# Correct engines for different radii



## dmcone (Oct 9, 2011)

Hi there,

Does anyone have a link or just a simple guide for understanding what the maximum radius different engines and rolling stock can safely navigate?

For instance, GP-30: 18" radius (or 15" radius), 40' box car: 15" radius, etc.

Maybe I am oversimplifying this or maybe this is a stupid question, but oh well.

Thanks for the help in advance!


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## gunrunnerjohn (Nov 10, 2010)

Well, you're certainly oversimplifying it, because it would depend on the specific manufacturer and design of the locomotive or car. Different manufacturer's similar models many times have different requirements.


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## tankist (Jun 11, 2009)

agreed with John.

to add,
without doing the extra short stuff like Greg Choo Choo does, i would say forget about anything less the R18 for practical use. 4 axle power units will probably run sufficiently good through it, and some 6 axles will pull through as well (although , looking horribly while doing so).


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## Massey (Apr 16, 2011)

TO give you an example of what John is saying. I bought an Athearn Genesis SD70MAC, it was a beautiful engine ran great and the engine itself would handle 18"curves with no problems. Now add a few cars behind it and the engine would throw the first car off the rails. The engine's couplers did not deflect enough to make the turn. I bought the same engine from KATO, same paint scheme and road number even and Kato model handles the 18" curves just fine and it will also not throw the first car off. Every thing is happy! Same engine different manufacturers different results.

Massey


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## tjcruiser (Jan 10, 2010)

I agree with the comments above. That said, I posted some math formulae a while back that can help determine the overhang of a freight car on a given track radius, or (conversely), the track radius required to achieve a maximum overhang ...

http://www.modeltrainforum.com/showthread.php?p=57304&postcount=6

Regards,

TJ


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## jzrouterman (Nov 27, 2010)

dmcone said:


> Hi there,
> 
> Does anyone have a link or just a simple guide for understanding what the maximum radius different engines and rolling stock can safely navigate?
> 
> For instance, GP-30: 18" radius (or 15" radius), 40' box car: 15" radius, etc.


Good advice by all. A GP30 runs great on 18" radius track, but even better on 22' radius. If you're wanting to do actual railroad operations like switching cars, then lay the largest radius track possible and nothing less than 18. A 40' box car will run on 15' radius track. But when being pushed through a 15" radius curve by anything larger than an SW type switcher, sometimes the couplers of the car and the engine will jam, resulting in a derailment of either one or both. 

I've always gone by the general rule to always lay the largest radius track possible. By doing this, you'd really be surprized at how many frustrating, future problems one can be avoiding.

Routerman


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## dmcone (Oct 9, 2011)

Thank you very much everyone. Yes, I definitely try and oversimplify everything. I will not be using any large cars on my layout. I will use 22" radius turns for the main line and 18" (or an occasional 15" if need be) for the rest.


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