We have just returned from the marvelous specil train from Union Station to Bakersfield and return. The Tehachapi Grade was spectacular. I was wondering if anyone has an idea of the radius of that loop and how it would correspond to HO curves?
If my math is correct? ----[:-^]----- a 24" HO radius would convert to 174’ while a 36" would be 261’
These seemed wider than that but also seemed fairly tight for passenger service. What do real railroads consider “tight”?
Thanks to our friends at Google maps, I found that the curve radius on the loop is about 591’, or about 81" in HO.
I believe that about the tightest curve the big stuff (4-12-2, DD40AX, …) will/would take is (again, about) 48" in HO. That is usually done at slow speeds and with great care. For real mainline operation, I’m thinking that 81" mentioned above is pretty close to the minimum.
The tightest mainline curve WAS supposed to have been in Canada: 34" in HO. It’s been straightened a bit, though.
Ed
That sounds right, in one of his books John Armstrong mentions something about the tightest mainline curve (in North American railroading) worked out to about 34"R in HO scale, but he didn’t say where it was. He did note that real trains would be restricted to like 20-30 MPH on a curve that sharp.
Prototype mainlines were generally built to maybe 1 or 2 degree curves when possible, which work out to like a couple of hundred inches in HO radius.
There were common-carrier, standard-gauge industrial tracks with curves at least as tight as the equivalent of 11-12 inches in HO scale. Pacific Electric acquired some flat cars specially equipped to take such tight curves.
With narrow gauge you have smaller radii. [:)]
Wolfgang
When the train wheels squeal, you know they are moving on a small-radius curve.
Here are the Norfolk Southern’s criteria for industrial sidings.
http://www.nscorp.com/nscorphtml/pdf/Customers/ID/trackdesign.pdf
SRN - thanks for the link.
I sure shows me how much we “cheat” or “selectively compress” our trackage in order to fit curves that we can manage. I go down to 22" radius and think that looks pretty good, but that would only be a couple hundred feet, not the 400-500’ tht is considered the most tight!
I was interested to see that the site specified a #10 turnout as minimum. WOW!! Wish I could. [sigh]
22" is 160 feet, or just over the width of a football field. A full turn can be made inside the length of a football field with endzones.
I’ve seen an awful lot of #7 switches used for industrial sidings (real ones), especially around here (CA Bay Area). That would include railroad-installed (on railroad property rather than private property). In the other direction, switches are #20 on mainline CTC controlled sidings on the BNSF line along the Columbia River–at least at Cooks Siding.
On my own half-completed layout (a largish (14 x 20) but relatively simple one), I use #10 switches and 48" minimum radius anywhere mainline locomotives and passenger cars go. For freight cars and switchers only, I go with #6 switches and various smaller-than-48"-radius curves–generally 36" and 24".
Ed
Prototypes don’t measure in radii, they measure in degrees. If I remember right a 1 degree curve is around 5730 foot radius curve, which makes a ‘tight’ 10 degree curve 573 ft. On a side note a Pentrax video I watched included a scene were a track gang was installing a #20 crossover, capable of handling trains ramming through it at around 45mph.
A lot different from our #6 turn outs and typical 22R min. in HO.
Courtesy of freemoslo, here’s a couple of useful charts for converting back and forth degrees/HO radius:
http://www.trainweb.org/freemoslo/Modules/Tips-and-Techniques/radius_to_degrees_of_curve.htm
http://www.trainweb.org/freemoslo/Modules/Tips-and-Techniques/degrees_of_curve_to_radius.htm
Ed
The trains sure squealed going around trhe curve where I lived when I was a kid. Just judging by the houses and street pattern, the track radius must be 300 or 400 feet. Trains moved at 5 to 10 mph, and went eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee.
