Presentation on theme: "Mousetrap powered car that is quick and cheap to build but performs well. Design by Bill Kuhl http://www.scienceguy.org Copyright 2010."— Presentation transcript:
1Mousetrap powered car that is quick and cheap to build but performs well. Design by Bill Kuhl Copyright 2010
2For a “College for Kids” summer class I wanted to design a simpler mousetrap car than the 3-wheeled bamboo mousetrap cars I had been experimenting with.In designing the Quicky Mouse mousetrap car I had the following objectives:Fast to build so it could be built in one hour class time.Cheap to build with easy to find parts.Good performance, this car should do well in distance competition.Adjustable steering, the steering can be adjusted to track straight.
3This was my first prototype which was 2 inches longer This was my first prototype which was 2 inches longer. On a very smooth surface it would travel a long distance very slowly. If the surface was less than perfect, it might stop. Like with many things, higher performance can have a trade off in reliability.
5These are tools that would be good to have for this project These are tools that would be good to have for this project. Two types of saws are shown, only one is needed. The needle nose pliers could be used for wire cutting also.
7The line I used is a Spectra fishing line, it is very thin, strong and does not stretch much. One 150 yard spool can be used for a lot of mousetrap cars.
8Use the smaller cable ties, I had trouble with the line catching on the cable tie with a larger one.
9The small screw eyes I used were from two manufacturers and were slightly different sizes but both worked well. Bundled in packages of 14 which will be good for 3 ½ mousetrap cars.
10Coat hanger wire is used for axles Coat hanger wire is used for axles. Try to find a coat hanger that has straight sections of wire.
11Sometimes solutions will appear in front of you in unusual places Sometimes solutions will appear in front of you in unusual places. I wanted a rubbery material for the wheel hub that would grip the axle and I spotted this tarp strap in my garage. Squares can be cut from the cord material easily with a scissors. CD ROMS can usually be found from free sources.
12If you can not find a tarp strap, no doubt other rubbery materials will work. The coat hanger wire axle fits tightly into the rubber and no glue is needed. Eraser material should work also but it is heavier.
13What is a “Lever Arm”?The term “lever arm” is used many times in this article so a little explanation is in order. The lever arm connects to the mousetrap spring and the opposite end is attached to the line. It pulls the string that is wrapped around the axle. For best performance it should be light but it also needs to be strong and stiff.
14Types of Wood Used – balsa sheet 3/16” or ¼” thick is cut into strips 1” wide. Hardwood 3/8” x 3/8” is cut into ¾” lengths. Oak square or dowel ¼” wide can be used for a strong lever arm.
15Finding the Materials in the Stores I thought it might be helpful to point with pictures to exactly where you might find the materials to make the Quicky Mouse mousetrap car. Most of the materials will be found in a hardware store or lumber supply store. Balsa wood will be found in a hobby shop. The fishing line will be found where ever fishing tackle is sold. I attempted to give further clues where the items might be found within the store.
38Preparing the Mousetrap I use Victor mousetraps which are often specified in mousetrap car competition rules. Many of the parts of the mousetrap are not needed or are used in another part of the project so the following steps will show how to modify the mousetrap.
39A needle nose pliers works well for taking parts off the mousetrap.
40Put one half of the pliers under the loop and lift the handle of the pliers upwards.
41Keep the wire with loop at the end of it for use later on the car.
49The construction starts by building a rectangle from the two long lengths of balsa and two of the short lengths. If you are using hot glue, be sure to spread it out to cover entire joint and push the pieces firmly together.
50Hold the pieces together until the hot glue has cooled enough to start to set. Make sure the pieces are at 90 degree angles.
51Pretty good looking joint, only a small amount of excess glue.
52Glue the other long piece to the first end piece.
54On the end where the mousetrap is placed, a short piece of balsa goes on top at the very end.
55Another short piece of balsa goes on top to support the other end of the mousetrap. Mark on the long pieces where the short piece should be glued based on the mousetrap location.
56Make sure the mousetrap is positioned the correct way, the arm part needs to be in line with the center of the mousetrap car. Glue the mousetrap to the two balsa support pieces.
57Glue has been spread at the proper location, place the balsa piece down quickly before the glue starts to harden.
58Mark on the two balsa mousetrap support pieces the left edge of where the mousetrap will be glued. Glue the mousetrap to the support pieces.
59Hot glue the small wood blocks at the edges in front and in the rear Hot glue the small wood blocks at the edges in front and in the rear. It might be easier to mark the position for the screw eye holes before gluing but you can mark afterwards also.
60I marked out a cross on the blocks and then used a push pin to start a small hole. The pink foam was used to cover the sharp end of the push pin when not in use.
61Push pin has started one hole, it will be easier to screw in the screw eye now. Make the holes are as straight as possible.
62The screw eye has been screwed in place The screw eye has been screwed in place. Do not screw it in entirely, then you can adjust the angle of the axle slightly.
63Two screw eyes in place and turned vertical so the axle will go through.
64By the 90 degree angle mark I had drawn below, it can be seen that the axle is not in perfect alignment. Adjust the screw eyes to get the axle in alignment so the car runs straight.
65That is better. Axle is straight now and the car should run straighter That is better! Axle is straight now and the car should run straighter. With wheels that can be removed, this adjustment can be done again if your car does not track straight.
66Glue the tarp strap material to the CD ROM so that it covers the hole with an even amount covering the edges of the hole. CA (super glue) works but no doubt other glues will work too.
67Mark the center of the wheel and drill through the tarp strap rubber with a 1/16” drill bit. Make the hole as straight as possible.
68Drill bit has gone all the way through the soft rubber material.
69Plastic straw spacers go to outside of screw eyes and wheels are carefully pressed on to the axles until there is a slight gap between rubber hub and plastic spacer.
70Assembling the Lever Arm There are many materials and methods for building the lever arm. Because of breakage problems with balsa lever arms, I used ¼” square oak strip that I found at a lumber retailer on my last car. The brass tube would not be needed when balsa is not used for lever arm, just glue to mousetrap wire and spring, then wrap with string.
71On my 3-wheel bamboo car I used two bamboo skewers glued together On my 3-wheel bamboo car I used two bamboo skewers glued together. The lever arm attaches to mousetrap wire with glue and wrapping with string.
72The brass was glued to the balsa lever arm, the balsa tended to break just beyond where the brass tube ended.
73A rigid but light weight lever arm can be constructed from strips of 1/8” balsa wood glued to form a T-shape.
74If you decide to use the balsa lever arm, I would suggest gluing 1/8” brass tube to balsa for the mousetrap connection.
75A needle nose pliers is good for placing the lever side of the spring in place over the lever arm. The spring Must be attached to the lever arm.
76Attaching the Cable Tie to Rear Axle Cable tie is attached to the rear axle.
78Clip off the extra plastic from the cable tie, a scissor will work for this but wire cutters works better.
79Put a drop of glue on the cable tie so it will not slip on the axle.
80I carefully used hot glue to fasten the cable tie on this car and it seems to be holding. Too much hot glue and the loop in the line might catch and not come off.
81Tying Knots – (Not About Marriage) There needs to be a loop tied in one end of a length of fish line and the other end is tied to the end of the lever arm. Tie the loop first and then tie to the lever arm and it will be easier to adjust the length. The line needs to be almost touching the rear axle but not touching the axle and certainly not longer than the axle.
82Tying a loop knot that will not slip is not difficult but the line is very thin making it slightly difficult to handle. Bend one end into a loop, create a circle with the two sides of the loop and tuck the end of the loop through the circle.
83Pull the knot tight and trim off some of the extra.
84The loop should come close to, but not reach the axle The loop should come close to, but not reach the axle. If the line is longer it will not come off the axle at the end of the lever arm stroke.
85Adjust the length of the line here when you tie it to the end of the lever arm. A square knot will work here. The extra piece of wire from the mousetrap was glued to end of lever arm.
86Winding the Line Up – Running Your Mousetrap Car Carefully pull the loop forward and hook it around the box part of the cable tie. It helps to lift the lever arm up slightly first before pulling the line.
87Lift the lever arm up slightly before pulling the loop over the cable tie.
88Wind the string around the axle, if you leave the axles long it is easy to get your fingers around the axle to wind the line. Turn the axle clockwise.
89Let the mousetrap car go, it will run best on a very smooth surface indoors.
90Be sure to check out my general information article about mousetrap cars and of course my website: