I will be doing an activity or two at Orange County’s Manufacturing Day for 8th graders. I thought if I could make some rubberband cars, they could race them and experiment with how to make them go faster/further. (I also plan to have a geodesic dome building table and of course some batteries and bulbs)
Woodworking is tough without the proper tools, but I can sometimes borrow. I got some 1×6 wood at Black lumber (scraps). I was able to use the woodshop in the IU Musical Arts Center to rip it and chop it into appropriate size blocks. I really should have been ready to use their drill dress for the axle holes, but I didnt have the right size bits (and didnt check to see if they did).
Now I had to cut out the notch where the nail holds the rubberband to the axle. I used our Carvey, a small CNC router machine. It took a couple of minutes for each one.
The axles are 1/4″ and 3/8″ and the holes need to be larger than those, so I bought a drill bit set at harbor Freight that goes by 1/64th. The 1/4″ dowel hole was cut at 19/64 and the 3/8″ at 27/64. Since I am on a deadline I need to do this by hand (really need to use a drill press). I made a little wooden guide to try to help me go straight…but I was not always successful.
I cut the dowels rods at about 7.5 mm for axles. I took the 3/8″ (rear) axles and found the center and used a jewelry had drill to create a pilot hole for the nail to attach the rubber band, then tapped a nail in.
The last hole is on top to hold a dowel rod which is the forward hold for the rubberband to stretch from.
I added some glue to the axles/wooden wheels.
I only had 24 of each wheel, so I 3D printed 4 other sets of wheels to get 16 cars (those these 4 have some cracks where the drill & wood were not cooperating). It took 45 minutes to print 2 fronts & 2 rear wheels on the Adventurer 5M
2″ wheels (24 for $20)
3/8″ x 12″ dowel rod (25 for $12 ) (used 4?)
1.25″ wheels (24 for $13.50 )
1/4″ dowel rods (25 for $8.50 ) (used 6)
30 grams of filament for 4 wheels (say 2.5 cents per gram x 4 sets of wheels)
Project cost : $20 + $1.92 + $13.50 + $2.04 + $3 ~ $40.46
(16 cars)
plus rubber bands (3.5″ for power ; 2.5″ for traction)
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