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How to Adapt a Mousetrap Car for Distance
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So your science teacher has assigned a contest on what mousetrap car can go the farthest, and you want to win! These simple steps will not teach you how to build your car, but they will give you good tips on how to adapt it so that you can gain the most distance possible. The keys to obtain maximum distance: reduce weight, reduce axle friction, and use a long lever for the best mechanical advantage. Use a small diameter axle and large diameter wheels. Each time the axle turns around, so does the wheel; A larger wheel means the car travels further with each turn of the axle. The tip of a long lever travels a greater distance than the original bar of the trap. This increases the length of string used, and conserves energy (slows the snap of the trap). The car moves slowly, but it travels farther because spring power is used more effeciently. Although your materials will be different, you will have to deal with the limited power of the spring, overcome friction, use traction, exploit "mechanical advantage", and minimize mass to acheive the maximum distance from your mousetrap race car.
Create a long and light "body" for the car. The trap and the wheels are attached to this "stick". As seen in the pictures, the body can be smaller than the mousetrap. Trim it down; the lighter the frame the better! (but form boards break more often than boards)

When situating the trap, make sure the spring is facing the correct direction so the lever arm rotates forward. Ensure the trap is as far forward as possible without touching the front wheels. The longer distance between the trap and the wheels, the better! (To a certain point.)

WHEELS! The wheels are a determining factor for a distance car. The front wheels don't matter in size or number; you can even have just one. As for the back wheels, you want the back wheels to be as large as possible, and the back axle to be as thin as possible. Old CD's work fairly well. A plumbing washer may be used to reduce the hole size in the middle of the CD (to fit the axle better).

To create traction, cover the wheels with tape, rubber bands, or balloons. If they slip, energy is being wasted. Adding tape to the rear axle may reduce slippage of the string.

To attach the mousetrap to the frame, use glue instead of bolts. The glue will hold just as well and the bolts just add weight! Make sure you have optimum placement of everything before gluing. A screw may give you a chance to change your mind, whereas glue is more or less permanent.

One possible vehicle. The long body allowed a long lever (boom-box antenna), this increases the mechanical advantage by spreading out the spring's "snap" over a longer period of time. The energy of the spring is released slowly.

The "body" of this car is 50 by 2 centimeters.

The motor The mouse trap "killing bar" or snapper arm was cut near the far side of the spring and bent straight. It was then inserted into the antenna. The trip switch and the latch bar parts were removed to reduce weight (they are not needed).

The drive-train The string attached to the antenna tip winds around the drive wheel. As the spring raises the antenna, the string spins the drive wheel and the car goes forward.

To improve distance, cut-out CD's were used for wheels. They are larger and lighter than the rubber ones in the above images. In order to reduce mass and make them even lighter, you can take the extra effort to trim four triangles out of each CD. A small sink faucet type of washer can be used to reduce the center hole of the CD down to the size of your axle.

Final Car with CD wheels

Results...The car shown travels 6.5 meters on a smooth floor. Notice the fuzzy rodent next to the "cheese" which was added for character.

Tips and Warnings:

  • If the string is just wrapped around the axle, the car may barely move. Adding a larger drive hub can improve pulling power. In some images there is a rubber tire on the axle, this acts as a "gear" and reduces string slippage.
  • Reduce friction on the axle by minimizing the surface area of the support that contacts the drive axle. An axle suppor of thin steel has less friction than a hole drilled through a wood block.
  • Increase friction where it is needed by using a rubber tire or tape around the axle where the string is wrapped. The string should turn the axle and not slip.
  • Increase friction by waxing the string with candle wax. By waxing it, the string has better pull on the axle.
  • Reduce mass by using a simple light stick for the body section. Reducing the mass also reduces the friction at the axle supports.
  • Use the longest lever available to extend the mouse trap arm as far as possible. The tip traverses a greater distance allowing more wheel wraps of string to play out. An antenna from a broken boom-box was used for the lever. Anything long, light, and not too flexible will work for the lever.
  • Reduce friction by applying Molykote┬« a molybdenum disulfide based powdered lubricant to the axles, wheels, and mouse trap spring.
  • Reduce shock by using a bit of sponge as simulated cheese. This reduced the car hopping as the lever arm slapped home.
  • The alignment of the axles and mounts is critical to reduced friction and increased performance.
  • Take a CD and the axle with you to the hardware store if you buy a washer. This may help you to get the right size the first time.
  • Be careful when dealing with tools, cutting wood, or with any hazardous materials. Use adult supervision when necessary.
  • There is a limit to the amount of available energy; the power of the spring. The car shown is near the maximum. If the lever arm were longer, or the wheels were any larger, the car would not move at all! In this case, the energy release can be "tuned" by pushing in the antenne some (shorten the lever).
  • Mousetraps are dangerous. You could break a finger. Use adult supervision. You could get injured.
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What are your thoughts (1 Responses)



posted on May 22, 2015 01:25:18 pm
I think you did a really great job on this! Thank you for the advice. :)



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