I reviewed your treatise on making switches DCC friendly. I have a HO railroad that haws a lot of code 70 Shinohara. The layout does not have scenery, yet. I also was a long time user of Keller's system with sound in steam & diesel. I did not have problems with keller's system operating on my track. I added a wire & powered the frog from the points. I do not have switch motors on all switches. Use Caboose ground throws on all yard/sidings. In using Keller's if a switch was thrown against a train -- a sound alarm went off, I then threw the switch and was back in business. No welded track! I am now in the prrocess of converting to NCE DCC. Is DCC really different enough (from Keller's command control) that I could have problems with my trackwork? I am somewhat hesitant to start a switch rebuilding project? What do you recommend? Thanks in advance. Vince

-- Vincent C. Vargas (vcvargas@aol.com), July 06, 1998

Answers

Vince:

You ask a lot of good questions and apparently one I have not successfully answered well enough to date. Like many people, you have an existing layout that you have not had any trouble with. You are writing because you are hoping in some way, your layout is different than the ones I write about because you haven't had any trouble. You are hoping you won't have to convert your turnouts.

So let me put this in big type so no one misses it, IF YOU HAVE AN EXISTING LAYOUT AND HAVE NOT HAD ANY TROUBLE, YOUR LAYOUT IS NOT DIFFERENT THAN ANYONE ELSES.

So how come you have not welded anything? You just haven't had the bad luck yet. And luck does have everything to do with it. It is theoretically possible it could happen to all of us. Those that have not used heavy wiring and feeders - like those recommended in my page - stand a much better chance of having this problem. In order to weld, you have to draw as much current as possible without tripping your system's built-in overload protection. Good wiring practices ensure than when a short occurs, it's a very definite "bad" short, not a "mild" (not a technical term, but I think it conveys the concept) short. If you have a short that is not severe enough to trip your system, than the welding process can begin or a fire can begin.

How often does this unusual short take place? Well, I'm still waiting for someone to say, "It has personally happened to me." All I know are people who say they have seen it happen.

So if it doesn't happen often, do I need to worry about it. Yes, most definitely. The power in the short is about as much power in a 30 watt light bulb. Do you believe a 30 watt light bulb can cause a fire? You should! Because of this, you should worry about the possibility of fire.

Okay, so your layout isn't unique. You've just been lucky. And you will probably stay lucky. But because someday your luck could run out, you need to have a clear picture of shorts in ANY command control system, including all the non-DCC systems. No, DCC is not different enough than your old command control system that you will have any greater problems with your trackwork.

If you have a layout you pretty much only operate by yourself or one or two friends, you probably won't mind the occassional short that shuts down your system. However, the more people, the more likely shorts will occur with enough frequency that it annoys you. How many people is the right number for installing lightbulbs or some other form of electronic localized shutdown? It purely depends on you, your friends, and how short everyone's fuse is. I can definitely say five people can get annoyed in a hurry.

The very common question is should I rebuild my switches? For in place switches, it probably isn't practical to consider rebuilding them. If you can and want to, do it. But don't feel you have to. This applies to EVERYONE who considers this. If you have a good sized layout and more than a few people operating the layout, consider adding boosters to make each zone smaller, add some form of short limiting, either an electronic shutdown circuit or a light bulb.

EVERYONE should read the sections in my page about track wiring and wiring track switches. It applies to you! Yes, you! NO ONE has to rebuild in place switches!

Yes, it's a good idea. But probably not practical for in place switches. So consider the alternative ideas of bulbs, additional boosters, or electronic shutdown circuits. (See Tony's Train Exchange for the latter.)

I hope this helps EVERYONE! Enjoy your DCC!

Allan Gartner "Wiring for DCC"

-- Allan W. Gartner (wire4dcc@aol.com), July 06, 1998.

Vince,

A short is a short no matter what the source or control system, DC, Analog Command Control, or Digital Command Control. The results are what is differnt, for several reasons.

The characteristics of the control system. With DC this is just the shut down of the cab involved. With command control, this is the shut down of everything under the same power sources, Power Station, Booster, ect. If the whole layout is under one, then the whole layout shuts down. If it is under multiples then the entire districts under it's control shut down.

The amount of power invovled Watts. With DC we are only talking a amp or so of current. With most analog command control systems. We are usually talking a few amps at 12-14 volts. With Digital Command Control we are looking from 12-24 volts at 3.5 to 20 amps. Watts = voltage x amperage. Total watts translates to heat. So as you can see the results here are very different. And are what is the main concern. This covers everything from welded contacts to personal safety and fire.

My layout has many turnouts and have been used from DC to CTC16, to DCC. No I did not have to go back and re-do my turnouts in place. Other then a couple problem ones. But I do make all I install now DCC freindly. Those that are on the layout and not are protected via 1156 automotive tail lamp and disconnect.

Go back and re-read Allan's message and his pages. You will be happier and safer for it.

--

Remember Always Have Fun and Enjoy!!, Don Crano NMRA #096211 Home Page Model Railroading with DCC http://pages.sssnet.com/donc/ Addition Q&A Forums:

DCC General Questions and Answers Host Don Crano http://www.greenspun.com/bboard/q-and-a.tcl?topic=Digital%20Command%20Control

Model Railroading Questions and Answers Host Larry Puckett http://www.greenspun.com/bboard/q-and-a.tcl?topic=Model%20Railroading

DCC Wiring Questions and Answers Host Allan Gartner http://www.greenspun.com/bboard/q-and-a.tcl?topic=Wiring%20for%20DCC

-- Don Crano (donc@sssnet.com), July 11, 1998.