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 Minimum radius turns
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Author Previous Topic: Track Planning Software... Topic Next Topic: Wyoming coal/Chicago follow up  

dsteele
Engine Wiper

Posted - 09/18/2005 :  08:14:04 AM  Show Profile
I'm continuing to research layout design. The NMRA Layout Design SIG "Primer" is opening my eyes to a host of alternatives for planning/ design of my "next" layout.

I have a number of questions and will address each in a separate thread.

What's the minimum radius for turns, in HO, if I want to run the longer, 6-axel, most contemporary locomotives, like the AC4400s, SD70MACs, and achieve a reasonably proto look? That is, I'm not wanting the front/rear ends hanging over the tracks too much going into and coming out of turns.

Is this issue addressed in the NMRA Standards?

What I'm trying to find out is two things: what's the minimum radius, and how much actual space will I need to accomodate at least the minimum radius curves/turns.

Thanks!

Dennis

Country: USA | Posts: 400

RichBeau
Fireman



Posted - 09/18/2005 :  09:20:31 AM  Show Profile
Well Dennis you're getting into some good stuff but consider some of the older authorities out there on track planning (John Armstrong, Tony Koester, etc) for a basic understanding of design considerations.

If I remember correctly minimum radius turns for HO 6-axle motive power is 32" with probably 2-1/2" centerlines but check the spec. Yes, they are addressed in the NMRA Standards. But this is minimum and most of the big stuff really doesn't look very good until you get up around 36". In fact the Free-mo spec uses 42" minimum radii and the big power pulling autoracks look very good on those turns.

--Rich



Country: USA | Posts: 2748 Go to Top of Page

RichBeau
Fireman



Posted - 09/18/2005 :  09:20:31 AM  Show Profile
Well Dennis you're getting into some good stuff but consider some of the older authorities out there on track planning (John Armstrong, Tony Koester, etc) for a basic understanding of design considerations.

If I remember correctly minimum radius turns for HO 6-axle motive power is 32" with probably 2-1/2" centerlines but check the spec. Yes, they are addressed in the NMRA Standards. But this is minimum and most of the big stuff really doesn't look very good until you get up around 36". In fact the Free-mo spec uses 42" minimum radii and the big power pulling autoracks look very good on those turns.

--Rich



Country: USA | Posts: 2748 Go to Top of Page

On30fan
Crew Chief



Posted - 09/18/2005 :  11:41:41 AM  Show Profile
I'll agree with Rich here. I'm in the planning stages of a P87 layout, and I've settled on a min rad of 42" and #8 turnouts and I'm not even planning on using anything larger than a GP38-2 or a 60' car.

Hidden return loops and the like could be tightened down some but the bigger the visible track radius is the better (to a limit).

For a standard HO layout I'd probably go with about a 36" rad. A loop this size will be 72" (36+36) across, but there will be no room outside it for any scenery. Add 3" to your min rad to give you some scenery and safety room (78")


Cheers,
Steve
San Juan Lumber Company
Niagara Frontier Traction Company

Country: USA | Posts: 506 Go to Top of Page

On30fan
Crew Chief



Posted - 09/18/2005 :  11:41:41 AM  Show Profile
I'll agree with Rich here. I'm in the planning stages of a P87 layout, and I've settled on a min rad of 42" and #8 turnouts and I'm not even planning on using anything larger than a GP38-2 or a 60' car.

Hidden return loops and the like could be tightened down some but the bigger the visible track radius is the better (to a limit).

For a standard HO layout I'd probably go with about a 36" rad. A loop this size will be 72" (36+36) across, but there will be no room outside it for any scenery. Add 3" to your min rad to give you some scenery and safety room (78")


Cheers,
Steve
San Juan Lumber Company
Niagara Frontier Traction Company

Country: USA | Posts: 506 Go to Top of Page

dsteele
Engine Wiper

Posted - 09/18/2005 :  6:23:55 PM  Show Profile
Okey dokey. Will include your info as I continue to research the whole layout design area. Lotsa fun!!

Dennis



Country: USA | Posts: 400 Go to Top of Page

dsteele
Engine Wiper

Posted - 09/18/2005 :  6:23:55 PM  Show Profile
Okey dokey. Will include your info as I continue to research the whole layout design area. Lotsa fun!!

Dennis



Country: USA | Posts: 400 Go to Top of Page

brakie
Fireman

Premium Member


Posted - 09/18/2005 :  8:15:59 PM  Show Profile
For long wheel base engines such as the SD90MAC,
AC4400s,SD70MACs,SD75s SD40-2s and other long wheel base units I would say nothing less then a 32" curve.
Oddly I don't think any of John's books will work in the case nor will Tony's wisdom..I suggest asking modelers that use these units for first hand information..



Country: USA | Posts: 6979 Go to Top of Page

brakie
Fireman

Premium Member


Posted - 09/18/2005 :  8:15:59 PM  Show Profile
For long wheel base engines such as the SD90MAC,
AC4400s,SD70MACs,SD75s SD40-2s and other long wheel base units I would say nothing less then a 32" curve.
Oddly I don't think any of John's books will work in the case nor will Tony's wisdom..I suggest asking modelers that use these units for first hand information..



Country: USA | Posts: 6979 Go to Top of Page

jrbernier
New Hire

Posted - 10/04/2005 :  2:36:13 PM  Show Profile
You can get these big engines around curves under 30" radius, but taking an 'train' around sharp curves is asking for trouble. Ou club layout has minimum of 36" radius, and we can run long trains behind 3-4 of these engines. That 36" radius curve is in the helix, and hidden.

Jim Bernier



Country: USA | Posts: 15 Go to Top of Page

jrbernier
New Hire

Posted - 10/04/2005 :  2:36:13 PM  Show Profile
You can get these big engines around curves under 30" radius, but taking an 'train' around sharp curves is asking for trouble. Ou club layout has minimum of 36" radius, and we can run long trains behind 3-4 of these engines. That 36" radius curve is in the helix, and hidden.

Jim Bernier



Country: USA | Posts: 15 Go to Top of Page

teejay
Fireman



Posted - 10/04/2005 :  3:15:37 PM  Show Profile
I agree with most of the others that something in the vicinity of 36" radius is necessary to avoid the ' toy look ' of smaller radii . When I was running into space problems , I cut a large piece of plywood using a 36" radius , about 3" wide and 4 or 5 feet long to use as a template . This allowed me to preconfigure the shape of the layout and get the right radius for all the curves . If the template didn't fit , I had to change something . In that way , I didn't run into any surprises . You can make several templates , both curved and straight and clamp them together to help plan the eventual shape . For me ,this method made it easier than trying to rely on just a drawing .
The templates can be used as subroadbed during actual construction .
Terry



Edited by - teejay on 10/04/2005 3:16:27 PM

Country: Canada | Posts: 5853 Go to Top of Page

teejay
Fireman



Posted - 10/04/2005 :  3:15:37 PM  Show Profile
I agree with most of the others that something in the vicinity of 36" radius is necessary to avoid the ' toy look ' of smaller radii . When I was running into space problems , I cut a large piece of plywood using a 36" radius , about 3" wide and 4 or 5 feet long to use as a template . This allowed me to preconfigure the shape of the layout and get the right radius for all the curves . If the template didn't fit , I had to change something . In that way , I didn't run into any surprises . You can make several templates , both curved and straight and clamp them together to help plan the eventual shape . For me ,this method made it easier than trying to rely on just a drawing .
The templates can be used as subroadbed during actual construction .
Terry



Edited by - teejay on 10/04/2005 3:16:27 PM

Country: Canada | Posts: 5853 Go to Top of Page

dsteele
Engine Wiper

Posted - 10/05/2005 :  08:39:04 AM  Show Profile
Thanks for the info, guys. Much appreciated. Terry, the template idea is really neat!

Dennis



Country: USA | Posts: 400 Go to Top of Page

dsteele
Engine Wiper

Posted - 10/05/2005 :  08:39:04 AM  Show Profile
Thanks for the info, guys. Much appreciated. Terry, the template idea is really neat!

Dennis



Country: USA | Posts: 400 Go to Top of Page
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