Mousetrap car

So, for physics, I had to make a mousetrap car that has to go at least meters. I made one, and I've run into a major snag. The car goes ~1-3 meters, and that's sporadically. I know this car can go ~5 meters consistently, as my brother has tested this car. Since he's left for college, he can't really give explicit instructions on how he did it, and I'm stuck wondering how he did it. So, the question is, what am I doing wrong that prevents the car from reaching my desired distance?

What I did:
1. Wind up the string into one tight layer with no overlapping.
2. Wind up the string again into a second more loose layer.
3. Tie the string to the mouse trap, making the string wound between the axel and tied to the mouse trap as tight as possible.
4. Set mouse trap.
5. Trigger it.

Car overview:

Back axle with 1 layer of string wrapped around it:


More information/pictures can be provided if needed.

Extend the length of the mouse trap by attaching skewers to the sides of the mousetrap flippy part. That way it will pull the string much longer than it would otherwise and the car will go significantly farther.

I'll consider doing that, but I prefer not modifying it.

If not there isn't much else I can think of. Is that the design that was given to you by a teacher or something? How does it run? Is it smooth and just not very far or is it bumpy/gets stuck?

If not there isn't much else I can think of. Is that the design that was given to you by a teacher or something? How does it run? Is it smooth and just not very far or is it bumpy/gets stuck?

This was a design that I came up with (within my teacher's limitations). The runs are very sporadic; sometimes it doesn't go at all, most of the time it goes ~1 meter, and rarely it goes to around 3. The car runs smoothy; the only problem I see is that my technique of winding may not be the best way of setting the car up.

So did you catch a mouse with it?

So did you catch a mouse with it?

I caught my fingers in it.
Moving on.

use the biggest wheels that you can find. CDs or something.

use lego gears.

attach them like this

\/string
-----------OO

where the second O is the small gear on the axle, and the first O is the string turning the big gear so that the big gear turns the little gear.

depending on the ratio between the two gears you might be able to get sixteen turns of the little gear for every one turn of the big gear

I don't think the problem is with the design with my car, but with how I'm setting it up. Also, I don't think I have enough time to modify the car substantially.

you could also try using less string, so that when all the string is pulled, the car can still move forward due to it's momentum.

I don't think the problem is with the design with my car, but with how I'm setting it up. Also, I don't think I have enough time to modify the car substantially.

If the problem isn't the design, then how are we supposed to help you?

If the problem isn't the design, then how are we supposed to help you?

The problem is with the method of how I'm winding up/setting up the car. Since my method's inconsistent, I need a new method on setting it up, or I need to address the flaws in my current method.

I don't think the problem is with the design with my car, but with how I'm setting it up. Also, I don't think I have enough time to modify the car substantially.

The skewers wouldn't be a substantial modification but it would be a dramatic improvement. I've made mousetrap cars before using that technique and it's much easier and faster. Also you'd have to tape the end of the string to the end of the skewers but that wouldn't affect much, just turn the wheels to wind the string. Also, I don't think the problem is winding the string.

When your car runs does the mousetrap go off really quickly and kind of jerks the car to move?

The skewers wouldn't be a substantial modification but it would be a dramatic improvement. I've made mousetrap cars before using that technique and it's much easier and faster. Also you'd have to tape the end of the string to the end of the skewers but that wouldn't affect much, just turn the wheels to wind the string. Also, I don't think the problem is winding the string.

When your car runs does the mousetrap go off really quickly and kind of jerks the car to move?

It goes off really quickly.

The skewers wouldn't be a substantial modification but it would be a dramatic improvement. I've made mousetrap cars before using that technique and it's much easier and faster. Also you'd have to tape the end of the string to the end of the skewers but that wouldn't affect much, just turn the wheels to wind the string. Also, I don't think the problem is winding the string.

When your car runs does the mousetrap go off really quickly and kind of jerks the car to move?

It goes off really quickly.

glue CDs to the rear wheel !!! and make it heavy.

You have steps 3 and 4 mixed up, you need to set the trap before tying the string to it. Otherwise the string doesn't actually do much. I'd recommend doing something to stop the trap going off while you tie it (like tie it open with another piece of string, don't rely on the trap's latch while you're fiddling around)

Also if you can help it, don't wind it so close to the ends of the axle, that just makes it rub against the body.

use the biggest wheels that you can find. CDs or something.

I did that back when I had this project in physics. Not enough traction. Basic idea is good though, from what I remember, the winning car had vinyl records or something as wheels; been way to long for me to be sure though, only remembered it in the first place since I saw it in one of the boxes while unpacking.