I'm trying to get a handle on running a steam loco on my 22" curves, and which would be more problematic - 4 small drivers in a row, say like on a Consolidation, or three tall drivers, such as on a Pacific. Pondering buying my first sound/dcc steam loco and want to make the right choice.
Most Pacifics were longer/larger than most Consolidations. But more importantly, with that trailing truck the cab of the Pacific will stick out a lot further on curves as well the the locomotive's pilot because of the four lead wheels compared to the Consolidations two.. On that basis, I recommend the Consolidation.
Mark
John, most manufactures will list what sizes there steam engines will take. If you go by that you are pretty safe. One of the reasons I don't have problems with Big Steam like some people think I should.
Your friend Ken
I hate Rust
Thanks Mark. Was leaning that way, or maybe to an 0-8-0, and this helps solidify that.
~G4
19 Years old, modeling the Cowlitz, Chehalis, and Cascade Railroad of Western Washington in 1927 in 6X6 feet.
cudaken John, most manufactures will list what sizes there steam engines will take. If you go by that you are pretty safe. One of the reasons I don't have problems with Big Steam like some people think I should. Your friend Ken
Thanks Ken - very true. I'm always a little leery of their recommendations, though, because I think they'll push it to sell engines. Almost all *say* they'll run on a 22" ... but color me leery.
Swayin I'm trying to get a handle on running a steam loco on my 22" curves, and which would be more problematic - 4 small drivers in a row, say like on a Consolidation, or three tall drivers, such as on a Pacific. Pondering buying my first sound/dcc steam loco and want to make the right choice.
22" curves seem broad enough, but steamers are challenged as the radius gets tighter. On my first layout, I had a double mainline with 22" and 24" radius. On my second layout, I went to 30" and 32" so I could run 2-10-2's and 2-10-4's and that proved a challenge.
I have 14 steamers with a variety of wheel configurations. In my experience, the Consolidation and the Pacific will take a 22" radius curve, but your track work better be pretty good.
It is not so much the tight radius at 22" that I would be concerned about but, rather, the quality of the track work.
Alton Junction
understood - certainly that is always half the battle. Crappy tracklaying will make any engine configuration problematic.
Swayin Thanks Mark. Was leaning that way, or maybe to an 0-8-0, and this helps solidify that.
I don't think you have to "drop down" to an 0-8-0. The Consolidation type has little more overhang than its pilotless brother, and was much more prototypically versatile performing well as both a switcher and road locomotive. While most models of Pacifics can handle a 22" curve, the overhangs are unsightly and there is a good chance a car coupled to its front won't make the curve.
Marklin steamers are not cheap, and they're designed to go around 18" curves...or less. Even their multi-coupled engines.
A Bachmann Decapod will go around 18" curves. It was a small engine in real life (the prototype of that specific engine, not the larger versions used by the Pennsy, for example..).
You need to know the real wheelbase of the drivers, and that is the distance between the bottom dead center of the two outer drivers. Even so, the central drivers can be blind, real or model, or they can have so much sideplay in their axles and in the rods that 18" is no problem. This is how BLI is supposedly going to make their UP 4-12-2 take 22" curves.
Most Pacifics, Hudsons, virtually all Consolidations, a few smaller Mikados, and the various Atlantic/Prairie/Mogul versions should be okay on 18" radii. I don't know about the American 4-4-0 or some Ten Wheelers...I don't have any experience with them.
-Crandell
All my non articulated steamers run OK on 22 but
the BACHMAN 4-8-4 looks a little weird from overhead
And my 2-8-2 handles 18s real well
I often ran the 2-8-2 on the 18 and the 4-8-2 on the 22
51% share holder in the ME&O ( Wife owns the other 49% )
ME&O
You haven gotten good advice from all, but I would suggest to all new people in the hobby that they go with larger curves. Accepting the fact that curves really should be larger now will save you lots of problems later. Something in the range of 28-30 inch radius should be considered a minimum for good looks and perfomance of all but the smallest steam locos. It will also be of great help with passenger cars or long freight cars.
Sheldon
The wheel size and configuration have nothing to do with each other. Smaller wheels were typically found on freight locomotives where larger wheels were for faster speed and less pulling power for passenger service. With 22" radius curves you should be fine running anything up to a 4-8-4 if you were to even go with an articulated locomotive you could still run them on 22" they just wouldn't look as good as it you ran them on larger curves. It all depends on what type of railroad your modeling or if you just like to run trains for the fun of it them thats ok too.
Allegheny2-6-6-6 The wheel size and configuration have nothing to do with each other. Smaller wheels were typically found on freight locomotives where larger wheels were for faster speed and less pulling power for passenger service. With 22" radius curves you should be fine running anything up to a 4-8-4 if you were to even go with an articulated locomotive you could still run them on 22" they just wouldn't look as good as it you ran them on larger curves. It all depends on what type of railroad your modeling or if you just like to run trains for the fun of it them thats ok too.
This is not completely true as it relates to the OP's question. Prototype or model one of the controling factors in the minimum radius question is rigid wheel base. As drivers get larger, they must by definition be farther apart. This increases the rigid wheel base and increases the radius needed.
Example: A Russian 2-10-0 has small drivers, 52" IIRC, its rigid wheel base is short only about 18'-6" in real life, yet it has five drive axes. A SP GS4 has 80" drivers and has a rigid wheel base over 20', but yet it only has four drive axles. A Russian 2-10-0 will handle a sharper curve better than a GS4 - every time.
After some thought, I have adopted an informal rule that whatever minimums the manufacturers state for minimum radius for their engines, I add at least 10% to that figure. That is my strict minimum, and that would be on a tight curve meant for walking speed. As Sheldon says, whenever you have the room you should spread out in any scale...it is worth it. If you wanted 26" minimum radius, but find that the space really accepts 28" withouth compromising your plan appreciably, you should absolutely adopt the higher standard...always. It just minimizes problems, and especially future ones where you introduce bigger engines and longer cars.
Also, wheel diameter and configuration absolutely, and positively, do impact the minimum curvature for a steamer. For a diesel, too. If you place axle bearings 5' apart, but forget that your drivers are 6' in diameter, what must you do to the axles? Space them further than 6' apart. And once you space them further apart, the bottoms of the wheels, which lie vertically below the centers of the axles, must also spread apart. In other words, those engineering types who designed steam locomotives soon saw that high-drivered Northerns were going to be rail straighteners in ways that no Pacific or Hudson ever was. If you have six 80" drivers on a K4 and add another 80" driver set so that you can call the Pacific a Northern, where does that extra axle go? It goes six-plus feet further away from the other three. And that means more wheelbase. More wheelbase jams flanges on large drivers tighter into flange faces on rails in a curve of the same radius. Happens on our models too, although it is much worse in the all-brass world.
Or, you could get a Stirling Single. Bachmann's "Emily" in the Thomas range is based on the Stirling single. http://www.bachmanntrains.com/home-usa/products.php?act=viewProd&productId=1583
Video of the real thing running an excursion in 1980's: http://www.youtube.com/watch?v=EgDM3IlhC1w&feature=related
The real thing does have a rigid wheelbase as the trailing wheels are held rigidly in the frame.
The Brits had a number of single drive axle locos in the 19th Century.
Andre
andrechapelon The Brits had a number of single drive axle locos in the 19th Century. Andre
One of which, a 4-2-4 designed to run on Brunel gauge (7' 1/4".) had the tallest drivers ever installed on a steam locomotive. Its rigid wheelbase was the distance between the lead truck pivot and the trailing truck pivot - the drivers were blind, had no tread taper and were preposterously wide (measured across the tread.)
Rigid wheelbase (with every wheel between fitted with flanges) is the key to what radius will be too tight for a specific locomotive. The tightest curves I have, 350mm radius, will accept low-drivered x-6-x (but not a 2-6-4T with somewhat higher drivers) and even one 0-8-0T with roller skate wheels (44" prototype diameter!) The real shocker is the Mantua 2-6-6-2T "Logger." (Which it wasn't - it hauled mineral products. After it was de-tanked and fitted with a tender, it was put to work hauling logs.) The model can actually take a 300mm radius curve - which matches what the prototype could take (68 degree curves. A 60 degree curve has a radius of 100 feet.) It does have considerable overhang, but won't yank short cars off the rails sideways. Of course, it has blind center drivers, so its rail interface geometry is the same as my little block of lead - an 0-4-0T with a somewhat extended wheelbase.
Just for grins, I have run a choice collection of 4-8-4s on my mainline (24 inch radius with spiral easements.) They can all take the curves, but every one of them looks seriously ugly. So, it isn't just whether the loco can run on the curve, it's the number of relay boxes, telephone poles and lineside bushes it will destroy in the process...
Chuck (Modeling Central Japan in September, 1964)
I would base my decision on what the function of the locomotive is to be. An 0-8-0 is usually a yard switcher and would not be used for mainline freight. The 4-6-2 Pacific with large drivers was mainly a passenger locomotive and the large drivers were for speed. The 2-8-0, 2-8-2, 2-8-4 and other steam locos with 8 or more small drivers were mainly freight engines. 22" radius curves should be sufficient for most non articulated locos so I would think more about what the loco is intended to primarily pull. Thats my 2 cents.
One other thing I will add about running steam and track work. Steam engines do not like dips in the track rather it be in a turn or straight. Part of my track is located where I could not see it. Had a good sizes town in front of it. My M1 A and Hudson would slow down in that area (small grade) so I thought it was the grade. With the town removed now I can see what is happening. There is a dip in the rails and when the drive wheels bridge the dip the center wheels lose traction slowing down the train. It will be a easy fix now I know there is a problem.
Cuda Ken
cudaken One other thing I will add about running steam and track work. Steam engines do not like dips in the track rather it be in a turn or straight. Part of my track is located where I could not see it. Had a good sizes town in front of it. My M1 A and Hudson would slow down in that area (small grade) so I thought it was the grade. With the town removed now I can see what is happening. There is a dip in the rails and when the drive wheels bridge the dip the center wheels lose traction slowing down the train. It will be a easy fix now I know there is a problem. Cuda Ken
One of our fellow forumiites recently pointed out to me that steam engines and 6-wheel axled diesels will find any flaw in your track work and react adversely to it. So true. Another piece of great advice was "fix the hump" which I took to heart. Nearly any smaller steam engine will run well on 22" radius curved track if the track work is solid. Whether a particular engine looks prototypical while negotiating a 22" radius curve is a whole other matter.
Rich
My Northern ran on my 22 no problem but seemed to big for a small layout so I took it off the roster
You could always take a file to the center driver and make it blind.