The Dispatcher's Delight

[rrlcommish]

The above-referenced layout is HO-2 in The Atlas Beginner's Guide to HO Model Railroading. I like it, but I have a question for those of you who may have built it or know what I am talking about. What is the purpose of Block 6? It only goes from the end of Block 8 to just past the crossover turnout that leads to Block 4. Why not just extend Block 3 over to the edge of Block 8? There must be a reason that the designers created that separate Block 6 (or not)? The main reason I am questioning it is that I would like to modify this track plan to add another siding to the Block 4 spur (a two-track "yard"), and if I want to isolate that new spur I'd need another Selector, as all 8 terminals are taken by the current design, and I hate to purchase another Selector for one block. Any thoughts? Thanks!

[Texas Zepher]

QUOTE: Originally posted by rrlcommish
The above-referenced layout is HO-2 in The Atlas Beginner's Guide to HO Model Railroading.

Do you mean this one?

QUOTE: What is the purpose of Block 6?

Unfortunately I don't have that book so the reference to blocks are lost on me. However if I was wiring this thing from scratch I only see the need for 7 blocks, unless one wants to make one of the spurs a "dead" section for loco storage. Can you describe this without the block references?
In my mind each of the passing sidings would be a single block. The short single line between the two passing sidings on the lower right would be a block. And I would divide the longer single track between the passing sidings on the upper left into two blocks. Each of the spurs would be part of the block containing its turnout.

QUOTE: and if I want to isolate that new spur I'd need another Selector

I'll turn the question around, why do you want to isolate that new spur? Unless you have a specific reason, why worry about it?

[rrlcommish]

Thanks for the reply. Bear with me, I'm new at this. You did get the correct plan, BTW. Block 6, the one I am questioning, runs from the main line, just to the right of the passing siding in the lower right of the diagram (roughly 4:00 on the plan) leftward over to between the two turnouts, approximately 6:00 on the plan. Then Block 3 runs from that point over to the turnout at 9:00 on the plan. Maybe I'm also confused (again, I'm fairly new) as to what constitues the main line and what is the passing siding on this particular plan. The curve at the bottom left of the plan is a 15" radius, so I assume that is one of the passing sidings. But technically (according to the track plan) the rightmost curve is also a 15", but I thought the track to the left of that was actually the siding. Sorry, I am digressing into two discussions here. Why do I want to isolate it? I was thinking for loco storage. But like you said, it's not necessary. Now that I reread your reply, you MIGHT be talking about the same part I am when you said "The short single line between the two passing sidings on the lower right would be a block."

Does all of that make sense?

[Texas Zepher]

QUOTE: Originally posted by rrlcommish
Block 6, the one I am questioning, runs from the main line, just to the right of the passing siding in the lower right of the diagram (roughly 4:00 on the plan) leftward over to between the two turnouts, approximately 6:00 on the plan. .. Now that I reread your reply, you MIGHT be talking about the same part I am when you said "The short single line between the two passing sidings on the lower right would be a block."

That is a good description. Yes, I think we are talking about the same piece of track. It needs to be a separate block if two trains are to run simultaniously. By being a separate block a train can move from that track onto either track of either passing track. This is reguardless of where other trains are. If it was not separate a 2nd train sitting on the passing track would not be able to enter that section until the original train was beyond the passing track on the other side. In my opinion, that is probably one of the most important sections to have a separate block control.

And when I was saying "passing" tracks I was generically refering to the set of two parallel tracks. For this discussion of blocks it is actually irrelevant which is the actual "main" and which is the "siding".

I just realized why this discussion feels a little strange. I've gotten so used to command control, I hardly every think about blocks anymore.