Paper clip control linkages

Intro:

During my last scratch build (the Bleriot linked below), I had to have my servos near my control surfaces so I only needed a very short control link. After some thinking, I decided to try some small, thin paper clips I had. They actually worked great. I bent one of them in a crash but was able to pull on the servo and control surface to straighten it back out.

The Pros and Cons:

Of course the pros would have to be the price. $1.49 for 200. Can't beat that. And also the ease. You can bend the paper clips without any tools. It isn't that difficult to get the paper clip to be the only part used to link the servo arm to the control horn and have no trim. Another pro is that in a crash, the paper clip is now the weak point and will bend instead of stripping a servo or damaging a control surface, hopefully.

The cons would have to be that they are so short and have to be. The wire that makes up the paper clip isn't very long, but also, if you make it too long it'll flex. Which means the servo has to be super close to the control surface. Which can cause Center of Gravity issues having the servos that far back. Which may mean extra nose weight if you can't move the battery forward. Another con would have to be it's durability. I had no issues, yet. But I wouldn't trust paper clips to a fast plane or one with bigger control surfaces.

Overall, I have to say that this is the perfect method for a small to medium foamie if you don't mind the possible CG issues by having the servos so far back. Or if you could simply move the battery forward (or use a bigger battery) to fix the CG issue of having the servos next to the elevator/rudder. But this method is great for ailerons.

The How To:

These are the paper clips I bought. I used different ones on my Bleriot plane. But the ones on the Bleriot seemed thinner. You could buy "giant" paper clips instead of standard, but those are only 50 for $1.49 and it's a lot harder to bend them by hand.

First is to straighten it by hand.

You still want to use a pliers.

Use the pliers to flatten all of the kinks out. I left the end of the paper clip bent so I can get a better grip on it during the process.

Put the bent end into the control horn, then estimate where you want to bend the paper clip to enter the servo arm.

Insert the paper clip into both desired holes in this manner.

I used a wire cutter / snips to trim off the excess paper clip. The same tool I use to trim zip ties. I know that normally this is a bad idea because the wire can damage the snips. But a standard paper clip is thin enough to not damage the tool.

After I trimmed it, I simply bend the ends by hand so they won't come out during flight. As you can see, the control surface is pulled up. This is because when you pull the paper clip towards the center, more of the bend slides into the holes, shrinking the length of the paper clip. I suggest making the paper clip too long on purpose. You can always bend the paper clip in the middle to shorten it.

Since the paper clip got too short, I pulled the end on the servo arm forward. This eased some of the tension, straightened out part of that bend, and made the middle section longer.

Another photo of the end result. You can really pull on the paper clip, by the servo and the control surface, to try and straighten everything out if you want it longer. Or straighten one of the bends a little bit then try to rebend it with the middle section longer. Worst case senerio, grab a new paper clip and try again.

This is a quick drawing to show what happens when you bend any wire too much. The wire will weaken and eventually break. You can actually heat up the wire and it will "reset" the molecules of the metal. But paper clips are cheap enough that you can just use a new one. My point here is to not bend and rebend the paper clip too much. And I certainly would never reuse one on a plane.

End:

I have crashed my Bleriot plenty of times and I didn't have to re-install any paper clips. I did in order to create this article, but that's just getting technical. If you try this, just be sure to check all of your paper clips after each crash and before every take off. But you should be doing that any way.