[NSRCA-discussion] Ackerman question

[verne at twmi.rr.com]

Yes, you are correct. 

I spend a fair amount of time getting this right on the workbench 
before the rudder hingeline is even beveled. I find it much easier to 
get the pivot point exactly on the hingeline if the leading edge of the 
rudder isn't beveled to accommodate the measuring required. Once I get 
it all set, I bevel the hingeline. Set properly, the cables maintain 
equal pressure throughout the throw and my servo arm rarely matches the 
width of the control horns. It's the offset, as you stated, that 
matters. I've had equally good results using both offset and with the 
pivot point right on the hingeline. I prefer to have it right on the 
hingeline for simplicity sake and the aluminum horns that Lamar Blair 
sells makes that easy if you bevel both the rudder and the tail post of 
the fin. Hope this helps.

Verne

----- Original Message -----
From: Lance Van Nostrand <patterndude at tx.rr.com>
Date: Monday, January 15, 2007 11:20 pm
Subject: [NSRCA-discussion] Ackerman question
To: NSRCA Mailing List <nsrca-discussion at lists.nsrca.org>

> OK, this ackerman thing got me thinking again about this and a 
> question 
> comes to light:
> 
> Many times we say that the servo arm should match the control arm 
> to 
> minimize cable slack.  However, if we use a smaller servo arm than 
> the 
> control arm I am now thinking that this does not exacerbate the 
> cable 
> tension problem. In fact, it does nothing except reduce the 
> surface 
> deflection.
> 
> If the goal is to use 100% of the servo travel (for precision) 
> than an 
> equally spaced servo/control surface would only let the servo 
> rotate +- 
> about 15 degrees for the average elevator.  This is less than 50% 
> of the 
> servo's capability.  I always used smaller arms at the servo, or 
> use a wheel 
> if I end up with too much slack.  I thought I was making the best 
> of a bad 
> situation, but now I am thinking that there is no bad situation.  
> If the 
> clevis is on the hinge line (or the servo connection and control 
> horn are 
> equally offset in the same direction) then you should get a 
> constant tension 
> regardless of the mismatch in servo/control arms.  Is this right?
> 
> --Lance
> 
> ----- Original Message ----- 
> From: "Richard Lindberg" <rclindberg at comcast.net>
> To: "NSRCA Mailing List" <nsrca-discussion at lists.nsrca.org>
> Sent: Monday, January 15, 2007 11:32 AM
> Subject: Re: [NSRCA-discussion] Pull Pull Cable Tension Question
> 
> 
> > Here's the URL for Ackerman setups:
> >
> > http://members.cox.net/bdfelice/Ackerman/ackerman.htm
> >
> > FWIW, Bob Pastorello, et al,  discussed this on the list in November
> > 2004...!
> >
> > Richard
> >
> /listinfo/nsrca-discussion 
> 
> _______________________________________________
> NSRCA-discussion mailing list
> NSRCA-discussion at lists.nsrca.org
> http://lists.nsrca.org/mailman/listinfo/nsrca-discussion
>