7.5 VS #5 Atlas Turnouts

You would probably be better off waiting to hear from somebody who actually uses those #5 switches, but I believe, given the equipment your planning to use, they should be fine as long as you don't try to run trains through them at 80-100 MPH.  Even prototype trains slow their trains down when running through tight (#5 vs #7.5) switches.

Chuck

A #5 is around a 50” radius on the diverging leg.

Yes, ...

wait. What?

I will not run any steam larger than a 4-8-4,  OK

(I would like to run larger)     wait, you will or you won't?

The larger articulated steam runs better on curves than the rigid framed ones. So the answer varies.

Ie= Allegheny vs. Texas type

As a point of continuing education, here's a little something from Page 26 in Ken Hoganson's Track Planning Book.

This diagram references Atlas switches, but a numbered switch is a numbered switch. The dimensions will be the same with all numbered switches, no matter who makes it.

That's good to know,thank you Rich.

Mark in Oregon

@Classy Woods, LLC posted:

Awhile back I posted a question regarding Atlas radii and what locomotives can navigate various radiuses.  I took the advice of a responder and downloaded the free version of AnyRail.  I highly recommend this!  The free version allows you to layout approximately 50 pieces of track.  It is very simple to use.  I may buy it the price is right.  Using grids, you are able to determine what fits your space.  With my room being 15' wide and 17' long I was amazed at what I could do with Atlas O 54" radii.  Of course, the caveat here is that I used #5 switches.   I will not run any steam larger than a 4-8-4, (I would like to run larger) and the largest diesel a SD40.  Will a #5 switch handle this?

A 4-8-4 or an SD40/ Sd40-2 Diesel should have not problems with an 054 and an  072 or approximately a #4 switch. A #5.5 is definitely a  high speed switch and eats up a lot of "Real Estate". What type of cars are you running? Scale Autoracks, scale pax cars, scale 86' autoparts boxcars?  IF non of those behemoths then 054/072 switches are more than plenty for you.

Thanks everyone!  Rich very informative.  Engineer Joe, I did not mean to confuse I meant I wished I could run larger locos, but I know the score it's okay, so I am l setting my goals at SD40s and 4-8-4 max size.  If I ever move and have more room than I can rethink things.  At this time my largest piece of rolling stock is an Atlas Master 60' double door auto parts boxcar.   

The larger steam locomotives may take issue with a #5 turnout as the "point radius" is around 48-50" as I recall while the #7.5 is over 80".

As for general curve radius , check the manufacturer specs on the engines you're looking at. For example, I looked at adding a 2-rail 3rd Rail H1 Northern to my collection. It requires a 56" minimum radius. But my MTH 2-rail Big Boy can make it through a 36" radius curve because the structure contains compromises to support the 3-rail version, plus its smaller drivers and driver wheelbase. By the way, it had no issues with the #5 Ross turnouts on the club layout, but made it abundantly clear it wasn't going through the one #4 leading out of the Harbor District.

Once your layout is pretty far underway, you're committed to the equipment limits set by the curve radius. I'm designing right now and did manage to pull off a 57" radius on the outer loop, so if/when I get a larger 2-rail locomotive, I'll be able to run it at home.

@AGHRMatt posted:

1. The larger steam locomotives may take issue with a #5 turnout as the "point radius" is around 48-50" as I recall while the #7.5 is over 80".

2. ...For example, I looked at adding a 2-rail 3rd Rail H1 Northern to my collection. It requires a 56" minimum radius.

3. Once your layout is pretty far underway, you're committed to the equipment limits set by the curve radius. I'm designing right now and did manage to pull off a 57" radius on the outer loop, so if/when I get a larger 2-rail locomotive, I'll be able to run it at home.

Hello Matt

1. Yeah, I personally think a #5 is pretty tight...

2. "H-1 Northern": would that be one of those awesome C&NW 4-8-4s? 😳😁

3. That's good planning. I look forward to someday seeing what you've come up with. 👍

Mark in Oregon

My original double mainline used all Atlas #5 switches and I had no issues. I read some posts and thought about bigger things. I then installed several #7.5 switches and problems started. I believe the longer frogs started giving trouble with some of my steam engines. They didn't stall at first. They did act up. They would jerk as they crossed over the dead frogs.

As time went on some engine got worse. Maybe because I run with the smoke and sound on? The extra current draw seemed to cause issues. I had ballasted my track for the first time so some of it was from glue residue and crud build up. I had to install extra wipers and power points on some of my conversions. I spent time cleaning rails for the first time in years.

The obvious cure would be to power the frogs. I just lost interest and haven't gone back yet. I remember the happy days when things ran well.

My layout has 7.5 Atlas turnouts on my four track mainline and I use Atlas #5's in yard areas.  Both of these switches and in fact all model RR turnouts are much sharper than the turnouts on real RR's.  Will someone please correct me if my memory is faulty, but I remember that on real RR's there is no 7.5 turnout, and that Atlas selected this particular turnout size so that their track planning software would result in a four inch side to side track spacing on a two track parallel mainline.  I model NYC, and I remember that the RR used No. 22 through No. 26 high speed turnouts on the mainline, and that trains reduced speed if they were required to cross over.

In two rail O scale, the old "rule of thumb" was that any US Hobbies locomotive was designed to traverse a turnout with a minimum 60-inch diverging radius.  Most large drivered Northerns and five coupled locomotives are limited re where they can operate.  Most articulateds are more forgiving due to their shorter rigid wheelbase, but large articulateds might have problems as they overhang on tight radius curvature, and the largest might have clearance issues with another large engine or long cars on an adjacent track while on curvature.

I operated Overland B&O 2-10-2s and a Sunset B&O 4-8-2 T4 (big mountain), along with a number of Mikes and pacifics from a couple different makers on Atlas 5 without any issue other than having to keep the engine attached to the "further back" hole in the drawbar so the tender does not strike the cab roof.  But they look alot better on  #6.  The 7.5 look great but offer nothing  operationally (for me) than a #6.

@astarr posted:

But they look alot better on  #6.  The 7.5 look great but offer nothing  operationally (for me) than a #6.

Funny now that you mention it; the #6 has been a mainstay of the Atlas HO line for years. Wonder why they opted to "skip" it in O scale? 🤔

Mark in Oregon

@Classy Woods, LLC posted:

Awhile back I posted a question regarding Atlas radii and what locomotives can navigate various radiuses.  I took the advice of a responder and downloaded the free version of AnyRail.  I highly recommend this!  The free version allows you to layout approximately 50 pieces of track.  It is very simple to use.  I may buy it the price is right.  Using grids, you are able to determine what fits your space.  With my room being 15' wide and 17' long I was amazed at what I could do with Atlas O 54" radii.  Of course, the caveat here is that I used #5 switches.   I will not run any steam larger than a 4-8-4, (I would like to run larger) and the largest diesel a SD40.  Will a #5 switch handle this?

Mike,  I run number 4,5,6,7.5,8 & 10 turnouts.  From my experience I would suggest to use the highest number that you can squeeze in.  It sounds like you are planning a rebuild in the not too distant future.  I would recommend to hold off spending money on small turnouts that you may well wish you did not buy.

Also, on any RR of any size another thing to consider.  Start any diverging route before the tangent.  Get your right of ways separated before the degrees of curvature are completed.  Why use up tangent length to get a siding included, that will only provide  short sidings?

I use Signature Switches for my curved turnouts.  Smooth operation, American made, custom radii available, Atlas compatible, code .148" or .125".

John Dunn who posts on this board has a very nice 2 rail all Atlas track RR in a similar size space which you are using.  Check out his work.

@Strummer posted:

Hello Matt

1. Yeah, I personally think a #5 is pretty tight...

2. "H-1 Northern": would that be one of those awesome C&NW 4-8-4s? 😳😁

3. That's good planning. I look forward to someday seeing what you've come up with. 👍

Mark in Oregon

Hi Mark.

Yes, the #5 is tight for large rigid steam, but for diesels they're OK.

The H1 is definitely the CNW. I bought the 3-rail version to run at the club on occasion and because I figured it would be unlikely that I'd be able to build with a consistent 60" radius.

On the planning, here's what I'm working on right now. The overall size is 30' by 11' covering the third bay in my garage. I decided to make it simple for ease of doing a build. I'm trying to figure out where to put in an access gate to the interior, though the layout is designed for remote control operations. The curves at the right are 52.5" Radius (O-105) and 57" Radius (O-114); the ones on the left are 58.6" Radius (O-117) and 63" Radius (O-126). The sweeping curves are larger (the ones in the foreground are huge). Turnouts on the main are ScaleTrax #6; the interior branch is all 36" radius designed for short freight cars and four-axle diesels.

Matt

Thanks. I'm not familiar with "ScaleTrax"; will have to look into that.

I remember "Trains" magazine did a cover story in 1970(?) about the C&NW H. I was quite taken with it...and I guess I still am. 🙂

After I posted my question to you, I found some YouTube videos of yours so have seen your H in action: my second favorite Northern, after the SP&S class. 😊

Thanks again for your response.

Mark in Oregon

@Strummer posted:

Matt

Thanks. I'm not familiar with "ScaleTrax"; will have to look into that.

...

After I posted my question to you, I found some YouTube videos of yours so have seen your H in action: my second favorite Northern, after the SP&S class. 😊

Thanks again for your response.

Mark in Oregon

ScaleTrax was/is an MTH offering featuring Code 192 rail and a thin center rail. The down sides were limited offerings/availability and the tie spacing, which seems to match concrete commuter ties rather than wood freight ties. It's insulated so you can set it up to run 2-rail equipment if you're electrically inclined. It also flexes easily. Rich Battista did a layout with it. The H1 video made it onto 3rd Rail's site and I think they have a couple left in 2-rail. I saw one on eBay a couple of months ago.

If I remember correctly, Atlas' choice of #5 and #7.5 for switches had something to do with the planned geometry of its pre-formed curve pieces and/or the expected distance between parallel pieces of tangent track.

Chuck

Atlas #5 & #7.5 turnouts produce a 4.5" C/L.

Atlas curve radii are in 4.5" centers.

If you remove 1 11/16" off each diverging leg of a pair of 7.5 Atlas turnouts for a single cross over you will be able to have a traditional 4"  (16 scale feet)  ROW C/L.