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Thread: quarter test ?

  1. #21
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    Quote Originally Posted by TwinDad View Post
    Probably not, but it *might* start a fire if you don't remove it.

    Almost by definition, if the quarter test doesn't trip your booster (or power manager)'s circuit breakers, one of two conditions exist:

    (A) The resistance of the wiring (etc) between the quarter and the breaker is such that the current is below the breaker's trip threshold, which is "safe" in that it's not going to damage the booster, but not safe in that the wiring and possibly the rails, etc. in the short circuit will be getting hot very quickly. [...

    I had a case on my layout where I dropped a "T" pin across the rails and didn't notice. The resistance of the T-pin was such that it didn't trip the breaker but it got hot enough to melt some ties and start to melt the underlying EPS foam. It was the smell of the foam melting that alerted me to the problem. There's still a scorch mark on the rails at that spot.
    Very nice description. And that is the reason I am very, very careful with 5A or 8A boosters. And plan to add breakers even to my Zephyr's 3A output. So for a large layout, use multiple sections with 1A-1,5A each (booster or circuit breaker, does not matter) instead of one big power district with 8A. Also, that is why you should do quarter tests, to make sure the system has a chance to shut down in case of a short.

    Heiko

  2. #22
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    Quote Originally Posted by TwinDad View Post
    (A) The resistance of the wiring (etc) between the quarter and the breaker is such that the current is below the breaker's trip threshold, which is "safe" in that it's not going to damage the booster, but not safe in that the wiring and possibly the rails, etc. in the short circuit will be getting hot very quickly.
    If that short happens to be a piece of rolling stock, you end up with melted plastic.

    Before switching to DCC, I witnessed more than a few ( including some of my own ) locomotives end up with melted trucks when they either derailed or ended up running through insulated joints on the frog end of a turnout thrown against them.

    Paul
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  4. #23
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    Quote Originally Posted by pbender View Post
    If that short happens to be a piece of rolling stock, you end up with melted plastic.

    Before switching to DCC, I witnessed more than a few ( including some of my own ) locomotives end up with melted trucks when they either derailed or ended up running through insulated joints on the frog end of a turnout thrown against them.

    Paul
    Ditto, melted my bachmann 4-6-0 tender rear axles that way.... warped the truck too :melty: and that was on Kato Unitrack T/O going the wrong way backward through.

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    Quote Originally Posted by zosimas View Post
    Ditto, melted my bachmann 4-6-0 tender rear axles that way.... warped the truck too :melty: and that was on Kato Unitrack T/O going the wrong way backward through.
    Yikes! Guess I was fortunate in my DC years to have avoided damaging anything via a short. My primary power pack was an MRC which tripped quickly. I had another custom built walk-around by GML which also popped fast.

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    Quote Originally Posted by Paul Schmidt View Post
    Yikes! Guess I was fortunate in my DC years to have avoided damaging anything via a short. My primary power pack was an MRC which tripped quickly. I had another custom built walk-around by GML which also popped fast.
    That was back when I had DC, was using an old railpower DC pack. Now I'm DCC and havn't had trouble... but now I want to go around with a quarter and check again.

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    Quote Originally Posted by TwinDad View Post
    Probably but it wouldnít have stopped the pin from heating up... This happened before I had the PM42 installed. Iíve done it several times since then and the clicking of the relays is impossible to miss (unless youíre deaf) no matter where you are in the room (or the house, nearly).

    Id much prefer an audible alert for this very reason. The bulb does no good if you arenít looking at it, and if the current is still flowing, something could be getting very hot...
    tried for humor to point out a real benefit.

    now I am going to say it as straight forward as I can.

    for DCC an ammeter is expensive. and you have to look at it.
    so looking at a glowing light bulb might be slightly easier...

    your problem with DCC is that the fuse you should pick to save your track from melting
    is under what you may well want to use on your layout.

    a fuse or Circuit Breaker (CB from now on) tight to your expected current use is your safest CB/fuse.
    most n-scale locos use about 1/4 amps. most track melts at 1 amp (take my word for it...)
    most train power supplies can get you to around 2 amps (remember that short...)

    what CB should you use? I'd reach for a 1.5 amp CB...
    now you can run 5 locos and throw the odd turnout without popping the CB.

    ...and your track and cars will melt if you have a short.

    so... If you put the light bob thingy some where easily seen
    you can look at it glowing dimly while you have 3 locos towing trains
    and when nothing is running it should be dark.
    If it is bright when only one train is rolling you know you have a problem.

    use a 6 volt bulb if you want a glow sooner.

    consider it a cheap ammeter.

    victor

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    A fast trip CB will catch shorts well before things get melts even if set well above the operating current. It’s the combination of time and energy that causes the problem. My experience with the T pins bears this out. Once the breakers were set up properly, the T pin trips, but I quit trying with half a dozen locos at full stall current because I didn’t want to overheat their motors. No system is perfectly safe of course.

    There is no spot on my layout that is easily visible from more than the immediate vicinity. Wherever you stand 70% or more of the layout is behind you. An audible alert is noticeable from anywhere immediately.

    If the bulbs work work for you, cool. They’re not for me though.
    Never mistake a guy who talks a lot for a guy who has something to say...

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