Articles - Modifying Tortoises
05/06/2001
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Circuitron makes switch machines called "Tortoises". They derive their name from the fact that they are slow-motion switch machines. As opposed to the snap switch machines, these machines move the turnout's points very slowly. This is more in line with the prototype. They are also more gentle on trackwork, which is important when you scratchbuild your own track (to reduce pressure on the point rails). The problems I experienced with the Tortoises on my second layout were primarily due to the shorts that would happen when the points were being thrown. I used Micro Engineering turnouts on that layout, which were partially to blame. However, a large part of the problem with shorts was also due to the Tortoise themselves. I use DCC, and what happened was that the internal mechanism of the Tortoise would effectively move faster than the points. So, the internal contacts would switch the power supplied to the live frog before the points had mechanically moved to the opposite track. This would lead to a short. Below is a description of how I modify my Tortoises to eliminate these shorts. Note: Now that I am scratch-building my own turnouts, I no longer have this problem with the Tortoises. I am leaving this article on the web site, should you have a similar problem. Another point to note is that, even though the Tortoise's fulcrum can be adjusted (the green slider part), if the adjustment is such that the turnout doesn't allow the Tortoise's mechanism to move "mostly" all the way to the left or to the right, the internal contacts may not make contact. This may lead to either no power to the frog or the wrong polarity. You will have to adjust the position of the actuator or the Tortoise itself to have a better range. I don't believe that that was my problem with the Micro Engineering turnouts, nonetheless it is another aspect of the issue of which to be aware. The first thing to do is to remove the label. According to the Circuitron THIS ACT VOIDS THE WARRANTY! Under the label are 5 screws that hold the two halves of the Tortoise body together.
Modifying Tortoises
Once the body halves are separated you'll see the internal workings of a Tortoise. It consists of a motor soldered to the PC board. There are series of gears to help reduce the speed of the throw arm. The throw arm (to which the linkage rod is attached) has a set of copper contacts that slide across the PC board.
Modifying Tortoises
Here I have removed the parts and marked the approximate location of the cutting line. Our objective is to increase the area of dead contact as the wipers make their way across the PC board from left to right (and vice versa). If you cut off too much, then the Tortoise will no longer be useful as a power router for the turnout's live frog. Above the PC board you can see the copper wipers on the throw arm.
Modifying Tortoises
Rather than removing all the material (which is not easy), I decided to just cut the contact areas so that the center parts will be dead areas. Use a volt meter to verify that you have made the separation. I used an Exacto knife to make the separations. This completes the modifications. I reattached the 5 screws and I'm in business. They work great, with no shorts. The only down-side I have experienced with this modification is that if the actuator rod is not fully moved to the left or right when the turnout is thrown, the copper contacts can stop in this "dead zone" and thereby not provide any power to the frog. I have found that by using a slightly thinner actuator rod, I was able to solve this issue for all the turnouts that gave me this problem.
Modifying Tortoises