Mousetrap Vehicle C

science
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Re: Mousetrap Vehicle C

Postby science » December 14th, 2009, 4:38 pm

anyone know how to make the vehicle go backwards? please??? thanks!

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Re: Mousetrap Vehicle C

Postby robotman » December 14th, 2009, 4:42 pm

cypressfalls_Robert wrote:does the type of string used affect the distance the car can travel?
If yes then I would llike to try sewing thread(any stiff threads) fishing line and any other stretchy type of string.

When i did it the string was only really a problem when it was really stretchy such as twine
I found that sewing thread broke fairly easily
I settled on Kevlar string that i got as a sample from a manufacturer
science wrote:anyone know how to make the vehicle go backwards? please??? thanks!

Read the Mousetrap Vehicle Wiki there is a whole section on ways to make it work ;)

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Re: Mousetrap Vehicle C

Postby winneratlife » December 16th, 2009, 4:18 pm

A few questions:

On the wiki, it says to add a bar to the trap. But, isn't that modifying it and thus breaking the rules?
For the third example on the wiki, it says to wind the string x times around the axle to travel x meters. Does this assume that the circumference of the circles is 1 m, or is the ratio of winds to wheel turns not 1 to 1 because of some other factor?
Also, building on the last question, how can one guarantee that the string won't fall off or have a slip thus messing up the distance? Do you just, say, do something like tape the end of the string (obviously not the winding) to the axle or something?

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Re: Mousetrap Vehicle C

Postby Dark Sabre » December 16th, 2009, 5:45 pm

On the wiki, it says to add a bar to the trap. But, isn't that modifying it and thus breaking the rules?

Check out 3.a. in the rules. It tells you there that "unmodified" means that all the original parts have to be there, but that you can add things to it or drill holes.

For the third example on the wiki, it says to wind the string x times around the axle to travel x meters. Does this assume that the circumference of the circles is 1 m, or is the ratio of winds to wheel turns not 1 to 1 because of some other factor?

It should say wind x times to travel y meters. The relation between x and y will depend on the ratio of the axle to wheel diameters. I think I'll work over that page later tonight.

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Re: Mousetrap Vehicle C

Postby robotman » December 16th, 2009, 5:52 pm

winneratlife wrote:Also, building on the last question, how can one guarantee that the string won't fall off or have a slip thus messing up the distance? Do you just, say, do something like tape the end of the string (obviously not the winding) to the axle or something?

There a a couple of ways
1. add a pin to the axle either via a spool that is attached to the axle by two nuts --/|==,==|\-- so it would look like that
( |====|=spool -- --= axle /\=nuts ,=pin
2. Glue/tape string to the axle
3.Drill through the axle (not recommended for small axles, actually not really recommended unless you have a lot of patience and drill bits)

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Re: Mousetrap Vehicle C

Postby winneratlife » December 16th, 2009, 6:02 pm

Okay great thanks guys.
Now, the only thing I don't understand is exactly how the car is propelled forward. I kind of get that the spring on the mousetrap turns the string, which turns the axle, which turns the wheels, but then isn't the car just one gigantic wind-up toy?

I'm thinking about something different though. Can you guys give me some feedback?

If one used two mousetraps, and connected one string to one mousetrap to the front axle, and one to the other mousetrap to the back (by taping the ends), and the strings were of identical length, and wound the string on the front axle but not the back, would it work? I mean, by turning the first two wheels, you are turning the second two wheels, essentially winding the second string, which will unwind when the other string stops unwinding for the return trip. The only problem I can think of is the loose string, but I think that can be fixed. However, I fail to see how it is superior to the other cars.

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Re: Mousetrap Vehicle C

Postby robotman » December 16th, 2009, 6:19 pm

That is one way to do it and it does work
You may want to make it a pin attachment so that after it has done its job (taking it out ) it will fall off and not cause an endless cycle of out and back

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Re: Mousetrap Vehicle C

Postby winneratlife » December 17th, 2009, 12:23 pm

I thought mousetraps were one time use: after it snapped, unless I deliberately reset it, the spring could not be wound again? After all, if the string falls off, there won't be any resistance on the way back like there was on the way there. This means either I use two different mousetraps or overshoot past the starting point. Also, I realized this last night, would the resistance provided by having to wind the string be a problem when going forward? Also, is this in any way better than the other cars, or is it just different?

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Re: Mousetrap Vehicle C

Postby robotman » December 17th, 2009, 12:48 pm

Well not reseting it isn't going to stop the spring from winding so as it goes out the spring will gather energy to take it back and when it is going back the first mousetrap will gather energy to take it forward again. The resistance of the string depends on the leverage that the string has, if you have a mousetrap that just has a kill bar it will be extremely hard to get the string to pull it up and give it energy to take it back. so you may have to add an extending bar off the kill bar.

Each design is generally the same once you get it perfected its just the ease of perfecting them changes
I used a double mousetrap powering system with "fancy" winding when i did it a couple years back as a state event.

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Re: Mousetrap Vehicle C

Postby winneratlife » December 17th, 2009, 1:00 pm

Okay, but in that case, I do have to let the string off, which, as I said earlier, would mean that the resistance I had going out won't be present coming back. How do I fix this? Maybe different mousetraps, or different string lengths?

Can somebody please give me a detailed explanation of how the thing works, along with maybe a diagram?

Thanks.

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Re: Mousetrap Vehicle C

Postby robotman » December 17th, 2009, 1:07 pm

to do the string falling off you have a spool and pin in your front axle with your desired amount of string
(i will have a video in a couple of minutes)

and for your back axle have a string that would also fall off and a wingnut brake which would open on the way out and wind back and lock the axle

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Re: Mousetrap Vehicle C

Postby winneratlife » December 17th, 2009, 1:26 pm

Oh, a brake. I guess that would work with a lot of fine tuning.

Still, no one has told me exactly the physics behind the forward motion of the car!

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Re: Mousetrap Vehicle C

Postby cypressfalls Robert » December 17th, 2009, 2:10 pm


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Re: Mousetrap Vehicle C

Postby Fireheart347 » December 17th, 2009, 2:54 pm

Can I clarify something? Is there no specific target distance for the vehicle to travel, it just has to be within the 7-8m, and come as close to the starting point as possible?

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Re: Mousetrap Vehicle C

Postby cypressfalls Robert » December 17th, 2009, 2:58 pm

yea, thats correct


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