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As I mentioned in an earlier article, while I was rebuilding my Twist I decided to make a slight upgrade. The control rod going from the servo to the rudder kept bending. I had attributed this to my poor landing skills but decided later that was not the case. So I decided to replace the supplied control rods for both the rudder and elevator with 4-40 diameter control rods. I think the rods supplied with the kit were metric but they were smaller in diameter than the 4-40 size, closer to 2-56 in diameter.

One problem I discovered was that 4-40 rod does not bend well in my z-bender pliers; in fact it doesn’t really bend at all. I had to figure out a way to either bend the rods or come up with a different way to connect the servo and control arm. I had already bought 4-40 rods that were threaded on one end. I could go out and buy some new rods that were completely threaded. I then could use a clevis at each end and a 4-40 nut to lock the clevis in place. For that matter I could CA the clevis on one side and just leave the clevis on the other side adjustable. I could do that, but I already had some 4-40 partially threaded rods.

I decide to make a ‘Z’ bend using a hammer and vise. I placed the clevis on the threaded end and screwed it down about half way. I then attached it to the control arm and marked the rod where the hole in the servo arm was for the rudder. I then did the same for the elevator control rod. I took my two new control rods out to my workbench in the garage, since that’s where I have my heavy-duty vise bolted to the bench.

Step-1: I placed the rod in my vise clamping it where the mark was. I was careful to keep the rod 90 degreed to the top of the vise. Then using a hammer I tapped the rod till it was bent a 90 degrees across the top of the vise.

Step-2: I then I took the rod and turned it so that the bent piece was parallel to the opening in the vise. I raised it above the top of the vise about a ¼ inch, and again I made sure the vertical portion of the rod was 90 degrees to the top of the vise. Using a hammer I tapped the rod forward until it was 90 to the top of the vise. Now here’s where I made my mistake. I tried to bend the last portion so that it was going the same way as the long portion to give me the classic “Z” shape. At this point the rod broke at the last bend. I started again with another rod and this time I didn’t try to make the last bend to complete the “Z”. So now the new rod looks more like an “L” than a “Z”.

I had to increase the size of the hole in the servo arm slightly to accept the 4-40 size rod. But other than that I found that this shape works just fine. This will probably work with other large diameter rods too. So if you don’t have a “Z” bend tool, or even if you have one but need to bend larger diameter wire then the tool can handle, try an “L” bend. I found that it worked well for me.

Fly Smart, Fly Safe,

Larry Dudkowski