[NSRCA-discussion] Elevator trim change

[george w. kennie]

Sorry Guys, I have some thoughts and opinions on this that are based upon my own logic, however flawed,and which may or may not coincide with someone else's logic.

Anytime you have a control system that is based on a system that incorporates an oscillatory motion (fore/aft up/dn) the ultimate result of this motion will generate wear somewhere within the system and wear translates to slop.

I think my contention would be that Lance had it right in the first place and was ill-advised by some well intentioned souls who may have had what they assumed to be good results, but failed to base their conclusions on really long-term experience(who really knows for sure?)

I have long felt that pull-pull cables (vinyl-coated steel) present the most reliable connection for the elevator and rudder inputs.They do not require that the horns be expensive ball-bearing units, they are the lightest by far and due to the fact that they are always under tension the generated wear manifests itself against only one wear surface instead of the two in the push-pull set-up. If the installation can be modified in such a way that the servo can be mounted just ahead of the stab the COE of the fuse can be rendered virtually inaffective. 

With time, you may experience some slight lessening in cable tension (very slight) which can quickly be rectified by disconnecting the clevis and spinning the eye a half turn at each connection.

I have used Kevlar thread and continue to do so, but not on two-meter projects.Kevlar stretches for quite a period of time before settling to it's final length.

Just my $.02
G. 


 


  ----- Original Message ----- 
  From: Lance Van Nostrand 
  To: NSRCA Mailing List 
  Sent: Monday, May 08, 2006 8:55 PM
  Subject: Re: [NSRCA-discussion] Elevator trim change


  This rots.  I've used pull pull forever and switched to the deps system due to heavy promotion by Mike Harrison and Bryan Hebert.  They say it will be more precise.  Can anyone corroborate this?  I'd hate to switch to a system that has more downside than upside.
  --Lance
    ----- Original Message ----- 
    From: Gray E Fowler 
    To: NSRCA Mailing List 
    Sent: Monday, May 08, 2006 10:51 AM
    Subject: Re: [NSRCA-discussion] Elevator trim change



    Fiberglass laminate CTE = 6 X10 -6/in/in/F 

    CF pushrod CTE = 1 X 10 -6 /in/in/F  ....could actually be 0 if fiber vloume is > 58% an all uni fibers 






    Gray Fowler
    Principal Chemical Engineer
    Composites Engineering 


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