I saw an advertisement for a Brass Selkirk by Sunset and noticed it had a minimum turning radius of 30". When I went onto the sunset Website I saw a NP Challenger with a 30" Radius.
I have an Athern Challenger that can handle a 18" radius and a Broadway 2-10-4 that can handle 22" radius. and 5 x 2-10-2s that can handle 22"
My question is: Is the 30" radius a conservative number or are the tolerances different for the brass? I really would like to know as I would love to get the Selkirk. And maybe the Challenger…
Yes, the tolerances are a lot different for brass, as is the market each is aimed at.
Bachmann, Athearn, BLI, etc. are aimed at the mass market, and make efforts up front to make their models take a very small, pre-specified minimum radius, regarless of how ridiculous they might look doing so. Extra lateral motion is provided in the drivers, and details that might interfere with a pony or trailing truck’s swing are modified or eliminated.
OTOH, brass locos provide less lateral motion for the drivers, and use metal pony and trailing trucks which will short when they touch fine details like brake and steam lines. Articulated brass models usually do not let the rear engine pivot (same as prototype), which raises the minimum radius for these models. For these reasons, brass models generally have a higher minimum radius than mass-produced equivalents. And if CNJ’s theory is correct, many brass models were built for the collector market, and operational capability took 2nd fiddle. A collector doesn’t care what the minimum radius is.
How much below the manufacturer’s specs you can go depends on your willingness to modify the model to make it work. Most manufacturers are going to be a little conservative to allow for production variances from one model to the next. Modifying low hanging details to permit swing room for pony and trailing trucks without short circuits would be the next step to reducing minimum radius. But the reduced lateral motion of drivers is going to be your end point because changing that is going to mean major modifications.
I wish the importers/builders of brass locomotives would specify the minimum radius their models are capable. This was done decades ago, but, with rare exception, not now. Some models require a much larger radius than one would normally think.
Minimum radius is designed into the model by the builder, whether a small shop hand-assembling 50 locomotives at a time, a custom-builder producing a one-off to order or a large (by model railroad standards) manufacturer popping plastic castings out of molds at a hundred units per hour. It isn’t dependent on the material so much as the intentions of the designer.
Minimum radii for brass locomotives were, and are, stated in conservative terms - partially because the minimum radius varies from unit to unit on hand-assembled locos. Back in the days before I standardized on Japanese prototype I owned an Akane 2-6-6-2. With almost no tweaking, it would take a 14 inch radius curve - ten inches less than was advertised at the time. It looked horrible doing so, but it could make it!
OTOH, any ten-coupled locomotive, regardless of manufacturer or material, is going to look seriously ugly on 18 inch radius curves. The same can be said for five rigid axle tenders behind locomotives with two six-coupled engines. The real question isn’t whether such a loco can be adjusted or modified to take a tight curve. It’s whether it can do so without looking preposterous.
Some of the older brass was built with looser tolerances–some of my older PFM and Akane articulated brass will negotiate a 24" radius with ease (but lots of boiler overhang). Newer brass is built to much closer tolerances–little lateral sideplay in drivers, and details such as brake-shoes and sand lines that keep the radii fairly large. For instance, my newest brass loco is a PSC F-81 Rio Grande 2-10-2, and a 30" radius would be, I think, an ABSOLUTE minimum–my minimum radius is 34" and it’s quite comfortable with that.
I’ve never really understood the “Collector” vs. “Runner” aspect of brass steam, since I’ve been collecting and running brass for almost thirty years (when you model my prototype, that’s all you can get, BTW). My locos are purchased to run, and I’ve had to make adjustments as far as minimum radius in order to run them. Granted, brass is not mass market (though it was much more common years back when it was relatively affordable), and I’ll admit that some of the locomotives I’ve purchased need tinkering and tuning, but brass is very easy and forgiving to work with, so smooth running is not an impossible task.
But yes, brass is made to much TIGHTER scale tolerances. However, newer brass runs just as well, if not better than, some of the newer, more tolerant plastic models.
But brass is still going to be probably the best bet for unique and one-of-a-kind locos, at least as far as I can see.
Brass vs plastic minimum radius is still wide open. I own a bras Alco models Virginian EL2 and Ajin made a newer and its minimum is 28 inch or was it even higher…
I have size constraints, would I want to use the Ajin? Nooooooo
I found my Alco EL2 will snake over 15" radious and number 4 turnouts.
Sunset is making the North Shore Electroliner, they were saying its minimum was 22 inch radius, but the prototype could actually go sharper than that because it had to run on Chicago Elevated curves, and computated over, thats sharper than 22 inch. They I believe are reworking the model so it takes the prototype curves.
Most of the plastic models are compromising to handle sharper curves which means articulateds have both driver sets swivel vs the prototypical rear rigid and front swivel.
MY NKP products 4-6-4 can do 18"-24" radius curves but the cab roof hits the tender. Duh…its correctly proportioned.
I think it has more to do what a manufacturer decides and how much detail and how accurately they produce the model. I have a brass NKP 2-8-4 and the LL NKP 2-8-4, and I presume they can handle the same curves.
If a model maker want to be able to sell their model they better expect what kind of layout it might be running on. Just because something is brass doensnt mean its minimum radius is going to be highly restricted. Just read the manufactures reccomendations.
My South SHore little Joe’s minimum is 26" but my 700 class for the same line is 15", so I will build my layout accordingly, keeping the Joe for mostly heavy main work while my 700 trots down that industrial line.
No, if anything, when the loco’s specifications are 30" then I would consider 32" to be the practical minimum.
The turning radius is not a matter of what material a locomotive is made from, but how it was designed. Things will be designed toward a target audience and price range. The toy train market will be made of cheap materials and will be designed to run around toy train track. Those people don’t care what the loco looks like on that track. Most people willing to spend the big bucks for a really good looking brass locomotive don’t want to ruin those good looks by running it around corners that make it look ridiculous.
Unfortunately I suspected as much. I have 24" minimum radius in one or two sections and I’ve considered a 2nd main line with wider curves for my passenger trains as the Rapido’s need the 30" + curves. So I may sit on this for awhile.
Regardless, thank you for the input as it was enlightening.
Fergie…FYI. Where I work, we had a T1a, T1b and T1c. All needed 34" to run properly. There is 0 side to side play, and because of the close coupling of the tender, the tender tended to hit the cab at anything under 28".