General > General Technical Chat

The "All American Five", & more dangers!!

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25 CPS:

--- Quote from: Gyro on May 02, 2020, 07:43:31 pm ---It used to be interesting to look at the dates on the brass door sills in the tube trains, the older lines like the Northern.

--- End quote ---

Agreed.  It was always interesting to look down and see who built the train and when.  To my mind, the British always made the best builder's plates.  It was educational doing that in the various places I grew up in back when a lot of cities still had old junks running on their public transportation systems.  I always loved the worst, oldest, most beat up stuff running because it was always the most interesting.


--- Quote from: TimFox on May 02, 2020, 06:04:08 pm ---I have not seen a reference to this, but I believe train cars with sliding power contacts to DC feed (third rail or overhead wire) use capacitors on the vehicle to mitigate rough connection.

--- End quote ---

No.  No need, the inertia of the whole mechanical system that is a subway train is far better a filter than a bank of capacitors would be.  The exception is for equipment that has chopper controls and there's a smoothing filter on the output side of the chopper which is to clean up the square waveform output of the chopper, not filter current collector bounce.


--- Quote from: TimFox on May 02, 2020, 07:10:20 pm ---The Chicago Transit Authority retired the last 6000 series ā€˜L’ cars in 1992, after 42 years of service.  IIRC, there were three forward settings on the speed lever:  resistor, series, and parallel (fastest).

--- End quote ---

Yes, normally those three power positions would be switching, series, and parallel as you mentioned but the CTA 6000 series cars and the 1-50 series cars which were single units with a cab at each end instead of a married pair were exceptions to the rule.  Those were basically repackaged PCC streetcars and those were permanently wired in parallel.  Westinghouse supplied the stuff on those cars and what the controller positions did was change the value of traction motor current being demanded by the limit relay and rheostatic controller, to control acceleration rate.  Eventually, or not so eventually depending on what position you stick the handle in on one of those, you get full speed no matter what vs. a traditional switching/series/parallel traction package does.

Electro Detective:

Butting in with a quickie query:

Were the techs of yesteryear using AVOmeters and Simpsons etc for checking and confirming railway voltages 600v and beyond?

or were there specific tools for that?

Were there any high zappage risks even for cautious operators with the right gear and PPE?

and Danger Money rates that made it sort of worth it?

jeffheath:
Say what you will about corvairs, but like AA5 radios were, they're cheap! They're the cheapest classic car there is other than all those bland moredoors.

25 CPS:

--- Quote from: Electro Detective on May 12, 2020, 10:41:05 pm ---
Butting in with a quickie query:

Were the techs of yesteryear using AVOmeters and Simpsons etc for checking and confirming railway voltages 600v and beyond?

or were there specific tools for that?

Were there any high zappage risks even for cautious operators with the right gear and PPE?

and Danger Money rates that made it sort of worth it?

--- End quote ---

For checking the presence of 600 V in a is it there/is it not there way the quick, easy, and cheap way was with a 600 volt test light be it a string of 5 120 V bulbs in series or a dropper resistor feeding one or two bulbs.  This was less expensive than giving everyone meters, but yes, techs troubleshooting more complicated faults would use Simpsons, AVOs, Tripplets, that sort of thing when a test light wasn't suitable.

As far as the safety aspect goes, under normal circumstances, it's neither here nor there compared to a modern Fluke meter.  You still need to be careful of live electricity and if you slip up and touch something that's live by mistake, it doesn't really matter what kind of meter's hooked up to your probes, there's always the risk of getting zapped when you're working on live power equipment of any kind if you mess up.  I can't really speak to danger pay since I've only worked on streetcars at a handful of railway museums whenever they've asked for help with difficult electrical problems so that's strictly volunteer basis, but I have used my own Simpson 260s and Agilent U1641A insulation tester multimeter and an Agilent U1213A clamp meter when doing so and a couple of other people have Fluke DMMs.

rsjsouza:

--- Quote from: Electro Detective on May 12, 2020, 10:41:05 pm ---Were the techs of yesteryear using AVOmeters and Simpsons etc for checking and confirming railway voltages 600v and beyond?

--- End quote ---
600V?!? Pffft! A Triplett 630-NA was rated to 6kV! Pizz o' cake!  :-DD

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