Passing siding question

[Blind Bruce]

On my interpretation of the "Hollow River RR" there is a passing siding on the East side. My question is: Can I wire the Tortoises in parallel so that each turnout will always be either main only or siding only?
I cannot forsee any problem with this but my operating knowledge is next to nil.
BB

[SpaceMouse]

Sure you can. I was trying to think of a situation where you used the passing siding as a runaround, and I still could not work out how it could be a problem.

[Anonymous]

A saw-by could require the turnouts be set differently, or at least be easier to do.

Example:
http://www.sdmrrc.org/Odds-n-Ends/saw_bye.htm

[cacole]

There is one situation where this could be a problem, and that is if you are trying to allow two trains to pass each other without stopping.

Assume that one train is on the straight through (main line) and one is going in the opposite direction on the passing siding. As soon as one of them is past either turnout, you want to change it so the other train can go on through without stopping. If the turnouts are connected together so they both turn to the diverging route, the turnout that the main line train is approaching will be thrown wrong for it to proceed; but if they have separate controls and separate motors, you would avoid this possibility.

But consider, too, what the chances are of your ever having trains in this situation. Is the passing siding long enough and your timing accurate enough to run both trains through the turnouts without having to stop one of them? I think this would be very unlikely in our model world.

[Blind Bruce]

cacole, that is scary in itself but considering that I will use Torti, their slow speed would exacerbate the issue.
Never knew what a saw bye was either.
BB

[johncolley]

Hint: All my Tortoises are connected to a two terminal block that is glued to the benchwork, for ease of switch machine replacement. However, for crossovers, or other tracks, where you need to throw two turnouts, such a weight scale track, or a thoroghfare track parrallel to a ladder I connect both tortoises to the same terminal block so both throw at the same time. I one turnout is straight and the other curved it is a simple thing to connect one to the opposite terminals, eh?

[dehusman]

Technically a sawby is when a train longer than a siding meets a train shorter than the siding and the longer train has to pull down to let the shorter train by. The longer train pulls down then backs up into the clear of the switch again. The back and forth movement is like the back and forth movement of somebody sawing.

You want to wire each switch to operate separately.

Dave H.

[Blind Bruce]

QUOTE: Originally posted by dehusman

Technically a sawby is when a train longer than a siding meets a train shorter than the siding and the longer train has to pull down to let the shorter train by. The longer train pulls down then backs up into the clear of the switch again. The back and forth movement is like the back and forth movement of somebody sawing.

You want to wire each switch to operate separately.

Dave H.

If the short train is indeed, shorter than the siding, then why doesn't the short train pull into the siding and let the longer one pass by?
BB

[Anonymous]

The shorter train may have a higher priority or take precendence over the other (depends on operating rules of the particular road I believe).

Andrew

[cacole]

I have a video about the Santa Fe that explains and shows a saw-by in action -- it was normally only necessary if both trains were too long for the passing siding.

With today's centralized traffic control the dispatch center should know the length of each train and be able to route the shorter one to the passing siding regardless of its priority.

The Santa Fe example was on a stretch of line in New Mexico that was not under CTT control, and the engineers never realized until they got there that both trains were too long for the passing siding.

[oleirish]

Ok guys I have a question,I'am installing Tortoises at the present,I'am useing LEDs red-open,green-closed.Can I install the 680-/\/\/\/\/\- one set in the main power feeds insted of each switch,It is becoming a nightmare under my control pannel!! What I mean is input is 12volts DC on one of the leads going to my tortoise has 2-680 resistors soldered at one end then the leds on each resistor leg,( pos neg) then to the switch,it is working allright,but boy what a mess!!!!!!!!!any help here would be great??I'am using DPDT switches.wired for reversing.
JIM

[Anonymous]

If I understand train movements properly, there is some confusion about what a saw-by movement is.

If two trains are going to meet at a siding too short for the longer train, and the longer train gets there first, then you have a saw-by. The longer train pulls up to the second turnout on the siding and waits for the arrival of the second shorter train. (If the shorter train gets there first, it just pulls into the siding and waits for the longer train to go by.) When the shorter train arrives it pulls past the front of the first train into the siding and down to the other end and waits in the clear for the longer train to pull away and clear the main. The engineer of the long train aligns the turnout, performs a break check and continues on. When the first train clears the other turnout, the engineer aligns that turnout, performs a break check and pulls his shorter train past the turnout. A trainman aligns the turnout for the main and they pull out and continue on their way.

What some are describing with two long trains passing at a short siding is called a double-saw. A double saw requires one train to be broken into two parts and there is much more back-and-forth movement until both trains have passed by each other and are ready to continue. Information on saw-by movements may be found on the web or in John Armstrong's (RIP) book, Track Planning for Realistic Operation -or- in Bruce Chub's book (out-of-print) How to Operate Your Model Railroad.

As for wiring turnouts, I recommend wiring each for individual operation. I wire crossovers and ladder tracks for multi-operation because they have to be aligned in all circumstances to work anyway. Good Luck - Ed

[selector]

You are correct, Ed. It is a double saw-by when one of the trains must be broken in order to pass on a singe line.