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Control horn/linkage stopper question

#1
For those that use them both, do you drill out the holes in the control horns so that the linkage stopper can rotate freely? Or do you just push them threw and put the nut on and tighten them down? I've done both. Seems like if you don't drill the FT provided ones out a bit they cause some deflection of the push rod when the servos move. Is that normal.

Thanks in advance. So far I've tackled the Versa and have just completed my Mustang. Can't wait to get it in in the air.
 
#2
On wood horns drilling may be needed. On plastic horns, I heat the linkage stopper or an equivalent sized wire and push that through the horn. You want a tight fit (rotates freely, but with no slop).
 
#3
in all the videos I've watched, the linkage stopper is only used on the servo arm. the wire is simply bent for the control horn, so it does rotate freely. in addition, yes you need to widen the hole in the servo arm for the linkage stopper to be able to twist a bit. Along those same lines, the linkage stopper is secured with a bolt, but that is NOT tightened against the servo arm. So far I've just kept it loose, but I think I should actually be securing it in the "loose" position by using loctite.
 

herk1

Trash Hauler emeritus
#4
I use these linkage stoppers on the vast majority of my planes:

http://www.horizonhobby.com/mini-ez-connector-(12)-dub915

I buy them in the jumbo pack like that because I use so many of them (I just completed my 69th electric foamie build last night, and yes it does use them!). Or you can buy just a couple of them at a time here:

http://www.horizonhobby.com/mini-ez-connector-(2)-dub845

The nice thing about those linkages stoppers is that they have a simple push-on retainer (made out of a rubbery material). Just take a pair of needlenose pliers and squeeze on the retainer, until it goes into a little groove that it sits in. If you have to take it off later, you can pry it off with a small screwdriver. I don't like the kind that has a nut to secure it on...because you don't want to tighten that nut down to the point that it stops free rotation, but if you leave it loose, will it come off due to vibration?

Like roversgonemad said, the linkage stopper shaft should rotate freely in the control horn but with no slop. If you have it so tight that it won't rotate, you will be making the servo bend the control rod when it moves, which will stress the servo and possibly lead to over-amping the BEC, leading to loss of control.

It doesn't matter whether you put the ez-connector (linkage stopper) at the servo horn or the control surface horn. I decide which one to put it on based on which horn has more room to ream out the fatter hole needed for the ez-connector (when compared to the smaller hole needed for the music-wire z-bend)...or based on which one has easier access for making adjustments at the ez-connector later on (if access is an issue).
 
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herk1

Trash Hauler emeritus
#6
Does that come with a pin vise capable of holding very thin bits? That's what I use. I got it at Radio Shack. I used it so much that I wore out the threads on the pin vise...and then when I went to buy another, I found out that Radio Shack didn't carry it any more...but I found another at Tower Hobbies. And now Tower Hobbies doesn't carry it any more. I Googled and found a pic that looks exactly the same:

http://www.sigmaaldrich.com/catalog/product/supelco/23820u?lang=en&region=US

...except that the two sets I bought cost ten or fifteen bucks, not fifty like on that site!
 

herk1

Trash Hauler emeritus
#8
Here's a photo showing the Dubro "Mini EZ connector" linkage stoppers on my latest build ($7 HobbyKing chuck-glider converted to RC control). In this case, the tiny control horns that I used on the elevons do not really have good room to ream out the larger hole needed for the linkage stopper, so I put the stoppers on the servo horns (plus for CG planning I needed weight forward as much as possible). The pushrods are 0.032"-diameter K&S music wire. The holes in the Dubro mini-EZ-connectors have room for up to a maximum of .047 music wire, which is the size I use on most planes, but on this tiny plane, .032 is sufficient. If you have a large plane where you want to use bigger than .047 pushrods, you can go to a larger size of Dubro EZ-connector (they make different sizes), but I use the "mini" size almost all the time (it's good for parkflyer-size foamies).
 

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#9
I used a drill bit to make the hole larger. The problem is the fit is not very tight so the bolts came off. I should have used thread lock. I went ahead and use a dab of hot glue to secure it to the servo arm. I was going to use electrical tape, but it was a bit ackward. I think linkage stopper then z-bend on the control horn is the best method. All the Horizon planes use a 2 part pushrod with heat shrink which is a method I deplore.
 
#10
I just use the tip of a #11 blade to carefully enlarge the hole. Gotta do both sides. I also use blue threadlocker on both ends of the servo connector. I had a nut come off one in flight. Fortunately it was on the rudder of my Mustang, so I got it back in one piece.