Hi,

We are in the process of building a sophisticated OO gauge layout . We want to use DCC but are unsure if it can go the full stretch. We have produced this summary in the hope of finding someone who has done this before or who can guide us in some small way. If you can help we'd really appreciate it. We have taken full advantage of Allan Gartners help pages and really enjoy running DCC interactively.

Overview of the McKinley DCC Railway

The layout consists of two long double track main line ovals. Each is approximately 60 Metres long in a room 6m x 8m. ( 20ft x 28ft) These two ovals are twisted and interleaved as to make the operation of the layout interesting. In addition, there are three double track circuits which join these two ovals in different ways to allow varied operation.

In all there will be over 120 switches and 500 metres of track. There will be about 90 block sections. 60 will be on the main line and the rest will be in station areas and sidings. Each block is capable of taking the longest length train.

There are two large termini, each with loco sheds and goods facilities. There is one major through station. There is one major goods yard with loco shed There is a large fiddle yard with 16 tracks. There are passing loops for slow trains There are through roads at the main station for non-stop trains.

It is envisaged that the layout will be run completely through the computer system / DCC with the exception of certain areas which will always be controlled manually via DCC. There will generally be just one or two operators. We want the layout to be busy with train movement in abundance being controlled by the computer and allow the human operator the perform a number of functions. See below

It is anticipated that the computer would be operating approximately 10 to 20 trains simultaneously. These trains will be following both programmed and random paths.

Every train will have a type and behave accordingly. The different types are: Slow and fast freight. Slow and fast passenger. Light engine and so on.

Slow freight trains will be passed by faster trains. Passenger trains will stop at stations. Express trains will only stop at major stations. Freight trains will not park in passenger bays at terminus.

Some examples of operator interaction are :

That the operator prepares a train at a terminus and then signals to the computer system that the train is ready for departure either as part of a timetable with known destination or for random movement around the network. Once the train has left the operator can mark the bay as free and allow the computer to bring a train into the terminus.

The operator has prepared a train and wants to drive it himself. He has to obey all signals and the computer system will know where he is going to and set the route accordingly.

The operator wishes to prepare a train at the terminus. He will tell the computer system that the station is isolated for him to make manual movements around the station using DCC to prepare the locomotive and carriages. Once this has been done then he release the terminus back to the computer system for automatic control.

The examples above would equally apply to freight operations.

Certain areas would always be under manual control. The locomotive sheds and goods sidings / carriage sidings are examples.

The system has to have a number of failsafe mechanisms built in.

1. Block control is essential ? There will be a number of trains chasing each other around the layout. 2. Sections of track adjoining junctions must have safety zones to stop head on collisions at crossovers and side impact collisions at switches. 3. The system must protect the layout from computer failure. A dead zone behind each train would be one way. In the event of the computer systems freezing there has to be a way of protecting 20 trains from hitting each other. 4. Three colour signals will be deployed on the layout. These will guide the human operator. Red must be obeyed.

In order to have so many trains being run automatically we are going to extraordinary lengths. We are changing the couplings. We rebuilding the locomotives to have all wheel drive and pickup. We are converting all points to be DCC friendly. Polarity of frogs will be switched by relays. Only the best point motors will be used and so on.

And we want it yesterday.The trouble is we dont know if it can be done. Can anyone help us with this project. Do you know of anyone who has built such an ambitious layout.

We understand how to use DCC in a basic manner and we have connected up WinLoc and driven trains and used sensors with the BD8 devices. We have switched points via the DS 54 from the computer screen. It is really the aspect of linking all of these things and satisfying the failsafe mechanisms above that we have difficulty with. In addition, we believe the DCC has some features which are not "computer" friendly.

1. Each locomotive has its own perception of forward (think about it). The computer doesnt know which way it is facing unless told by an operator. 2. The computer can exercise wonderful control of the locomotives throttle but doesnt know where it is ( and I have heard the hype about the unreleased BLD 16s) 3. Interacting with the essential failsafe mechanisms above is a mystery

Thank you for reading this and I hope I have spurred your interest. Please feel free to e-mail me with any information you think might be useful.

davidtownend@atlas.co.uk

-- David Townend (davidtownend@atlas.co.uk), February 15, 2000

Answers

You have hit the nail on the head as far as identifying key problem areas for total computer control. Knowing which train is where is a primary control issue. Transponding DCC units are not here yet. You may have to resort to running the computer controlled trains with DC so that block signals can stop a train regardless of the loco code address. (See Tony's Train Exchange Station Stopper device, @ ttx- dcc.com.) Obviously the computer needs to know and control track occupancy detectors and signal status. A reasonable compromise is to avoid bi-directional single track and any figure eight type uncontrolled crossovers. Folded dog bone track looping can give an effective illusion of two-way operation on through trains with out actually having it. You can isolate keep-out areas for human operators to work in while the computer controls other sections of track. But... Go through your control algorithms very carefully. When you get 'em done..Sell the software to the rest of us!

-- Don Vollrath (dvollrath@magnetek.com), February 15, 2000.

I have to disagree with Don. Digitrax has DCC transponding now, standalone transponders and at least one decoder with transponder. If the railroad is still in the palnning stage, then by the time you are ready to run something, transponding should be more widely available, at least from Digitrax.

Dale Gloer

-- Dale Gloer (dgloer@ca.ibm.com), February 16, 2000.

To clairfy on Don's and Dales points. Don, the whole system is double track. There are no bidirectional sections. We looked at running the system with conventional DC. We tried the CTI system. Initially it looked good. The problem was one of cost. Transferring one locomotive controller ( The smart Cab module) from one DC block to another on a layout this size required over a 1000 relays( 4 per Train brain board). TB boards are $80 each. Multiply this by 250 = $20,000 on relays alone!

I'm always open to other ideas.

Dale, accepting the digitrax transponding system will come out, I then know where a train is.Agreed.

The key issues remaining are: 1. flexible block control of trains and by that I mean not having to programme each train movement specifically for each block, and then change each color signal. I need a smart system which automatically will isolate the last block and set 3 previous blocks and their color signals to the appropriate danger level. i.e. There would be nothing to program on the train except its path from junction to junction. if the following train got too close it would be automatically slowed down and stopped. If it failed to respond to the commands (and see below) it would hit the dead zone behind the train in front and get stopped by the hand of god - which is better than collision.

2. Very important - the part about having a computer fail-safe system to save my valuable railroad stock from crashing into each other when and not if the computer freezes!

3. Can loconet and the computer software handle the number of real time events We are talking of approximately 20 sensor inputs per second a lot of calculations to make. Update the Monitor and then 40 actions being transmitted every second!

On a seperate point, do you know where a really big DCC layout might be hiding in the US.

-- David Townend (davidtownend@atlas.co.uk), February 16, 2000.

David,

I guess the question is what is really big, here are a few I know of.

The Sebring Model Railroad Club, in Sebring, Oh, my back yard. The have a 25ft x 70ft layout, with 3000ft of track, and 100 pounds of ballast. Running on a Digitrax Chief, and 8 boosters. Detected and Signaled. Digitrax wireless radio, Located in a Pennsy freight station which they own. No URL I know of. Pics at: http://www.alliancelink.com/robstrains/local.htm BTW the pic in the top right corner of the Pennsy station, this is a model of the station that the layout is in. If you need any additonal info or contacts for them, let me know I can help there.

The Gratiot Valley Railroad, Digitrax, CTC, 900 car staging, 400ft of mainline, 200 block detectors. Mount Clemens Michigan http://www.michvhf.com/~gvrr/

PSMRE, 1700 square feet, Digitrax wireless radio, total automatic control for set up as exibit when needed. Located in the Washington State History Museum http://psmre.tacoma.wa.us/psmre.htm

Santa Susana Railroad Historical Society, Large railroad, Digitrax radio CHief, 2 5 amp boosters, 2 8amp boosters, Winlock, DS54 turnout control, detected and signaled, up to 30 operators in a given session. Located in a 1903 Southern Pacific Model #22 depot which they own. Simi Valley, CA http://www.trainweb.org/ssmrc/index.htm

Don

Remember Always Have Fun and Enjoy!, Don Crano Akron, Oh NMRA #096211 mailto:donc@sssnet.com Visit Model Railroading with DCC at: http://pages.sssnet.com/donc/

-- Don Crano (donc@sssnet.com), February 16, 2000.

I just want to clarify that the PSMRE layout is automated using relay block control on the mainline only. There are six blocks which will allow five trains to run. At present four trains run on the automated system. We do use DIGITRAx and have 7 power boosters and we have the same problem with computer control since we do not have feedback from the trains. We have WinLoc and are looking at KAM IND. programs. Our new web address is: http://www.psmre.org HAve a look and if we can help you drop a message.

Al

-- Alfred Babinsky (uintahrr@aol.com), July 15, 2000.