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HO Radius Question for 4-8-8-4 ?

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  • From: Shelby, OH
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HO Radius Question for 4-8-8-4 ?
Posted by Hawk007 on Saturday, November 19, 2005 11:35 PM
Hello,

I tried to do a search here for a radius question and track specs on running a 4-8-8-4 smoothly. I think I had heard that 24 inches would be ok to do that but it would haver to be run slow through the curve. but I also heard that a 36 inch would be the best for faster running with the trach curved inwards, or on a tilt

Can any one help me with this? I also have 4-6-6-4s and other larger locos.

thanks in advance

"Sometimes the Most real things in life, are the things we can not see." 

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Posted by selector on Sunday, November 20, 2005 2:21 AM
You'll have to consult the manufacturer for that info...on their website. Generally, 22" is the minimum for four (4) coupled and flanged drivers in HO with NMRA RP-25 wheels. The BLI 2-10-4's need 24", according to the info I have.

I have a Lionel Challenger, and Lionel maintains it is good for 18", but "recommend" 22" and up. Frankly, it doesn't look great on my 22"ers, either, but that is what it has to run over. It does it very well.

If you can manage it, your bigger locos will look terrific on curves greater than 28".

One final tip. My Challenger found every dip and kink in my track, and so will your Big Boy. Make sure your track has no dips from join-to-join, and that transitions into and out of grades are silky smooth if you have any curves nearby. The problem comes when the front truck and engine get around the curve, but are being lifted by the kink or abrupt transition. While this is happening, the rear engine wants to stay flush with the boiler in its "detent" or neutral position, and becomes misaligned with the curve when it gets to the point where the track rises to meet it.

Be warned.
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Posted by cacole on Sunday, November 20, 2005 4:52 AM
I have two Rivarossi 4-8-8-4 models as well as their Cab Forwards, and they can go around a 24 inch radius, but don't look very good doing so. If you don't mind seeing the front of the boiler hanging way out over the edge of the track, they could probably go around a 20, or maybe even an 18 inch radius.

I think Lionel was the first to model a 4-8-8-4, and it looked really stupid going around a curve.
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Posted by claycts on Sunday, November 20, 2005 9:54 AM
The instruction sheet for the Rivarossi 4-8-8-4 says 32" min. I researched and that was for the TENDER. I have NOT tested on any radius yet but I had a 2-6-6-2 that worked on 18" fine. My $.02
George P.
Take Care George Pavlisko Driving Race cars and working on HO trains More fun than I can stand!!!
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Posted by oleirish on Sunday, November 20, 2005 11:48 AM
My Rivarossi Y6B works fine on 18" curves[2c][2c]
JIM
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Posted by knewsom on Sunday, November 20, 2005 9:27 PM
I have a Rivarossi 4-8-8-4 Big Boy and it will go around the 18 inch radius on my test track.
Thanks, Kevin
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Posted by jecorbett on Sunday, November 20, 2005 10:02 PM
The minimum radius probably depends on the manufacturer. I have an old Rivarossi Big Boy and I read that they made them with oversized flanges so they could be run on 22" curves but I never tried it. My curves were 30" or more except for one tight spot I cheated and put in a 28". Even if you can get them to negotiate tight curves, the big engines won't look good doing it. These are engines that are made for large layouts where they can pull long trains. I would think they would look pretty silly pulling a 5 car consist around a 4X8 oval. These engines weren't made to be switching your local.
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Posted by Leon Silverman on Monday, November 21, 2005 6:32 AM
The fact that you mention you have been doing research on this question implies that you are currently in the layout planning stage. If so, keep in mind that if you use curve radii below 24" as a minimum, then if you have a parallel track next to this curve, its radius will have to be at least 3" (e.g. 27" ) larger to avoid interference. At 30" radius, the outer curve should be 2-1/2" larger .
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Posted by claycts on Monday, November 21, 2005 6:16 PM
QUOTE: Originally posted by jecorbett

The minimum radius probably depends on the manufacturer. I have an old Rivarossi Big Boy and I read that they made them with oversized flanges so they could be run on 22" curves but I never tried it. My curves were 30" or more except for one tight spot I cheated and put in a 28". Even if you can get them to negotiate tight curves, the big engines won't look good doing it. These are engines that are made for large layouts where they can pull long trains. I would think they would look pretty silly pulling a 5 car consist around a 4X8 oval. These engines weren't made to be switching your local.

May look silly but this is supposed to be fun. heck I used a Challenger around our tree last year on 22"R. Kids loved it.
Take Care
Take Care George Pavlisko Driving Race cars and working on HO trains More fun than I can stand!!!
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Posted by tomikawaTT on Friday, December 16, 2005 9:59 PM
For what it's worth, the UP Big Boy was designed to handle a curve radius equivalent to 42 inches in HO - at a dead crawl when maneuvering in an engine terminal. No wonder big articulateds look less than wonderful on our typical model curves. Of course, it would be nice to have a space the size of Wyoming to use for a layout!
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Posted by challenger3802 on Saturday, December 17, 2005 2:09 PM
I've a challenger that's a year old now (how time flies), and it negotiates curves of 18" min, however it does look rather daft on them and nearly grinds to a halt as it goes round such tight curves.

With an engine this size the greater the curve you can give it the better it looks.

And, unrelated to this topic, it looks great going at slow speed. Full throttle looks silly in HO scale.

Happy Christmas
Ian
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Posted by selector on Saturday, December 17, 2005 2:29 PM
QUOTE: Originally posted by challenger3802

And, unrelated to this topic, it looks great going at slow speed. Full throttle looks silly in HO scale.

Happy Christmas
Ian
That is true, in my opinion. On my DT 400 Digitrax throttle, speeds higher than an indicated 35 or 40 are unrealisitc. For my IHC Mikado, anything over 20 seems bogus. And, yes, the locos look best a yard speed going past the viewer anyway.
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Posted by Medina1128 on Sunday, December 18, 2005 1:55 AM
The only time I remember seeing a steam locomotive with its drivers thrashing, was on the opening credits to the old b&w episodes of the Superman series, starring George Reeves... "More powerful than a locomotive...".. and yes, even IT looked ridiculous.
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Posted by luckyboo57350 on Sunday, December 18, 2005 2:15 PM
I run Bigboys, Challengers, EFE-484,s and various other UP big locomotives on my layout. I have a min. standard of 40" R for my curves and I also use no. 8 turnouts on the mainline and steam ficility area. Track in some areas is handlayed. The 40"R in HO scale is the correct tightest radius the prototype Bigboys on a 1 : 1 scale can move through. Any tighter the centipede tender rear wheels will derail.

On my layout I run double mainline trackage useing UP common standards centers of 13ft on center which is about 2" from center of the track to center of the other track. when my bigboys meet there is plenty of room for them to pass in the curves. I have in the pass work with smaller radiuses, 18" totally unrealistic and exsteamly tight. I recommend 24"R or Greater. If useing double line track. I would recommend 36" R. At 36"R, bigboys will have no problem passing other trains and other "Bigboys". This will cover both boiler over hangs. Any thing smaller you will need to add the difference in to acomodate the boiler overhang to pass other trains. I hope this will help.

I model the UPRR based in Cheyenne

Sincerly:
Curt

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Posted by ARTHILL on Sunday, December 18, 2005 3:45 PM
I may be weird, but I think the big overhang looks interesting. It is an exagerated effect from what makes an articulated look good in the first place. HO is an exercise in compaction and exagerationSpace issues can never be really be prototype and look good. This Z and N gauge buildings up a mountain side looks good. Overhang on curves is a matter of style and I think exageration looks good in this case.
If you think you have it right, your standards are too low. my photos http://s12.photobucket.com/albums/a235/ARTHILL/ Art
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Posted by selector on Sunday, December 18, 2005 11:57 PM
Hmm, I can't say I agree, Art. The selective compression is meant to fool us into believing that a short distance is actually longer. There is no fooling the eye that sees an overhang the likes of which one never sees in real life. It is too apparent, and I see it every time. I could live with the overhang on 30" curves, but my 22" curves really don't do the Challenger justice, IMO. To me, it is the same effect as real water...it just doesn't work.

I will probably be redoing my layout in the next six months, and I will have no curve shorter than 24", with all mains curve at 30" and up. Can't wait.
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Posted by Adelie on Monday, December 19, 2005 8:19 AM
When we built my Godson's layout, it was designed knowing a Rivarossi Big Boy might be roaming the rails. I designed that with eased 24" curves, and as far as I know, he's never had a problem with it.

Easements are wonderful things!

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