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TucsonRails
07-01-2011, 08:14 PM
What's the recommended turn radius for HO scale? Looking to design a shelf layout and hopin to get a lower deck system.

wheeler1963
07-01-2011, 08:31 PM
Depends a lot of what type engine and equipment you'll be running. A Big-Boy or DD40X is gonna need a lot of room. A small switcher doesn't need much. 24" is used as a good standard now days.

trailrider
07-01-2011, 08:55 PM
Obviously, the greater the radius of the turn the easier time you will have with engines and rolling stock negotiating the curve. The problem is that most folks, including yours truly don't have the room for very large radius curves. (In point of fact, model railroad curve radii don't come close to prototype curves except for very tight branch lines or logging railroads!)

"Standard" HO scale sectional track commonly comes in 18-inch, 22-inch, and even 15-inch curves. Flex-track can, of course, be bent to form whatever curve you want. But it is somewhat more difficult to keep a consistant radius. You can obtain larger radius sectional track made by Shinohara, which IIRC, you can obtain through Walthers. In my own instance, because I want to run passenger trains, I had to compromise by using 20-inch radius Shinohara on my main lines and 18-inch Atlas snap track for tighter curves. Shinohara makes sectional track in sizes from 16-inch to 30-odd inches.

TucsonRails
07-01-2011, 09:28 PM
So if I did a 4'x8' layout, using the 22" radius would that work for a turn?

Selector
07-01-2011, 10:50 PM
So if I did a 4'x8' layout, using the 22" radius would that work for a turn?

We don't know. As the first reply stated, it depends. If you run a long modern diesel, some will negotiate an 18" radius while some won't. So, you need to match your locomotive and longest pair of cars with the smallest curve that rolling combo will take.

A safe bet for almost all non-brass locomotives is 22" radius in HO. However, not all of them will work on that small a radius. A 2-10-4 steamer won't, plastic or brass, and the example of a DDX-40 probably won't either. Neither will any HO passenger car longer than about 75 scale feet that also has diaphragms.

tooter
07-01-2011, 11:11 PM
What's the recommended turn radius for HO scale? Looking to design a shelf layout and hopin to get a lower deck system.

If you want a continuously running shelf layout, you can run small 4 wheeled engines and short rolling stock which can negotiate very small curves. This is a test layout with a 6 inch radius circle...

wR7LLFAj4DY

It is possible to fit a continuously running HO gauge oval track layout onto a shelf with a depth of only16 inches. ;)

Greg

TrainboyH16-44
07-01-2011, 11:28 PM
A 24" radius will run almost anything...a 22" might have some difficulty with 80'+ equipment, like long passenger and intermodal cars. If you're only having boxcars and whatnot with 4 and small 6 axle power, 22" would work. I've designed my N scale railway to have 18" curves, that will run anything - equivalent to about 36" in HO.

brickbuilder711
07-02-2011, 02:11 AM
It depends on your layout...

If you want to run centerbeams, autoracks, 89' flats, or any really long car down your track, you want a 24" radius.

I am designing a switching layout which at minimum is 22" (mainly 24). It can take the above, but the mainline's biggest car is a Tri-Rail Bombardier Car which may be a bit tight.

Though I am not running Tri-Rail, if I really wanted, I would probably need a larger radius.

But if you're doing like a coal layout then you can get away with 22".

galaxy
07-02-2011, 03:06 AM
It really depends on what you want to run. THe more modern the locos and RR cars are, the larger radius you will need.

If you are going to run small steam or GP-anything and some SD-somethings {up to SD-50}, you can get away with 18"R curves.

Bigger than that and you will really need bigger radii. THat would include passenger cars over 65-ish scale feet long in HO as well.

Atlas has come out with new "snap switches" that have 22"R divergent routes so you COULD, on a "plywood prairie" have an outside 24"R curve oval and switches matching into an inner circle/oval of 22"R curves IF you have an external support system for your table {such as the 4x8 recessed into a 2x4 framework}, making it bigger than just 48" wide, allowing for clearance as the locos go around, OR if you do a 5'x9' "Plywood prairie they will easily fit.

Even then, the larger steamers and modern longer diesels and longer RR cars {such as auto racks, deep well intermodals and anything over 65 scale feet} still may not like your 22"R and 24"R curves.

TucsonRails
07-02-2011, 08:24 AM
Well thanks for the advice. I'm sure I'll end up running longer engines and rolling stock, so I'll rethink my layout. Thanks again!

BSVRR
07-06-2011, 09:43 AM
you can still go with a shelf system and use gussets on the curves, maybe even incorprate some kind of down lighting in the gussets.

Dollie's Dad
07-06-2011, 10:50 AM
I have a very limited space in which to build my layout, roughly 9' X 11'. The space is closed on three sides, so I was pretty much restricted to a U-shaped arrangement. To get maximum use of the space, I decided to go with two levels, with a helix connecting them. I would have loved to go 24" or larger radius, but it just didn't work. Instead, I used 22" radius on the helix, and 24-26 everywhere else.

I was surprised to find that I could run almost anything on that, including a Broadway GS-4. The only problem was the overhang of the loco hits the vertical spacers on the helix. I'm going to re-work those by moving the vertical supports outboard of the sub-roadbed, and I should then be able to run that engine all the way up and down the helix without hitting anything. I've also run an SD70ACe and a couple other 6-axle diesels on it without trouble.

The one thing that doesn't work, though, is just how silly those large engines look on a tight radius. They have a very 'toy-train' appearance to them, so I will stick with my original plan of only running 40' freight cars and B+B diesels. I will only roll out the big iron for special occasions.

BRS Hobbies
07-06-2011, 11:33 AM
Some really good information in this thread.

I generally recommend 21 5/8" to 22" as a minimum curve radius to accommodate most HO locomotives and rolling stock. You can get by with 18" to 19 1/4" radius curves if the locomotives and rolling stock are relatively short in length. Generally, the wider the radius the better but sometimes tighter radius curves are needed to fit a layout in a certain space.

One good way to avoid the unrealistic look of using tight radius curves with long locomotives and rolling, is to cover the tight radius curves with tunnels. This works especially good with tight radius turn around loops.

Best regards,
Brian

Wojo
07-06-2011, 08:51 PM
For what it's worth, I'm currently running a home layout with an outer loop of 26" radius, and an inner loop of 24". The curves have easements leading into them, and have a slight superelevation. I have no problem running Walthers P2K E units and passenger cars right out of the box on either curve. All main line switches are at minimum #6 frog.

I do not have a problem with 6 axel diesels either. Of course, the longer passenger cars would look better on broader curves such as 36" radius, but I do not have the room, so my regular passenger cars are PRR MP54s, prototypically correct at 62'.

Alien
07-12-2011, 02:16 PM
There are two different answers to the question of minimum radius depending on where you are coming from. "What will my trains get round?" and "What looks right to me?" There are some good answers already given to set you off in the right direction but try to answer the two questions for yourself by arranging a test piece.

Good idea above to hide sharp curves in tunnels, but also consider other ideas such as cuttings, buildings, etc. appropriate to the area modeled. Your 22" radius semi-circle could be 18" at the back (hidden/staging) and 26" at the front (visible).

Can I offer some words of caution.

Beware of bending flexible track too tightly. It can suffer from an effect known as gauge narrowing. This is where the ties will twist slightly (due to the webbing connection between them) so that they are no longer perpendicular to the rails. This may cause tight spots with larger locomotives. The simple solution is to use set track for the tighter curves and flexible track for curves above those radii. (The more advanced solution is to build your own track!)

Uncoupling magnets and curves don't mix.

Beware of stopping double-stack trains with loose containers on super-elevated curves.

1991conrail
07-13-2011, 10:33 AM
I think the biggest radius you can go on a 4x8 is 22 inch, but for most bigger cars and stuff i would go 24 or up.

tooter
07-13-2011, 05:02 PM
Can I offer some words of caution.

Beware of bending flexible track too tightly...

You can convert Atlas Flex Track into Atlas Snap Track down to a 6 inch radius with no gauge binding by first sliding out the free rail, prebending it, sliding it back in again, trimming the rails square, and adding Snap Track connector ties on each end...:)

http://i17.photobucket.com/albums/b90/compost_bin/Train/66d550c1.jpg

http://i17.photobucket.com/albums/b90/compost_bin/Train/04db002c.jpg

http://i17.photobucket.com/albums/b90/compost_bin/Train/4d95239a.jpg

None of these tracks are pinned down to hold their curvature. They are all laying on the table just like Snap Track. The two radii shown are 12 inches and 6 inches.

Greg

Espeefan
07-14-2011, 10:49 AM
Agreed. I've gotten flex track down to 5 3/4" radius for use with my trolleys, and it works just fine.

Alien
07-15-2011, 07:04 AM
There is no disagreement about being able to bend flexible track down to tight radii, so long as you use the appropriately sized trains such as trolleys and the short wheelbase stock shown in the photos above. Some industrial railways and tramways are like this in real life.

What I did say was this may be a problem with larger locomotives, implying that a (border-line, hypothetical) larger locomotive my find it easier to get around an 18" set track curve than flexible track bent to 18" radius. Take another look at the photo with the graduated square. If the ties were not twisted, they would all be pointing at the corner of the square. I'm not saying that it is wrong or doesn't work, just pointing out possibilities for fine-tuning. The rustic track is probably more realistic for some industrial models!

Alien
07-15-2011, 07:04 AM
There is no disagreement about being able to bend flexible track down to tight radii, so long as you use the appropriately sized trains such as trolleys and the short wheelbase stock shown in the photos above. Some industrial railways and tramways are like this in real life.

What I did say was this may be a problem with larger locomotives, implying that a (border-line, hypothetical) larger locomotive my find it easier to get around an 18" set track curve than flexible track bent to 18" radius. Take another look at the photo with the graduated square. If the ties were not twisted, they would all be pointing at the corner of the square. I'm not saying that it is wrong or doesn't work, just pointing out possibilities for fine-tuning. The rustic track is probably more realistic for some industrial models!

trailrider
07-15-2011, 09:27 AM
Regardless of how you create the curves, they must be of consistant curvature throughout the bend. I personally prefer sectional track for anything tighter than 24-inches. The other thing is that you should use flex track at the beginning and end of each curve in a transition.

So far as what locos and rolling stock to use, I will grant that the longer (and most of the modern locos are longer) equipment will have a tougher time of negotiating tight radius curves and turnouts. As I model the '50's and '60's era, I only have one diesel that needs to take the tight curves. It appears to do it okay. With earlier six-axle diesels, most of which are older Athearn products, I removed the wheels from the center axles, but left the axles and gears within the truck sets. You can't really tell unless you get right down to track level and have a light behind the engine. Similarly, I have kitbashed 2-10-2's, 2-10-4's and a 4-8-2 that negotiate 18-inch radius curves and #4 turnouts with ease. These were made from Mantua/Tycho 2-8-2's. A 4-8-4 was kitbashed from Mantua Pacific 4-6-2's. The trick is to use blind drivers (which came with the original kits or r-t-r locos) on all but the end drivers. You also need to shim the end axle bushings between the frame and the bushings with a .015" shim, and shim under the blind driver axles, between the axles and the cover plate with the same thickness shim. The connecting rods are jointed at each wheel, so they will compensate for the difference in the height of the drivers. What this does is lift the blind drivers off the rails so they don't catch on the outside rail coming out of the curve. Lead and trailing trucks may need to be modified and/or the inside of cylinders, frame, etc, may need to be cut away slightly to allow the trucks enough movement.

The other thing is to compromise on some of your equipment length. While I have no trouble running full-length 85-foot passenger cars, I make considerable use of 72-foot Athearn and Con-Cor "shorties", and stick pretty much to 40-50 ft. freight cars. The shorter cars take up much less room, so in a train, I can get the illusion of running farther.

Green board all the way!

Espeefan
07-15-2011, 10:25 AM
There is no disagreement about being able to bend flexible track down to tight radii, so long as you use the appropriately sized trains such as trolleys and the short wheelbase stock shown in the photos above. Some industrial railways and tramways are like this in real life.

What I did say was this may be a problem with larger locomotives, implying that a (border-line, hypothetical) larger locomotive my find it easier to get around an 18" set track curve than flexible track bent to 18" radius. Take another look at the photo with the graduated square. If the ties were not twisted, they would all be pointing at the corner of the square. I'm not saying that it is wrong or doesn't work, just pointing out possibilities for fine-tuning. The rustic track is probably more realistic for some industrial models!

OK, what I meant to say was that I had experiened none of the gauge narrowing you described, and unlike Tooter, I just tacked mine down on homasote. Not saying this isn't possible...keep your handy dandy NMRA gauge nearby when doing this, but It has not been a problem for me. PS: trolleys and critters are not immune to these problems. Being very light, they'll jump right off the rails if there is a problem.

Six axle diesels and 4-8-4's through 18" radii are an ongoing problem for many of us who like the big stuff but don't have the necessary real estate. :D

Wojo
07-15-2011, 10:36 AM
Trailrider:

You are absolutely correct about consistant curvature, regardless of radius. Another issue is the so called verticle curve which is due to uneven roadbed and sub roadbed, but resuts in undesired uncouplings and occasional derailments.

Building a home layout is a compromise. I am in the process of revising my layout to extend the run. I plan on retaining my current main line minimum of 26" which allows me the freedom to use the somewhat larger engines and cars introduced in the late 1960s, as well as short trains of Walthers passenger cars. If I were to increase the size of the curves to 30"+ radius, I would seriously limit what I could do within my allocated space.

Clear Block

engineerdylan
07-19-2011, 05:30 PM
I run ho bachman ez track witch is 18' R with a athern dash 9 44 cw it runs pretty good i recomend athern BUT NOT BACHMAN FOR LOCOS

BSVRR
07-19-2011, 07:38 PM
You're going to find good and bad units in any product line from my experience. I have a cheapo Bachman GP40 and 2 Spectrum Dash 8's that I would rank in my top 5 runners.

tooter
07-19-2011, 10:43 PM
Take another look at the photo with the graduated square. If the ties were not twisted, they would all be pointing at the corner of the square. I'm not saying that it is wrong or doesn't work, just pointing out possibilities for fine-tuning. The rustic track is probably more realistic for some industrial models!

Hi Alien, :)

The "staggered ties" look on that little prebent curve is because there are alternating connecting tabs on the Flex track which keep alternating ties from coming closer together. So you end up with parallel pairs with "pie shaped" spaces between them. The tabs can be removed from the underside with an Exacto knife to even everything out, but I like the unevenness.;)

Greg

KSRailroader
07-21-2011, 10:36 AM
I'm running 18" radius curves due to tight space. My locos are all GPs (38 & 40s) and it works well for me. I run nothing over 60 scale ft and have never had an issue.