center to center spacing HO

Just getting back into the hobby. Seems to me I remember spacing for
parallel track double track is 2" in HO.. Is that right? How about for
various radius curves, especially 24", 28", and 30"?
Reply to
tkranz
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Wider spacing is *NEEDED* on curves. Even at 40" radius I'd suggest 2.25" at minimum, and more on sharper radii.
We laid the club's "double" tracks at 2" spacing (as per NMRA proposed module specs at the time), meaning 38" and 40" coaxial curves ... it's NOT enough, and we have sideswipe problems. Passenger and other long cars swing "inside" the curves, articulated steam swings "outside", and various combinations cause problems. We have to restrict long cars to the inside track, and big steam to the outside track. It's not been enough of a problem to relay the hand-laid track (yet), but if/when we do, we will surely use more generous clearances.
2" is fine on straight track.
Dan Mitchell ============
Reply to
Daniel A. Mitchell
Did the NMRA change the standard before it was adopted? The module standard is 2.5" spacing on curves.
Reply to
Mark Mathu
Hi.
Unfortunately the NMRA recommendations for curve spacing are nebulous and outdated. With a little experimentation and measurements with the equipment you intend to run, optimum spacing can be determined. When on the outside track, the inside overhang of long cars is critical as determined by the truck pivot point distance. With steam locos, the outside overhang at the pilot and cab ends are critical as determined by the driver wheelbase. Other cases require different determination. Curves and couplers interact also.
These are graphically illustrated on my site.
For more details with methods and extensive discussion of problems and solutions, see first site below in curves.
Hope this helps.
Thank you,
Budb
Author of:
MODELRAILROAD TECHNICAL INFORMATION
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PROTOTYPE TECHNICAL INFO FOR MODELRAILROADERS (Revised. New address)
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Moderator of: MR TECHNICAL HELP GROUP
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HELP GROUP
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Reply to
bigbud
Folks, We tried 2" spacing on parallel tracks and we were constantly knocking cars off the other tracking when handling cars on one track. We went to 2.5" spacing and it worked out much better, and doesn't look bad. Bill
Reply to
Bill
Don't handle the cars!
Greg.P.
Reply to
Gregory Procter
Another case of the NMRA getting it wrong.
Reply to
Terry Flynn
One of the problems that cause side swipping at the curve is not using transition curves from the tangent to the radius. Notice how much the corner of the car bucks out when going from a straight tangent directly to say a 36" radius curve. Once the rear of the car moves into the curve the front corner moves back toward the track center some. I have "violated" NMRA spacing, going narrower, for the prototype look and used transitions, or easements to make up for the unprototypical radii. Works with passenger cars, autoracks and the like.
Bob
Reply to
rgp21
I agree that transition curves can help, but won't solve all the problems. The bottom line is that 2" spacing is still too close, even on 40" radius curves. Side-swiping interferrence will occur with a lot of equipment (long cars and articulated steam, especially) unless a greater separation is used.
Dan Mitchell ============
Reply to
Daniel A. Mitchell
Did the NMRA change the standard before it was adopted? The module standard is 2.5" spacing on curves.
Reply to
Mark Mathu

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