All moving parts of an RC car can be changed or adjusted. These include:
- Motor lock
- Motor pinion
- Spur gear
- Cardan shaft
- Cardan shaft/differential coupling
- Drive shaft driver
- Drive shafts
- Wheel axles
- Steering linkage / servo saver
Engine and transmission
The motor lock (1) is regualted by an adjusting screw. In addition to another fastening screw, the adjusting screw runs in an arched groove. As it is guided in this groove, the motor can be installed in flexible positions. The distance between motor pinion (2) and main gear (3) can be adjusted by variation. With this setting, care must be taken to ensure that the two gears are not too tight, but also not too loose. A minimum clearance is optimal to allow easy running and to prevent the teeth from jumping over. Too tight or too loose adjustment would lead to increased wear of the gears.
The clutch (4) is often a semi-rigid connection between the main gear and the rest of the powertrain. A self-locking nut presses a tight spring against the grinding driver and this against the friction surface of the main gear. If the torque difference is too great, the coupling will grind. In this way, the torque transmission to the wheels can be limited. The contact pressure of the coupling can be adjusted via the said nut and the spring. Tighter tightening leads to higher transmissible torques. However, it makes sense to limit these moments. RC cars, for example, which are designed for use on gravel, experience a considerably increased counter-torque in high-grip situations (on asphalt). Such situations place an excessive load on the gears in the gearbox and the differentials. Since in conventional use on ballast, torques of this size usually do not have to be transmitted due to slippage on the wheels, it makes sense to adjust the clutch so that slippage occurs on the clutch when the RC car is moved on asphalt. Of course the handling of the clutch adjustment is very individual and will only be illuminated here as an example.
The cardan shaft (5) is often made of aluminium in RC cars and we are connected to the differentials with drivers (6). If these drivers are made of aluminium, they tend to wear out strongly. It makes a lot of sense to exchange them for steel parts or to always have spare parts with you. The wear of these cardan/differential couplings (6) sometimes has a considerable rotational play of the cardan shaft.
The differential gear (see picture below) is used to distribute the drive torque to 2 wheels to be driven. On 4WD vehicles there is a differential gearbox at the front and rear. Due to the special arrangement of the gear wheels, it is possible to allow driven wheels to travel uneven distances at the same time without slipping. This is the case when cornering, because the wheel inside the bend covers a shorter distance. The already discussed slipping clutch relieves the partly filigree gears inside the differential gear. Since the differential basket is usually made of plastic and tends to heat up, the differential is often not easy to move in the long term. This problem can be prevented by using aluminium differential baskets.
The drive shaft drivers (8) on the differential transmit the drive torques to the wheel axles via the drive shafts (9). Partially one finds (e.g. with the Black Commando) the drive shafts and wheel axles as a part connected by a cardan joint. When adjusting the wheel carriers (camber and track), care must be taken to ensure that the drive shafts are loose and free moving at all times. If the drive shafts are compressed, this leads to failure of the differential mechanics and increased wear of the tires and gears. Besides, there is a loss of performance.
The wheel axles are the most frequently defective parts in an RC vehicle. They bend or break very quickly when the ride is stopped by a collision. The predetermined breaking point is located at the hole for the bolt for the wheel drivers (hexagon). Excessively hard impacts cause the wishbones and ball bearings to break, but this relieves them. Wheel axles should always be kept in stock in larger quantities as spare parts.
The steering linkage can be made very precise by the consistent use of aluminium parts. It is then almost maintenance-free. It is also very important in this context to replace the servo lever with an aluminium part. The so-called servo saver is a torque coupling that no longer transmits force from a certain moment and is decoupled. The servo motor is protected by using a servo saver. If the steering mechanism is blocked, the servo cannot reach its target position. If this should otherwise be prevented, the servo motor would burn out, as the servo keeps trying to reach the target position, but cannot do it in case of a mechanical blockage.