Double Deck layout question

[Flagler]

What is the best way to construction the Peninsula in 20 ft  X 20 ft Garage  that has the double deck wrapped around the walls.
I will have about 20" between the bottom and top deck. The peninsula will be 6ft wide on the top deck

[craigolio1]

Post in the centre, cantilever supports?

[superchief]

I built a 2x4 stud wall in the center, anchoring the baseplate to the floor with concrete nails and the end of mine is only 4ft 6in at the end, but I used 1x4 grid bench work on the lower deck and put legs at the end and about 4 feet back from the end and then X braced the legs front to back and side to side. I have bumped into the end very hard and it did NOT knock the train off the track, very sturdy. Good luck, Gordon

[Cajonpassfan]

It really depends on the design of the lower deck. With your upper deck 6' across and 20" separation between decks, you may not want to have the lower deck full depth because of limited visibility. The shallower the lower deck, the more  stability for the upper deck, instead of a "T" structure, you end up with an "H", with less need for diagonal bracing. Having said that, I find gravity takes care of stability with relative ease...given proper bracing.
Otto K.

[pnolan48]

I suspended mine with a 1/4" threaded rod from the ceiling. Yours may require more than one. This method sure cleared out supports from the first deck to the second.

[Flagler]

I plan on the lower  deck being only 18-20" wide on each side of the peninsula.The lower Deck will also be used as a giant reverse loop
with the junction being along the wall side before entering the area

[Cajonpassfan]

I plan on the lower  deck being only 18-20" wide on each side of the peninsula.The lower Deck will also be used as a giant reverse loop
with the junction being along the wall side before entering the area

Well there you go. That means your upper deck will only cantilever 18-20" and your center support structure will be almost 3' wide; plenty stable if done right IMHO.
Otto K.

[Flagler]

The upper deck will be one large city scene 6 ft  X 16 ft . What is the best height for this level.  I was planning on 54" off the floor.
I am 6ft tall. I know it will be hard to reach the middle,but it can be done.I use unitrack,so that will help

[glakedylan]

do you plan on operating while seated or standing? that is the primary factor.