bump n go robot help?

robot,

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To clarify, I am talking about a very simple toy robot, not really a robot at all but a toy that looks like a robot, there are no fancy electronics, just a dc motor, lights and wires, everything else is done by mechanics. Here is a link that shows the toy I am talking about

Thanks, the toy i am talking about is even simpler than that, I have described it further in a reply to my original post. There are no electronics involved in the bump and go mechanism. Sorry I did not describe this as a toy in my original post.

robot,

mechanical

searching

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These kind of toys usually have a simple mechanism driven by a single motor, it`s not easy to describe tho. Usually, a vertical motor drives a pair of wheels in a free turning cage. It`s a kind of differential - imagine the solid back axle of an old car with the prop shaft vertical.

The whole toy balances on these wheels, stabilised by a couple of protrusions on the underside of the toy. Because of the design of the bottom of the toy, when there`s little resistance, the robot moves forwards, but if it is stopped by an obstacle, the resistance on the wheels causes the the cage to be spun by the motor, thus steering the toy in a different direction - Imagine how a dodgem (bumper) car works except the steering wheel is turned by the motor when the driving wheels are obstructed.

So, I think the chances are either one of the wheels is loose on it`s shaft, or the cage is somehow jammed. Maybe you can post a link to a photograph of the underside?

Ron(UK) (Old Toy Collector)

describe

Thanks a lot Ron, that's how I thought it worked but still cannot quite understand how it accomplishes this but it seems that there is too much resistance on the wheels most of the time so it ends up spinning when it shouldn't, I can get it to go forward and back a little but then it seems to get stuck in a spinning motion even though there is no obstacle, I thought it might be the joins in the wooden floor but it does the same thing on a smooth table. Anyhow thanks for your confirmation on how it works, this makes me confident that i least understand that part right. I will post a reply when I get time to take it apart and look at it, hopefully it is not just wear and tear that cannot be fixed, the rest of the mechanical mechanism is in very good order, I have another of these robots and it seems to have the same problem so it looks like wear and tear, which maybe a bad thing for me.

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Thanks for your help Ron, your advice gave me the confidence that i at least knew what I should be expecting from the robot, it turns out the weight and balance of the robot is very important to it's operation, it seemed a stretch that this would be the case but i tried putting the front of the robot casing and arms on and now it works fine, obviously the weight of these extra parts is important, I had not put them back on because I still had more electrical work to do on it so exactly how this bump n go mechanism works is still a mystery to me, I have seen it referred to as a mystery action, now i know why, kind of cool that it remains a mystery really.