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zeeglen
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re: Poor contacts stop model trains on the track
zeeglen   9/6/2013 7:28:27 PM
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@bhmcintosh Glen, this story made my day, especially the bit about having to remove outside biological influences from the long term test setup!

Following up, that cat has passed on, and her replacement was also fascinated with the slowly moving locomotives in for repair.  I had to watch her closely, scold her when she jumped up on the workbench and got too close to the test tracks, and not test-run the locomotives when away from the bench.  She liked to sit on the back of my chair and supervise my repair work.

One day she watched me take apart a locomotive, and this time I let her sniff over all the little gears, shafts, bushings etc.  From this inspection she made some sort of connection in her pussycat mind and realized this was NOT a mouse, but some sort of silly human contrivance.  Therefore it was far beneath a cat's dignity.  She never bothered my trains again.

Bellhop
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re: Poor contacts stop model trains on the track
Bellhop   4/1/2011 7:21:37 PM
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I remember seeing a system advertised that used high voltage to generate a plasma at the contact points. I don't know if it actually worked, but it must have looked pretty cool with the lights out!

zeeglen
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re: Poor contacts stop model trains on the track
zeeglen   1/22/2011 1:15:30 AM
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Hint: Start small and encourage your wife to get interested in creating the artistic scenic details. Many of the creative feminine gender who began with building dollhouses have added model rail to their hobby repertoire. My own DW learned the artistic part while I did the trackwork. Like Jack Spratt we managed. She created some very beautiful 3D landscapes out of plaster, styrofoam, and other raw materials. Model rail is a combination of both art and science. And is fun too.

bhmcintosh
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re: Poor contacts stop model trains on the track
bhmcintosh   1/19/2011 4:32:45 AM
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Glen, this story made my day, especially the bit about having to remove outside biological influences from the long term test setup! :-) It's a dangerous train of thought (sorry about that) however; now the wife's worried that I'm going to add model railroading back to my stable of hobbies that take too much time and money!

zeeglen
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re: Poor contacts stop model trains on the track
zeeglen   1/5/2011 10:06:04 PM
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Right you are. To really appreciate the visual impact of a tiny train slowly winding it's way through mountain passes, valleys, prairies, cities, bridges etc the speed should be no more than 1 boxcar per second, and in many other cases even slower. (Unless one is modeling the TGV or similar). Thanks to all who commented, your insights are appreciated. There are so many talented individuals in the engineering community who enjoy a hobby as an extension of their engineering careers. I do not believe there is any other career that is as conducive to play-at-home activity, we are lucky to be who we are. Have fun.

zeeglen
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re: Poor contacts stop model trains on the track
zeeglen   1/5/2011 6:12:26 PM
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Jack, this is another reason why home-brew electronics can beat off-the-shelf commercial offerings. Had a similar problem with another brand of N scale steam locomotive where the thin wires between tender pickups and loco motor would melt the plastic drawbar under similar conditions. The PTC current limiter device in the commercial power supply took too long to heat up, too much thermal mass. By the time the PTC shut the current off the damage had been done. Yet the supply must also be capable of sufficient current to drive multiple locomotives in parallel for long periods of time. To get around this problem I later built my own PWM power supplies with per-cycle electronic overcurrent shutdown and hiccup mode recovery. At the beginning of each pulse a current above a preset detection threshold killed the pulse in a few microseconds and waited to repeat the cycle on the next pulse. No more locomotive damage. A sidenote was that I could include realistic momentum simulation with a long time constant and the same rise/fall ramp rates, unlike the commercial RC (resistor capacitor) exponential offerings. Other means of current limit are automotive light bulbs used as PTC to each block of track. If a short occurs the bulbs light up, the increased resistance limits the current. Modern DCC decoders drive the motor with a pulse frequency about 15KHz. Motor inductance limits the current in this case even if the voltage is higher than the motor spec.

Engineer62
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re: Poor contacts stop model trains on the track
Engineer62   1/5/2011 6:07:10 PM
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Very good article, many thanks. Allow me to point out that too many model RR's (all scales) are run at too-high scale speeds - most unrealistic. Thus, good "low speed", i.e. correct speed, operation is vital. Happy New Year to all!

jack1234
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re: Poor contacts stop model trains on the track
jack1234   1/5/2011 5:18:17 PM
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Glen Chenier. that was a great contribution to the world of model railroading. and thanks for the description of everythng you did. great work.

jack1234
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re: Poor contacts stop model trains on the track
jack1234   1/5/2011 4:47:37 PM
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nobody seems to be talking about limiting the current to the motor. thats what burns out the motors. the article mentions that his first attempt caused his first "simple" wires to burn out. he was using a power supply which supplied too much current. Check the motor specs to determine the max current for the motor and then limit the power supply to about 15% below that. PWM can also be used but again with a current limit. Voltage does not burn out the motor. it is I^2R that does it.

Mongo647
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re: Poor contacts stop model trains on the track
Mongo647   1/3/2011 5:00:05 PM
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One other comment on the poor power wiping contact issue, the DCC that DWilde1 talks about runs at a Fixed AC (18 VAC I think) on the tracks, with control signals delivered on the same circuit. Modules in each using device rectify then modulate the power, so are very tolerant of poor/varying contact resistance, so low voltage problems vs contact wiping etc are less of an issue.

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