Mech Actuation: Dynamixel AX-12A
The best actuator (or servo if you prefer that term) that our club has found for actuating the Mech's legs are Dynamixel AX-12As from Robotis. They are relatively low priced, rugged, and if used properly will last a long time and through many battles. There are more expensive actuators available and many of our clubs members have eventually gone that route for increased speed or more weight capability but the AX-12A are a good entry point for the price and still produce very competitive Mechs.
Robotis also has a relatively new actuator model available for nearly the same same price, the Dynamixel XL430-W250-T. It has roughly the same torque-speed characteristics as the AX-12A but has a higher resolution, so in theory it should have better position accuracy. I've played around with the XL430-W250-T's for the turret on '99 but found in practice it didn't give a whole lot of improvement in positioning due to friction in the actuator. The main drawback that I found of the XL430-W250-Ts is that they are really cumbersome to mount compared to the AX-12As. The few mounting holes they do have aren't event threaded, so my recommendation is to steer clear of them.
A question we often get asked is "I've found an RC Servo on Amazon (or elsewhere) for some ridiculously low price. Will they work instead of the AX12As?" The simple answer is no. They simply don't have the power available for the weight of the Mech, FPV equipment, target plates, Airsoft gun, controller, batteries, and target plates. We had several teams attempt to use them over the years and they all result in failure. Another less expensive option RTEAM has looked at are the Dynamixel XL-320s. We've attempted to build a light class Mech with the XL-320s but as yet have not had success with them either. Maybe in the future, if we can optimize the weight of the gun and target plates, they may be an option.
There are also several slightly less expensive knock-offs of the Dynamixel AX-12As on the market. I have no experience with them and cannot say if they will or will not work for the build of '99. My general opinion is: You get what you pay for.
Robotis also has a relatively new actuator model available for nearly the same same price, the Dynamixel XL430-W250-T. It has roughly the same torque-speed characteristics as the AX-12A but has a higher resolution, so in theory it should have better position accuracy. I've played around with the XL430-W250-T's for the turret on '99 but found in practice it didn't give a whole lot of improvement in positioning due to friction in the actuator. The main drawback that I found of the XL430-W250-Ts is that they are really cumbersome to mount compared to the AX-12As. The few mounting holes they do have aren't event threaded, so my recommendation is to steer clear of them.
A question we often get asked is "I've found an RC Servo on Amazon (or elsewhere) for some ridiculously low price. Will they work instead of the AX12As?" The simple answer is no. They simply don't have the power available for the weight of the Mech, FPV equipment, target plates, Airsoft gun, controller, batteries, and target plates. We had several teams attempt to use them over the years and they all result in failure. Another less expensive option RTEAM has looked at are the Dynamixel XL-320s. We've attempted to build a light class Mech with the XL-320s but as yet have not had success with them either. Maybe in the future, if we can optimize the weight of the gun and target plates, they may be an option.
There are also several slightly less expensive knock-offs of the Dynamixel AX-12As on the market. I have no experience with them and cannot say if they will or will not work for the build of '99. My general opinion is: You get what you pay for.