Installing a fail safe device on a nitro-powered RC vehicle is required when racing at a track or driving on street corners and car parks to prevent loss of control in the event the radio signal is disrupted or lost completely. Without a fail safe device, the vehicle can run out of control and potentially injure people or property. There are two types of fail safe systems that you can install on your vehicle: electronic and mechanical.
Attach the channel 1 (steering) and channel 2 (throttle) servo leads into the fail safe unit and then install the channel 1 and 2 leads from the fail safe to the receiver. Make sure the leads are installed securely and in the right place. It’s a good idea to read the installation instructions, but most units are installed the same way.
Bind the fail safe device to your radio system. This is usually done by turning on your transmitter and then pressing a button on the fail safe unit. Most fail safe systems have an LED that will flash and then turn solid when the binding process is successful.
Test the failsafe unit by powering up your transmitter and vehicle’s radio system. Turn the steering wheel all the way to the right and squeeze the throttle trigger to open the carburettor in the full throttle position. With your free hand, turn off the transmitter while holding the steering wheel to the right and the throttle wide open. Both the steering and throttle servos should return to their neutral positions the moment the signal is cut off.
Simply wrap the rubber band around the base of the carburettor and then loop the other ends to the throttle arm.
You want the rubber band to pull the throttle arm closed, but make sure it is not too tight or the throttle servo may not have enough torque to open the carburettor to the full throttle position. You may have to try several different sizes of rubber bands to achieve the best results.
Turn on your transmitter and power up the car. Test the throttle to make sure the carburettor opens and closes normally. Next, squeeze the throttle trigger to the full throttle position and with your free hand turn off the transmitter. The throttle should immediately close when the signal is lost.
Install one end of a return spring on the throttle servo horn and the other end to some point on the chassis. This will force the servo to return to the neutral position in the event of a signal loss. Most hobby shops have return springs that are designed for this particular task and they’re usually very inexpensive.
Install a 2 by 3mm machine screw through one of the loops at the end of the spring and secure the loop to one of the extra holes in the throttle horn.
Attach the return spring close to the throttle servo and the other end of the return spring to a convenient screw on the chassis upper deck.
Turn on your transmitter and power up the vehicle. Test to make sure the throttle opens and closes normally. Next turn off the transmitter to check if the return spring returns the servo to its neutral position.
Most hobby shops that specialise in the RC hobby will have several different brands of electronic fail safe devices. They all do the same thing and that is returning the servos to their neutral positions in the event of a signal loss. Choose one that fits your budget and is small enough to fit inside your vehicle’s radio box. There are two methods available to close the throttle mechanically in the event of a signal loss. Closing the throttle returns the carburettor to the idle position and prevents the vehicle from running out of control. The first method is to install a rubber band around the base of the carburettor and to the throttle arm. The second method is to install a return spring to the throttle servo horn. Choose the method that best suits your needs.