Minimum Radius for MTH Diesels/Atlas Passenger

You didn't say 2-rail or 3-rail. The 3-rail MTH Diesels will handle 21" Radius (O-42) and the 3-rail Atlas Cal-Zeph cars should be run on at least 36" radius (O-72). For purposes of better appearance, though, since you have 10 feet of width to play with, you can do 54" radius (O-108) with six inches of clearance on either edge which will also give you better operation by reducing the drag of the train going through the curves.

In a 2-rail context, you should be able to run everything on 48" radius, but will get better appearance and operation on 54" which will also allow you to run some small-to-medium steam as well. MTH scale-wheeled diesels will all make it through 36" radius provided the track is even and kink-free, but 42" is better.

Sorry yes it's 2-rail.  

Thanks!

AGHRMatt posted:

You didn't say 2-rail or 3-rail. The 3-rail MTH Diesels will handle 21" Radius (O-42) and the 3-rail Atlas Cal-Zeph cars should be run on at least 36" radius (O-72). For purposes of better appearance, though, since you have 10 feet of width to play with, you can do 54" radius (O-108) with six inches of clearance on either edge which will also give you better operation by reducing the drag of the train going through the curves.

In a 2-rail context, you should be able to run everything on 48" radius, but will get better appearance and operation on 54" which will also allow you to run some small-to-medium steam as well. MTH scale-wheeled diesels will all make it through 36" radius provided the track is even and kink-free, but 42" is better.

Matt thanks for this response.  

What does it take to run something like the big MTH steam?

I'm thinking of a major project where I build an elevated 6-8 ft tall platform in the barn perhaps being able to stretch the width for the layout out to 12 ft.  I know this is nice to have.  

Finally got the barn done and I realized I can start thinking trains.  

It varies depending on the driver wheelbase. My scale-wheeled Big Boy and Blue Goose Hudson can both handle 36" radius (O-72) on a hidden curve at the club layout because of their hi-rail heritage (basically they're built as hi-rail locomotives with scale wheels and flanges on all the drivers). The irony is that they have problems on a 50" radius curve (O-100) because of kinks and uneven rail height (causes the engine to ride on the pickup roller). MTH uses one-piece side rods and the drivers don't have a lot of side play, so a big Northern would require a larger curve than a Hudson or Mikado. A Texas requires 72" radius (O-144) because of the driver wheelbase (I was so tempted to buy one of those) and full set of flanges. The problem with the MTH steam is that there's not a lot of data from owners as to what they can squeeze through. I found out about the Big Boy from Mike Pitogo (ran one around his Christmas Tree) and the Hudson from a former forum member who had one from the earlier release. I go back and forth about buying another unshrouded ATSF Hudson with scale wheels and selling my Hi-rail version.

I like the flexibility I get with the MTH scale-wheeled engines and those are the only diesels I buy now. I can run most of them reliably at the club (long-wheelbase six-axle diesels have issues because of uneven spots in the track, which we're fixing) and the scale-wheeled rolling stock handles the layout well. I've been looking at selling off my hi-rail engines with a few exceptions (never thought I'd be going there).

I always get in trouble with this comment.  For mainline O Scale you really should have 72" radius, which requires more than 12' for a circle.  Otherwise, long passenger cars need lots of space between them with oversize diaphragms, etc., and steamers need the tender spaced out for a flying leap by overzealous firemen.

Incoming - er, Opinion.

bob2 posted:

I always get in trouble with this comment.  For mainline O Scale you really should have 72" radius, which requires more than 12' for a circle.  Otherwise, long passenger cars need lots of space between them with oversize diaphragms, etc., and steamers need the tender spaced out for a flying leap by overzealous firemen.

Incoming - er, Opinion.

I actually agree, and if I had the space I'd build to 72" or larger radius even with 3-rail track (I think about building outdoors quite a bit and you KNOW there will be broad curves). Scale sized equipment looks better on larger curves, no matter how many rails it may be rolling on.

AGHRMatt posted:

A Texas requires 72" radius (O-144) because of the driver wheelbase (I was so tempted to buy one of those) and full set of flanges. The problem with the MTH steam is that there's not a lot of data from owners as to what they can squeeze through.

That MTH Texas type likes big smooth curves. Mine will hop off the rails on curve's rails that aren't smooth (bumps).

My layout was mainly 60" radius on it's plans. That started out too small and ended up even smaller. I can get my one upgraded Allegheny to tip a little on the tight curves! I need to rework the drawbar. I then planned to make the outer loop 72" and that fell short too. I drew it out and added easements. Somehow it's tight in spots? I'm starting to think I should have went for 84 or 96"!

 Some of my yard tracks ended up with a very tight radius entering into them. My MTH diesels never give me any problems. Now those darn big steamers are another story!  You just have to set the yard limit speeds nice and low under 25, that's all. The articulids are your friends!

Okay, 72 inch radius would be great.   But most or many of us do not have the space.    Personally I wanted an "operations based" layout meaning trains doing something with switching and transfers and some secondary passenger trains.    I could never be satisfied with a big loop.   My basement would let me do a 10 ft radius oval.   But that just does not appeal to me.    I settled on 52 inch radius and can run everything I have reliably and I have a trackplan that hosts up 8 operators in various jobs.   so the big compromise on radius gave me the kind of layout I wanted.

I have been in 2-rail O scale since about 1976-78.   My original layout was alll handlaid track and 48 inch radius.   I learned back then that most steamers up to a mikado will run on those curves and all diesels I had access to.   Also I had a string of Walthers full length passenger cars and they were fine on the curves too.   

An interesting tidbit, brass from golden era of the 70s through about 2000 at least almost always had sprung drivers that worked.    6-axle diesels actually adjusted to rough track and stayed on the rails.    Steamers did the same.   They could take little bumps and one wheel at a time would go up or down as needed.   

Now the descendents of the 3 rail market have ridgid frames on the 6-axle diesels.   They are actually less forgiving and less prototypical (in that regard) than the old stuff.

prrjim posted:

Okay, 72 inch radius would be great.   But most or many of us do not have the space.    Personally I wanted an "operations based" layout meaning trains doing something with switching and transfers and some secondary passenger trains.    I could never be satisfied with a big loop.   My basement would let me do a 10 ft radius oval.   But that just does not appeal to me.    I settled on 52 inch radius and can run everything I have reliably and I have a trackplan that hosts up 8 operators in various jobs.   so the big compromise on radius gave me the kind of layout I wanted.

I have been in 2-rail O scale since about 1976-78.   My original layout was alll handlaid track and 48 inch radius.   I learned back then that most steamers up to a mikado will run on those curves and all diesels I had access to.   Also I had a string of Walthers full length passenger cars and they were fine on the curves too.   

An interesting tidbit, brass from golden era of the 70s through about 2000 at least almost always had sprung drivers that worked.    6-axle diesels actually adjusted to rough track and stayed on the rails.    Steamers did the same.   They could take little bumps and one wheel at a time would go up or down as needed.   

Now the descendents of the 3 rail market have ridgid frames on the 6-axle diesels.   They are actually less forgiving and less prototypical (in that regard) than the old stuff.

 

 

Definitely true. My favorite trucks for rolling stock are Weaver plastic because they're equalized and the wheels stay on the rail head. I have some Atlas cars that are temperamental and I take off the truck crossbars to get them to equalize a bit (a couple still derail). I don't run most of my six-axle diesels at the club because we're getting thermal expansion/contraction and my longer-wheelbase six-axle diesels are finding the high/low spots. For some strange reason, I can't bring myself to install hi-rail wheels (thanks a lot, guys), but my Geeps and C40-8's seem to be doing fine. If I were smart (well, so much for that), I'd chuck the center axles into a lathe and cut off the flanges and take a few thousandths off the diameter, but that somehow seems wrong.

My only word of advice would be to go as large as you can with your curves.  You say you have 12'x50', allowing 6" clearance on each side would give you a 66" radius (11' diameter), not too shabby (with the space I currently have all I can get in would be an 11' diameter circle if I went as large as possible). 

This would give you an 11'x49' loop if that's all you wanted, but given the space you have you could start curving and bending the design into something that would be appealing/interesting and still allow a long run for your passenger trains.

O scaler Terry Terrance has producing a O scale 2 rail promotional video to be shown at the NMRA National.  Five prototype operation theme Mid Atlantic O gauge railroads are featured (along with a P48 one) - all with minimum radius curves under 62" running good sized (appropriate to the prototype)  steam power and  full length passenger cars.  Terry chose the railroads to showcase what is possible in O scale today with available equipment and creative design - even in relatively confined spaces.  Assertions that O scale equipment requires 72" minimum radius to look good and operate reliably are just blatantly false, and the kind of old bad advice that serves to dissuade some from considering O scale 2 rail.   The video will be available for internet viewing in a day or so.  When it is up I'll post the link in a new thread.

For retirement I built a new house (mostly single story) with a good sized basement designed with model railroading in mind.  If all I wanted to do was build a loop running railroad I could have gone with very wide radius curves.  But if I used 72+" radius curves I would not be able to fold the railroad down the middle of the room - essential if I wanted to capture the look and feel of Pennsy's high density mountain railroading.  I knew from earlier layouts that my large PRR power (including the rigid frame Q2 4-4-6-4) could run around 50" curves.  I agree that wider curves look better - but often it comes at the price of less operational interest in a given space.  Even with a big basement compromises need to be made.  Before starting construction I used 3rd PlanIt CAD software to iteratively design the track plan - trading off factors such as aisle width, layout depth, minimum radius, gradient, route length, town/industry sites, and operation features like maximum train length.  I eventually settled on a 62" minimum radius and 3 7/8" track centers (3 /1/2 on tangents), but in quite a few  places I went wider.  For hidden staging  I went down to 62" (prior layout used 50"r in staging).  For those thinking about building an O scale 2 rail layout of any size, consider it a long term commitment worthy of in-depth planning before diving in.  My recommendation to  anyone considering building a model railroad is to first read  John Armstrong's Creative Layout Design for Realistic Operation.    You'll still set your own standards and make the design trade-offs - but at a minimum John will provide you  food for thought based on decades of experience. 

Below is a photo of action on my 62" radius Horseshoe Curve - despite the tight curve I'm a happy camper. 

Blatantly false is a bit strong, especially since I said" opinion".  I have curves of 60",64", 70", and 74".  The 80' and 85' cars are closely enough coupled that they do not operate on the lower loops.  My articulated coach has more space than the prototype, and cannot get around the 70" loop.

Here is another opinion: I have a lot of locomotives that are unsprung, including a few Mikados and some E-7 Diesels.  I also have poorly laid track with dramatic superelevation.  The only time I have any trouble is when axle holes are bored inaccurately.  They pull the same as sprung locomotives, and look just as good to my eyes.

Still opinion.

Well things are looking even better.

The boss thinks building a second floor in the steel building (The Barn) measuring 30 x 50 is a fine idea.

This of course will take some time but will give us a full unimpeded 1500 sq ft of layout space.

I'm excited!  96" radius  minimum. 

I plan to start on the project pretty quick. Lots of time though to discuss layout ideas.  I have a dog-eared copy of Track Planning for Realistic Operation from my previous two layouts.

Here we go!

Chuck

It's all opinion!    Some of it may even be based on experience.

Speaking of dog-eared - my dream layout is a four track multi-level dog bone shaped layout.  I would flatten the dog bone so it looked a little like a Mickey Mouse hat, and put couches in the central area. 

As it is now, I have a four track loop in a 14x 27' building.  Adequate, but not exciting.