Can I fit 2 072 3 rail loops in this space?

I'm not sure what you mean by loops, where the aisle is, etc., so I drew a couple of options to see if either of them are close to what you're asking

DoubleDAZ posted:

I'm not sure what you mean by loops, where the aisle is, etc., so I drew a couple of options to see if either of them are close to what you're asking

 

Dave, The green aria is the table. 2 Large ovals as you have depicted in blue in your drawing. The bridge would go across the open section.

I assume by open section you mean an entryway. Is it on the left, right, top or bottom. The rectangles are 8.5”x45” to represent the bridge.

Where is the entrance to your room?  It's definitely possible to do three concentric ovals in 11 x 20.  But your benchwork would be of the "open doughnut" variety- a series of perimeter modules with an opening in the middle, that would have to be accessed by a lift gate, duck under, or swing-out section.

If the entrance to the room is on the right, I also think you could do a folded dogbone, with the turnback loops offset from each other.  You wouldn't  have very long runs though.

I strongly encourage you to think about other options.  My train room is 11.5 x 18.  After buying nothing but scale-sized trains for more than 10 years, I gave up on the idea of two concentric ovals.  I'm afraid I'll get bored with it after only a short time.

Dave Ripp. posted:

Working on my bench work no track plan yet. I'd like to fit 2 o72 loops .... 11x20 

Sure, no problem. They will fit in the space. Use the biggest curves that will fit. 

If you assemble only two concentric ovals, you'll be brain-numb in less than 4 hours. Switching, cross-overs, sidings, reversing loops, avoid laser straight-aways. The more features you build-in, the more interesting the operating sessions. 

Benchwork is a chicken-egg proposition. I would suggest settling on a track plan before you build the benchwork. It will be harder to make the layout fit the benchwork, rather than the other way around.

Comments not withstanding, here's what 2 concentric O72 ovals would look like.
The track is Atlas.
The White crossovers are 45.5" wide to represent the bridge. Since I don't know more about the bench work, I placed one on each straight.
The center-to-center track clearance for the crossovers and straights is 4.5". The crossovers maintain the center-to-center clearance around the layout during the design phase.
The Green rectangle is about 6.65" wide and I don't know if 2 tracks will fit on the bridge.
The Yellow rectangles are 3" wide to show center rail distance to wall or edge of layout. As you can see, it would be close on the bottom if the bridge is placed on the left or right side of the layout, though you do gain 1/2" because the bridge is only 45", not 45.5".

If there is an aisle into the center, a lot can be done to add sidings, etc., so this is not intended to be a suggested design. Its merely to show the space.

Thanks guys. Sorry I left in the middle of your replies I will be able to access all sides and will include switching. I just wasn't sure if the curves will come to close to the lift out bridge or if they would even fit on the other end. Dave looking at your double loop rendition I may be ok.

Where exactly is the lift out bridge going to be? If on the left or right, is there a reason the width is limited to 11’? Or can it be stretched 3-6 more inches?

On the right side the green area is table the rest is open..

Is that already built? Here are some alternative configurations. The Dark Black is what you showed with the left side expanded to 6' instead of 3' since you have access all around. The Light Red would make thing symmetrical around the bridge. The Blue is offsetting what you showed to compensate for the location of the bridge.

BTW, what brand track will you be using?

Suggestion: don't put switches on the liftout.    There are enough issues working with a liftout to keep track aligned, and with 2 tracks, you double those.    Adding switches and wiring to power them adds another level of complexity and the switches add weight.    If it was unavoidable, then do it, but there is so much other space to put in the crossover, I would just leave the liftout with straight track.

Dave, for the record, I mentioned in my comments that the switches were just there to maintain the 4.5” center-to-center clearance and represent the length of the lift out bridge, not to be a part of the bridge, or the final design for that matter. I certainly hope you understood that. 😱

Thanks Dave and Jim, no switches near the bridge but I will fit some in for my industrial buildings and a passing siding for my station.  I'm using MTH Realtrax.

FWIW, those switches are Atlas #5. I use 4.5” because that’s what Atlas has on their dual track truss bridge. If you have large engines, the clearance may need to be greater on any concentric  curves you end up with in the final design.

Thanks Dave, Once I get the framing done next week I'll plywood it and throw some trak out to see what i like. I've lost some real estate by opening up the middle I got tired of damage from climbing on the layout. You've given me a goo start. 

Dave Ripp. posted:

Working on my bench work no track plan yet. I'd like to fit 2 o72 loops I have a 45 inch double track truss bridge with 8.5 inches of track width space so I may have to change the curves at the bridge end or widen the middle isle. 11x20 

Ok, remember when I said that doing the benchwork and then making the layout makes it harder? Well, I've been trying to do a track plan for you that is something other than a symmetrical oval. When you throw in a 45" bridge attaching to a three foot wide benchwork, AND want 072 curves, there just isn't enough room. The 072 is diameter is measured from the center rail. A circle of 072 is MORE that 72" outer edge-to-edge.

So, here's my question. Is your isle centered to a door entering the room? 

Tom No, that area is very open. 2.5 feet on the 5 foot side 6 feet on the bridge end. The 5 x 20 foot side can't be changed that part was saved from my last layout. I could possibly bump the open isle to 42 inches but would prefer to put a deep swale under the bridge on the 5 foot side. I definitely need the curves to stop before the bridge. I do have smaller curves I may have to sacrifice on that corner.

the simple answer to this questions is yes.    072 track has a complete curve diameter of about 72 inches depending on brand.    That is 6 feet.    Your area is 11x20.    An inside loop with 072 curves fits (minimum) and an outside loop with a larger diameter track fits.     You have some straight sections to fill out the loops.

Now if you want to keep the tracks a certain distance apart, say 4.5 inches.   You may need to lay the outside loop with flex track to get the curves the size you want.

Do do have a particular need to have the two sides broken up as a 3 foot section and a 5 foot section with your path in the middle?

What is your reach?  Chances are you won't be able to reach on the 5 foot side and will need access hatches to crawl under.   Trains sometimes like to die and derail on switches.  That makes for a lot of crawling under.

If you can make it 4 feet on either side your reach will improve some.  You will still have trouble with the corners.

Have Fun!

Ron

Ron, I have no problem with the reach on the 5 foot side. I kept this part of my old table and it is already built. At the top and or left side is also part of the old table and since I didn't want to deal with climbing on or under the table I decided on the open space between the 3 and 5 foot area as I'm almost 57 and don't enjoy crawling as much as I used to. It was going to be 2 feet but my friend Brian suggested I go at leas 2.5.  The 3 foot section at the top and the 3 foot section on the left will be against the walls. I also have a top side creeper but it didn't help with the table 10 feet wide. There will be 3.5 feet on the bottom or 5 foot side and 6 feet at the bridge end.

Dave, is this a fair representation of the room and layout space? You mentioned 2.5' on the 5' side and 6' on the bridge side as well as being able to access all sides, but didn't say how much. I changed the curves in the upper right to O54 so they'd stop before the opening where the 45" bridge (green) will be. Given that the 5' side is already built, the bridge would straddle it and will have plenty of support on that end. I took out the crossover switches, but kept the 4.5" center-to-center clearance. The top tracks can be moved down 1.75" and the bottom tracks can be moved up as much as 7.25". Because the blue line will still have straights leading into and out of the bridge, the engine overhang should clear on both ends, but you'll have to test that to be sure.

Thanks Dave, The table is on 5 inch casters so I've always been able to pull it away from the wall when I need to. Hopefully this won't be necessary anymore. Your rendition is great though. I'm considering leaving a 1.5 foot area instead of butting to the wall. Just enough room to get in if I need to but not a viewing location. I will decide that latter. Like yesterday I got called into work again but it helps pay for the hobby.