This is part 5 of our tutorial series on building Arrma Limitless from scratch. In our part 4, we learned how to install a radio receiver. Now, we shall cover how to install a servo motor horn.
List of Tutorials
Below is the list of all the tutorials in this series.
- Getting Started
- Installing Servo Motor
- Installing ESC
- Installing Receiver
- Installing Servo Horn
- Installing Motor
- Spray Painting the Body
- Applying Decals
Things You Need
You need the following things to proceed.
- Servo horn
- Servo motor installed
- Radio transmitter and receiver installed and bind
- ESC installed
- A charged LiPo battery
What is a Servo Horn
The servo motor horn is the linear object that connects the servo to an RC steering system. It is usually coupled between the servo output shaft, also known as spline, and the RC servo saver – the mechanism that comes with a spring and is attached to the steering. It works by transmitting the servo’s rotation to the RC steering system in order to steer the vehicle left or right.
The end of the horn that connects to the servo should have minor ridges that match the number of teeth of the servo spline. It is to ensure no slippage when the servo is rotating.
Choosing The Right Horn
An Arrma Limitless roller already includes a servo horn that comes with 23 teeth (23T). However, if you’re using a servo with 25T, you need to get a different horn that matches the number of teeth.
Ensure you use an offset servo horn with one raised end. See the picture depicted below. The left image is the original servo horn that comes with Limitless and features a raised design on the left end. If you use a flat or straight horn, as shown in the right image, you will cause your servo saver arm to twist downwards causing unwanted abrasion on the cover of your receiver box.
We recommend using a metal horn (steel or aluminum) to ensure it is strong enough to withstand the high torque required to steer a Limitless RC car.
Installing Servo Horn
Before you install the horn, you may want to securely close the receiver box with all four screws because the servo horn will be positioned on top of the box.
Connect the LiPo battery to the ESC and turn on the ESC. This will also power up the radio receiver. Ensure you have already bonded your receiver to your radio transmitter. Then, switch on the transmitter and set it to the neutral position. Also, set your transmitter steering trim to center.
Once the above is done, your servo output shaft should be in the center position meaning the steering is centered. Now insert the servo horn perpendicularly on the output shaft.
Do your best to ensure that the servo horn is perpendicular to the servo motor. It may not be completely at 90 degrees but very close.
Then, secure the horn to the servo with the screw provided. The final result should look like the image below.
Continue to Part 6 – Installing Motor >
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