[PRCo] Re: Detroit__Control

[Jim Holland]

Good Morning!

	As I mentioned, diodes are mounted in the equipment with 2-cars having
diodes wired opposite each other and grounded to right rail and similar for
2-other cars to left rail.   Controllers have diodes to match.   This
allows 4-car independent control.
	Single tracking is a simple matter of having a relay reverse polarity to
match up for direction of travel and this can be equipment operated ala the
prototype setting up signalling.   And reverse loops would have similar
functions.   No different than railroad people working with both positive
and negative in the rails  --  they need a section of track in the loop to
allow for the change in polarity!!!   You can run in opposing directions on
single track, just not at the same time!   If it was at the same time, then
cornfield meets would be the order of the day.   Passing sidings would
allow for cars to flow past each other in opposite directions.

	While the above is cheap, DCC offers even better control and the advantage
that voltage remains constant in the overhead.   This helps to alleviate
contact problems inherent at low voltages and low speed and allows for
smoother more realistic and prototypical operations.

>>> John F Bromley wrote:

>>> Not Pittsburgh - Ivor runs the Boston Arborway line
>>> with a full subway including detailed stations and
>>> an amazing 4-car control system.......

>> Jim Holland wrote:::::::

>> Sounds like the  *Detroit--System*  of control which
>> has been written up in  *Traction--&--Models*  on
>> various occasions.   Don't know if Basil Motoligin
>> was instrumental in its development or not, but
>> believe he was a big user of it.   Basil (I-F  I
>> remember the name correctly) had a beautiful "O"--Scale
>> Detroit model system.   Basically worked off diode
>> control with 2-cars-(trains) using right-rail
>> for ground, 2-cars-(trains) using left-rail for
>> ground thus the total of 4-car control.
>> Would have to ferret out the articles for more details.

> "Edward G. Skuchas" wrote:

> The Detroit system is an inexpensive method to have multiple car control on
> the same trackwork.  The cars need to be properly set up for operation.
> Typically the individual will have his whole car fleet arranged into the 4
> different types required for independent operation.  So you have to
> dedicated to the system.  Visitor's cars will only work on certain circuits.
> The other thing that I noted was that the trackwork needs to be arranged in
> a certain arrangement.  Tracks cannot converge and diverge because you would
> have multiple car control for the same trackage.  I believe that the
> operators try to keep separate loops of operation for the cars. I was at one
> layout in Detroit where two loops went down the same street.  The two tracks
> down the street looked like single track, but they were laid next to each
> other and kept electrically separated.  So if your layout can be kept
> separate, you have a neat layout to operate, as was this layout in Detroit.
> The guys operated this layout so much and tweaked it to really operate well,
> that I saw an HO car back pole through all of the over head wire at full
> speed without any problems.  I don't know of any one in any scale do that
> today.

> Ivor's layout can operate 8 cars over part of his layout (some of the
> surface trackage and all of the subway section) because he has a double
> overhead wire in those areas.  It also has an ingenious system to alternate
> successive cars' poles onto one wire and then the other.

> The Detroit system offers a proven simple way to have multiple car operation
> without a lot of expense.  It has its uses, but also its limitations.  And
> Ivor's layout is one of the finest I have ever seen.  So is Phil's.

> Regards to the modelers.

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James B. Holland

Holland  Electric  Railway  Operation....... 
___"O"--Scale St.-Petersburg Trams Company Trolleycars and...
______"O"--Scale  Parts  mailto:pghpcc at pacbell.net

______Pennsylvania Trolley Museum http://www.pa-trolley.org/
___Pittsburgh  Railways  Company  (PRCo),   1930  --  1950
N.M.R.A.  Life member #2190; http://www.nmra.org

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