Not much has happened that’s exciting on the IED project. The robot’s pretty much just been working. We added 1/2″ of drop in our treads to make turning easier and more importantly to make bump climbing possible with the location of our electronics. A second arm motor was added because the first motor alone was right on the edge of specification and a second motor made the system work better in unideal conditions.

However, our robot was somewhat counting on getting some high strength motors from Vex. We needed a direct drive drivetrain for size and space reasons, but we wanted to run faster than the piddle speed direct driving a tank tread sprocket gets you. Our plan was to get two Vex Motor 393s and run the high speed gearing. However, due to a mix up we received the Motor 269s instead, which are essentially the same specifications as the old 3-wire motors. Initially, I was disappointed and thought the motor change was pointless. After installing them, though, I’m really won over by some of the new features that make the motor perform a lot better.

First, the clutch is gone and metal gears are installed. This is really a lot nicer than you think. The clutches had their share of problems and often would strip or desync or get crooked. Plus, the plastic gears still found a way to shatter anyway, so they didn’t really serve their purpose. A shaft adapter is included to let you drop-in replace the motors with your 3-wires, but we didn’t use them. Our shafts were already about .66 inches too long so the removal of the clutch actually made the implementation perfect. Also attributable to the lack of a clutch: there is so much less slop in the drivetrain now. It’s great.

Second was a very small change to the Vex motors that really shows IFI’s attention to detail in design. In the motors they switched the side that the motor power wires come out of. This is awesome. Before, it was very difficult to mount a motor on the very last hole of a standard Vex chassis, because very little clearance would exist between the motor and the metal siding. Now with the motor coming out the opposite side, this problem is eliminated. Also worth noting is that the vast majority of motors are mounted as low as possible (spinning section upwards) for CG reasons. This stops you from having to wrap the motor wire around the motor. Overall, a tiny change that makes every application that much easier.

The motor with a controller is the same price as the old 3-wire motors, which is really nice, since the motor controller is essentially a free 1-foot extension cable. The previous motors had very short cords and virtually every motor had to be extended. And if you don’t need it, VEX ships you a zip tie with every Motor Controller 29. How thoughtful is that?

The only problem the motor seems to have is that the distinct “motor whine” is a different, louder sound. It’s a lot less “electronic hum” and a lot more “DESTROY DESTROY”. But that’s not a serious problem at all.

Using these motors has basically converted me. I’m going to replace every motor I own with these (and four 393s of course), they’re just fantastic.

EDIT: I got a PM today letting me know that the “motor whine” isn’t actually normal operation, but that my joysticks are decalibrated causing the motor to be sent a very small PWM command. Whoops! Thanks for the heads up.

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