Zero clearance with O-72 4.5" center to center track spacing

Good Question Ron, as I am in the final planning stages I am interested as well.

Ron,

The arrival of a Centipede (MTH) several years ago was an eye-opener for me as far as clearances were concerned. They required a good 1-1/2" more clearance outside of the outer rail than I had at some places. The nearest object had to be at least 2-3/4" from the outer rail on curves. On the inner side, about 2-1/2" was OK.

That was the equivalent of a center-to-center spread of 7"-8" on double track curves. Much wider than you would like for proper appearance.

You will have real problems running them on most other club members' layouts. I'm guessing that few will have the required clearances, not only between tracks, but also between track and rock walls, trees, buildings, bridges, etc. The Centipedes truly are in a class all to themselves as far as clearance issues are concerned. 

As far as keeping your curve spacing at a minimum to minimize the appearance issue, one solution might be to simply limit what equipment is allowed to run with each other on adjacent tracks. That way you could reduce that 8" spacing. It's not ideal, but then again real RRs have a book of rules with limits as to what equipment is allowed on what trackage.

If your railroad is OK with the Centipedes, I don't believe anyone will have problems with bringing over big articulateds. Scale cab forwards and scale Challengers have been OK with plenty of room to spare on my "Centipede-friendly" layout.

Jim

Jim,

Thank you for the reply.  I get different numbers when I measure my Centipedes.  In the pictures below, I used a ruler with a 90 degree base to get a good vertical obstruction.  I set the ruler as close to the track as possible without the engine hitting it as it goes by.  I do this while the engine is moving because it sticks out another 1/16" from its stopped position.  The engine going in reverse sticks out a bit more than the engines going forward.  The measurement is actually a hair over 2 1/2" from the center rail. 

Overhead picture shows the Centipede has very little impact to the inside of the curve.

Below shows an O-72 curve with O-81 curve paced exactly 4 1/2' center-to-center.  It almost misses the GGD 80' HW; another 1/4" should do it.

It looks to me like track spacing of 4 3/4" center to center will do it for my current equipment.  I don't have GGD's 85' streamliner yet, so I may need more distance.

My concern is some of the really big articulates will need more room. If one of these engines shows up for a meeting at my house, I can handle it but will have to run it on the outside track with no, or short, equipment on the inside track.   (The double track mainline loop is L shaped, so the outside track becomes the inside track on two curves.)

On my all-Pennsy layout, I used the MTH Centipedes to set my tunnel portal, structure and signal mast clearances.  I kept 4.5" center to center spacing on curves because the 5.5" required to clear ANYTHING (Big Boy on inside track and 84-foot scale passenger car on the outside track) didn't look good.  With 4.5" spacing the Centipedes (or Y-3) on the inside will clear any freight car up to a 50-foot boxcar on the outside with about 1/8" to spare.  My curves are superelevated which makes the clearances closer.  When they're running, I just make sure that the Centipedes have the only passenger train on the railroad so that clearance is not an issue.

A Big Boy cannot run on my layout anyway, the tunnel clearances are too close.

Just got finished [with help of others] planning and designing the TMB maodel train club layout. even with wide turs ranging from 6.5' to 7.5' radius, we transition form 4" center to center on the straights to 5.5" on the curves.

Steve

We've gotten a little off the original topic and request, but this has been informative.

I took some more clearance pictures of my equipment, and I could live with 4 1/2" center to center as long as I don't run my Centipedes on the inside O-72 track and my 80'/85' cars on the outside O-81 track.  Other combinations should work.

Here are shots of the Centipede on the inside track and K-Line 18" cars (a HW and a streamliner) on the outside track.  The picture makes it look closer than it really is.

Here is a shot with a Weaver 60' B60 baggage.  Lots of room.

By going to 4 3/4' center to center I could run all my late 1940s PRR and SRR equipment on any track, at any time, and in any consist.  Or I could stay at 4 1/2" but make sure my 80'/85' cars are behind my Centipede.  If I'm not running the Centipede, all is good.

However, I still don't know what problems I will have when a club member brings over that scale Big Boy, Challenger, Cab Forward or Allegheny (see first post).  I don't want to have any restrictions on what they can bring, so I may have to keep the inside track clear while running these engines.  

It would still be nice to know what clearance requirements these big engine need so I can plan my scenery accordingly.  Back to the original request: For those forum members out there with one of these large articulates and O-72 curves, if you know the clearance needed for your engine(s) could you post it here.

Thanks

Ron

Ron,

How big is your layout, and what configuration is it (around the wall or island type)?

You could have inner 072 and outside 090 that would eliminate the issue = but look odd with the large track spacing.  And or as others have suggested run the large loco on the inside curve and or only run one Loco at a time.

George,

My layout, when finished, will have an upper level dog bone bent 90 degrees in the middle, with a single track oval lower level underneath one leg of the dog bone.  One leg of the upper level will be around the wall, one leg is an island.  The upper level will have a double track mainline that is, according to RR Track, 1.6 scale miles long.  My goal is to have the double track spacing as close as possible, and right now that looks like 4 1/2" being careful on how I run my Centipede.

The majority of my curves for the double track will be Atlas O-81/O-90, with one curve at O-72/O-81 and a couple that are broader. (Note: only the double track curves are Atlas, most of the rest of the track is Ross as well as all my switches.)

My original goal was to see what the minimum spacing would be to run the larger articulate engines, but it looks like 5 1/2" minimum is needed.  To me this will not look good, so I'm abandoning the idea of having a layout capable of running any engine on any track.  Running any engine on the outside loop of my double track main, with no train running on the inside loop, is now my fall back position.

However, I still need to know what the clearance requirements are for these large engines so I can plan my scenery placement. If I can get some good data from other forum members I can start planning the placement of tunnel portals and buildings.  If the data is standardized to O-72 curves, adjusting to larger curves at 1/8" per 9" increment should work well for planning.

Ron