template for rockers

[cadeuceus]

Hi all, I made a dolls cradle the other day and needed to have a particular curve for the bottom surface of the rockers. Not having an oval jig, i looked for something to use as a router template. After trying several items that were too rounded (meaning that there was too little contact between the rocker and the ground, causing the cradle to tilt over its C of G), I hit upon a curved section of my daughters Brio train tracks.

Just the right curvature to allow for smooth rocking and not too curved to cause a tip over. I used the track to make a plywood template and then used the template to make the rockers. Literally 10 minutes later I had two identical and smooth rockers.

Having purchased a bit of Brio (train based toy stuff) and thinking that it was too expensive (but also having a daughter who loves it and a wife who buys it), I can now say that I love Brio. :U:U

Hope this helps. Gavin

[bpj1968]

It's amazing what you can use. I often use paint cans to get the curve i need.

Have a look here to make your own train tracks
Train tracks (http://www.woodworkforums.com/showthread.php?t=27847)

[cadeuceus]

hi - the entire premise was to use a curved surface that was not a circle. To use a paint can would have necessitated using a portion of a very large can of paint, other wise the curvature of the cirle would have been too much pf a circle. i have in the past used a portion of the curve of the rubbish bin to to form the arc.

The idea of using a portion of the circle allows the formation of an arc, but only if the diametere of the the circle is much larger than the circumference of the arc that you want to achieve. The reason for not using a circle is that the contact point between a circle and a straight line is a very small point of contact. An arc has a greater surface to surface contact and therefore is less likely to tip over the centre of gravity.

Of course, I have had a few drinks before typing this so am less likely to be succinct in my reasoning.
Gavin

Gavin

[Wooden Mechanic]

Mark your two points and bend a steel ruler from one point to the other, fluctuates the arc size to whatever you want?

Harlan

[derekcohen]

Draw half the curve freehand on a bit of ply. Just approximate what you want.

This represents half the full curve - all you have to do is fold over the template you have just made so that the curve is symmetrical.

Now make another identical from this one.

Regards from Perth

Derek

[cadeuceus]

Not to be snitty, but note that I was sharing a method of making a template around which a router base could be moved - not asking how to achieve an arc.

I know about bending the metal ruler as well as folding the template in half as well as using a piece of string attached at either periphery with a moveable scribe attached to the string and also using a larger round section such as the aforetipped paint can BUT it had to be quick, reproduceable and able to guide the router base in an arc.

The metal ruler would not be a suitable guide for the router base as any ruler flexible enough to bend around an arc would be unstable as a guide surface for the router base. The arc had to be smooth enough to allow for a dolls cradle to rock gebntly when a 3 year old rocked it - and a freehand arc that is replicated to the other side is unlikely to be smooth enough to allow for smooth rocking. The variable nature of freehand is unlikely to for a perfect arc.

Anyway - the method as i described has given me a perfect plywood arc template for future rockers.

Thanks for all inputs,
Sir snit