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Discussion in 'FAQs' started by Doug, Oct 4, 2006.
Can anyone tell me what the min. turning radius for an HO scale train is?
It depends on the train. If you are running a sw1500 with 40 foot cars, or old time steam with 36 footers, 15" will work. If you are running modern long 6 axle diesel power with 89 foot cars, you will need to run 26-30 inch radius. Some long equipment will get around shorter radius, but it looks terrible doing it. Also sometime long equipment will go around a tight radius, but the overhang of the couplers is such that it flips the car behind off the track!
The NMRA web site discusses this with tables for each scale and track radii. I believe it is section S-7 or S-8.
Generally accepted minimum radius is 18", and most sectional track manufacturers use that as their minimum. But as Russ stated, it's pretty much up to the needs of the equipment that the track services. Get a piece of flex track and test out your stuff. I've found that many of my cars are not happy with anything under 22" so I just don't run them anymore. In the future I'll be sticking to 50' and shorter cars.
I have an Athearn GP35 doing an 11 1/2" radius curve under the Christmas tree quite easily though I wouldn't recommend building a layout like that.
There is no such thing as a minimum radius for a scale. It depends on the length of equipment you're using and whether you have truck- or body-mounted couplers.
See my post in this thread in the N scale section: http://www.the-gauge.com/showthread.php?t=22326
The rule of thumb states that a minimum radius 3 times the length of the longest car or locomotive will work reliably in almost all cases. As others have pointed out, going smaller than that can be done but it means doing some testing and modification (be prepared for failures!) and/or using truck-mounted couplers.
my thoughts, your choices
I think I would not go tighter than 22". Even at 22" the overhang on the longer cars is way past what any full scale railroad would sanction. You are looking at a 48" turn around. 44" for the track and about 2" at each quadrant point for clearance. Don't forget those 2" for the clearance.
hey, i just had an idea. lets compile a list of cars and locos that will go around 18, 22 and 24 inch curves
anyone else in?
Atlas SD24- 18 inch
I made a streetcar loop on a 2 x 4 table. As well as streetcars, I managed to get Roundhouse (MDC) old timers (36-footers) around it and a few larger cars. Could have been a 9" or 10" radius.
When I built my layout a few months ago, I really struggled with this. Its all in the Loco, and let me tell you, its not always the easiest information to find. THe guy at my LHS tried to sell me a loco that swore up and down it would make a 22 inch turn, but when I made him test it, it turns out it didnt, in other words, dont always believe what they may tell you. Also, the minimum radius is not always listed on the box. More than once I had to emial the manufacturer to get the info.
Hope this helps
I've found that radius is also closely related to the type of layout you are building (real duh, huh). It seems that a minimum radius is more critical for a peninsula or table layout where you are trying to squeeze track within a width constraint. While designing my layout, which is an around the wall shelf type, radius doesn't play that much of a role. It does, but it's not as critical. My room is 7 x16 ft, which means that I can get away with the smallest radius possible up to a 40" radius, if I want one big sweeping curve. Even if I try to use the smaller radii, I never seem to net any major gains. I can gain some realestate, but not as much as I would have thought.
My layout is also relatively high with the mean track height at 55", or just below eye level for me. It's only 18" deep, so reaching something at the backdrop is not bad. Having the layout this high has the advantage of straightening out a radius, so what may be a 24 inch radius, may well be undicernable from a 36" radius. I can't see using super wide radii, just because I can, neither. So, in my case, I'm going to shoot for no less than 30"R for the main for operational purposes and whatever for the branchline.
26" radius will handle the 80'-89' cars as long as they all have truck-mounted couplers. You need at least 30" to run long cars with body-mounted couplers. If you want passenger cars with diaphragms, I think you need even more - anyone with experience care to clarify?
I didn't have a clue when I set up my empire and set it up for four axel engines and 40 ft cars , then I got some passenger cars 18in curves are TOO SMALL they stayed on the track, I think due to the truck mounted coupelers but they looked real stupid. I changed to 22in curves its better but still should be wider , unfortunatly I don't have room to open them all up to 22.
On one curve I had to move some scenry to clear the passenger cars , that same curve had lots of room for a 40ft boxcar.
So now (when it's too late) I'm a strong advocate for planning ahead.