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

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Discussion Overview

The discussion revolves around the issue of a mousetrap car that functions when held but fails to roll on the ground. Participants explore potential causes, including friction and design factors, while sharing personal experiences and insights related to mousetrap car construction.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant suggests that the issue may be related to friction, but is uncertain and seeks advice.
  • Another participant proposes that design factors, such as the length of the lever, diameter of the shaft, and wheel size, could affect the car's performance and gearing.
  • Suggestions are made to reduce friction in the bearings and to experiment with different wheel sizes or lever lengths to improve torque.
  • Several participants share nostalgic memories of building mousetrap cars using cotton reels and rubber bands, indicating varied experiences with the concept.
  • One participant mentions the possibility of rolling resistance as another factor affecting the car's performance.
  • A request is made for a diagram or detailed description of the car's design to better understand the issue.

Areas of Agreement / Disagreement

Participants express differing views on the causes of the problem, with some focusing on friction and others on design aspects. The discussion remains unresolved with multiple competing ideas presented.

Contextual Notes

Limitations include potential missing assumptions about the car's design and the specific conditions under which it is tested. The discussion does not resolve the mathematical or technical details related to the performance of the mousetrap car.

Who May Find This Useful

Individuals interested in engineering, physics, or DIY projects related to mechanical devices may find this discussion relevant.

Shannia Petit-Homme
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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.
 
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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.
 
Shannia Petit-Homme said:
mousetrap cars,
well that's something I have (in 60 years) never seen or heard of before !
 
When I was a kid we made them from cotton reels.
 
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CWatters said:
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 :smile:
 
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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.
 
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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.
changing-gearing-m3.jpg

How to build: here.
 

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Shannia Petit-Homme said:
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.
 

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