Overhang/Underhang on 72" radius (O-144) and above

Matt,

you may be able get your own answer. I'll assume your drawing is to a scale. Can you create a same scale rectangle 85' long by prototype width, and place it along the curve sections you wish to investigate? By centering on the track centerline you'll get a visual of any overhangs, and may be able to measure that too.

Please note that this is the 2-Rail SCALE Trains Forum, and the original poster is talking about 72 inch RADIUS curves, and NOT 072 3-Rail track (072 3-Rail track is only 36 inch radius).

Good idea Chris. I did try that, but the Big Boy articulated is the problem as I can't accurately determine the boiler swing-out.

Dewey:

Thanks. Your heart's in the right place.

If that plan is from RR-Track, you an print out your track plan in scale and set your rolling stock on there to see for yourself.

Why is the wider radius curve on the inside instead of the outside?

I am very comfortable in using the NMRA standard which at 72" radius for a class 1a RR is 4 5/16".

Have you given consideration to using a spiral easement?  Adds pizazz to any curve. 

Jim:

Would have done that, but don't have a Big Boy or 85-foot passenger equipment (don't want to borrow it). The outside curve is sharper because the tangents leading in/out are longer. This causes the tracks to spread apart in the curve.

Tom:

Thought about easements (still thinking that through.)

Everyone:

Good suggestions so far.

quote:

The outside curve is sharper because the tangents leading in/out are longer.

Is there a reason you can not make the tangents end where the curves can be concentric?

B/J Matt is seeking more separation.

Matt, you may consider gradually widening the centerline number prior to the curve with a  camouflaged subtle pair of 7/16" "S"s to go freom 3.5 to 4 5/16" 

I just did a test with several large engines on 72"/76 1/4" radius and found the MTH C & O Steam Turbine  to have the most overhang against 85' passenger cars.  4 1/4" did it as long as we did not use raised lettering.  It was close.

When building anything that would be a pain to reconfigure I encourage not to only think of what entertains  you today, think 5 or 10 years down the road.  We have no firm idea where our interest may go as time marches on.

If you are looking for believeability a good rule of thumb is to use equipment and spacing comensurate with overall size of layout footprint available.

Thanks. I'm looking at that and the NMRA recommendations. Looks like the safest route is to achieve a 4.5" separation at the midpoint via easements. That would also reduce the risk of contact at the ends as the easement radius broadens toward the ends. The trick is making the easements long enough to eliminate the requirement for the longer tangents.

Thanks again. This has been another interesting "think outside the box" study.

I don't have 72", but have 70 and 74", and some big articulateds.  If you are in the area, we can try it.  I have a wall where the largest locomotives seem to hit without any derailments or other untoward consequences - maybe that would help?  A lot depends on how good your track is, and whether you have superelevation, and where your truck mounts are, and . . .

That would be helpful.

I've been meaning to come down there for some time. Hopefully things will free up in the next couple of weeks. Are you guys running DC or DCC down there? I have a small stable of MTH scale-wheeled that would look nice on the layout?

Got some photos E-mailed to me and they show that the clearance is close, but does clear. That said, though, I think the requirement of flawless track work says I'm chasing something that won't provide the right "risk/reward" ratio. Going back to 4" on tangent. Thanks for the input, everyone.

Lima, sorry, having a senior moment this year.  The locomotive which we found with the widest overhang was the MTH C & O Steam Turbine.

We tested several mfgs of a dozen or so large bulky locomotives including the SI, Big Boy,  H-8 & the EM-1.

The MTH Steam Turbine had the most overhang of all other engines but not by more than about 3/16".  Almost equal overhang at front or rear of loco.

I am guessing this is what a photo of a C & O Steam Turbine looks like in pure text??  Do not know what happened??

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