Gravity Versus Scale Modeling

Having just received a Micro.Mark Bending Machine (#81356, $79.95, for wood, plastic, or metal) via UPS, I took it into my workroom and learned how to bend N-scale track. It involves putting the flextrack between two rollers, tightening down four set-screws, and turning a crank and examining the type of curve you're getting. Then you adjust the screws and try again. The critical thing is keeping the track straight so you don't end up with a spiral. With a little practice, you can make dandy roller coaster track.

With a 90-degree dip in hand, I fastened a full piece of flextrack to each end of the dip track and used a whole table full of cut-up blocks of Corningware foam insulation (which I'd bought just for the roller coaster) for supports. The track decline before the dip and incline after the dip were 45-degree angles. A little Atlas ore car was put at the high end of one of the flextracks and let go. And you can probably imagine what happened next!

Not only did it derail and go flying off the table. Oh, no, that was just an insignificant detail. The main occurrence here was an ore car going so fast it was almost invisible! I had learned something about gravity that we all kind of intuitively and covertly know, but now the concept was very overt and staring me in the face: In order for a roller coaster to act appropriately in a 1/160th scale (N) model, it would need 1/160th scale speed, and in order to get that it would need 160th scale gravity, and not even Captains Janeway, Kirk, Picard or Sisko could manage that one!

In other words, if the acceleration of gravity is 32.17' per second per second for a great big freight car, then it is also that for an N-scale car, and the upshot of all this is that I can expect experiments to show that as long as my roller coaster is on Earth and subject to Earth gravity, I will most certainly get cars going 160 times too fast! For example, if a real coaster car was on a decline that let it accelerate exactly half as fast as a dead fall, so that it ended up traveling 48.25' in two seconds (dead fall is 32.17 + [32.17+32.17] = 96.51' after two seconds), then a 160th scale N-gauge car should go 0.3' (less than 4")  in two seconds, but it doesn't. It goes 48.25' as well (leaving inertia, friction, wind and other factors out of the calculations for the purpose of clarity).

Common sense told me it was time to throw in the towel (and the physics book). But I never like to let a little thing like FUNDAMENTAL LAWS OF THE UNIVERSE get in my way! Oh no. And so my journey into the roller coaster Twilight Zone continued.

The only way I could get sensible speeds out of the ore car was with subtle track bends. I experimented for a day and found that each piece of flextrack should have 3 hills and 3 dips, all using a vertical curve radii of 8.75". The first hill should be 2" tall and the other 2 hills 1" tall. This track would cause an ore car to accelerate down the 2" high hill of track and slow nicely on the first 1" hill and nearly stop on the second 1" hill but still make it over the hump. Since this kind of subtle curvature was understandably only 160th as pronounced as that of a roller coaster, I had to ask myself if it was worth going on. To me it was, because I still had a very interesting system evolving, and I had a yen (and a few dollars, too) to push the envelope and see how far I could take it.
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