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Author Topic: DCC Outside  (Read 1829 times)
YellowHillsCentral

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« on: December 03, 2007, 12:07:21 AM »

Mr. Bachmann,

I am laying track in the spring for my Yellow Hills Central Railway. Which DCC is best for the outside? I want to be able to use all of the sound options and have at least ten engines. Which one would you use??

Thanks a bundle!
Shay Ludlow
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bobgrosh

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« Reply #1 on: December 03, 2007, 04:00:01 AM »

... want to be able to use all of the sound options and have at least ten engines. ...

since he sells E-Z-COMMAND well...

Not to be a hard nose, but, it would be helpful if you rephrase your requirements.

Huh? have at least 10 engines Huh?

Most DCC system can address 9,999 locos. You could have 2 locos sitting on the track, or 50 of them. Select any one of them, turn a knob and it goes. Want to run more than ONE AT A TIME? You will probably need to have more than one KNOB to twist.

First thing is, smaller cheaper or older systems often have a limit as to the number of locos they can CONTROL (operate, run) at one time. Usually 22 or 27. You could have 100 of them on your layout, you just won't be able to run more than 22 - 27 at the same time.

Larger, newer, or more expensive systems usually have a limit of 99 or 127 locos all at the same time. So, If you only have 10 locos, any system will handle that.

Also, a pair or more of locos, (AB set or ABBBBBA set), all with the same address, counts as ONE LOCO.

So, your first requirement should read, "I plan to have no more than xx locos running at one time."

Now lets look at a typical Cab. ( In DCC the thing you hold in you hand to control the loco is a Cab.)
A Cab has one or two throttles (knobs to control the speed) and buttons to control the functions, (lights and sounds) as well as buttons to control turnouts, lights and sounds in buildings, and system functions like power on/off or "PANIC" (Stop all locos)

Advanced users like two throttles on their cab, ( two knobs on their handheld). It's very nice for helper operations, or just doing switching while also running a slow freight. Most Garden railroaders will not need more than one dual throttle cab. Single throttle cabs are fine for additional operators. And, very simple (basic) single throttle cabs are best for visitors.

This next thing is a little hard to grasp, so read it twice.

If your system can run 22 lot even 100 locos at one time, you can do that with just ONE CAB, even one with only one throttle (knob).
 
You select a loco, move it to the mainline, get it up to speed. Then, select another loco, move it to the mainline and let it run. You could do this 22, 27, 99, or even 127 times depending on the system limits. Many systems provide a way to scroll through a list of active locos so you can easily adjust the speeds or blow whistles, etc.

In reality, About 8 trains on one cab is about the limit a teenager can do. Two is all I can manage.

Now watch out for a little deception. Some manufacturers state 22, 27, 99, etc as the number of locos you can run. That is fine if you need that many running at once except for one thing. They don't tell you how many CABS their system will handle. If it has a built in cab, and will only accept one additional expansion cab, then you better have the reflexes of a 14 year old game freak to run 22 locos using just two knobs. Make sure you know how many throttles the system will take AND WHAT ELSE IS NEEDED TO BE ABLE TO ATTACH ADDITIONAL THROTTLES.


So, Your next requirement will be; "I plan to have as many as "y" operators running at the same time and will need throttles for each of them.

Now the third requirement.
How many watts of power will it take?

If all ten of your locos are sitting on sidings, not moving, they take very little power. Perhaps about 2 watts or less per loco.

A small, or just very efficient loco (expensive brass loco with 60:1 gear-heads) will usually use 10 watts just to cruse along with a couple cars on level track.

A large diesel with 4  or 6 motors can easily use 100 watts on a gentle grade.

Fortunately, DCC is not like DC. For DC, if you start with a pack that is too small, you will have to remove it and buy a bigger one. With DCC you just add another booster each time you outgrow you system power capacity. As long as your initial booster can handle one or two of your biggest locos and have a little in reserve for turnouts, it is fine. Later you can add more boosters and perhaps more power supplies (to power the boosters). You never have to discard boosters in order to go to a more powerful system.

So, for the third requirement you might say something like this. I plan to start with one Shay and a few 0-4-0's pulling short trains on 4% grades." - OR - "I plan to start with an ABBA set and 12  streamline passenger cars with a 1% grade and R3 curves." - OR - "I dislike dismals and will only ever run small logging trains like a shay with maybe 12 cars."

SIDE NOTE:
I used watts instead of amps, why? Well, Watts is a measure of POWER. Amps are useless unless you also know the voltage applied to the rails.
If a given loco, pulling 12 cars up a 2% grade at a scale 40 MPH uses 60 watts, it will take the same 60 watts of power to accomplish the task, regardless of the DCC voltage.
If that loco that uses 60 watts on a 12 volt DCC track, that's 5.00 amps.
If that loco that uses 60 watts on a 16 volt DCC track, that's 3.75 amps.
If that loco that uses 60 watts on a 18 volt DCC track, that's 3.33 amps.
If that loco that uses 60 watts on a 22 volt DCC track, that's 2.73 amps.
If that loco that uses 60 watts on a 24 volt DCC track, that's 2.50 amps.

Remember. The DCC voltage on the rails is constant for a given system. The higher the voltage, the lower the amperage to produce the same amount of power.

Way too much emphasis is placed on the amperage of a system when selecting it. What is important is the total power (Watts) available.
For example:
A 24 volt 5 amp system can deliver 120 watts of power to the loco.
A 20 volt 8 amp system can deliver 160 watts of power to the loco.
A 16 volt 10 amp system can deliver 160 watts of power to the loco.

At first glance the 10 amp system seem like a better choice, but, in reality, if you have 4 locos that need 40 watts each to pull a train, both the 8 amp and 10 amp systems will max out at four locos. ( 4 locos x 40 watts = 160 watts ). On the other hand. A single loco on 20 volts will be able to run faster on 20 volts and faster still on the 24 volt system.  Also, higher voltage means less problems due to dirt and less power loss on longer tracks.

Summery:
So, since garden railroaders often run fewer trains and do not use computers for automation, or have as many separate loops, the number of locos the command station supports is less important.

Since we are not restricted by narrow isles to the number of operators, the number of throttles we can attach is sometimes more important.

Since the track is dirtier than indoor track, higher voltage is important.

Since more power can be added by adding more boosters, the amperage is less important as long as the total power from one booster can handle our biggest SINGLE loco or consist.

Be careful, these recommendations are in some cases just the opposite of what the DCC "experts" will tell you. Most DCC experts don't have a clue when it comes to running large scale outdoors. Their advice is almost always based on the common practices for "HO" and "N" scale.
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Jim Banner

Enjoying electric model railroading since 1950.


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« Reply #2 on: December 03, 2007, 03:43:41 PM »

An excellent analysis of large scale garden railroading with DCC.  I have to agree that more volts/less amps gives more power from each booster but would like to add that this may cause a significant increase in motor temperature for a given speed and load.

The one other thing I would add when choosing a system is to choose one that can incorporate radio throttles, even if you do not intend to use them immediately.     
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