Hello Everyone,
Is there any correlation between lenght of rolling stock or locomotive and minimum track radius in HO scale? For example, a 40' hopper car would run well on a minimum 16" track curve or a 72' locomotive would run well on a minimum 22" track curve.
Prepare yourself for a lot of different opinions on this one.
Here is my take.
Regarding minimum radius, 16" is below minimum standards for HO scale. 18" is widely considered to be the bare minimum. 22" to 24" radius works well for short equipment. 26" to 28" radius is better. 30" to 32" is best for a minimum radius. If you want maximum flexibility and the space to pull it off, 34" to 40" radius would be highly desirable.
As far as equipment goes, if you are running steam, every pair of driver wheels requires a broader radius. For example, an 0-4-0 will negotiate 18" radius, but a 4-6-2 really needs 22" to 24" radius to perform well. A 4-8-4 really needs 26" to 28" radius to perform well. A 2-10-2 or 2-10-4 really needs 30" to 32" radius to perform well.
As for diesels, 4-wheel (2 axle) trucks perform well on 18" radius and broader, but a 6-wheel (3 axle) truck diesel really needs 30" radius and broader to perform well.
Just my based upon my own personal experience.
Rich
Alton Junction
Thanks for the feeback Rich. I'm working on a layout design for steel mill operations that will connect to a larger layout. The steel mill will use mostly smaller rolling stock and probably switcher locomotives. With that thought in mind, I was looking to see how low of a radius I could go.
The first club I belonged to was a round robin type where we would visit each other's house for layout construction and operations. Half the club members were trolley addicts and they would use 10" radius curves and we found out a small switcher and 40' cars would go around those curves. Since you are doing a steel mill with those small cars that would be approriate, you can put down some small radius track and check out your equipment and find a true minimum radius for your operations.
Rick Jesionowski
Rule 1: This is my railroad.
Rule 2: I make the rules.
Rule 3: Illuminating discussion of prototype history, equipment and operating practices is always welcome, but in the event of visitor-perceived anacronisms, detail descrepancies or operating errors, consult RULE 1!
There is a GENERAL forumula. The radius is generally recommended to be 3x the length of the rolling stock. Let's take a 85' passenger car. 85/87.1 (scale) = .97 or 11.72". Take that and multiply it by ~3.
That's for smooth reliable operation that looks appropriate. And most will tell you 32" is about right for passenger service. But Bachmann will make passenger cars that run down to 18" thanks to their innovate coupler design. But the curve between cars, and track overhang isn't prototypical looking. There's large gaps.
Also when running long cars, you have to increase distance around parrallel curved tracks. Most parallel tracks are 2" apart (HO scale). Around curves you'll have to increase this to almost 2.5" for passenger trains around tight curves. This is to keep "clothes lining" rolling stock from bumping into each other around curved tracks.
Don - Specializing in layout DC->DCC conversions
Modeling C&O transition era and steel industries There's Nothing Like Big Steam!
My layout has mostly 18 inch curves in HO. I run Transition Era equipment, mostly short diesels and 40 or 50 foot freight cars, plus some short passenger cars.
I have to be careful about what I buy, but I have a 2-6-2 Hudson and a 2-8-2 Mikado steam engines that negotiate all my curves very well. I think both of these have some unflanged, or "blind," driver wheels.
Most of my freight cars have body-mounted couplers. My passenger cars have either old truck-mounted couplers or body-mounted swing couplers that allow tighter curves.
As you leave the Transition Era, though, everything started getting longer. I have one diesel that won't take my curves well, even with nothing attached to it.
Going back in time won't help, either, particularly if you are running older large steam engines or passenger cars from those thrilling days of yesteryear when intercity travel by train was a luxury, not the ordeal it's become now.
It takes an iron man to play with a toy iron horse.
BuckeyeDon Hello Everyone, Is there any correlation between lenght of rolling stock or locomotive and minimum track radius in HO scale? For example, a 40' hopper car would run well on a minimum 16" track curve or a 72' locomotive would run well on a minimum 22" track curve.
BuckeyeDon Thanks for the feeback Rich. I'm working on a layout design for steel mill operations that will connect to a larger layout. The steel mill will use mostly smaller rolling stock and probably switcher locomotives. With that thought in mind, I was looking to see how low of a radius I could go.
The walthers hot ladle torpedo cars are "very touchy" due to the design. I would not go lower than 18" on those btw. Ingot cars can go down to 15" with a plymouth switcher.
Something like an EMD SW1001, moving coke cars, ore cars, coal cars, ingot cars or hot ladle torpedo cars for steel mill operations. Any cars going out of the mill area would go to a staging yard where larger locomotives would move them to other areas of the layout.
BuckeyeDon Something like an EMD SW1001, moving coke cars, ore cars, coal cars, ingot cars or hot ladle torpedo cars for steel mill operations. Any cars going out of the mill area would go to a staging yard where larger locomotives would move them to other areas of the layout.
"One difference between pessimists and optimists is that while pessimists are more often right, optimists have far more fun."
I built a small Christmas layout that used 15" radius curves. I ran a small 040 switcher with short passenger cars with no problem. Short ore cars should be fine with this.
I've been to a few steel plants and iron mills in my life. There was some tight turns and long gons going over those old rails. Trackwork was not too cared for. The plant switchers were broken down seventy ton jobs to rubber tired loaders with a coupler mounted on the back. Hoppers and ore cars rarely went near the plants and materials were conveyed in. Flats and gons and purpose built steel coil cars were the norm around the plants and rolling mills.
Pete.
I am not sure HO works that way. Train sets come with an oval of Snap Track with 18 inch curves. Every manufacturer in the industry does every thing they can to make their product stay on the 18 inch curves. There used to be, maybe still are, a lot of kid's toys out there. Any piece of rolling stock that will work on the train set curves has a much bigger market than those that won't. There are a lot more kids running trainsets than Master Model Railroaders running hand laid track. I would not count on any HO rolling stock working on less than 18 inches.
Car length is the determining factor. 18 inch curves work with four axle diesels, 40 and 50 foot cars, and medium size steam, 4-6-2 Pacifics and 2-8-2 Mikados. Passenger cars are tricky. Some, the Athearn passenger cars in particular, will run on 18 inch curves. Full length 80 foot passenger cars need at least 24 inch radius curves. Truck mounted couplers will get a long car around sharp curves better than body mount.
David Starr www.newsnorthwoods.blogspot.com
A compact area with short cars being shunted over sharp radius curves can be pretty cool.
Also consider the turnouts.
Another thread highlights the difference between turnouts, where the diverging track is curved througout the turnout...which would be really cool for you area in places...and turnouts that are straight through the frog and diverging route. These types of turnouts generally require a bit more space.
Depending upon which code of track you use, Atlas makes a snap switch in code 100 that has an 18 inch radius...I think, at least it used to be 18, and a code 83 product that has a 22 inch radius curve as the diverging route.
Peco also makes curved radius diverging paths in their code 100 line...small radius turnouts .
- Douglas
The question really isn't so much "How tight is too tight" to operate, as things can be made to run on very tight radii if needed, but some "cosmetitc surgery" will be needed.
But when dealing with larger equipment, it does look funny on smaller radii.
Things like the Bowser C630/636, Atlas 8-40C/CW, even a Scaletrains GEVO will handle 18" radii, hauling coal, frac sand, oil/ethenol tanks, 60' flat cars, grain hoppers, 60' or shorter box cars, etc... But they look pretty funny doing it.
Conversely, 80'+ cars, like autoracks, will not handle that 18" radii without heavy modification.
So when dealing with tight radii when needed, things can be made to handle it, but the question of "will I like seeing it" is vital.
Ricky W.
HO scale Proto-freelancer.
My Railroad rules:
1: It's my railroad, my rules.
2: It's for having fun and enjoyment.
3: Any objections, consult above rules.
Did a lot of experimenting years ago as some people like to use longest radius possible. Found out 18" radius looks fine on 40' cars both inside and outside radius curves and flat cars and other low profile cars can still look fine beng a bit bigger. 50' cars run fine but look bad. Many engines can run fine and don't seem to look bad larger but smaller look better and some that will work that are really large look very bad so make your own mind with engines, particually diesels as they generally have a profile that is not broken up.
A clearance car such as this will determine if new equipment will work with existing tunnel, structure and sise-by-side clearances.
NYCT took an old 60' car, cut it in half and extended the car to 75' the new length that the wanted to buy. This told them where they needed to enlarge the tunnels or in some cases to restrict the 75' cars from operating on that line. It also demostrated the location of the trucks and kingpins.
Most of the 75' cars are gone or will be going away soon. New cars are all 60' cars
The relationship of the truck and kingpin vis a vis the end of the car will determine the end overhang or the middle overhang.
On your railroad, just try the cars out and see if they work. I have some brass cars that never worked on my railroad because I never installed 60" curves. They make a very nice static display.
Subway cars of LION are 50' long and will handle all of my curves. 85' cars will not run on my layout. Some equipment is too tall to run in my tunnels.
The Route of the Broadway Lion The Largest Subway Layout in North Dakota.
Here there be cats. LIONS with CAMERAS
From the instructions of the Marklin/Trix Big Boy... (Found on the internet - I do not own one.)
Important information about the operation of this locomotive: This locomotive can be used on curved track with a minimum radius of 360 mm / 14-3/16", but we recommend larger radius curves. Due to the overhang of this locomotive's long boiler, signals, catenary masts, bridge railings, tunnel portals, etc. must be set out further from the curved track for clearance. The track must be well mounted for the high weight of the locomotive.
JW
Hello All,
On my 4'x8' HO pike I have asymmetrical curves comprised of code 100 track.
The 180º curves at each end consist of 90º 15-inch radius and 90º 18-inch radius with a 2-inch straight section between the curves as an easement.
I regularly run a 4-unit consist of GP40s and a 3-unit consist of GP30s pulling Tyco 34-foot operating hoppers with no problems.
There is also a crossover made up of 4 Atlas Snap Switches that uses the short curved sections provided with the turnouts. These are placed back-to-back to form a dreaded "S" curve.
The MU's can negotiate this "S" curve, albeit at slow speeds.
I added a modified PECO curved turnout on the 18-inch radius curve side, before the crossover to eliminate half of the "S" curve.
For the coal unloading/loading sidings I used PECO #2 turnouts.
The 4-unit GP40 consist negotiates the lower loading siding pulling 16, 34-foot Tyco operating hoppers.
A curved asymmetrical 3% grade is used to get the 3-unit GP30 consist pulling 8 loaded Tyco operation hoppers up to the unloading tracks.
This 180º asymmetrical curve consists of 90º 22-inch track to 90º 18-inch radius with a 2-inch straight easement section in the middle.
On the upper unloading siding, with #2 PECO turnouts, the loaded Tyco operating hoppers are shoved over the unloading track to the waiting empties below.
This is a slow-speed operation as the cars on the lower track are spotted under the unloading track while the loaded cars on the upper track are shoved over the unloading track mechanism.
A 15-inch radius 360º spiral trestle (helix) brings the empties back down to the mainline pulled by a single GP30 cut from the 3-unit consist.
I also have a wye for turning the 0-6-0 USRA with Vanderbilt tender used for excursion train that pulls 42-foot Olde Tyme cars up the 3% grade and down the historic spiral trestle. A 0-6-0 Side Tank Porter acts as a helper up the grade.
The wye is comprised of 2 15-inch sections to form each leg of the wye along with #2 PECO turnouts to an Atlas Mark IV wye turnout.
Hope this helps.
"Uhh...I didn’t know it was 'impossible' I just made it work...sorry"
Thank you everyone for the advice! Much appreciated.
At one time Atlas made 15" radius sectional track. I would never consider it for mainline track but in a tight switching area with short locos and cars, you can get buy with it. I've gone as tight as 18" in my industrial switching area but an SW7 switch engine and 40 foot cars is the largest equipment that has to negotiate these.
As for mainline, make your curves as broad as possible no matter what kind of equipment you want to run. If you can do no bigger than 24" radius track, I would limit myself to 4 axle diesels. You might get by with a Consolidation steamer (2-8-0) but for the most part, 6 drivers max. If you want to run full length passenger cars, I'd suggest a minimum of 30" radius. One thing you want to take into consideration is appearance as well as performance. You might get larger equipment to take tighter turns but it won't look good doing it due to the overhang.
John-NYBWAt one time Atlas made 15" radius sectional track.
They still do...HO CODE 100 15" RADIUS TRACK.
John-NYBWOne thing you want to take into consideration is appearance as well as performance. You might get larger equipment to take tighter turns but it won't look good doing it due to the overhang.
Absolutely!
Occasionally I'll get the urge to run The Royal Gorge excursion train with four (4) 85-foot passenger cars and an F7 ABB on the head end and an F7 A on the rear, for prototypical reversing operations.
The F7 units appear OK, but the overhang of the cars looks ridiculous over my tight asymmetrical curves.
Oh, how I wish for a larger pike, but this is the lot I am dealt.
After 50 years in the hobby and starting my last layout I view radii much differently now. Instead of what is the minimum radius I can do I try to view turns as what is the maximum radius I can use and strive to work that into the plan. I know there are people who have to use smaller radius curves but try to upgrade if at all possible. 22" opens up far more types of equipment then 18" and still fits a 4x8 sheet of plywood.
Hello all,
ndbprrI know there are people who have to use smaller radius curves but try to upgrade if at all possible. 22" opens up far more types of equipment then 18" and still fits a 4x8 sheet of plywood.
As one that is limited to a 4'x8' space, I find this does not hold true with the advent of DCC operations.
If you only want a single oval of track to run larger motive power and rolling stock you will soon tire of watching them go round-and-round.
In the age of DC this might have been a viable solution.
However, in the age of DCC some seek more operational possibilities.
By limiting the size of motive power and rolling stock, to match the limitations of trackage, the advantages of DCC can be realized.
Of course, I would like a larger pike to run a greater variety of motive power and rolling stock but at this point I am constrained by the dreaded 4'x8'.
Railroad modeling is a series of compromises and selective compression, even on the largest pikes.
If your goal is to run 4-6-6-4s, 6-axle diesels and 85-foot passenger and well cars, then yes, a single oval of 22-inch track is desirable.
But if you want the challenge/enjoyment of DCC operations then a rethink of motive power and rolling stock versus track radii is inevitable.
BuckeyeDonIs there any correlation between lenght of rolling stock or locomotive and minimum track radius in HO scale?
I only saw one other person (dknelson) mention this, and that is the answer is a resounding, "no" if the couplers are mounted on the truck. When a coupler is mounted on the truck it follows the curve of the track. It aligns to the center of the track so there is no "swing out" that causes the problems on sharp curves. This is how Lionel gets O-gauge equipment around 15.5" radius curves (O-31). In HO all the Tyco, Marx, original LifeLike, and Bachmann equipment was like this.
Then there are the compromise cars a few people have mentioned. This is where the coupler is on a swinging arm that decreases the swingout decreasing the radius that car will work on.
Finally there is the trick of pivoting the truck toward the center of the car. AHM/Rivarossi/IHC used this (in combination with the truck mounted coupler) to get their 85' passenger cars reliably around 18" curves.
here's a thread I created in 2019 about setting up a test track for minimum radius:
https://cs.trains.com/mrr/f/88/t/276727.aspx
starting post:
I commented about my loco testing on the other two posts about small radius curves and logging locos. I expanded my test sessions and couldn't believe how many of my HO locos do not derail running through a 15" radius curve, even at full speed.
The S curve test track consists of 3 feet Atlas straight track to build up speed, then one 18" radius Atlas curved snap track, then a reversed 15" Atlas curved snap track, then 2 feet of straight.
Here's a list of all the locos that wouldn't derail on this setup after several passes, even at full throttle:
Bachmann Spectrum 3 truck Shay (hit or miss, suggest 16" minimum)
Bachmann Spectrum Baldwin 10 wheeler 4-6-0
Bachmann Spectrum Decapod 2-10-0
Proto 2000 SW8 (no surprise)
Proto 2000 FA1-FB1, lashed up
Atlas Classic RS-3
Proto 2000 E8/9 six axle (!)
Athearn Genesis Mikado 2-8-2
Rivarossi Berkshire 2-8-4
IHC Santa Fe 2-10-2
The Berk and Santa Fe slow down a bit running through the 15R and of course they look silly but they would not derail!
This test might prove useful to owners of larger locos where a small section of the layout has to be 15R to fit.
50' cars and passenger cars look laughable on a 15" curve but they do make it through.
If you model streete cars a 9" radius would work. In a steel mill, a 6" radius would be ok.
I just finished my steel mill. I am using an Atlas MP15DC and a Walthers SW7 to move the same cars plus gondolas and coil cars. I used 18" for most curves with a few being a little wider (20 to 22) and one smaller (maybe 16.). I was more concerned with S curves and clearance than actual radius. Everything I have used so far has not had any issues.
Rick