I have one of the Lynxmotion 2wd carpet rovers from over a year ago and I recently started getting back into Robotics(it’s been a long time). I had used the older Parallax servos modified for continious rotation. After centering the servos I have a problem where my rover will sway to the left or the right and I have tried to compensate with different pulsouts for each side with no positive results.
I noticed this morning that there is some serious servo slop on both sides, you can wiggle the tires from left to right and get at least 1/4" of slop, which means that the plastic bearing is either worn or the shaft that the servo horn mounts to is worn out. There is next to nothing for weight on this rover, so I know it’s not too heavy.
I am now looking at other servos, something that doesn’t wear out as quickly. the HS-422 has dual oilite bearings, but I am wondering if metal bearings would do better?
The only other option I was thinking about was to go with something like the Solarbotics GM8 motors, but I would have to get an H-Bridge to drive the motors and modify the rover to accept these motors.
I have used Solarbotics motors for many projects, though mostly the GM2 and 3. They have never caused me any problems and are good quality. Another thing to consider is whether you would like more speed or more torque. Torquewise I would go with a servo and speedwise I would use the GM8.
We are the exclusive distributor for the Hitec 1422CR Servo. It’s a 422 that has been built from the factory for continuous rotation. It is by far the best servo for locomotion. It’s a magnatude or two above the Parallax (GWS) servo.
How much of a difference would it be to move to the HS-475HB servo that you also carry? I don’t mean price, but as far as how long the servo bearings would last?
I took apart these Parallax servos and I was right, the bearings wear right out on these…
Maniac05, how did you mount those motors? I didn’t see anything for mounting them other than maybe “cough” double sided tape?
Yeah, that is an inherent problem with the Solarbotics motors. I was only using mine for small projects so there was not really a lot of stress on the motor mounts but if say, you want to build a sumobot, you’re screwed. I used five minute epoxy spread evenly on the side of the motor to attach it to a chassis.
Jim, does the Hitec continous rotation servo have an easy way to adjust center? One thing I like about the Parallax servo is the hole in the servo case so you can turn a screw and adjust the centering of the servo without having to crack open the case.
Use the carpet rover base but instead of continuous rotation servos use the 7.2v gearhead motors (GH-4?) from lynxmotion with the encoders that attach to the back for closed loop control and drive them with the scorpion dual H-bridge.
This uses more pin-outs but lets you play with systems more and you can develope feedback control algorithms which may be an interesting project…PID control of a differential drive robot is a pretty cool endevour and there is plenty of material on the subject.
Another approach would be similar to the above but instead of the motor/encoder pair, modify some servos to be continuous rotation, drive them with dual H-bridge and get feedback from back-EMF.
Well, I will probably be ordering some of these from you soon then. My Octabot II kit comes with two of the Parallax servos for motors. As soon as they give out, I order some 422CR’s from you.
First, I have to get the little robot working. I just ordered a Basic Atom starter kit and I got an IRPD on my last order.
I have a parallax servo that came with my Stamp II board and my aluminum skull is using the Hi-Tec 422 servo. Since I have both to compare, the Hi-Tec servo is smoother and quieter vs. the Parallax servo. I have become a true fan of Hi-Tec.
They both do the same job, but I have noticed the Parallax servo has more gear noise than the Hi-Tec for what ever reason.
sorry…