Build a Mouse Trap Car: Backwards Motion Help

[Kerri23]

I am suppose to build a mouse trap car ...it must go 2m forward, pick up an object and go 2m backwards without me touching it. i can get it to go forwards and pick up the object but not backwards. my design is fairly simple..there's a string attached to the axle.. the other end is attached to the part that comes down on the mouse. you pull that part back and wind up the string by turning the axle back. when the part that hits the mouse springs forward, it unravels the string and spins the wheels. but i have no idea how to make it go backwards. ( it goes backwards if you wind it up the other way though)

any hot ideas would be appreciated.
-note: i can only use one mouse trap

 

[Danger]

Welcome to PF, Kerri.
Have you considered devoting all of the mechanical bits to forward and backward propulsion, and simply Velcroing the 'mouse' and the front of your vehicle?
Keep in mind here that I think farther outside of the box than most. Rules can't be broken, but I like to bend them into the form of singularities.

 

[charng]

One possible solution to make your mouse trap car go backwards is to add a ratchet mechanism to your design. This mechanism will allow the wheels to spin in one direction (forward) when the mouse trap is triggered, but will lock the wheels in place when the string is pulled in the opposite direction (backwards). This can be achieved by using a small gear attached to the axle and a pawl (a small lever with teeth) that will engage with the gear when pulled in the opposite direction. This will prevent the wheels from turning backwards and allow the string to wind back up, pulling the car backwards. You may need to experiment with the size and placement of the gear and pawl to find the right balance for your design. Good luck with your project!