Will 3/4" difference in radius matter?

[MVW]

Hope you guys won't mind a rather mundane question in regards to radius of mainline curves. I'm looking for a little advice from those with more experience. I'm building what will eventually be a large layout ... one HCD at a time. I'm just adding my second HCD, so the minimum mainline radius is again in play.

My first HCD had 13 1/4" radius curves with easements. Yeah, that's really pushing things toward the edge, but that's not the issue (for reasons I won't get into). As I'm extending track onto the second HCD, I'm finding that a slightly tighter radius, about 12.5", would work better for me. This is in an area that is not important visually, as much of the curve will be obscured by buildings.

The question: Will dropping to 12.5" radius (with easements) come back to bite me in the hinder? I will be running full-length passenger cars. Longest wheelbase locos will likely be a 2-10-2 or 4-8-4 (neither of which I own at the moment). Again, I'm more concerned about operations than the visuals for this particular curve.

Should I make the drop, or sweat it out to get every fraction of an inch possible into that radius?

Thanks!

Jim

[conrailthomas519]

I would draw out your radius full size on paper, or cardboard. Place your models coupled together on that drawing making sure that the centerline is in the middle. Once you done that YOU will know right away if the tighter radius will actually work with YOUR equipment.

[rogergperkins]

Running on a 3/4" less radius curve does not seem to me to be a potential problem.  I say this without knowing what kind of track you are using.

I have been using Kato Unitrack for about 10 years and have double mainline and some of the track is the doubletrack version.  MTL heavy weights run fine on the shorter radius curves.  Kato GS-4's also run fine.

One good pre-test is mark out the curves before you lay the track.

[inkaneer]

My question would be why use a HCD?   I know they are touted as a way to get up and running quicker but if, as you say, you are building a large layout  then you may later regret using HCD's.  Single HCD's, which from the radius you mention it appears you are using, will limit your curves.   As a general rule large radius curves are better than smaller radius curves.  You don't say how much room you have or how big the layout will be but if you have the room go with a modular open grid construction with minimum of 24 inch radius curves.  You can build it one module at a time just like the HCD's. All of this predicated on how much room you have and how big will this 'large' layout be. 

[davefoxx]

I think the proper answer is, "It depends."  For example, the difference between a 20" radius and a 19-1/4" radius is probably negligible or none as far as rolling stock running reliability goes.  The difference between a 9-3/4" radius and a 9" radius could be very significant, depending on the equipment that's running.  In your case, I think the difference between a 13-1/4" radius and a 12-1/2" radius probably won't matter much, again, depending on your rolling stock.  I would be concerned about the 2-10-2 and the 4-8-4 even on 13-1/4" radii, but, if they'll make it, they should probably make it on 12-1/2" radii, too.  Test them first, if possible, or banish them to other less restrictive areas of the layout.  Prototype railroads have to do this sometimes, too, when locomotives are too big or too heavy.

I can state affirmatively that I built a small layout with 10" radius curves that had easements.  I was able to run a Life Like E8 and full length Walthers passenger cars with no issues (other than it was ugly looking):


DFF

[MVW]

Thanks, all, for your responses. I'm gonna give the 12.5" radius a spin. If it don't work, I'll just have to rip it up and and do it over.

Inky, I'm set on HCDs for several reasons, but in this case, reach is the controlling factor. Since this particular section can be no more than 30" wide, I'm not considering other options than HCDs for benchwork. After all, if wider was an option, I'd just go with a 34" or 36" wide HCD. 

What you say makes sense, but portability is another major factor that's causing me to stick with HCDs. I've built and used modular sections in the past, and I'll take an HCD any day.

Dave, I would be amazed if the manufacturer doesn't at least claim the 2-10-2 and 4-8-4 will work on 12.5" radius. And if they don't, as you suggested they'd still be free to roam on about half the layout, which will have broader curves.

Thanks again, everyone.

Jim