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## Re: [Z_Scale] Re: Z SCALE

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• ... Short answer: because electricity doesn t work like that - it s all relative. So providing there is only one side cross connected anywhere (which is the
Message 1 of 10 , Aug 3, 2010
> what i dont understand is when both loops are in difference directions then i have the plus side of one pack connected to the neg side of the other pack via the common rail why dont i get a short?

Short answer: because electricity doesn't work like that - it's all
relative. So providing there is only one side cross connected anywhere
(which is the case with a common return and Märklin controllers as they
each have their own transformer) then if you join them together one one
side that simply becomes a common voltage between the two. Join both
together and bad things happen.

If you join one side together and then connect a voltmeter across the
other two you'd see a voltage that varied according to how you turned the
knobs. With one on zero and the other turned you will see the voltage for
that one (-8 to +8 or thereabouts), turn them both the same way and you
will see a low voltage or even 0 if they were turned the same amount.
That is of course the normal case when you run a train between loops -
there is little voltage difference between the two loops.

The bad case is if you turn the knobs in opposite directions, you will
then see up to + or -16v on the voltmeter, which is more than the models
are designed to take in normal use.

They are a good deal more robust than you might think however because
they are designed to survive a variety of situations where the model
carries more power than you would like - just as they get a certain
amount of 'will it bounce' considered in the design strength.

Other scenarios that are usually considered in designing models include

- derailment where one truck comes off the track and ends up with the
wheels shorting the other rail. At this point the short is through the
wires in the locomotive

- Similarly where a locomotive moves from one section to another which
already contains a locomotive that is currently not being fed power. At
that point the second locomotive is potentially being powered through
the wiring of the first.

- Running through electrofrog points the wrong way

- Putting a locomotive using overhead on the track the wrong way around

But 16v across a model designed for 8 isn't very good for it - especially
if its more than briefly.

Alan
• thank you how come my meter reads 14v dc on a marklin z power pack with no load on the track when model max is 8v dc can i isolate the other rail by putting a
Message 2 of 10 , Aug 3, 2010
thank you
how come my meter reads 14v dc on a marklin z power pack with no load on the track when model max is 8v dc

can i isolate the other rail by putting a cut in the uncut rail on a marklin 8588 isolation track or will that not work

tony

--- On Tue, 8/3/10, Alan Cox <alan@...> wrote:

> From: Alan Cox <alan@...>
> Subject: Re: [Z_Scale] Re: Z SCALE
> To: z_scale@yahoogroups.com
> Date: Tuesday, August 3, 2010, 5:04 PM
> > what i dont understand is when
> both loops are in difference directions then i have the plus
> side of one pack connected to the neg side of the other pack
> via the common rail why dont i get a short?
>
> Short answer: because electricity doesn't work like that -
> it's all
> relative. So providing there is only one side cross
> connected anywhere
> (which is the case with a common return and Märklin
> controllers as they
> each have their own transformer) then if you join them
> together one one
> side that simply becomes a common voltage between the two.
> Join both
> together and bad things happen.
>
> If you join one side together and then connect a voltmeter
> across the
> other two you'd see a voltage that varied according to how
> you turned the
> knobs. With one on zero and the other turned you will see
> the voltage for
> that one (-8 to +8 or thereabouts), turn them both the same
> way and you
> will see a low voltage or even 0 if they were turned the
> same amount.
> That is of course the normal case when you run a train
> between loops -
> there is little voltage difference between the two loops.
>
> The bad case is if you turn the knobs in opposite
> directions, you will
> then see up to + or -16v on the voltmeter, which is more
> than the models
> are designed to take in normal use.
>
> They are a good deal more robust than you might think
> however because
> they are designed to survive a variety of situations where
> the model
> carries more power than you would like - just as they get a
> certain
> amount of 'will it bounce' considered in the design
> strength.
>
> Other scenarios that are usually considered in designing
> models include
>
> - derailment where one truck comes off the track and ends
> up with the
>   wheels shorting the other rail. At this point the
> short is through the
>   wires in the locomotive
>
> - Similarly where a locomotive moves from one section to
> another which
>   already contains a locomotive that is currently not
> being fed power. At
>   that point the second locomotive is potentially
> being powered through
>   the wiring of the first.
>
> - Running through electrofrog points the wrong way
>
> - Putting a locomotive using overhead on the track the
> wrong way around
>
> But 16v across a model designed for 8 isn't very good for
> it - especially
> if its more than briefly.
>
> Alan
>
>
> ------------------------------------
>
> Z-scale:  minimum siZe, MAXIMUM enjoyment!
> Yahoo! Groups Links
>
>
>     z_scale-fullfeatured@yahoogroups.com
>
>
>
• On Tue, 3 Aug 2010 13:34:11 -0700 (PDT) ... Put a load on it. The newer ones are also quite smart and don t simply output 0-8v smoothed DC but know how to give
Message 3 of 10 , Aug 3, 2010
On Tue, 3 Aug 2010 13:34:11 -0700 (PDT)
Tony Dalileo <tony_mrr@...> wrote:

> thank you
> how come my meter reads 14v dc on a marklin z power pack with no load on the track when model max is 8v dc

Put a load on it.

The newer ones are also quite smart and don't simply output 0-8v smoothed
DC but know how to give better motor control than that.
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