Intermittent Motion

I'm experimenting with intermittent motion. I'm trying to make a counter so I want a wheel to turn a tenth of a turn each time I turn the handle on my model. Two things - the display wheel turns 36 degrees each time I wind the handle - second, after ten increments I'll need an output of some sort that can be passed onto another counter. That way I should be able to stack counters and count up in tens, hundreds, thousands...

The picture left is my first attempt. Two ten teeth gears, one with all but one teeth removed, the other with the teeth trimmed. I generated the gear profiles here, imported them into Illustrator and edited the profiles.

Having tried out the profile by pinning it onto a piece of foam board (top picture) I created a 3D version. Only the single tooth piece was 3D - the other gear was made with a double thickness of card. Time to test.

Didn't work.

The problem being the perennial one of cardboard engineering, tolerance. As the single tooth gear turned, it caught on the other gear turning it prematurely. I can't see a way round this (any ideas?) It would word fine in metal or wood with proper bearings but not with card. Next - I'm now trying a pawl drive. More news soon.

Bridge Investigation

Investigating Bridges : Education Download


Eighteen pages of parts, information and instructions on the investigation of arch bridges and beam bridges. This kit is ideal for school and home use and includes a paper river for you to cross and all the parts you need to make an arch bridge and investigate structural strength in beam bridges.

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Boxers - New models to download and make

New models for you to download and make. There are three boxers in the set, Squid Boxer, Box Boxer and Bee Boxer. Each model is ready to download, print out on your own printer and make. Once compete they make fascinating talking points or great gifts for a friend.

Fabulous fun for the crafty and curious!

More details here