# Minimum Radius Curve for USAT SD-40



## jr747 (Feb 7, 2008)

I tried doing a search for this and didn't find an answer.  Does anyone know what the minimum radius curve is for the SD-40?  My smallest curve is 8'  I didn't think it would be a problem but I wanted to make sure before I purchase one.  I know the minimum curve for the SD-70 is 10' so I can't purchase one of those/DesktopModules/NTForums/themes/mls/emoticons/sad.gif.  

Thanks.

J.R.


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## Mark Stearns (Jan 4, 2008)

J.R I have an Sd-40 and my minimum radius is about 7.5 feet, I originaly had problems with it pulling the first car off the track but then I modified the coupler on my battery car to have a longer swing by attaching the coupler to a longer bar taken off a USA tank car. Now the coupler has the abbility to swing a lot further side to side so it no longer pulls the first car off the track. It didn't affect the ability to back the car either it still pushes just as well as it pulls a full train of 15 to 20 cars with no problem.


Mark


Wedgewood Mining Co.


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## bruce a m (Jan 2, 2008)

I use 8 & 10 foot radius for the SD-70 & SD-40's. I do use the optional coupler box assembly too and they run very good. Bruce


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## jr747 (Feb 7, 2008)

Bruce,

That's interesting that you run you SD 70 on 8 and 10' radius track.  When I went into Charles Ro, the person told me that the minimum radius track is 10'.  Did you have to do any modifications?


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## Jim Agnew (Jan 2, 2008)

I run my SD70's on 8 foot *diameter* track with no problem.


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## Trains (Jan 2, 2008)

I know the Aristo SD-45 will run on 4 foot radius. I think a lot of people get radius, and diameter mixed up.


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## jr747 (Feb 7, 2008)

I hate when I mix up radius and diameter. I meant diameter. 

J.R.


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## jr747 (Feb 7, 2008)

Bruce,

With the coupler box on the SD 70, are you using Kadee couplers?


J.R.


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## aceinspp (Jan 2, 2008)

I run both the SD40s and SD70 on 8 and 10 curves biggest problems I was wiping out my switch stands till I added longer headblock ties and throw bars.  Later RJD


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## Art (Jan 3, 2008)

I run the PA, SD40, and SD70 on 8' diameter curves with no problem. I could coax them around a tighter curve but I won't as I believe it puts a strain on the motor blocks. 

Art


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## bruce a m (Jan 2, 2008)

Hi I use theUSA Trains optional coupler box assembly and I put a Aristo-Craft coupler in it. I use Aristo-Craft couplers on all of my locos and cars. Later Bruce


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