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<DIV>I am flying a 35% IMAC plane with a single servo on rudder. Of course, I am not using 3D setting. I am saving around 3/4 lb in servos and trays. </DIV>
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<DIV>Clearly the ratio between the servo arm and the rudder horn can not be equal if we want to set for precision and gets the mechanical advantage. Usually I use 35-40 degree rudder throw. The servo moves around 60 degrees. The ratio has to be between 0.58 - 0.66 since I want to use the 100% of the servo travel. Looks like is very difficult to work this out and have a perfect system. I could be wrong as usual. I didn't have chance to read all e-mails. My question is: What is the best compromise? </DIV>
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<DIV class=signature id=signature>--<BR>Vicente "Vince" Bortone</DIV>
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<BLOCKQUOTE style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #1010ff 2px solid">-------------- Original message -------------- <BR>From: <glmiller3@suddenlink.net> <BR><BR>> Lance, <BR>> <BR>> I did this on my first Focus II, but since then have just used the servo arm <BR>> directly. I think the loads on a pattern plane are significantly less than on <BR>> the IMAC giants. <BR>> <BR>> George <BR>> ---- Lance Van Nostrand <PATTERNDUDE@TX.RR.COM>wrote: <BR>> <BR>> ============= <BR>> Jim, <BR>> I've done this on heavier IMAC style planes but never thought it could be done <BR>> light enough for pattern. If you have thoughts on this, I am interested. <BR>> Thanks, <BR>> --Lance <BR>> <BR>> ----- Original Message ----- <BR>> From: J N Hiller <BR>> To: General pattern discussion <BR>> Sent: Sunday, May 11, 2008 8:58 PM <BR>> Subject: Re: [NSRCA-discussion] Rudder pull-pull <BR>> <BR>> <BR>> Lanc
e I us
e a bell crank to get equal length arms and control horns. This <BR>> allows continued use of full servo travel and removes the cable tension from the <BR>> servo shaft and mounting grommets. The servo is connected with a short link with <BR>> ball end fittings. It works well especially on elevators. <BR>> <BR>> Jim Hiller <BR>> <BR>> <BR>> <BR>> -----Original Message----- <BR>> From: nsrca-discussion-bounces@lists.nsrca.org <BR>> [mailto:nsrca-discussion-bounces@lists.nsrca.org]On Behalf Of Lance Van Nostrand <BR>> Sent: Sunday, May 11, 2008 5:38 PM <BR>> To: General pattern discussion <BR>> Subject: Re: [NSRCA-discussion] Rudder pull-pull <BR>> <BR>> <BR>> <BR>> You all are so fast on this stuff that by the time I read the post the thread <BR>> is old. <BR>> <BR>> <BR>> <BR>> Ackerman exists if the rudder has control horns (as opposed to a wheel, which <BR>> is very hard to build into a rudder). The onl
y idea
l way to have constant <BR>> tension is to use a symmetrical servo arm that is offset from its pivot (servo <BR>> screw) the same amount as the rudder control horn attachment point. This will <BR>> work every time and is simple, however with a 1" thick rudder post and two 3/4" <BR>> control horns you will need a 2.5" servo arm (1.25" each side of center) and the <BR>> servo throw will only be equal to your rudder throw (maybe about 30 degrees) <BR>> which gives you poor mechanical advantage and poor use of your servo. If you <BR>> use a shorter servo arm and more servo throw the cables will go slack. The <BR>> round servo wheel is a compromise by offsetting this slack tendency and letting <BR>> you get more servo throw. It's not a perfect match but it can be very close. <BR>> <BR>> <BR>> <BR>> Anyone that can do the math on this and present a complete answer can get a <BR>> recommendation to advance from a shade tree aerodynamicist to
an ap
prentice. <BR>> <BR>> <BR>> <BR>> --Lance <BR>> <BR>> <BR>> <BR>> ----- Original Message ----- <BR>> <BR>> <BR>> From: John Pavlick <BR>> <BR>> To: General pattern discussion <BR>> <BR>> Sent: Friday, May 09, 2008 9:02 AM <BR>> <BR>> Subject: Re: [NSRCA-discussion] Rudder pull-pull <BR>> <BR>> <BR>> <BR>> Chris, <BR>> <BR>> The only benefit that I know of is that you don't have to deal with the <BR>> Ackerman angle like you do with arms / horns. The cable is always the same <BR>> distance from the hinge center no matter what the angle is. <BR>> <BR>> <BR>> <BR>> John Pavlick <BR>> http://www.idseng.com <BR>> <BR>> ----- Original Message ----- <BR>> <BR>> <BR>> From: chris moon <BR>> <BR>> To: nsrca-discussion@lists.nsrca.org <BR>> <BR>> Sent: Friday, May 09, 2008 9:13 AM <BR>> <BR>> Subject: [NSRCA-discussion] Rudder pull-pull <BR>> <BR>> <BR>> <
BR>>
; Can someone explain the benefits (real or otherwise) of the pull-pull <BR>> wheel type rudder servo arm vs. a regular servo arm? Is there some real <BR>> benefit, or is it bling? <BR>> Thanks <BR>> <BR>> Chris <BR>> <BR>> <BR>> <BR>> <BR>> ------------------------------------------------------------------------------ <BR>> <BR>> Stay in touch when you're away with Windows Live Messenger. IM anytime you're <BR>> online. <BR>> <BR>> <BR>> ------------------------------------------------------------------------------ <BR>> <BR>> _______________________________________________ <BR>> NSRCA-discussion mailing list <BR>> NSRCA-discussion@lists.nsrca.org <BR>> http://lists.nsrca.org/mailman/listinfo/nsrca-discussion <BR>> <BR>> <BR>> ------------------------------------------------------------------------------ <BR>> <BR>> _______________________________________________ <BR>> NSRCA-discussion mailing l
ist <B
R>> NSRCA-discussion@lists.nsrca.org <BR>> http://lists.nsrca.org/mailman/listinfo/nsrca-discussion <BR>> <BR>> <BR>> <BR>> ------------------------------------------------------------------------------ <BR>> <BR>> <BR>> _______________________________________________ <BR>> NSRCA-discussion mailing list <BR>> NSRCA-discussion@lists.nsrca.org <BR>> http://lists.nsrca.org/mailman/listinfo/nsrca-discussion <BR>> _______________________________________________ <BR>> NSRCA-discussion mailing list <BR>> NSRCA-discussion@lists.nsrca.org <BR>> http://lists.nsrca.org/mailman/listinfo/nsrca-discussion </BLOCKQUOTE></body></html>