An oldie but goodie, cotton reel tanks are great fun. Add your own tweaks and race them!

Step 1: What you need

Erm... what's in the picture:

- a cotton reel
- a rubber band
- a pencil
- a match

plus sellotape, scissors etc

(For advanced models you can add extra stuff - but this will do it)
If it just jumps around and throws the pencil at people, it is because there is nothing to limit the speed of the rubber band unwinding. These things need something to provide a delicate amount of friction. A washer carefully made of candle wax as marcusmorris says works nicely. Normal washers don't, and I can't see cork ones working great either.
<div style="margin-left:15px;"> <object width="425" height="344"><param name="movie" value="http://www.youtube.com/v/QOmxOX6GG3k"></param><param name="wmode" value="transparent"></param><embed src="http://www.youtube.com/v/QOmxOX6GG3k" type="application/x-shockwave-flash" width="425" height="344" wmode="transparent"></embed></object></div>In my day we used candle wax for the escapement mechanism - nice, slow and controlled. Also, we cut notches in the rims of the reels so the tanks could climb obstacles. We used penknives for this purpose. Every schoolboy had a penknife back then (indeed the UK Scout movement insisted on it) but perhaps it is more prudent to suggest the use of a file or a junior hacksaw in these modern times where the possession of anything vaguely sharp is considered by the authorities to be highly anti-social and the slightest bloodying of a finger is sufficient reason to take a knife manufacturer to court for failing to print an appropriate warning on the item.<br/>Enjoy the video!<br/>
Made them as a kid 40 years ago but called them spool bugs. Try using an already used wooden match instead of the pencil. Less weight goes easier around on the floor.
lol how about an unused match!
Ya like a chostick a thin one though
Mine just jumps around and throws the pencil at people! Whats wrong?
theres nothing wrong you just made a sweet tank wepon that can poke peoples eyes out :P
Try not winding it as tight or slackening the band.
Neat, i think i'll make this with my son and have some fun.
Nice! But I dont think that the pen is the best thing to use here. A small lightweight stick should be ideal.

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