It sounds like you are looking at cutting in some turnouts in the middle of the end curves on both layouts. It's highly unlikely there will be any turnouts that will directly fit in those curves without relaying the curve. Just a caution.
Secondly, please try to make sure there is adequate access to all parts of both layouts after they are joined. Butting the long side of either layout up against a wall is going to cause access problems.
Any more advice needs more information like track plans and/or pictures.
Fred W
It might help to post some pics of the layouts. I did something similar and have a removable bridge. Also consider that you will only be able to use one power source when they're connected.
Springfield PA
A triple Wye might also work (could build as a module) as it allows either "L" or straight through designs. There is a Wye just west of Union Station in Springfield Mass. North is Boston and Maine, South is Amtrak and CSX, west is CSX to the West Springfield yard (perhaps used on your interconnect module for staging?). Amtrak uses the B&M track for a turn around. (Union Station is an elevated station and yard).
Google road map link is here. The satellite view holds more track detail.
Co-owner of the proposed CT River Valley RR (HO scale) http://home.comcast.net/~docinct/CTRiverValleyRR/
Well, I hate to be vague, but it depends. Without knowing what the trackplan is on either layout, it is difficult to say what might work or look prototypical. If you want to run trains from one layout to the other than you would want to design it one way, or you might want to design it as kind of a "loads in - empties out" arrangement. In other words, have the connection be two tracks, a main and a siding where cars are interchanged. A prototype for this is in Attleboro, MA at CP Boro on Amtrak's Northeast Corridor. In Attleboro, loads from Selkirk, NY for the Cranberry Subdivision are brought down by the B725, backed off on the siding (called branch 5) and the Middleboro local hands off empties destined for Selkirk to the B725 and that train takes them back up the corridor to Mansfield and on to Framingham, MA for their trip to Selkirk and beyond. So those two tracks (the Middleboro Mainline and Branch 5) are the interchange point of two seperate subdivisions of CSX, not unlike the two seperate railroads that you have. So that might be an idea and is relative simple to add.
Jim L
My Dad has a 4x8 layout that I'd like to connect to my 5x10 layout.
Anyone have interesting ideas for a junction between them? Might be an interesting opportunity to model a diamond with an interlocking tower.
Also considering just connecting them directly - making them into one big loop.
Connecting them in an L shape might also yield some interesting possibilities.
Radius on the 5x10 is about 29 inches where we'd be connecting them. Radius on the 4x8 is about 22 inches.
I did a search on "Junction" in the MR Track-plan DB and didn't find a lot of inspiring ideas. I also found a Kalmbach book with the first chapter on crossings. I'll have to check it out.