# Minimum operating radius of bigger steam engines



## TravisTheLionHeart (Apr 3, 2013)

Hi all.

I have a steam era HO layout and am currently running a 4-8-4 gs-4 daylight on my main. I love the bigger steamers and would really like to run a few in the future. However, the main thing stopping me from doing that is on my small layout, I only have about 19"/maybe 20" radius curves.

So my question is this, does anyone happen to know the absolute minimum radius curve some of the bigger locomotives can handle. Keep in mind I don't mind if they might look a little silly or awkward on the tighter curves. I just want to have fun running trains without derailing :thumbsup:

My 4-8-4 gs-4 runs perfect on my curves with no issues but I'm also interested in 4-4-4-4, 
2-10-2, and 2-10-4 configurations.

Thanks a ton in advance for any help, you all are the best!


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## Brakeman Jake (Mar 8, 2009)

The manufacturers generally specify the minimum radius their models can handle.And you're right to be worried,20 in. isn't too much in HO,specially for 2-10-2 and 2-10-4 that usually require very large radiuses.


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## TravisTheLionHeart (Apr 3, 2013)

You're right Jake, most of the manufactures give a radius number. They seem a little vague to me though, with terms like "Recommended Radius" and "suggested Radius." Most are saying 22" for the bigger steamers. Although, 20" Radius is definitely a little odd... and not something the Manufacturers are going to gauge their products to. Plus I own several locos that are "Recommended" at 22" but work fine on my smaller curves... 

Oh what to do, what to do


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## little fat buddy (Jan 14, 2011)

well im not a steam guy i like steamers but i am a modern modeler and most stuff for big modern deisels is 24 inch minimum radius for certain locos and rollingstock so id say 24 to 26 inch radius would work for larger steamers.


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## TravisTheLionHeart (Apr 3, 2013)

Hmm gotcha. Well it sounds like I may have to sadly hold off getting to run some of those bigger guys until I can do some expanding. :dunno:

Aw well, something to look forward to!


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## Shadowplayer (Oct 31, 2014)

I have a Challenger that will not run on anything tighter than a 22 inch without derailing. Its all those wheels on the tender that get ya.


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## tkruger (Jan 18, 2009)

I run older Mantua and Riverossi steamers. They run on 18r. The larger Mantua locomotives used blind drivers to do this, no flanges on some of the wheels. Most newer models are not this way. I avoid running an locomotive at the minimum radius. This is because the loser to the minimum you get the greater the chance for derailment.


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## TravisTheLionHeart (Apr 3, 2013)

Shadowplayer said:


> I have a Challenger that will not run on anything tighter than a 22 inch without derailing. Its all those wheels on the tender that get ya.


Wow, I had no idea any form of a challenger would run anything close to 22". 

Do you happen to know if you have any medium/large engines that do run smoothly below 22" radius?. Not to sure if that's even a thing, but I'm just really curious now.


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## TravisTheLionHeart (Apr 3, 2013)

tkruger said:


> I run older Mantua and Riverossi steamers. They run on 18r. The larger Mantua locomotives used blind drivers to do this, no flanges on some of the wheels. Most newer models are not this way. I avoid running an locomotive at the minimum radius. This is because the loser to the minimum you get the greater the chance for derailment.


Hmm, definitely good to know that. Thanks for the info! 

How reliable would you say those older mantua's and Riverossi's are? Have you had much trouble with them or are they pretty dependable?


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## CTValleyRR (Jul 26, 2014)

HO Scale sectional track comes in fixed radii, 15" (rare), 18" (common, especially in train sets), 22" and 24". Shinohara makes it in 2" increments from 18" all the way up to 36". Manufacturers will recommend one of these diameters for their equipment.

Manufacturers aren't going to tell you not to buy their stuff, so they give you a suggested or recommended minimum. Some will do better than this. I have some Bachmann Spectrum Heavyweight coaches that are recommended for 24", but I can run them slowly around 18" curves in short consists. If it works for you, great, but expect trouble if you're using a radius lower than the minimum. You're not just talking about the loco itself cornering and staying on the rails. The tighter curves cause more friction, reducing pulling power, and the loco may behave differently when pulling a consist or backing up.


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## TravisTheLionHeart (Apr 3, 2013)

some very true stuff you're saying indeed.

I also have some spectrum heavyweight cars, They've actually been nothing but trouble since I got them, but not because of the turn radius. Lights not working, bad wiring shorting out the entire track, different coupler heights, and a nightmare to take the roof off and get inside the car to name a few. No oddly enough, going around the track smoothly is the only thing they've always done great... Go figure


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## Brakeman Jake (Mar 8, 2009)

Steamers that have the long rigid wheelbases are the ones likely to have derailment problems.While 0-4-0s,0-6-0s and the likes usually handle tight radiuses quite well,the larger 2-8-4s,4-8-2s and the even bigger 4-8-4s often have issues.The most critical are the ten driver equipped (0-10-0s and similar) will generally require pretty wide radiuses to accomodate their long wheelspreads.

Oddly enough,the giants (4-6-6-4 & 4-8-8-4) will often deal with surprisingly tight radiuses thanks first to their articulated designs but also because they usually have shorter rigid wheelbase trucks.


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## TravisTheLionHeart (Apr 3, 2013)

Thanks Jake, I had no idea the really giant steamers could handle smaller curves better than the engines with huge ridged driving wheels, but it makes sense.

With that mindset then, do we think a 4-4-4-4 could possibly handle a 19" or 20" radius curve, being that there are only spans of 4 ridged driver wheels?


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## Brakeman Jake (Mar 8, 2009)

Only testing can tell.Not only the drive trucks have to be articulated,the non powered ones have to be allowed to slide sideways,so that the minimum radius required is dictated by how far they can slide.I don't think this particular model (T1) could handle sharp curves,or at least,it would look terrible doing it.


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## Mr. SP (Jan 7, 2015)

*Minimum Radius*

A 4X8 is a small layout. To run big steam locomotives a larger layout will be needed
Get your curve radius as big as possible. 30+ radius will make running big steam locomotives 
more reliable and will look more prototypical


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## TravisTheLionHeart (Apr 3, 2013)

Got it! Well, as I said earlier I'm okay with waiting a little longer until I'm able to expand the layout. I'm pretty content where I am now and don't want to start cutting corners. (no pun intended.)

Thanks everyone for your help, I always prefer to knock ideas around with a few people who know more than I do.


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## DavefromMD (Jul 25, 2013)

"How reliable would you say those older mantua's and Riverossi's are? Have you had much trouble with them or are they pretty dependable?"

I had a Mantua Pacific 4-6-2 from the late 60s that still ran like a champ. I sold it last year to go DCC.


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## tkruger (Jan 18, 2009)

DavefromMD said:


> "How reliable would you say those older mantua's and Riverossi's are? Have you had much trouble with them or are they pretty dependable?"
> 
> I had a Mantua Pacific 4-6-2 from the late 60s that still ran like a champ. I sold it last year to go DCC.


I have found them to be extremely reliable. Mantua used a very simple design. Basically a worm gear drives a gear on one of the axles. The rods on that set of wheels transfer the power to the other drivers. If everything is properly lubed and the wheels quartered there is little friction and it runs smooth. Fairly quiet to. The Riverossi steamers were of good build quality for the time. I have found them to occasionally have louder motors. Main difference I have found between the two is that the Mantua seem to pull better due to the added weight of the cast boiler. The plastic Riverossi boilers look better stock due to the molded details.

The Riverossi Big Boy, Decapod and Cab Forward are favorites of mine that they made.
The Mantua Decapod, Berk and Pacific ar the ones I prefer of theirs.


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## TravisTheLionHeart (Apr 3, 2013)

Wow, okay awesome guys. I really haven't had too much experience with either Mantua or Riverossi before; I'm glad to see they've got some quality engines.

Is there a certain timeframe that the best engines were made... or do they still make them pretty solid even to this day?


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## CTValleyRR (Jul 26, 2014)

Pretty much anything you buy today is fairly solid -- if you stay away from the generic train set ones (like the ones you see advertised in non-hobby magazines). I have a cheap Walthers Trainman FA loco that is actually one of my best locos. The detailing is skimpy and mostly cast on, but it runs great. These days, more money generally gets you more and better details, or extras like DCC and sound, not a better runner.


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## tkruger (Jan 18, 2009)

TravisTheLionHeart said:


> Wow, okay awesome guys. I really haven't had too much experience with either Mantua or Riverossi before; I'm glad to see they've got some quality engines.
> 
> Is there a certain timeframe that the best engines were made... or do they still make them pretty solid even to this day?


Both Mantua and Riverossi are currently out of business. I have found that the Mantua steamers with cast boilers are far better pullers than the newer ones with plastic boilers. The weight makes a huge difference.


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## lajrmdlr (Apr 25, 2014)

TravisTheLionHeart said:


> Hi all.
> 
> I have a steam era HO layout and am currently running a 4-8-4 gs-4 daylight on my main. I love the bigger steamers and would really like to run a few in the future. However, the main thing stopping me from doing that is on my small layout, I only have about 19"/maybe 20" radius curves.
> 
> ...


Just because a steam loco can run on smaller radius. they don't look very good w/ all that overhang on *BOTH* ends. LOL


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## morland (Sep 25, 2012)

tkruger said:


> Both Mantua and Riverossi are currently out of business. I have found that the Mantua steamers with cast boilers are far better pullers than the newer ones with plastic boilers. The weight makes a huge difference.


Rivarossi was bought by Lima and then was bought by Hornby. Hornby is making and selling Rivarossi engines:

http://www.hornbyamerica.com/shop/hornby/rivarossi

MRC now owns Model Power and Mantua, they are making and selling them.

http://www.modelpower.com/


I would look at a place like Trainworld for better prices than what the manufacturers have on them.

Mantua
http://www.trainworld.com/search/?bymanufacturer=5716&bycategory=&byscale=

Rivarossi
http://www.trainworld.com/search/?bymanufacturer=6044&bycategory=&byscale=

-Trever


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## TravisTheLionHeart (Apr 3, 2013)

Thanks again everyone for all the info! I've learned far more than I thought I would on this one. One of the many joys of life.

I'll definitely keep my eyes on both those brands as they really seem to have some fantastic looking locos.


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