Correct Steps for Installing a Servo

Correct Steps for Installing a Servo

Why is it that when I adjust the remote control trim to the extreme, the front wheel still leans to the left or right? Why are the angles on the left and right different? Why is the steering angle of the tire so small? These three problems are all caused by issues with servo installation, remote control travel settings, and frame connecting rod adjustments.

Now, let's discuss in detail the correct steps for installing a servo:

1. First of all, of course, install the frame according to the frame manual. Ensure that the lengths of the left and right connecting rods connected to the steering cup are consistent. Unequal rod lengths can easily cause asymmetric left and right angles. (Also make sure that other components such as the gearbox are installed with relatively small errors on both sides. If the gearbox is offset to one side, then having symmetrical connecting rods is in vain.) To ensure that the lengths of the connecting rods on both sides are consistent, it's very simple. After installing the main body of the connecting rod and before installing it on the frame, just hold the two rods in hand and compare them to see.
2. After talking about the connecting rods connected to the steering cup, let's talk about the connecting rod between the steering assembly and the servo. The length of this rod should be installed according to the length specified in the frame manual as a priority. It's best to have calipers. If not, it doesn't matter. Because most manuals have 1:1 illustrations. After installation, just place it on the manual and compare it with the completed effect diagram.
3. After talking about the frame parts, let's talk about the electronic equipment part, mainly the remote control. There are three parameters on the remote control that need to be adjusted:
   The servo's neutral trim. Commonly, it is the TRIM option in the remote control parameters (some are TRM, and some also have SUB-TRIM options). Adjust all to 0. This parameter generally has a shortcut key, such as trm1 or trim1. Set all to zero as mentioned earlier.
   b. The servo's steering range: Turn on the remote control and adjust the servo's steering range on the remote control to 100%. Generally, on the remote control, the steering range is the EPA option. Some remote controls may use TRAVEL or similar.
   c. The servo's D/R value. D/R stands for Dual Rate. There is currently no accurate translation for the neutral position. It means bidirectional output ratio and can limit the output ratio on both sides simultaneously, suitable for adjusting the steering output range on the field at any time. Regarding b and c, a basic knowledge needs to be popularized. That is, the final output angle of a servo is equal to EPA * D/R. For example, if the EPA is finally set to L 90%, R 100%, and D/R is 80%, then the final servo output is L 90% * 80% = 72%, and R 100% * 80% = 80%.
4. After adjusting the remote control parameters, it's time to install the servo. When installing the servo, the basic steps are to first install the servo on the servo mount without installing the servo arm or servo guard. Only fix the servo to the frame. Then connect the servo to the receiver, generally on the CH1 or ST socket.
5. After the servo is fixed, turn on the remote control and set it as described above. Then turn on the electronic speed controller (for fuel-powered vehicles, turn on the receiver power switch). Then the servo will stop at a fixed position. This position is the absolute neutral position of the servo on your remote control.
6. Then, without turning off the remote control and servo, install the servo guard or servo arm on the servo output gear. The installation angle is very important. The principle we choose for this angle is to select the angle that makes the front wheel closest to the center as the best installation angle. Note that we can only try to select an angle as close to the center as possible. Basically, it is impossible to achieve 100% exactly in the center at once. The servo guard or servo arm should have been installed on other connecting rods in advance and then installed on the servo last.
7. After installation, the front wheel is already relatively close to the middle position. Then adjust the length of the first connecting rod from the servo to the steering assembly until it is adjusted to a length that makes the tire exactly in the center.
8. After completing the above steps, when the servo is in the center and the remote control does not need to adjust the TRIM, the front wheel is already straight. But it's not over yet. Next, adjust the EPA on the remote control, that is, the steering range mentioned earlier, and adjust it to an EPA value where the output angles of the left and right tires are consistent. Please don't be overly concerned about the problem that the left and right EPA values cannot be exactly the same. This is not necessary. No vehicle can make the left and right tire angles completely identical when the EPA on both sides is exactly the same. We can only try to make it as close as possible. If the EPA difference is too large, then there is something incorrect in the steering system. At this point, the installation and debugging of the servo have been completed. Finally, if you think the steering angle of the servo is too large, it can be achieved by reducing the D/R.

Additional Questions and Answers

If the EPA has been adjusted to the maximum and the tire angle is still very small, what should I do?
Answer: Replace with a longer servo arm or use the hole farthest from the center of the servo gear in the servo guard to increase the tire angle.

If after turning left and returning to center, it is biased to the left, and after turning right and returning to center, it is biased to the right, what is the problem?
Answer: There is inherently some play in the steering system. This is a normal phenomenon.

Sometimes when touched, the car will be biased to the left (or right), and after being touched again, it may return to normal. What's going on?
Answer: There is play in the servo guard.