michalk>
Life is what you make of it ... never wish you had done something.
Aviator, experimental aircraft builder, motorcyclist, SCUBA diver
musician, home-brewer, entrepenuer and SINGLE!