Mousetrap race car is not working

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Discussion Overview

The discussion revolves around troubleshooting a mousetrap-powered race car project that is not functioning as expected. Participants explore various mechanical issues related to the car's movement, including axle rotation, friction, and the design of the string mechanism.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Homework-related

Main Points Raised

  • One participant notes that the car does not move despite the axle spinning well, suggesting that the issue may not be friction.
  • Another participant proposes testing the car on different surfaces or adding rubber tires to improve traction.
  • A later reply indicates that the string mechanism may not be functioning correctly, as it pulls the axle up and down without causing the wheels to roll.
  • Some participants suggest that changing the direction of the winding of the string could resolve the issue.
  • One participant introduces the idea of a delay mechanism to manage the sudden release of energy from the mousetrap, potentially improving performance.
  • Another participant expresses confusion about the string's routing and requests clarification on the design structure.
  • Concerns are raised about the axle's thickness and its impact on wheel rotation speed, with one participant suggesting that the axle may be too thin.
  • Participants discuss the possibility of excessive friction due to design changes, questioning whether the issue lies with the mousetrap or the new attachment method.
  • One participant emphasizes the need for drawings of the mechanism to facilitate better evaluation and discussion.
  • Another participant critiques the design, noting that the spring-rod's angle may not be applying sufficient tension to the string, leading to wasted movement.

Areas of Agreement / Disagreement

Participants express multiple competing views regarding the causes of the car's malfunction, and the discussion remains unresolved as they explore various hypotheses and suggestions without reaching a consensus.

Contextual Notes

Limitations include unclear assumptions about the design and mechanics of the mousetrap car, as well as unresolved details regarding the string's routing and the effects of friction.

Cheesycheese213
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Hello, so for school I'm building a mousetrap with my group for a project, but our car isn't moving. We filmed it snapping, and it doesn't seem like it is because of friction, since the axle spins pretty well. We thought that it was because the thing that holds the axle bends, but after fixing it, it still doesn't roll. We tested it without the mousetrap being set, but when pushing the dowel towards where the mousetrap would snap, it did not move the wheels or the axle. We noticed that when pushing it back, it did roll. I have a picture of it set, but we're not quite sure why it still doesn't work. Could anyone help? Thanks!
upload_2017-2-28_18-51-10.png
 
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Oops did I post this in the wrong place? Sorry!
 
Since the axis spin, it's likely a problem with friction. Have you considered to test it on a different surface, or clue some rubber like tires on the wheels?
 
We looked at it again, but the axle doesn't spin at all, the string just pulls it up, and then down. But, when we wound it the other way (the way the wheels would roll), the wheels spun, just in the wrong direction. Do you think we attached the mousetrap on the wrong way? Thanks so much!
 
Difficult to tell from the picture, but go ahead and test it. It's probably sufficient to change the direction of the winding rather than to turn the trap. The principle is simple: the energy stored in the spring has to be transported to the axis. so it's always a matter of traction and friction.
 
Oh okay thank you so much!
 
The release of the stored energy is probably very sudden. So either you invent some delay mechanism to get an energy supply for a longer time period, an intermediate storage if you will, e.g. a ribbon that get spun first and releases its energy afterwards, or you must ensure there will be no wheel spins anywhere, neither on the cords you use, nor on the axis. It's the same effect as with spinning wheels in car races.

And watch out your fingers! :wink:
 
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I see! Thank you so so much! :smile:
 
I cannot see from your diagram where the string goes. It looks like it passes under a pulley of some sort mounted on the front axle, then proceeds to a bobbin at the rear, but not in a straight line.
Please explain the structure there.
 
  • #10
Now it drives, but it didn't move far. We noticed that after the highest point the dowel goes to on the mousetrap, it stops pulling the string. Did we do something wrong? Thanks!
 
  • #11
It is attached to one side of the axle, the right side, and there aren't really any pulleys, or anything, it is just attached to the axle. Thanks!
 
  • #12
We aren't quite sure why it doesn't work, but we think it is because the axle is too thin, and the wheel spins too fast. The axle is made of one of those barbecue skewers, and the car is about 30 by 12 cm
 
  • #13
Sorry for bothering again, but we changed the thing attaching the axle to the chassis to cardboard, and now when we pull the string the wheels won't spin that much, maybe 3 rotations before they stop. Is this because there is too much friction or is it still the mousetrap? And if it is, how should we fix it? Thanks!
 
  • #14
I think you need to provide some drawings of the mechanism so that others can evaluate it. Just saying you changed something and it doesn't work doesn't provide enough information for any meaningful discussion.
 
  • #15
It looks like a very strange design. It looks like the spring-rod is pulling the string mostly in a direction that is perpendicular to the string, so it isn't really applying much tension to the string. A lot of movement is wasted in slack motion of the string.
 
  • #16
Khashishi said:
It looks like a very strange design. It looks like the spring-rod is pulling the string mostly in a direction that is perpendicular to the string, so it isn't really applying much tension to the string. A lot of movement is wasted in slack motion of the string.
I'm sorry (I'm dumb), but I don't really understand what you mean? Thanks!
 
  • #17
It worked! Thank you everyone!
 

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