frog angle, min curve?

Hi,

If the camera angle is low, the switch and/or curve will appear sharper than it really is, so it is very difficult to determine the frog angle from photos.

Real RR's used #20 and up for frogs on the mainlines and the sharpest frog I have read about is a #5.25 frog used by the Pennsy in industrial areas and in some yards.

Hope this helps.

Ed

 Wow! #20!!! I may redesign my plans

#20! You're talking something like a 3-degree angle of divergence! A turnout like that must be one long son-of-a-gun.

As an example of the sharpest curves used on a mainline mountain railroad (completed in the 1920's), the Cascade line in Oregon uses a lot of 10-degree curves with speed restrictions of 20 to 25 MPH typical. 10-degree curvature equates to a radius of 574 feet, or about 12 feet in O-scale. It simply isn't practical to scale curves down proportionately and we do whatever we can get away with in the model world.

http://en.wikipedia.org/wiki/M...railway_curve_radius

http://www.trainweb.org/freemo..._curve_to_radius.htm

SP/UP Cascade mainline near Heather Oregon, note special rail supports to withstand lateral forces on sharper curves.

In flatland country, many of the 20th century line improvements went with 1-degree curves to maintain mainline speeds; that's a radius of over a mile!

My neighbor used to work with UP and says that #22 & #24 turnouts were not uncommon and some of the longer turnouts had a two point actuators due to the extream length of the points.

I have checked the frog angle of a local trolley line and their tight sidings use #6 frogs.

Next time some rivet counter complains about something on your pike ask him what frog angles he uses.

 Wow, I'm really surprised how far off the idea of wider curves are in real life than model. I thought that a 6ft radius was big, and #8 switches. #22 and bigger than twelve ft........No way we could get this in a normal basement setting. I have a max speed programmed in the engines of 70MPH. I'd better slow my trains down even more!!

 Will, I did not know that. Very cool.

To make O Scale practical, you need to have standards for the type of RR you want to model.  As a general rule, 54" R was considered a minimum radius.  I have seen many RR's with this radius and mikes and pacifics can handle it with ease.  A #6 switch has a radius of curvature of 83" so this is not a problem for any engine. #8's look better but are space consuming.  If you want to go to 48" R, then you need to be happy with smaller engines like consols and ten wheelers.  If you want to go with bigger engines, then you need a bigger radius and/or some modification to the bearings to allow more side play.

Hope this helps.

Regards,

Ed

 Nope Ed, pretty much a large diesel fan here, except for a few Alleghenys creeping in. A lot of great info getting posted here. I'm going to write it so I don't forget. I like the charts too. Curve to radius in HO, I figure is double for O.

 Seems like a #22 switch frog would be just about straight if a # 6 is 83" Rad !!

Will, who do you work for.  I am a track designer with AECOM in Philly.

On high speed frogs the frog point can be made movable like Matt's.  Note absence of guard rail on the movable point frog.  Measures somewhere near a #27 frog.  Forget where I got this photo.

Here's the frog point Tom was referring to. This is a Ross #8 curved turnout (60"/48" radii.) In a 3-rail operation, the frogs get pretty wide and a frog larger than a #5 will have problems with scale-wheeled equipment. We even had a few errant 3-rail cars pick the frog on this particular turnout. With the movable point, scale-wheeled equipment runs through it just fine. From what I've read, even in a 2-rail model operation, the frogs start causing problems when they're larger than #10.

Here's a scale-wheeled train running through the turnout.

When we were working of the Detailing Track book, we had a CAD drawing done of a #10 turnout. In O scale, it is over 3 feet long.

As for minimum radius, I model the Abingdon branch of the N&W. The tightest curves on the branch were 20 degrees (two horseshoe curves). In fact, the "minimum radius" for the prototype 4-8-0s (and 2-8-8-2s for that matter) was 20 degrees. That's a real world radius of about 288 feet, or 72" in O scale.  Imagine a 6 foot radius as the minimum for a 56" drivered 8-coupled locomotive. I use 44" as my minimum, most curves are 48" and a few are larger.

The compromises on curve radius and turnout frog number is what makes modeling in O scale possible. It's not useful to get too wrapped up in what the prototype does because there is no reasonable way to reproduce it on a modest home layout.

Joe G.

 Thanks for all the info guys. It just really hit home to me. I pulled out my G scale 10 and 11.5 curves, and figured the curves were huge for O. It's kind of humbling to admit that's what I thought. Oh well, at least they'll be big enough to appear like the real thing in the scale world.

 I would love to see more of Gene's layout also. I've tried to follow his column as well. How's your's coming Joe? I'd better take another look.

You probably found the photo on Wiki.  The 'original' illustrates "Bewegliches Herzstueck", and was taken at the Bonn station.

I looked into this because I was fascinated by the locking arrangement, and while the switch machine looked German, I thought it might be a recent British installation.  Because there is only a single point, rather than two [ = switch blades ], the detector rods are apparently moved by a single "upside down T" fastened to the bottom of the point, with inspection covers over the attachments' adjustments, and protective 'guard rails' as well.  An interesting item for you "Track is a model too" guys to replicate.

Best rgds, SZ

Check out my blog at www.oscalemag.com/wordpress. I regularly post updates on railroad projects. I just finished up an Altoona Works single stall engine house for review. I'm finishing up the second turntable details at Abingdon, and I've been playing with Radio Controlled Battery Operated DCC (aka Dead Rails) using Tam Valley Depot components.

 Oh no! We lost Joe!

 I guess I can't talk you out of battery. A lot of guys use it and love it. The benefits are good. Aristo had a system a long time ago that I considered in HO.

 I just had another drill bit the dust and no use buying batteries because they cost more than a new drill set. I see a lot of posts about track wiring evils and I must say they sound like over kill.

 For me, track power is the way. I have no trouble running large consists and pulling large trains all day. To each's own. It depends on what your up against, and just how you prefer to conquer it.

I am looking at going with battery also.  You need to check out the Tam Valley system.  All the joys DCC without dealing with loss of signal due to dirty track.  You can do any consisting that you can do with DCC or anything else for that matter.

 In six years, I've never had an issue because of dirty track.

You must have a great layout room.  My layout lives in a garage.  I can tell you DCC gives me problems (and it's done right busses and drops as they should be).  That and I am down right lazy and rather run trains than clean track. 

Joe, your battery powered tool problem is solved by Homer.   Ridgid tools offer lifetime warranties which include their batteries.  You just have to fill out the paper work which many do not do.  No paper work, no warrantee.

The CNJ Bronx Terminal got away with some tight switches & curves