Standard gauge radius curves

You have another option for your curves. USA Track is now making 57" Standard Gauge curves, exactly halfway between 42 and 72. Your 400E will look much better on 57" curves than on 42", but you won't need as much room as for the 72". You should be buying USA Track anyway. It is much better quality than the current Chinese made MTH/Lionel Corp track, and it's made in USA. 

 

http://www.standardgaugetrack.com/

I used the 042 on three of the four corners of my small square layout and 072 for the other corner which is the front of the layout.  There is a video of it on my youtube channel, linked below.

Are you making one loop of track? 24' of straight with 2 6' by 6' corners for 72 curves.

The 24' straights form a dogbone with 2 tracks instead of 1 track with switches.

 

Too get the 72 look in a smaller area use a combination of 72 track and 57 track to form your half circle at each end. 3 57 pieces at the apex of the half circle and 2 72 pieces leading and 2 more coming out will give you a half circle. The new diameter will be somewhere between 57 and 72.

 

Too finish the front, continue the curve with 2 72 pieces then a custom cut straight segment finishing with 2 more 72 curves in the opposite direction to join the straight track that  forms the 2nd straight line.

 

Mirror everything for the other side and you should be fine. On the track closest to the walls I would give a minimium of 3" of clearance from the center rail to the wall. You can go as tight as 6" between center rails on the throat section. This would leave one center rail 3" from the front.

 

Materials would be 16 72 curves and 6 57 curves plus all the straights.

As you work your tracks close to the mentioned wall, be sure to check the clearance as the engine comes out of the curve. I found that a track center line (center rail) needs to be about 4 1/8" from the wall. This will provide clearance for any engine, including the 400E, to clear the wall when transitioning from an o-42 curve to/from straight track.

filmtrain, I really wouldn't worry about how the train looks on 42" curves.   The wider 72" curves look more "realistic", but that's a relative concept with tinplate, and it really  only becomes a consideration on a permanent layout.  For a Christmas setup, trains on the 42" curves will look like a toy train, which is perfect.

 

12" is certainly not too tight to fit two tracks side by side.   As Owen says, check your swings where you enter and exit curves, and you'll be fine.

 

24' straightaway is a GREAT stretch, that will be very fun to run!

Well thanks guys for all the info. I actually just put a loop down on the floor and tried the 042 and it is just too tight. The 400E end of the cab almost touches the tender, I mean it is very very close plus the front truck wheels, one of them keep coming off and that is running it extra slow. I don't want to put time and money into this adventure and then not be able to get all the fun out of it specially if I running two 400E engines as my main trains. More bad news for me is I measured the areas and just can't do the 072 so my answer would complete is I have to go with the Standard Gauge Track 057 which should be perfect but I am heading out of town this coming week so I need to get most of the layout done this weekend. I emailed Kirk from SGT and hope to hook up with him and get some track. Not sure if he is around this weekend or if they stock that size but all I could do us ask. Thanks again guys. Frank

Sounds like something is wrong with that front truck.  I regularly ran my Commodore on 42" curves at rather high speeds without any problem -- looks silly but no worse than a 773 on 0-31.

I agree with Gilbert Ives.  The 400e was designed to run on 42 curves.  I know mine navigates them fine.  Whatever is happening is not directly related to the 42 curves, and using wider curves may not solve the issue.

 

Sounds like it might be a bum spring in the pilot truck. If one wheel isn't pressing down on the rail it could come off on curves. Easy to check, easy to fix if that's the problem. 

Mine was doing the same thing last year.  On the curve, the outer front wheel would just seemingly ride up the rail and derail.  But it is fine now.   Must have fixed itself in the past year while sitting in the box.  Helpful, I know.