We designed this trundle wheel specially for this year's Techfest in Aberdeen where our theme for the week was TOOLMAKING

This is a simple project, well within the capabilities of Primary 2 children. The 'clicker' card (blue in illustration) may be left off to make it even simpler.

The wood used for the trundle wheel may all be 10mm square. The wheel shown, however, has 8mm square wood for spacers. This restrains the card disc better.

The paperstick axle is a tight fit in commercially provided card discs, but a little glue may still be needed to prevent the disc turning on the axle.

The card disc shown is 63mm in diameter - 2.5 inches really! Circumference is therefore approx 198mm. If you count five revolutions to the metre you won't be far out! (Just 1% in fact) For a really accurate wheel you can stick a narrow masking tape 'tyre' around the disc. Fiddly - but it works.