Instructables
Picture of Train Seesaw


A motorized "Brio type" train climbs this seesaw--and its weight flips it down the other side.  The track (actually it's a channel) is 3D printed and can be customized as to angle, radius, length and color.

http://www.thingiverse.com/thing:65965



 
 
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Step 1:

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Start by printing track.  I left holes to screw the track to plywood.

Step 2:

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The turning pieces (30 degrees each--3 of them make a 90 degree turn) are cut off from the straight piece (using Autodesk 123D--free).

The diameter of a complete circle is 12.5 inches.  Make the top longer, but use the 15 degree cuts at each end, and you will achieve a larger radius.  Change the angle if you want something completely different.

Step 3:

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You can clip the pieces together using a printed clip (I only designed the corner clip--corner to straight and straight to straight will be longer clips).

Because the seesaw must be held firmly in place (and the approach pieces also), I used 1/2 inch #4 woodscrews.

Step 4:

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Two straight pieces of track are held together using the pivot piece.  The pivot piece is not centered--so that the track will tend to rest in one direction.

Step 5:

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Press the 3/8 inch (ID) bearings in the support pieces (vxb.com for bearings).

Step 6:

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Cut a 3/8 inch diameter wood rod (72mm long) and press it into one bearing, through the pivot piece and into the other bearing.

Step 7:

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To make the seesaw reliably land on one end, I glued a chunk of surplus plastic (a bad print) under the right side.

Step 8:

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Set up your layout and let the train go!