Aug 26 2011

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Wacky Track or Shake Shake Bridge


In Misty Island Rescue, Thomas must cross the Shake Shake Bridge, a bridge that shakes violently when an engine crosses it. I didn’t intend on making a replica of the Shake Shake Bridge, I actually meant to make an imitation of Wacky Track, bendable wooden track, but sometimes things don’t turn out like we intended. That’s not a bad thing, often I learn more from my mistakes than my successes.

Since I’ve solved most of the interesting problems related to making wooden track (except ascending track, but I don’t think it’s possible without a special bit), I have been looking for challenge. So I decided to make a segmented track that could bend to make special layouts. Short sections of track are easy, I just needed to figure out the best way to join the segments.

IMG_2936Before I could cut short sections of track I needed to manufacture more straight track. I won’t repeat those steps here, but you can check out one of my previous projects to see the steps.


IMG_2943To cut the straight track into equal sections, I set up a stop block on my miter saw using a 1/2″ brass setup bar as a guide. Then I proceeded to cut all three pieces of straight track into 1/2″ sections. I stopped cutting each piece when I had about 1-1/2″ to 2″ left. I didn’t want to get my fingers any closer to the blade and I needed longer pieces for the ends.


IMG_2944Here are all the 1/2″ sections lined up. Using the technique I have showed before, I also cut the female connector into one of the scrap pieces.


IMG_3020To connect all the segments I was planning on using two pieces of 5/16″ piano wire. So I drilled a hole slightly larger than the diameter of the wire on each side of one of the sections of track. I then used that section to mark each section of track so the holes would theoretically align.

I say theoretically because I had to chuck a few sections where the drill bit wandered and the holes just didn’t line up properly.


IMG_3087Cutting the piano wire turned out to be harder than I expected. I couldn’t make any progress with a hacksaw and the many various side cutters and other wire cutters I own wouldn’t even make a dent. I finally ended up using a pair of end nipper pliers and a hammer to cut the wire.

Yes, I know this is dangerous to do with a hardened hammer (not to mention hardened pliers), but I couldn’t find my ball peen hammer and I was impatient.


IMG_3021I cut holes in enough sections of track to try out how well the track would bend. Then I slid several pieces onto the piano wire to test how well it would work.

I found that with two pieces of piano wire the track was way too stiff; I could barely bend it. This wasn’t going to work.


IMG_3022Next I tried threading some rubber bands through the holes to make the track piece more flexible. While it was more flexible, this method also had some flaws. First finding rubber bands long and skinny enough for a much longer section of track would be difficult, and second, the track still would have a tendency to want to snap back straight after it was bent.

I could have tried some copper wire next to make the track keep it’s shape, but my goals for the project changed. My son said he wanted a Shake, Shake bridge instead.


IMG_3059Not sure what I was going to use for an elastic material, as has happened so many times, my wife saved my butt. In her craft supplies she had a spool of Stretch Magic — a stretchy cord used for making bead jewelry. It is strong and comes in a long spool so I could cut it any length I needed.


IMG_3032The method I finally used for connecting the segments together was to drill a third hole in the middle for a single piece of piano wire and to thread the Stretch Magic through the two side holes. This seemed to give the track just the right amount of flexibility and made the track twist more like an unsupported section of rail might.

I originally tried with just one stand of Stretch Magic on each side, but the holes I drilled were larger than the diameter of the elastic so there was too much play between each section of track. To fix this I tripled up the elastic.


IMG_3054I tied the elastic in a knot at each end to keep it in place and under tension. To keep the knot out of the way I also counter-bored the holes at each end.

In one end I drilled a hole slightly smaller than the diameter of the piano wire to keep it fixed in place. At the other end I drilled a hole that was slightly larger so the wire could slip in and out as the track bent.

If you look really closely you might be able to see that the end piece split up and down right around the middle hole, but I was able to glue the piece back together right around the wire.


IMG_3042Here’s a picture of how the track twists. It’s a little stiffer than I would have liked, but my son likes how the track turned out and that’s what really matters in the end.

If I make track like this again, next time I may want to number the segments so I can put them back together with the grain matching. I didn’t think of this until I had already put the track together; I didn’t want to take it apart again just so I could make it look better.


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