OMG! 42" radius curves?

If you mean 42" diameter (21" radius), the problem may come when you couple some cars behind the engines. Body-mounted Kadees may cause some binding going into or out of a curve. If you limit yourself to cars no longer than 40', you may be OK.

Jim

Tom,

You're doing it right if all you are wanting to run are the smaller power. Your U-Boats will work but will look a little odd..LOL You are going with the heavier O-Gauge track and not the light duty 027 stuff?

As long as you're on 4 wheel trucks, you'll be fine.  Overhang is another issue.

I can run my U-25b, F units, GP30, and Weaver 0-8-0 all on 24"r. Joe F. is 2 railing a Kline Hudson for me that I full expect <32"r operation from. I've learned all kinds of tricks lately. Let the Kadee boxes pivot, use longer shanks, blind center drivers, avoid S curves, use easements, etc...

In my opinion 2 rail can be run on much smaller radius than what most people will tell you. Yes, everything looks better on bigger curves but most of us have real world space constraints. I personally made the decision to build a 2 rail pike in what is normally a 3 rail space. I have a 34x18 space and my max. radius will likely be 36"r. Of course I will be resorting to a lot of the tricks I mentioned above. I don't have a problem having the flanges cut off of the center drivers on my larger steam. I also tend to favor smaller prototypes too.

Hi!

I am building a layout right now and at one point at towards the end of my branch line I have a 36 inch radius curve.  Atlas GP35 and SD40s run around it no problem, and so do all my cars coupled in any order up to my new Atlas Trainman bulkhead flat cars and 33,000 gallon tank cars.  Even when they are hooked up to short cars like 70 ton hoppers....

My bench work is high and I am really surprised once I built it how the curve doesn't look at tight at I thought it would. 

I used to be hung up on a 60 inch radius minimum but if you are not running 89 foot flats, it doesn't have to be that big to run fine. 

Don

Let's be clear as to whether we are talking about diameter or radius.

A 42" RADIUS curve is 84" in diameter, or O-84...no problem there.

A 42" DIAMETER curve is O-42, which should be OK for about 90% of 3-rail O locos and rolling stock.

A 36" RADIUS curve is O-72.

3-rail O is the only segment of the model railroad hobby that routinely uses diameter instead of radius to describe curves.

He did say radius - we can forgive the spelling.  And this is the 2- rail forum.  Somebody else assumed "diameter" even though he was quite explicit.

Remember, HO always ran on 18" radius - a lucky kid had room for 24".  Double that, and you are still way under the magic 60" minimum that a lot of us use.

I like big steam, and have locomotives that strain on my 74" loop.

The curves were Gargraves 042". The U-boats will take the curves but  have problems with the trailing cars. I still have several of the old Atlas/Roco cars with truck mounted couplers. I will put one  behind the U-boat and see if that will do the job!

21" Radius.....that's tight.  Let us know what you experience.

Well, he fished me in.  The thread title says "raduis" and his first post says "radius" so I sort of assumed radius.  Sorry - apologies for my assumption.  21" radius is for streetcars.  Opinion.

All of this goes through my O36 curves, and amazingly, my On30 runs on the same track! 

Jeff C

Yes.  But, if you look at some of the freight operations that some of the traction lines did, moving 40' cars was not uncommon.

21" will also work for 0-4-0 switchers.....

I totally agree. I've been doing some testing lately and you would be surprised what will actually negotiate 27"r or even 24"r. My Atlas F unit can take a 48' Gondola through 27"r without a problem. Would it look better on broader curves? Sure. But if that is all the space you have then at least you can do it.

You mention another key point. Keeping the layout higher and, if I may add, putting yourself on the inside of the curves if possible. That goes a long way to mitigate the look of the tighter curves.

If the choice is use a tight curve or scrap 2 rail and go back to 3 rail I'll take the tight curve thank you...

Some of you guys are STILL CONFUSED!

3 rail O gauge is diameter, period.

per Rich Melvin

"Let's be clear as to whether we are talking about diameter or radius.

A 42" RADIUS curve is 84" in diameter, or O-84...no problem there.

A 42" DIAMETER curve is O-42, which should be OK for about 90% of 3-rail O locos and rolling stock.

A 36" RADIUS curve is O-72.

3-rail O is the only segment of the model railroad hobby that routinely uses diameter instead of radius to describe curves."

That does seem to be the case, doesn't it?  If you're in 3-rail O gauge, your curved world is measured/described in DIAMETER.

If you're a scale guy--any scale from Z through Large Scale--your curved world is measured/described in terms of RADIUS.

My Gargraves curves are listed as 042 Diameter, that is 21 inch radius! I am sorry if I caused any angst! I was just trying to point out that many diesels are more agile than we think! The couplers are another story. That is why I maintained a small fleet of Atlas/Roco cars from early Atlas. They can be made even more agile by using a Kadee couplers in the existing draft gear and using an ore car behind the locomotive!

All are born confused, some grow into being confused, some work diligently at being confused.

This is the 2-rail forum.  Discussing diameter at all is incorrect and bringing it up might be confusing to people who may search this thread in the future.

I'm still confused by the OPs point with the OMG.  That's a perfectly normal middle of the road 2-rail curvature.

1.  I agree -- but some of the specialized couplers / coupler adaptors required to handle steam road cars on these sharp curves were quite interesting.  MR did a great article on some of them back in the '50's;  my fav was a pair of back-to-back hinged knuckles placed between two 'conventional' cars.

2.  And I wholeheartedly second the thought expressed by j'speed above:  If the track is at near eye level, especially when viewed from the inside of the curve, the sharper radii should be far less noticeable.

Best rgds, SZ

But - but - but . . .

If you state "radius" when you mean "diameter" it simply doesn't make any difference what forum you are on - those two words have very specific meanings, and are not ambiguous.

However, if you say "O42 curve" almost every O gauge hobbyist, no matter how many rails, will assume you are talking about diameter.  Two railers, aware of this nomenclature, always simply state "xx radius" in such discussions.

Not opinion.

Wait , what's a curve?

Dear Tom Platten,

As a member of the Railroad Museum in Sioux City, we are building an 8 x 32' layout for public viewing to go along with our 15 x 80' HO and a 4 x 8 N scale. The O layout is in 3 rail but since I am building it and I am a 2 railer the outside rail will run a set of Atlas Zephyr Cars pulled by 2 E8s that are 2 rail on Gargraves track. How can I wire it? I am thinking about using a DPDT switch for power through an MRC Command Master 20. Am I on the right track. 

Thanks

Dick Donaway

You know...the squiggly thing.....   

Okay.  Change that: O-42 track.  To the uninitiated that could be esoteric.  To anybody who has suffered through sixth grade geometry, the difference between radius and diameter is clear.  I guess that is opinion; sixth grade was a very long time ago.

This sounds like something out of Monty Python, needs to be cleansed and moved to the 3-rail forum so more 3-railers may see it and provide comment.

Well it started to 42 inch RADIUS, and then the poster realized he had miss-typed and it should have been DIAMETER.   Let's not crucify the guy.    He might actually become an avid 2-railer!

Most O Scale 4 axle diesels, especially the early ones (1st & 2nd generation) up through maybe GP40, will most likely handle 42 inch radius, although high end detailed brass may not.   They will work fine with 40 and 50 foot cars.    I assume scale practice body mount couplers for better tracking.

On the other, even though many will go around 21 inch radius (42 inch diameter), especially with the toy-train type 2 motor mechanisms, they will probably not be able to pull cars with body mount couplers.    As the radius gets smaller, the fixed pilots swing out too far and the couplers can't mate.     I can run an old Weaver RS-3 (single motor drive) around 24 inch radius (48 diameter) easily by itself.   However the center line of the pilot is outside the rail head on the outside of the curve.   I can't couple anything to it.    The same is true for GP7/9/30/35/38/40.   F-units are a little more forgiving, I think they have a slight shorter wheel base.

If you use the 2 motor mechs, they will usually go around tighter radius, and if  you use truck mounted pilots as most 3-rail stuff has, you can run on these small radii and stay coupled.   

That's fine with me so long as all my posts are removed first.  I no longer post in that forum.

I appreciate not posting to a given forum.   I have noticed in the last few months, that a certain member generally jumps on my posts with a nasty comments and digs.   I have cut back posting as a result too.    I wonder if this guy goes after every one or is specifically cyber-stalking me.   

At any rate, if he keeps it up, he will the forum all to himself.

Gosh guys, I was just kind of excited about the fact that many of my two-rail diesels could run on my mezzanine layout. I had no wish to open a "can of worms". I don't post on this form very often unless I need a question answered. I think I will post even less often now! FWIW, My Weaver & Atlas U-boats now pull my train around around the loop with no trouble. I used an Atlas/Roco Ore car with a Kadee 805 coupler on one end. This give me sufficient ability to swing with the curves!

Tom

Please don't hesitate to post here or read the stuff.   Sometimes there are some strange comments made, but you can just ignore them.   Sometimes comments are made just to generate comments too!   iT gets pretty boring when everyone agrees sometimes!   Most of just try to be friendly though.

Tom,

Let me add my wishes too that you continue to post here.

Your mistyping of radius for diameter was really no problem. Most of us understood what you meant from the context of your post. I wish a few more here would take the effort to think a moment about what a poster is trying to say, rather than jumping all over him for a common mistake.

Your amazement about those engines going around those curves could only be the case if we were talking about 42" diameter - should have been obvious to all.

Please don't hesitate to join a conversation or ask a question here.

Jim

Please ignore the ill intended comments. As a side note, funny how some "old school" 2 railers complain about not enough offerings because of our small demographics and do everything they can to push people away from 2 rail o scale. Keep doing that, be mean, condescending and play country music in your YouTube videos, young people will join 2 rail like that in a heart beat.

FYI... I've been doing a lot of minimum radius testing lately. So far I can run F units, GP30, U-25, and an SW8 on 24"r pulling a 48' Gondola with body mount Kadee couplers. The GP30 is an Overland with a horizontal motor btw.

Thanks for that last comment Jonathan.  This is exactly the quandary I find myself trying to plan for a ~10x15 room.  I like 3-rail (for the tight curves) but long term my heart is in 2 rail for some degree of realism so I'm considering just going all out 2-rail now instead of starting 3 rail and converting. Atlas O track system and products, round the room maybe with peninsula(s), scheme is linear point to point copying the local prototype rural beaten down shortline. I'd sure be great to squeeze a return loop in here somewhere; only 4 axle diesels , short 4-10 car trains tops.

WAIT...WHAT??????  Can you rephrase that??????

Rick

Thre is no reason a 2-rail layout cannot have curves as sharp as a 3-rail layout.  If you want 27" diameter 2-rail track, all you have to do is make sure your rolling stock and locomotives have the same clearances at wheels and couplers as does the Lionel Scout.

While I believe that the pizza cutter wheels help reduce derailments when going around such sharp curves, there are 2-railers who will tell you a fine scale wheel will do anything any other wheel will do, so long as your trackwork is exact.  I think you will need the wider .172 wheels to make it around 2-rail O-27.

Opinion - I will never try it, and even my 40" box cars would not make it around such curves.  The wheels would strike the center sill and coupler draft gear, and the sideframes would hit the stirrup steps.  Plus, they would look like a Lionel Scout.  Maybe a string of ore cars and a Plymouth switcher?

Yesterday I took my MTH Proto 3/2 PRR K4 with scale wheels and ran it on my son's Lionel Fastrack 3 rail O-48 (24"r) layout. Even though it is listed as 31"r minimum it didn't have any trouble on the 24"r. This is just one example and performance will certainly vary from model to model. One of the things I like about MTH, Weaver, and 3rd Rail is that their are designed as 3 rail models first- so they will negotiate tighter curves. I know that this is taboo for most folks here on the 2R forum, but some people don't have space for broad 2R curves but would still like to have a 2R pike. These models are excellent for that purpose.

That is what I've been doing...my target locos so far are are Atlas, Weaver and MTH...RS-3, GP38, switchers-types. Weaver RS-3 is available in 2 and 3 rail with both listed as "O-31 curves". If the cars tolerate the curves I can deal with overhang...when I'm done overgrown-ROW scenicing one will never know the difference  . I eliminated 2-rail option last year after reading multiple forum comments but being partial to micro-layouts I always tend to think outside the box, push boundaries and seldom follow the herd; going 3 rail was bothering me so bad, I knew I'd always look at the layout and think "what if..."; I'm too old to be planning 2 or 3 layouts from now, THIS has to be it. The e-book Guide to Modern O Scale stated O-40ish/31 curves as usable but restricting for the most sharp curve needs only...so here I am back where I started. I know all about benefits of big sweeping curves but I just can't do it so I'll be starting at the other extreme playing some sort of 2-rail limbo...my cars, locos, track planned accordingly.