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Poor contacts stop model trains on the track

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agk
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re: Poor contacts stop model trains on the track
agk   12/23/2010 3:46:30 PM
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This article takes me back to year1992. I converted LEO hand pulled toy train engine compartments into electric train by fixing them with casette player motors,capstan shafts and pulleys.The metal wheels were from steei made in a lathe. The tracks were made from aluminium U channels(inverted) with wooden repers. Connect them with a battery adopter it use to run nice for some time and stops later due to the carbon deposited on the tracks and wheels. I got the idea of applying switch cleaning oil on the tracks and tested and found that it runs continiously for hours together.all the children around played the train and it was amusing!

gah4
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re: Poor contacts stop model trains on the track
gah4   12/23/2010 10:26:46 PM
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I remember from many years ago, a quick Google search shows December 1965, a Popular Electronics article on a pulse power supply for model trains. I believe it used a constant pulse (width and amplitude) plus a variable DC to allow smooth control at slower speeds. Even larger gauge trains run poorly at the slowest speeds, but the article claimed that pulse power allowed slow operation.

zeeglen
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re: Poor contacts stop model trains on the track
zeeglen   12/24/2010 1:27:25 AM
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Aluminum develops a non-conductive surface oxide which will insulate current flow to the wheels. Model rail tracks today are almost always made of nickel silver (actually copper nickel zinc alloy) whose oxide is electrically conductive. Your switch cleaning oil probably retarded the buildup of oxide. It sounds like you had a lot of fun with the conversions. Nice when folks can use their engineering skills for "play". Not many careers provide that option.

zeeglen
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re: Poor contacts stop model trains on the track
zeeglen   12/24/2010 2:01:10 AM
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Yes, pulse width modulation in various forms is almost universal today thanks to the transistor. It makes a small motor develop a higher low speed torque than pure DC, very useful when performing operations such as realistic yard shunting or spotting freight cars on a siding. It can also overheat a motor if the voltage is too high with the duty cycle low (I^2R with very little back EMF), so the pulse peak must be kept within the limit of the motor full speed DC voltage rating. Many a Z scale motor has smoked at low speed when used with a PWM power pack intended for HO scale. In the article pulse width modulation was used but did not help the main problem which was the opening of the current flow to the motor. This was simply dirt and poor design. One of the fun things about model rail is combining the hobby with some of the cool things that can be done with electronics and mechanics. Sometimes after a hard day's debugging it is relaxing to come home, pick up a soldering iron, and build a gadget that flashes LEDs at a grade crossing. For examples see Model Railroad & Misc. Electronics http://home.cogeco.ca/~rpaisley4/CircuitIndex.html

DWilde10
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re: Poor contacts stop model trains on the track
DWilde10   12/24/2010 2:22:16 AM
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Way to go, Glen! That's the spirit that makes American ingenuity world famous. As a lifetime follower of model railroading I contend that my study of Dad's cabinets full of Model Railroader magazines is one of the primary reasons I'm really good with complex embedded computer systems today...

sharps_eng
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re: Poor contacts stop model trains on the track
sharps_eng   12/24/2010 10:29:06 PM
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I was disappointed how unsophisticated the electronics was in model rail, but like so many real-world situations there is so much legacy kit investment out there you can't innnovate overnight. Every newcomer confidently attempting to sweep away the troubles of past systems completely underestimates the challenges of power distribution, control technique and packaging of the circuits. Model rail as a whole is its own universe, with only passing similarities to other fields. So at the same time I have to be impressed with how much modernisation is getting done, much by hobbyists with no engineering background.

agk
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re: Poor contacts stop model trains on the track
agk   12/25/2010 2:39:44 PM
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Yes zeeglen I had lot of pleasure and fun as you said while doing it for play

David Ashton
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re: Poor contacts stop model trains on the track
David Ashton   12/25/2010 10:26:21 PM
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Nice work Glen. Lets hope you're on your way to becoming a wheelwiper tycoon... Have you patented it? I had a 000 gauge train set (slightly bigger than your Z gauge I think, made by a British company Lone Star, and now defunct) when I was a kid, and remember similar problems. I had quite a lot of stuff but heaven knows what happened to it. It's a nice hobby in that it's wide open to engineering applications. And if you can make it pay a bit on the side, good on ya!

zeeglen
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re: Poor contacts stop model trains on the track
zeeglen   12/27/2010 7:18:47 PM
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@DWilde1 and Sharps_eng - there are control systems available that interface with personal computers for manual or programmed operation of multiple trains. One system uses the traditional block method, another more sophisticated is standardized Digital Command Control (DCC) in which every locomotive is fitted with a programmable miniature digital decoder for motor and lighting and onboard sound control. Track power is bipolar encoded data which addresses and commands locomotives individually. Speed lookup tables can be programmed to compensate for mechanical variations between multiple locomotives coupled together so that acceleration and deceleration effects are matched. Motor back EMF is measured as feedback for a constant speed control loop. Other equipment such as signaling and turnouts (track switches) are also addressable from the same power/data bus. Many manufacturers provide inter-operable off-the-shelf equipment, the decoders are usually surface mount and can be made small enough to fit into a Z scale locomotive. Much of the home-brew electronics is unsophisticated, that is the ideal way for an electronics beginner to get started by learning how to build something on perf board and from that how transistors etc function. It was the other way around for me, I needed something for my Heathkit H8 to do and that led to learning model railroading and assembly language. It was fun programming the driver wheels to spin a few half revolutions on startup just as the big steamers used to do, then gradually incrementing the pulse-width register to simulate acceleration. That's the whole point - combine your mechanical, civil, electronic, photographic, and artistic skills and use them for fun.

zeeglen
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re: Poor contacts stop model trains on the track
zeeglen   12/27/2010 7:23:57 PM
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Thanks David. The patent application was eventually approved but would have cost a small fortune if continued to completion. Have to wonder how many of today's engineers got started from having a model train as a kid? Or coming from related scientific hobbies such as ham radio or astronomy?

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