# Bump and turn toys: how do they work?

I remember that when I was a kid, in the 1980s, I had some toys made in Taiwan that basically worked like this: they moved forward uniterruptily until they bumped into an obstacle; then they moved back a few centimeters and then keep moving forward with an angle in relation to the original trajectory of 15-30º clockwise; unless they bumped something while turning back, so a forward movement was triggered, which made then move in a smaller angle.

With this routine, they could basically move everywhere in the house. I don't know very well their mechanism, all they had in common was was a wheel (or wheels?) under a metallic circle under the toy; or maybe an arc of circle where a wheel could change its direction by changing its position on the arc. My memory is fuzzy

Do you people have any idea of what was the mechanism of these toys? I am pretty sure they were quite simple as I don't remember seeing anything complicated inside them. Also, I am not a specialist in robotics, and I couldn't find anything about this type of thing by searching on google.

There's two parts.

The wheel you're remembering is a castor wheel that's designed to stick at straight forward when the car is going forward, and will turn to about 20 degrees when the car goes backwards. There used to be some really cheap remote-control cars that just had a button that did that (so, no response to hitting a wall).

If you took that mechanism and combined it with a front bumper connected to a microswitch, then the bumper could actuate a timer that would reverse the car for some set amount of time, then go forward. I suspect that's what these cars you remember did.

• Thank you. Do you have a link to a video or something that describes that? Or just pictures. I don't remember the name of any of these toys. Mar 6, 2020 at 16:41
• Sorry. I'm going from my recollections from the 1980s. Mar 6, 2020 at 17:22

I think I know exactly what you are talking about. I don't know the physics of it all but it's not castor wheel or microswitch.

They are called 'Bump and go' toys which uses "universal/bump and go wheel"

Here's an example (source):

Universal wheel is the driving wheels, it have two rubberized parallel wheels mounted on a rotating dish. While the toy is moving straight, the dish doesn't move. Once it hit any object, the disc rotates, toy moves backward by few millimeters and proceed to move straight again in different direction. I had cracked open a few as a kid and all the electronics inside were for lights and sounds.

I have checked cheap remote-control cars mentioned above as well and they are definitely different things.