"Ron(UK)" wrote in message
...
trigon wrote:
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.


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)


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.