# SD-45s and Curves



## John J (Dec 29, 2007)

What is the minamum curve a SD-45 can make?

What about a SD 40 -2 ? 

I am making a maintainence yard and need to know how small a curve I can make.

I have 

4 SD-45s 

2 SD-40-2

4 NW-2 with three calfs 

1 Aristo F A& B unit.

The longest cars I have are 

8 Aristo Streamliners

and 3 sets of the USA 5 car articulated well cars. 

JJ


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## Greg Elmassian (Jan 3, 2008)

JJ, I would not try under 8 foot diameter. Since all 3 axle blocks on Aristo locos are the same, this is the limiting factor. The USAT can usually go a bit tighter, thanks to the swiveling axle. You are also going to have troubles under 8 foot with the streamliners, and don't forget S curves on long cars. 

Question: with all the space you have, why would you not spread out a little? 

Greg


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## NTCGRR (Jan 2, 2008)

Go for 10 dia min everywhere, then your body mounts won't be a problem.


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## Greg Elmassian (Jan 3, 2008)

DCC will help too!


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## John J (Dec 29, 2007)

I am building a mound of dirt about 2 ft high. On this mound I am building a maintainence yard with car barns. If you have every been to Durango. The Durango and Silverton has a track that goes around the parimiter of the yard to turn trains around. I am thiniking of a track around the out side edges. 

My first thought was one building but it would have to bey 4 ft x 32 ft to get it all in. The next problem was Where to put it so you would not have to walk around it. So I thought of a mound with buildings on it and a girder bridge to it. That way it can be part of the layout and you can step over the bridge. 

JJ


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## Greg Elmassian (Jan 3, 2008)

You can build something long without tight curves, is the minimum curve related to the approach to the yard? 

Greg


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## John J (Dec 29, 2007)

Posted By Greg Elmassian on 24 Apr 2011 02:13 PM 
You can build something long without tight curves, is the minimum curve related to the approach to the yard? 

Greg 
In the post right above I said I was thinking of a track around the pramimiter of the yard. I

I may end up with a 20 ft diamater track 

JJ


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## Greg Elmassian (Jan 3, 2008)

That's great, and more of the diameter I thought you had. So where is the minimum curve for the SD45 coming in? in the 4 foot wide part? If you want to turn locos, maybe a hand-operated turntable? 

Greg


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## mgilger (Feb 22, 2008)

JJ 

When I first started my RR, I planned on running no bigger than 4 axle engines, so I thought 6.5 foot curves would work. Well as the years passed, so did my interest in running bigger trains and that brought a couple of SD45 to the layout. They ran just fine on the 6.5 foot curves, but I had to weight down the trailing car so it did not get pulled off the track. I ran this way for another 3 years and then decided to pick up a couple SD40-2. Well the SD-40-2 would also make it around the 6.5 foot curves, but no way would the trailing car stay on the track, no matter how much weight I put in. I was forced to change all my curves to 12-16 foot, which I did back in 2008. Best move I ever made. 


The point of the story, I guess, is that even though your current plans might make sense,plan for the future. If your layout will support wider, then start off wider. It's a big pain to change an existing RR after it's been down a few years. 

Mark
*http://mmg-garden-rr.webs.com*


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## John J (Dec 29, 2007)

Posted By Greg Elmassian on 24 Apr 2011 05:39 PM 
That's great, and more of the diameter I thought you had. So where is the minimum curve for the SD45 coming in? in the 4 foot wide part? If you want to turn locos, maybe a hand-operated turntable? 

Greg The Minimum curve question was for the curve around the outside of the Maintenance yard. The whole yard is going to be elevated. I thought of a turntable for the engine shop but no the car shop.

What I am thinking of is a Transfer table for the engine shop. And that is what lead to the track around the outside of the area. 

My ordinal thought of 4 foot wide may not " LOOK " right. ( using the 10 ft rule) So there may be several narrower buildings.

This is still in the planing stages cause I wanted to have Free Discussion ( quote from Fatman and Little boy.) 

The free discussion was very very successful. I got some great Ideas. 

The discussion is not closed....If you have any more ideas let me know

JJ


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## Greg Elmassian (Jan 3, 2008)

Another idea JJ... if you need to turn locos, then another idea is to put in a wye in the yard... of course one leg of the wye would be "wider" than your 4 feet, but it's another inexpensive (and cool looking) way to turn a loco. You might be able to find a place for the "tail" a lot easier than a curve. 

In light of now understanding better what you want, you can "horse" a SD around a 6.5 foot diameter curve if there's no cars attached, just the loco... it's not pretty, but it can be done. 

Regards, Greg


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## eheading (Jan 5, 2008)

Actually, if you REALLY want to have the SD45 going around the 6.5' curve, I believe you can do it with a trailing car if you do two things; remove the centering spring from the coupler on the engine, widen the cutout in the engine for the coupler.

Ed


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## Ted Doskaris (Oct 7, 2008)

JJ,

I fully agree with Marty about using 10 foot diameter track as a minimum.

Are you using body mount couplers or truck mount couplers on the cars?

Are you using swinging type couplers on your USAT 3 axle locos?

Whilst the USAT 3 axle locos have a clever design for the end axles to pivot, they chose to mount the two axle portion of the truck with is pivot point closer to fuel tank. 








This results in the loco's pilots to project (overhang) more so on the outside rail on curved track. 








Thus, using a typically fixed mounted Kadee type coupler assembly on these locos, the loco will tend to pull an attached car off the track for even 8 foot diameter track.

I discovered this and wrote about it for the USAT SD70s I retrofitted with custom adapted, swinging Kadee coupler box assemblies.
Doing this, I was able to get the SD70 to work on 8 foot diameter curve track when pulling a train with body mount car couplers.










See article,"*USAT SD70MAC experiences*", hosted for me by Greg E. on his web site.

-Ted


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## Jerry McColgan (Feb 8, 2008)

Hi JJ,

Perhaps the real question is not whether your locos can handle an 8' curve (I suspect they could unless you have body mount couplers) as much as whether you are considering 8' (R3) turnouts as well?

I tend to agree with Marty and Ted. You might be able to get by with 8' curves and 8' turnouts but I suspect you would end up much happier with 10' curves and turnouts. 

I also think a lot has to do with the mix of brands of locos and turnouts. LGB locos (which you did not mention) tend to do a lot better with 8' curves and LGB turnouts than other brands. Even my new 10' Aristo turnouts were a bit problematical until I got everything perfectly aligned and removed any track insulators that created slight gaps between the rails as rolling stock entered the curves.

Two axle streamliners are probably better than 3 axle heavyweights when it comes to handling sharp curves but my older Aristo Streamliners don't like being backed up much (they do not have body mount couplers). 

Perhaps you have a particular need for sharper curves and it is the space available that is behind your question. A lot of times I get by with sharp curves and sharp turnouts because I don't have room for wider curves and turnouts. Usually I can get everything to work out.

Another factor is how many 8' curve sections are involved. Just about anything will go through one or two 8' curves but when the curve is 90 degrees or more or an "S" curve is involved everything can change.

When I redid my Caboose Layout I intentionally replaced all the 8' curves and R3 turnouts with a minimum of 10' because I am running primarily non-LGB trains on it. There was just too much non-LGB stuff that did not like running on 8' curves and turnouts.

You are not just building for what you now own but also for what you might own in the future.

Good luck,

Jerry


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## Dan Pierce (Jan 2, 2008)

Jerry, for storing the SD-45, you can use R1 switches. These engines will go through a 4 foot diameter circle, they just can not be connected to anything. 

SO, if you want to store them in a yard singularly, this will work. 

I have run 4 different SD-45's on my indoor layout which is all LGB R1 curves. No derailments. I even built a tow bar and can pull freight cars with no problem!!! 

Note that the other end of the tow bar is attached to a freight truck. 



http://1stclass.mylargescale.com/danpierce/SD45/SD45_2foot_radius.jpe


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## Jerry McColgan (Feb 8, 2008)

Posted By Dan Pierce on 25 Apr 2011 12:38 PM 
Jerry, for storing the SD-45, you can use R1 switches. These engines will go through a 4 foot diameter circle, they just can not be connected to anything. 

SO, if you want to store them in a yard singularly, this will work. 

I have run 4 different SD-45's on my indoor layout which is all LGB R1 curves. No derailments. I even built a tow bar and can pull freight cars with no problem!!! 

Note that the other end of the tow bar is attached to a freight truck. 



http://1stclass.mylargescale.com/danpierce/SD45/SD45_2foot_radius.jpe 




Hi Dan,

You have a valid point in that it is often the locomotive coupling that determines the minimum radius curve the locomotive can negotiate. In many cases the coupler used has a direct bearing on the curve capability. The Fa-1 is a good example in that the rear of a FA-1 can handle a tighter curve than the nose can.

Unfortunately recent locomotive designs often do not include hook and link capability and seem to favor wider curves with limited capability for tight curves.

There is also a limited compatibility between some loco models and turnouts made by different manufacturers. Like you I have a LOT of LGB R1 turnouts on my indoor layouts (I think there are over 50 of them).

Your tow bar concept is interesting. Do you have a topic with more details about it?

Jerry


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## aceinspp (Jan 2, 2008)

Well You got one good SD45 loco if you can get it to operate around a 4 ft dia curve. I got to see this. Later RJD


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## Dan Pierce (Jan 2, 2008)

That was 3 different SD-45's that go through 4 foot diameter curves, not just 1!!


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## pimanjc (Jan 2, 2008)

JJ,
I certainly enjoy having the Wye coming out of my train shed and onto the outer mainline from two directions. I can enter the mainline going either direction or reverse directions.
All of my curves are 8ft diameter or larger. The SD45s or Aristo heavyweights have no problems. I haven't tried a USA streamliner on the 8ft curves yet. 
JimC.


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## Ron Hill (Sep 25, 2008)

My Aristo Dash 9 does well on my 8' curves. The only problem I have found is that the center axle on the Dash 9 will derail if the curve is out of level. The Aristo trucks are one piece, two of three axle pivot but if the stationary axle hits a high spot in the track as it enters a curve, it will derail the middle axle. As long as the curve is level, the locomotive does well. 
Ron


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