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Help With A Mouse-Trap Car Answered

Okay, for physics class, we need to make a mouse-trap car, and I need some help. Basically, the only thing we can't have any electronics, or another mouse-trap. I've seen the ones on ibles here, and lots on google. The basic idea, is to have two CDs, each with a rubber band, or balloon around the edge for traction. But I am asking you, if you were making a mouse-trap car, what would you do?

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guyfrom7up (author)2009-02-27

things from expierience: -don't put traction on the wheels, you don't really need it. -make it long, straightness is key -put a 1 foot piece of carbon fibre tube (found at a hobbystore) on the mousetrap (cut off the neck breaking mechanism and just slip the tube over the wire, making everything straight) -from there pull a string that pulls a small axle. Attached to that axle it a medium wheel. That wheel pulls a string that pulls the axle of the drive wheel, which has CDs attached (works kinda like a gear box). That's what wins. Also, don't go for anything fancy super low friction, it usually just adds friction, like adding teflon tape to the axle.

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bumpus (author)guyfrom7up2009-03-01

Could you explain the carbon fibre part please? And I was thinking the same thing about the axel! :D

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guyfrom7up (author)bumpus2009-03-02

I saw it on a make thing with kipkay (still not a big fan of him) except he used aluminum tube, but I found carbon fiber was just a little bit more expensive, it hardly bent at all, and it was much lighter. Google "make mousetrap car" or something like that for the podcast.

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caitlinsdad (author)guyfrom7up2009-02-27

sounds more like a rolling catapault...the extra weight of ball bearings might negate the reduction in friction.

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bumpus (author)2009-03-02

I'll add pictures tomorrow. :D

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caitlinsdad (author)2009-02-27

I've only seen "direct drive" with the string wound on the axle. Could you rig it up to a pulley system to get more torque or do that and even gear it up? Go with the drag racer top fuel design with smaller CDs or those cut smaller for the front wheels. It might even do a wheelie if it starts too fast. NASCARize your dragster with robot stickers.

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bumpus (author)caitlinsdad2009-03-01

If I had robot stickers.. :P

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Chicken2209 (author)2009-02-28

Make did this, I think as a weekend project just search it on their channel on youtube, it will most likely tell you to use a kit, but atleast you get to see another example

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bumpus (author)Chicken22092009-03-01

Thanks for the tip Chick.

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Gjdj3 (author)2009-02-28

Some people here have been saying to just use cds but I wouldn't recommend that. My class had to do this and the kids who didn't put any grips around the edge had trouble getting the car to start rolling. This is probably only a problem if you're racing on a hard surface but I still wouldn't take any risks.

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Kiteman (author)Gjdj32009-02-28

I wonder if a compromise is feasible - wrap a tread around the wheel to get things going, and it unrolls during the power phase, to leave a smooth treadless wheel for the rolling phase.

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Gjdj3 (author)Kiteman2009-02-28

That sounds cool. It probably wouldn't be too hard to do either.

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Kiteman (author)Gjdj32009-03-01

Bumpus, are you reading this? Try the unrolling-grip idea, let us know if it works. (Even if it doesn't, you should get credit for being aware of the changing requirements regarding grip during the run.)

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bumpus (author)Kiteman2009-03-01

Yes, I am reading this. And the unrolling-grip is a good idea. We're starting to build our cars tomorrow, and I'll have a better idea of what I'm working with. Thanks for the help everyone!

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NachoMahma (author)Kiteman2009-03-01

. The tread will need to be "sticky" enough that the CD will get traction on it, but not so "sticky" that it won't separate under it's own weight. A cut rubber band should work well. . Maybe just making the edge of the CD saw-toothed would work, but I'm not sure how that would affect rolling resistance.

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Kiteman (author)NachoMahma2009-03-01

A cut rubber band is what I was thinking of.

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NachoMahma (author)2009-03-01

. If you use lubricants, make sure they are low viscosity. Automotive engine oil is not a good choice.

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Labot2001 (author)2009-02-27

Do you have any limitations? My car (I have an ible on it) did pretty good, but I could have made it MUCH better if it weren't for all our restrictions. When is this due anyway?

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bumpus (author)Labot20012009-02-27

We have a while to work with them. Do tell about the restrictions.

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Labot2001 (author)bumpus2009-02-28

She gave us a kit, and we couldn't use anything other than what was in the kit. If you're allowed to use whatever you want, I suggest making it longer as Kiteman said. Also, I put my mousetrap backwards (compared to everyone else in class, along with the kit instructions) and it worked really well. The string was given more time to unwind, so it carried further (though not always faster) than the other cars.

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DJ Radio (author)2009-02-27

I think there was one ible on how to make mouse trap cars. It used disks as wheels.

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Kiteman (author)2009-02-27
  • Friction is your enemy! Cut down rolling friction with large wheels - old CDs seem to be popular.
  • Longer vehicles are easier to make run straight.
  • Make sure the string is not fixed to the axle, so that the car can coast as far as possible when the trap finishes pulling.
  • Are you restricted to a specific trap? Rat-traps are larger and stronger than mouse-traps
  • Weight is an issue of balance - light vehicles will accelerate faster, heavier cars will free-wheel further. Try building a light one and experiment with adding weights.

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iBurn (author)Kiteman2009-02-27

If you use CD's you may want to put some sort of rubber around the edges, or else they'll just spin in place and the car won't go anywhere....

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Kiteman (author)iBurn2009-02-27

It would have to be a thin, fairly hard rubber, though, otherwise you lose a lot of speed when coasting.

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iBurn (author)Kiteman2009-02-27

Also true, you really just need some sort of light weight traction along the edge of the wheels...I might have to make one of these now, I've only made the ones powered by CO2 canisters...

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