RC Components

Hi again,
Industrial servos cost a load. The servos which come with a typical RC kit can develop a torque of around 25 Ncm (if I remember correctly). This is probably enough to operate the throttle of an engine, but certainly not enough to operate the steering or transmission of a large robot. You can get big servos which are compatible with common brands of RC gear (like Futaba), but these cost a lot too. When I looked at large servos the horrible, poor quality ones were upwards of £100 and the decent ones upwards of £400. Industrial servos are likely to be more expensive than this as they will be built for continuous use.
The small servos can, however, operate switches. When I built a robot I used the servo arms to operate microswitches, which switched the current going to the 12 V DC steering and transmission control motors. This gives rather crude control: you push the stick left to turn the wheels to the left, and the longer you hold the stick for, the further the wheels turn, etc. I did the speed control the same way: hold the stick forward to increase speed, and the longer you hold it for, the more the speed increases. With a little practice it is a manageable system to use, and it saves a lot of money, but you might want something more user friendly.
If you've got plenty of time and experience of electronics you could build your own servo. You need a motor (which can be reversed) connected through a train of gears to the output shaft, some kind of feedback which allows the position of the output shaft to be "read", and electronics which take the signal from the RC receiver, compare it to the position of the shaft, and tell the motor what to do. It'll probably save you money (you can scrounge parts) and teach you a lot, but it's a big project in itself.
has technical details for their servos.
Best wishes,
Chris

Hi again,
Industrial servos cost a load. The servos which come with a typical RC kit can develop a torque of around 25 Ncm (if I remember correctly). This is probably enough to operate the throttle of an engine, but certainly not enough to operate the steering or transmission of a large robot. You can get big servos which are compatible with common brands of RC gear (like Futaba), but these cost a lot too. When I looked at large servos the horrible, poor quality ones were upwards of £100 and the decent ones upwards of £400. Industrial servos are likely to be more expensive than this as they will be built for continuous use.
The small servos can, however, operate switches. When I built a robot I used the servo arms to operate microswitches, which switched the current going to the 12 V DC steering and transmission control motors. This gives rather crude control: you push the stick left to turn the wheels to the left, and the longer you hold the stick for, the further the wheels turn, etc. I did the speed control the same way: hold the stick forward to increase speed, and the longer you hold it for, the more the speed increases. With a little practice it is a manageable system to use, and it saves a lot of money, but you might want something more user friendly.
If you've got plenty of time and experience of electronics you could build your own servo. You need a motor (which can be reversed) connected through a train of gears to the output shaft, some kind of feedback which allows the position of the output shaft to be "read", and electronics which take the signal from the RC receiver, compare it to the position of the shaft, and tell the motor what to do. It'll probably save you money (you can scrounge parts) and teach you a lot, but it's a big project in itself.
has technical details for their servos.
Best wishes,
Chris