Elev. Pull pull Question

[Bob Pastorello]

If we align the clevis attach point with the hinge line, doesn't that "undo" the desired Ackerman effect that we need? (Thanks Keith)
    I agree with stuff over the hinge line in principle, but would appreciate any informed technical explanation (go, Dean!!), as I like to understand the "why" of stuff.

Bob Pastorello
NSRCA 199  AMA 46373
rcaerobob at cox.net
www.rcaerobats.net


  ----- Original Message ----- 
  From: Dean Pappas 
  To: discussion at nsrca.org 
  Sent: Monday, November 29, 2004 10:42 AM
  Subject: RE: Elev. Pull pull Question


  Hello Bob,
  Go buy some DuBro # 867 control horns. They have almost 3/4" of overhang between the bolt and the little hole for the clevis, in the little screw-on pieces.
  Use those pieces, but set the bolt and nut aside, and see if the little holes line up with the center of the hinges.
  If not, then drill new holes in the black plastic bits so that they do line up: one straight line through both holes and the center of the hinge.
  Now when you get the horns all the same length, it will be much easier to get the throws matched in both directions.
  This is absolutely necessary for matching two elevator halves properly, but is also a good idea for rudders.
  The problem with the stock setup is that the cables slacken at the ends, and tighten at neutral.
  While this might sound like a good thing, it is awful: the servo has to fight the tightening cables as the surface comes closer to neutral,
  then as it gets there, the surface may try to "spring" to the opposite direction.
  The servo and gear train will prematurely beat themselves up chasing this problem.
  You want the cable tension to be almost constant throughout the throw.
  There will be pictures of this when I get the Excelleron review out the door.
  One of the previous posts pointed to a website that showed the proper geometry.
  DuBro and Rocket City both make parts that are useful, for this problem.

  Check DuBro.com and put #867 into their search engine, you can see the lonng overhang part. It's either 5/8" or 3/4" from bolt to clevis hole.

  Later,

  Dean Pappas 
  Sr. Design Engineer 
  Kodeos Communications 
  111 Corporate Blvd. 
  South Plainfield, N.J. 07080 
  (908) 222-7817 phone 
  (908) 222-2392 fax 
  d.pappas at kodeos.com 

    -----Original Message-----
    From: discussion-request at nsrca.org [mailto:discussion-request at nsrca.org]On Behalf Of Bob Pastorello
    Sent: Friday, November 26, 2004 8:58 AM
    To: NSRCA
    Subject: Elev. Pull pull Question


    May seem obvious, but I could use some help here....setting up my Excelleron, centers are okay, cable tensions are pretty close, centering is good.  Up elevator is fine, on Down elevator, ONE elevator moves farther, but they track together except at the endpoint, as close as I can tell.

    Anyone have suggestions on how I'd fine tune this out...??
    Hope everyone had a great T-day!!

    Bob Pastorello
    NSRCA 199  AMA 46373
    rcaerobob at cox.net
    www.rcaerobats.net

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