The next step is to get the servo arms aligned properly. JR servo wheels have an odd number of teeth on the spline. This means that if can get good alignment with one position rotate the horn 180degs and it will be within ½ tooth of its position before. Now this is where we use subtrim. See you guys though subtrim was for moving the surface to the center point. NOPE it’s for getting the servo arm aligned properly to give equal travel on both sides. The goal of a precision setup is to get everything as mechanically correct first. Then use the electronics in the TX to fine tune it. The larger the subtrim values the harder it will be to match up the two elevator servos so they throw exactly the same at all travel points. We want these elevators to be absolute mirror images.

To get this step correct you are going to have to play a little bit. Slide a pushrod tube section onto the clevis or control horn side of the titanium ends. This is shown in the photo on the 2nd from the left. Bring this pushrod up servo arm. We want the pushrod connection to the center of the servo wheel screw to form a 90deg angle. This means that the servos movement will be equal as close as we can get it off this center position. I use a Motel room key or old credit card to get the angle as close as I can. The photo below will show you the connection and the 90 deg angle. You can’t set the servo arm 90degs to the case of the servo. This is a common mistake. You need it 90 deg to the pushrod. This means that the servos rotation of equal angles each side will give the same linear distance of travel to the pushrod. This 90deg point means is getting your linkage as symmetrical as possible.

If your servo wheel needs some subtrim to get it perfect. Then adjust it with subtrim. See how much it takes. Say a value of 10 is really good. Yet a value of 35 or 60 is not so good. If you have a really low value like 10 you are good. If not then try and rotate the servo wheel 180degs to the other side of the wheel. This will get it closer on the spline and require less subtrim. Again subtrim it perfect and then look at the number. Your goal here is to pick the number that is the smallest. I was lucky. The R-elev servo was dead on with no subtrim at all. The L-elev needed about 6 for a subtrim to get it perfect. Why is this. Well the servos are brand new, so its not worn servos. It has to due with the electronic differences very small differences in the servos. Today’s digital servos are awesome and so close to each other its great. But there can be minor little differences. I want to minimize these differences. This subtrim is the first step in this task of matching up the two sides.

In the photos I had to cut a Days Inn card key to make my tool. Just be sure to use the true edge so that you get the 90deg angle. Align to the center of the 2mm bolt on the ball link or DARE link, and the servo screw. The photo shows the 90 deg angle after the pushrod is assembled. We are not there yet. But right now you get it as close as possible. The final adjustment of the pushrod length will get us dead on…The idea now is to choose the proper side of the servo wheel. If you choose the wrong side your sub trim values will be high and can affect your elevator tracking down the road.

While the servos are still powered up….Place a section of masking tape on the pushrod. This will give you an accurate mark location. This is gives an accurate location to cut. Remember the threaded sections on the titanium ends are smaller than original and we want to get the pushrod length as close as possible some only maybe a single turn or two is needed to center of the elevator mechanically. Place masking tape on the elevator at the tip to align it with the tip. Again this will not be the final location for alignment but we want to get it really close. Then the fine thread of the 2mm fitting will give use precise adjustment

I use a fine tip Sharpie for this mark the CF tube where to make the cut.