It's been quite a while since the last post. Quite a few things happened - despite no activity here - including moving to a new place 2 years ago, purchasing various wood-working equipment, buying a PC oscilloscope and attending my first Nuremberg toy fair, just to mention a few.
The layout I was working on is still accessible, and the plan is to eventually finish it, however for now the focus is continuing the work concerning deceleration. Continuing where I left off the last time, right after obtaining a formula for the approximate deceleration time for the ESU v3.5 decoder, used in their Brawa V100 locomotive, the problem is that just knowing this piece of information isn't enough to determine the length of track the locomotive will travel while decelerating until standstill.
This can be easily seen through a quick example. Click on the picture to enlarge the sample. There are 2 charts representing instant speed (s) versus time (t), taken for 2 different decelerating objects. Both objects are travelling at a constant speed 3 for the first 3 time units, before starting deceleration at t=3. They all reach standstill at t=7. The first one has a more "smooth" speed curve, going through intermediate steps before hitting 0, while the second one cycles abruptly from speed 3 to 1 at t=4. Computing the distance travelled yields 17 (3x3 + 3x1 + 2x2 +1) for the first object, and 15 (3x3 + 3x1 + 3x1) for the second one. Therefore despite taking the same time to decelerate (4 time units), the distance travelled is not the same.
Knowing that obtaining the distance travelled will be needed as well, I got to work in September 2016 trying to get the required data. A tripod (Manfrotto MK055XPRO3-BHQ2) was bought along with a slider (Dynaphos GT-M80) for taking overhead shots of the V100 and the exact position where it would stop following a deceleration. Since the instant speed is needed as well, the DSLR camera was turned to video mode - and a tradeoff between frame rate (the higher the better) and resolution (if too low, the precise position of the locomotive can't be determined; if too high, the frame rate drops). Since the camera couldn't physically "track" the locomotive in real-time, optical corrections had to be computed and the results adjusted. Why ? Looking from right above the locomotive's end and measuring its position on a track-side ruler - just as seen in the photo nearby - will result in a very different reading than if the camera moves 5 cm to the side (go on, give it a try). Next, the captured videos had to be analyzed - frame by frame - to get the position of the locomotive at each step, apply the corresponding optical correction, and compute an approximation of the instant speed. Not a lot of fun, considering that processing a movie would take about 2h.
How to get the instant speed in a more human way ? The next post will show the way.
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