Steering on the Smaller Prototype

Ok, it’s currently held together with electrical tape, but, the smaller prototype now has steering and the ability to reverse.

There are several issues though. For one, the description of the motor controller on the supplier’s website was wrong. They said the controller was programmable to allow for any combination of forwards, reverse, and braking. In the instructions for the controller though, it’s clear that this isn’t the case and I’m stuck with the unwanted braking function. The guys at Hobbyking have given me a full refund and apologised for the incorrect information on their website. They’ve also allowed me to keep the controllers which means I have been able to drive the prototype even though it’s weird trying to reverse; after moving forwards you have to reverse the throttle once to engage the brakes, return the throttle to the neutral position and reverse again. This might not sound like much of an issue but it’s sometimes difficult to find the neutral position.

In addition to this, some of the wheels are turning faster than others. This is odd because all of the motors are wired in parallel and are the exact same motors. Granted they’re just cheap motors but I imagine some must have more friction in the gears than others. In particular, you can see in the following video that the front left wheel finds it difficult to spin, whereas the middle left wheel moves more freely than any other. This has a resulted in a tendency for the front left wheel to cause drag, but an advantage of this is that the middle wheel wants to lift the front wheel off the ground making it easier to overcome larger obstacles. Thinking ahead to the final version, I imagine there’s some clever software programming that can be done to automatically transfer power where it’s needed.

You’ll see that in the video the batteries run flat near the end resulting in a bit of anti-climax, but for a moment, despite all of the issues, it was working incredibly well. Just being able to control power to individual sides has made a huge amount of difference to its ability to overcome large obstacles and has renewed my faith in the rocker bogie design.

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