minimum curve radius

[ericw95]

Hey guys, I am creating a layout for my room and am constricted by space. I recently acquiered a used 4-8-4 northern from a friend, and I have a 2-8-0 consolidation that is pretty new. What is the absolute minimum curve radius I can use to make both locomotives run without derailing frequently?

[skipgear]

The bigger the better but most Bachmann N scale will run on 11" radius ok. The Northern will have problems pulling a long train on that tight of a radius though. The 2-8-0 should be fine.

[ericw95]

Thanks man, yeah I only have 9 cars for both as of now so its not too big of a load. I am trying to fit the layout into a 2.5 x 4 space with at least 4 switches so 11" leaves me with a little bit of room to play with.

[sumfred]

The 2-8-0 will do a 7 5/8" radius.

I'm in the process of testing all of my steam power as to the minimum radius and all three 2-8-0 did this without problems.

I also use 9" Peco turnouts and again there is no problem.

Unfortunately I do not own a 4-8-4 Northern, so I can't comment.

The 4-8-2 Bachmann Light Mountain needs a 9 3/4" radius.

Fred

[ericw95]

thanks alot, I was pretty sure the 2-8-0 would be fine but I am just worried about the 4-8-4 when I finally decide to put up the layout. I have done a few tests without the track nailed down and it can handle the outsidecurves well, but not the switches as they have two 9 3/4" and three 11" curves running between them. It makes it around two of three times without derailing, but I am hoping some eof the issues will be fixed when the track is down and soldered to eliminate any kinks between rails.

[darticus]

Same problems here. How do we know the minimum for different trains. Is this printed somewhere? I have the Norfolk Western, Light Mountain, Heavy Mountain, 2-6-6-2 Articulated Spectrum a Athearn Challenger and a Walther Y3. Ron

[rrtreerat]

N-Scale Rull-o-thumb; A three axle steam loco of any wheel size, including most articulates, will pretty much handle any curve you throw at it.
But when you throw in an extra axle, wheel diameter comes into play, small wheeled locos like the 2-8-0, 2-8-2 H&L, and 2-8-8-2 should negotiate 9.75" without any hic-ups. But when you start into the larger 'Mainline' power such as 2-8-4's and 4-8-4's, big wheels and a long fixed wheel base almost demand larger than 11" radius.
This not to say that they won't handle such a tight radius but that you will have to expect more derailments from them. The Bachmann 611 spectrum, that I have one of, which runs on smaller than usual drivers handles 9.75" all the time but every once in a while 'hop' and all the drivers are on the ground spinning.
Now one thing all steam engines like is a good 'transition curve' to take you from tangent track into your 9.75" and 11" radius curves, this is best achieved by the use of flex track on sanded cork roadbed but in a pinch the old Atlas trick of including a section of 19" radius curve between the tangent and your tight radius will work just about as well.

[darticus]

Sounds like your giving my J hope. I check it out again tomorrow. It is having trouble running this total layout. Front wheels jump off or the 8 wheels jump. Really would like to get this going on my layout. The light mountain works fine.  Ron

N-Scale Rull-o-thumb; A three axle steam loco of any wheel size, including most articulates, will pretty much handle any curve you throw at it.
But when you throw in an extra axle, wheel diameter comes into play, small wheeled locos like the 2-8-0, 2-8-2 H&L, and 2-8-8-2 should negotiate 9.75" without any hic-ups. But when you start into the larger 'Mainline' power such as 2-8-4's and 4-8-4's, big wheels and a long fixed wheel base almost demand larger than 11" radius.
This not to say that they won't handle such a tight radius but that you will have to expect more derailments from them. The Bachmann 611 spectrum, that I have one of, which runs on smaller than usual drivers handles 9.75" all the time but every once in a while 'hop' and all the drivers are on the ground spinning.
Now one thing all steam engines like is a good 'transition curve' to take you from tangent track into your 9.75" and 11" radius curves, this is best achieved by the use of flex track on sanded cork roadbed but in a pinch the old Atlas trick of including a section of 19" radius curve between the tangent and your tight radius will work just about as well.

[ericw95]

So, if a 4-8-4 has 8 fixed wheels, why would it have more trouble than a 2-8-0 with 8 fixed wheels going around tight curves? Sorry I'm inexperienced and am slightly confused with some of this.

[ACY]

The 4-8-4 has a huge wheelbase which is much larger than the 2-8-0. The 4 lead and trailing wheels also cause issues of tighter radius curves.

[ericw95]

gotcha, so then could a 4-8-4 navigate a curve arranged in a radius of:
11" radius section-9.75" radius section-11" radius section-9.75" radius section-11" radius section
without too many derailments? I am trying to fit as many switches as I can into a small layout.

[ACY]

gotcha, so then could a 4-8-4 navigate a curve arranged in a radius of:
11" radius section-9.75" radius section-11" radius section-9.75" radius section-11" radius section
without too many derailments? I am trying to fit as many switches as I can into a small layout.

Nope, you need to use 11" radius curves, otherwise you will lose a great deal of reliability.

[ericw95]

alright thanks for the help I'll see if it was ordered yet and try to get another 2-8-0 instead