are 0-42 fast track curves possible?

The intent of this thread is to explore O42 (O44.5), and if it is possible with FasTrack.   It is, and results in a reasonable center spacing that accommodates even the large and scale LC+ SD60M.   Cool!

The MTH RailKing Imperial Big Boy operates on O31 curves.   I imagine the overhang on O44.5 is quite a bit less than the overhang of O31, but as I do not own one, cannot test.

Most likely the very broad spacing of FasTrack with 6" centers would work, so someone interested in operating the MTH Big Boy could do O36 inside, and O48 outside.   OR, O31 inside and O44.5 outside with 6.5" center spacing.   Anyway, that consideration is a different topic from the original thread topic.

Obviously, the VL Big Boy needs O72, so is out-of-place in this thread discussion. 

An analysis of what center spacing clearance is needed for different locos at different curve diameters might make an interesting discussion in a new thread.  I have data points to contribute  to a new thread as above:  at O36 and O44.5 diameters, LC+ steamers, train-set passenger cars, and the LC+ scale SD60M work on the 4.25" center spacing.   Who else can add?   

So, I added a discussion thread minimum parallel centers discussion

If you use the Lionel FT 6" spacing, Nd run everything on nothing smaller then it's speced min radius, you will not have any issues of things hitting.  I believe that's why Lionel went with that spacing when they designed FT.  I have set up O36 inside of O48 on the floor and run long passenger cars on the outside (Lionel HHP-8 set) and a RK Cab Forward on the inside and not had any hits.

On my home layout I used some CAD software to make basic models of locomotives and long passenger cars and created track curves to 'run' them on to see how close I could space track without issues as I wasn't doing concentric circles with my loops.  If I did it right I should have any issues once things are running.

I was curious about running larger cars (what is the limit you can push) on the outside O44.5 curves.   And I wanted Menard's double-stack cars anyway, so this was my rationalization for pulling the trigger on a 4-car set .

So with these large and nice cars on the outside O44.5 behind the scale SD60M, they run fine, and look pretty good.   They just barely touch the end handrails on the MTH SD70 loco on the inside circuit with the overhang on the tight O-36 curves at the very-tightest point.   I will check later to see if this is just an anomaly due to track shifting a bit.   So, this testing concludes that the double-stacks are fine on the outside as long as the inside locos and cars are more traditional or LionChief  -sized equipment.   I suppose that most folks with a small 4'-wide layout like this are not going to be running long modern equipment anyway, but a person can with a bit of care.  It is interesting to see what does and does not work on these paralled-curve ovals of 4.25" center spacing .

I will post pics later.

I liked the look of the 4.25" center parallel straight alignment, so I thought I would see what a lengthened layout might look like with a long run:

Here is a 4x10 with a figure-8 in the inside track, so trains can reverse in either direction: