Mousetrap car won't roll on ground but will when being held

[Shannia Petit-Homme]

I have made multiple mousetrap cars, and they've all have the same problem. They all have rolled when I held them however when I would put them on the ground they would not go. I think the problem may be a friction problem, however I'm not sure. I don't know what to do. Any advice/help would be greatly appreciated.

 

[CWatters]

It could be friction but it could also be the design. The length of the lever, the diameter of the shaft (that the string is wound on) and the diameter of the wheels all affect the gearing. The gearing affects how well the mouse trap spring can overcome friction in the wheel bearings and small bumps on the ground.

Try reducing friction on the bearings, then try either smaller diameter wheels or a shorter lever arm or larger diameter shaft. These will increase the torque at the wheels making it easier to get going, but at the expense of reducing the distance it will go.

 

[davenn]

mousetrap cars,

well that's something I have (in 60 years) never seen or heard of before !

 

[CWatters]

When I was a kid we made them from cotton reels.

 

[davenn]

When I was a kid we made them from cotton reels.

Vaguely remember doing something with a cotton reel and a twisted up rubber band through the middle

 

[CWatters]

That's it. One end of the band was fixed to the reel, the other end went through a short length of wax candle with a hole through it to a popsicle stick.

 

[George Keeling]

This question sounded very cruel. I had never heard the term before either. But there are clearly a lot of mousetrap car fans out there. Doc Fizzix is one. Now I see how it gets the name.

How to build: here.

 

[haruspex]

may be a friction problem,

Or a rolling resistance problem.

There are different designs. Please post a diagram, or a very good description, of yours.