Curious about minimum radius being used

[Anonymous]

Most of us would prefer larger radius's than we can have. If you have the space for it, a 48 inch radius is pretty good. The criteria for what is good and what isn't is determined by the ever present "given and druthers" and the real estate you have for the layout.

I have seen some poor - in my opinion - layouts because guys have wanted a certain specified large radius and the ensuing layout results reflect champagne tasted in beer budget area. Sometimes, if space is at a bit of a premium, using smaller radius's like 30 inches then enhancing a certain area with 48 inches will work to expand the layout yet provide the owner with those wonderful visual curves they are after.

Of course I have no idea of the parameters of the space you have so if 48 inches works, thats great. The majority of layouts use less than 30 inches if you do an "average." However, when you exclude all the small and medium sized layout spaces, the "average" radius increases - since you don't have smaller layouts "pulling down the average." So if for example, if I said what is the minimum radius for guys that have a 30 by 30 foot space or larger, logic tells you the radius will be substantially higher than the "national" HO radius average, including all layouts.

Again to walk on the wild side, I would say that guys who want 48 inch radius's are more interested in a diorama layout with visuals most important and operations secondary. With other guys who are willing to go with smaller radius's in a large area, ops would be more important. But of course, all bets are off if the space you have is very large.

PS: I have written this after I realized I missed some posts, in particularly yours describing you 30 by 40 foot area.

[jkeaton]

I'd love to have a 30" or greater minimum radius - but I haven't got the space. (Well, I could, but I'd be building a couple of modules or a switching pike.) So instead I'm building with a 22" radius mainline, lots of 18" radius on secondary trackage, and quite wiling to go to 15" or tighter where required and the equipment will handle it (the short ore cars and 70 tonners shuffling around the mine and smelter won't mind). That way I can run trains (important for the boy, the baby, and the grandpa - my accomplices in all this) and have switching and scenery. I am using a hilly/mountainous setting to 'hide' some of my tight trackwork - or at least make it seem more reasonable.

Jim

[Jetrock]

I use 12" curves in HO on my mainline...I find that small two-truck diesels (GP and F units) don't like it but make the curve, while smaller diesels (44/70 tonners and S1's/SW's) do just fine, pulling 40-50 foot equipment with body-mounted couplers. Of course, I'm modeling urban industrial track located in a city, so super-sharp curves are appropriate to the prototype, and most modelers don't have that excuse.

A lot of modern modelers can't or won't dedicate as much space to a layout as folks used to--and fewer square feet means sharper curves, even though folks who want to run modern equipment get quite upset when their 80' freight cars or Dash-9's don't run well on 18" curves.

[CNJ831]

QUOTE: Originally posted by TBat55

Now I understand. It's the couplers that cause problems on tight radii.

By no means are couplers the only factor! Three-axle truck won't make it around tight curves unless there is a lot of play in the bearing or the center set of wheels is blind...sometimes even these adjustments aren't enough if the radii is really tight. Truck swivel/pivot is another factor. Some loco superstructures just won't allow all that much without hitting some part of the body. Repositioning the trucks can create a bogus-looking model. Steamers atre particularly sensitive.

Even if the above situations are allowed for in some manner or other, the physical forces acting of a string of cars being hauled around a sharp curve will limit their length, their truck size, and number of axles just to prevent constant derailments. It's a complex problem...not just related to couplers.

CNJ831

[TBat55]

Now I understand. It's the couplers that cause problems on tight radii.

[ndbprr]

Well since I staretd this thread I think some more thoughts are in order. Yes I have a 30' x 40' basement for the first and probably the last time in my life. I have built 8 layouts over the years and was never satisfied with the compromises they demanded. I decided that on this one I would make the buildings and turnouts full scale. That means #12 - 16 on the mains and #6-8 for the industrys. So while the space will be big I am not going to cram things this time. Could I do this layout in a 15' x 20' space with a fast clock? Yep but I won't. Full size and 1:1 clock in real time. It will still take 6-8 people to operate with two yards and 86 industries as well as the corridor traffic. Other things I am thinking of trying are North Philadelphia tower made big enough for the operator to be in the tower with a forced perspective of the railroad. Building fronts on the edge of the layout made of clear styrene with scribed windows and bricks or stone and very light coloring to view the trains through the buildings. Carl Appel did the Virginion and Ohio back in the late 40's and early 50's with 60" radius in OO scale and it was gorgeous. I want to think outside the box on this one. We don't know if realistic length trains will look any different in realistic size scenery. I intend to find out. Stay tuned!

[Anonymous]

QUOTE: So what does it take to FORCE equipment to work on 18" (even if it "looks funny")?

The most common methods are truck mounted couplers, cutting of underbody details to allow for more truck swivel, blind drivers etc. Most of these "fixes" can create other problems. In reality there are some locos that you won't be able to get go around curves because of the long wheel base...

Using articulateds that are designed to go around 18" radius usually means there is a huge overhang and the the spacing has to be wider. Some will go around the curve but the coupler overhang is so severe that you cant couple cars to it. So technically they can go around 18" radius, just like the ad says they will. IMHO They still look funny....

[Anonymous]

Ok I'll ask the newbie dumb question... how and where do you introduce easements for curves? I think I understand the concept but would appreciate more explanation. Can you also address easements or similar concepts on turnouts? Thanks

[challenger3802]

I've got 18" curves on the mainline which even the articulated engines will negotiate (with a bit extra kick on the throttle). The 15" curve into the platform area is a killer for all but the smallest of engines though. Thats what you get when living in a small apartment.

Ian

[TBat55]

Even if space was available for 30" curves, I'd still use 18" somewhere. Yards, tight spot, etc. Seems inevitable.

So what does it take to FORCE equipment to work on 18" (even if it "looks funny")?

Long cars would overhang more, so maybe wider track spacing and clearances? I suppose large steam locos could have the flanges removed from the middle drivers and still work. Make 3-axles into 2-axles. Articulateds could be more articulated.

Any comments?

[northern_blues]

Guy, I took a look at your pics of your layout. Nice! that canyon is a piece of work!

Back on topic. I am wanting to build my first layout so I found the NMRA site and read the specs for the type of rolling stock that I want to run which worked out to a recommended 30" radius. I've been trying to run 3rd Plan It ever since and have peninsulas or return loops with a 30" radius.

I can have a layout with 30" radius all right, but it will be nothing but curves and no straight track [:)] I think that's probably why some people's radius are a little smaller than they want because we need to fit in straight track, industries, etc. Right?

After I decided to bump my specs down to 27" radius, my prospective layout started to look much better, actually.

[Anonymous]

I think this question has several angles and many answers.

Most model railroaders never have enough space. Smaller radius saves space. Therefore most train guys are trying to get away with the smallest curves possible to have more railroad in the space. This is compounded by the fact that we all seem to want to be able to watch the trains run. Necessitating a circle or loop of some kind. Just a circle with no straight track in 18" radius is 3'x3' square. A 4' x 8' sheet of plywood with 18" radius curves only has five feet of straight track between curves at the most. Bump it to 24" radius it is 4' of straight, 30" radius it is 3' of straight (it won't fit widthwise, just for comparison of straight away sake).

Most people starting in the hobby are at 18" radius because most train sets come with sectional track with this radius. A 36" diameter curve fits nicely on a 4' X 8' sheet of plywood with a little left over for the margins. Most larger stuff won't run well (or at all) as has been mentioned by others. Perhaps it is problems with small radius that leads some beginners to think that getting trains to run well is too much hassle.

Then there is the bunch that says, "you can force a cab forward around a 18" radius and it won't look good , but it will work". My response: things seem to work great on that little sheet of plywood test somehow don't work so well in the layout....Most guys who have been modeling for a while make a distinction between radius theory and practice. Most of them have stories about tight radii that didn't work out somehow.

Among modelers who are building larger layouts with more space, 30" or somewhere near that has been the standard for many years. I think that the percentage of modelers in this category is much smaller than the train set bunch. Everyone I know who has been around a while (and has the space) has minimums somewhere around 30". Because of the space taken up by the curves, one needs more than a 4' x 8' to make this happen. Usually room sized layouts and larger.

Then there are those who want big radii and don't have the space (everyone). I think most of us fit into this category. These guys recognize the issues with tight radii and choose designs and equipment to minmize the problems inherent with small radius curves. These guys don't have huge 2-10-2's on 18" radius curves. They choose smaller gear to run. I think the problems come up when people try to force stuff meant to go on larger curves on the tight stuff.

I think maybe the question should be first, "How big is your layout?" followed by "What is your minimum radius?".

For the record, my space is 13' x 22', minmum is 30" mainline, 28" (one curve) staging.

[IRONROOSTER]

The rough rule of thumb I heard was 18" for shorty passenger cars less than 60', 24" for 60-70' and 30" for 75' plus. It was acknowledged that you could run 85' cars on a smaller radius if you did a few things like use truck mounted couplers and modify the body to allow the trucks to swivel. But appearance suffers pretty badly and you may have operational problems on 18" radius requiring slow speeds.

But 30" has always been more desired than realized. I first read it in John Armstrong's book "Track Planning for Realistic Operation", but he even acknowledged folks were using 24" radius 80' cars and recommended using easements so they would operate better. I haven't made a study of it, but it seems to me that there are more layouts today in MR with 30" minimum radius than there were when I started in 1971.

Enjoy
Paul

[camarokid]

I would'nt know what to do if I had space for a 48" radius. The room or building would be so large it would make my head swim. My current layout has a minimum radius of 26". When I tear it down this summer, to get rid of that spaghetti bowl look, I'm going to up the radius to 34". Not much difference, but for my room size it will mean less bench work to lean over and under.
Archie

[CNJ831]

QUOTE: Originally posted by ndbprr

It would appear from the posts that most people are using less than 30" radius in HO for their layouts. Back in the early 60's when 85' passenger cars and longer engines started to be produced it was pretty much accepted practice that 30" radius was the MINIMUM this equipment should be used with. I am interested in the fact that a significant number of posts indicate less than 30" appears to be the standard today. I would like to know if the posts are skewed by factors not being mentioned like a young adults with limited space or relative newbies building first layouts.

Addressing your question from the historical point of view, back in the 1960's the typical minimum radius was 18"-22", pretty much just as it is today for 75% of HO modelers. The 1950's and 60's was the era of spaghetti-bowl layouts with lots of track packed into a small area, so radii were always pretty small. Trackplans with large radius curves appearing in MR or RMC were a rarity back then, regardless of whether long cars looked good on them or not.

Even today, few hobbyists have the available space for layouts with very large radius curves and I've personnally seen few with curves greater than about 26" radius, unless they were basement-filling empires or wall-hugging shelf designs. Just check the most recent poll in MR's other forum regarding layout size and infer the probable radii necessary to operate on them. Most are far too small to have any sweeping curves.

CNJ831

[johncolley]

I use large radii to enhance the appearance of the trains, going 48" and larger on visible track I do go down to 36" on hidden track such as tunnels and helix. Also important is the use of easemnts between tangent and curve as well as between curves of different radii. I have one module that is a 45 degree direction change, around a river bend, having a 72" radius with generous easements. My 14 car GN Empire Builder streamliner with a pair of E-7's just flows through it! Note that is an 8 ft module!

[Leon Silverman]

Years in hobby have nothing to do with minimum radius used by a modeller. Assuming that modeler is interested in running large equipment, available space is the prevailent criteria. Your are fortunate that you can run models that have protypical operating characteristics but manufacturers have adopted their models to run on these smaller radii in order to generate higher sales volume. Witness the fact that there are no non-brass ready to run true Articulated Steam engines on the market today.

[cwclark]

you can go as low as 15" but you'll have to use short engine trucks like a EMD GP -(whatever) or a GE B (whatever) unit ...EMD SD's or GE C's won't make it thru a 15"..there are some situations where as little as 10" can be used but that is for switching in tight areas and speeds..very, very slow...the safest would be no less than 18" radius but for me that's even too sharp..i have nothing less than 24" on my layout and my widest radius is 36"...Chuck

[CP5415]

I'm using 22" curves for all but one curve on the mainline. I do have one 30" curve on the mainline & I'd love to have them all at that radius but space restraints kept me from keeping them all large.
I haven't , YET, had any problems with anything going around my layout.
I do have one 30" curve on the mainline & I'd love to have them all at that radius.
Gordon

[rrinker]

The 'standard' minimum in HO has LONG been 18", because that's what sectional track came as. Plenty of designs even used 15" because Atlas and others made that too.
You are lucky to have such a large space to be able to use 48" minimum. That takes over 8 FEET to loop around. Not even a consideration in my basement. 30" minimum is pushing it in my space, but I am determined not to go below this, on the main lines anyway. Industrial areas where a 4-axle diesel will push around 40' cars, I will likely go as low as 24" or 22".

--Randy

[ndbprr]

It would appear from the posts that most people are using less than 30" radius in HO for their layouts. Back in the early 60's when 85' passenger cars and longer engines started to be produced it was pretty much accepted practice that 30" radius was the MINIMUM this equipment should be used with. I am interested in the fact that a significant number of posts indicate less than 30" appears to be the standard today. I would like to know if the posts are skewed by factors not being mentioned like a young adults with limited space or relative newbies building first layouts. Also those who have been in the hobby for say 20 years or more what radius are you using? My current layout abuilding is using 48" as an absolute minimum and the only on the switching portions. The mainline will be at least 52" and larger. I have asked on several forums if anyone ever built a layout with 48" radius and thought it was overkill. The resounding response was no and there was never a negative response.