I own a Kato Western Pacific heavy Mikado, but what’s the difference between it and the light model ?.
Tracklayer
Easy answer is weight, also the heavy has a larger boiler diameter appox 10" it is obvious if you look at the 2 side by side.
Take a look at this page that goes into more detail about the differences, and provides a side by side specification of the two types.
http://www.steamlocomotive.com/mikado/usra.shtml
You might want to bookmark the www.steamlocomotive.com website as it is a treasure house of info on steam locomotives.
Regards
Ed
The reasons for the differences had to do with the railroads needs for bigger locomotives balanced by the physical plant in terms of bridge and via duct capacity and clearances for tunnels, bridges, and other lineside structures. The motive power department might want huge hauling capacity of a “heavy” locomotive but the cost and delay of physical plant up grading might rule out its acquisition. The Nickle Plate had to strengthen and up grade a number of bridges in eastern Ohio to accomodate the Berkshires and other high speed heavy motive power.
Will
Thanks egmurphy, I really appreciate it.
Tracklayer
Also, The heavies had a six axle tender and the lights had a four axle.(I think?)
The USRA heavies (Pacifics and Mountains as well as Mikes) carried about 10% more weight on each driving axle than their ‘light’ sisters. The reason was that most of the western granger railroads didn’t have the physical plant to support the heavier weight, while the eastern coal haulers did - and needed the extra power and tractive effort.
When it came to steam locomotives, one size did NOT fit all!
The USRA series of engines had ‘light’ and ‘heavy’ - The basic difference why this was done was due to axle loading. A ‘light’ engines would have no more than 50,000 lbs of axle loading. A ‘heavy’ would exceed that figure.
As far as tenders, I believe all were delivered with the standard USRA ‘medium’ tender(at least the non-articulated road engines). That said, there were USRA ‘copies’ built after WW1 and they may have had larger tenders(or larger tenders were added to existing ‘original’ USRA engines). IIRC, the Southern PS-4 is based on a USRA ‘heavy’ 4-6-2 as a starting point, and has an Elesco bundle on the smokebox and many had 6 axle tenders(plus that special green paint scheme).
As far as ‘western’ roads; the CGW had ‘light’ 2-8-2s’s, the GN and Milw had ‘heavy’ 2-8-2’s - just depends on the railroad service they were used in.
Jim Bernier
Also on the Union Pacific the USRA lite Mikes if I remember from the article from MR were actually heavier than their existing Mikes. Thus, the Union Pacific dubbed the USRA Mikes MK Specials.
When I asked almost the same question about two years ago, the answer I received was that the only difference between a light and heavy any-type (Mike, Mountain, Pacific, etc.) was the diameter of the cylinders. Some of these answers seem to disclaim the answer I received, so it would be interesting to see just what really is the difference. Maybe it’s only the cylinder diameter as I was told, maybe it’s the boiler size, maybe it’s the combines weight. Somebosy out there MUST know the answer. Where’s Alco or Baldwin when you need them?
I believe the Kalmbach Model Railroader Cyclopedia Volume I, Steam Locomotives can be considered authoritative. It states (page 73 in my 1960 edition) that the light and heavy USRA Midados used the same 63" drivers and running gear but had the following differences:
Weight on drivers, lbs: Light, 224,000 Heavy, 240,000
Tractive force, lbs: Light, 54,600 Heavy, 60,000
Grate area, sq. ft. Light, 66.7 Heavy, 70.8
Cylinders, inches
(diameter & stroke) Light, 26 x 30 Heavy, 27 x 32
Boiler diameter Light 86" Heavy, 96"
John