Counter weight thickness
- Can anyone point to a single model HOn3 N.G. outside frame locomotive with accurate, true scale thickness counter weights? I speak mainly of the K-27, K-36 and K37.
Most engines usually just have a thin sheet metal stamping. By my simple calc's the proper thickness ought to be on the order of .065-.070 inch thick or even more!
A great YouTube video of wheel slip on the D&S K-36 shows the wheel weights to be probably as thick as the drivers or maybe even thicker!
As there is often a lot of nit picking on fine scale details here, I haven't seen this issue addressed.
- If the driver has a mounted counter weight there will not be a weight on
the crank. It will just be a crank. Remember the size of the counter
weight is related to the weight of the rods plus a factor for the push
of the cylinders and as the push grew they ran out of effective room on
the small diameter drivers. The Model Die Casting consolidation came
with several different cranks to allow modeling locomotives with/without
driver counter weights.
- On 05/26/2013 06:22 AM, Arthur G. Chappel, Jr. wrote:
> If the driver has a mounted counter weight there will not be a weight onBaldwin used plain outside cranks on outside framed engines up to circa 1902,
> the crank. It will just be a crank. Remember the size of the counter
> weight is related to the weight of the rods plus a factor for the push
> of the cylinders and as the push grew they ran out of effective room on
> the small diameter drivers. The Model Die Casting consolidation came
> with several different cranks to allow modeling locomotives with/without
> driver counter weights.
with conventional counterweights on the spokes. The Crystal River 2-8-s (later
D&RGW C-21s & C25), and White Pass's OF 4-6-0s and early OF 2-8-0s provide
examples. Beginning around 1900 BLW started experimenting with outside counter
weight cranks, first just fitting them on the main drivers and keeping plain
cranks elsewhere: One or two of the New Mexico & Arizona (later Coronado RR)
2-8-0s had this arrangement. Even with full transitional narrow outside counter
weight cranks, BLW retained the conventional counterweights on the drivers: The
K-27s had this arrangement. From circa 1905 on, Baldwin used wide counter
weighted outside cranks of about 120 degrees included angle, and plain s
pokes on the drivers. This is what we find on the K-36s and K-37s, White Pass's
68 & 69 (C-30 equivalents), and both the Shannon Arizona and Quincy & Torch Lake
versions of the Crystal River 103 (D&RGW C-25).
In most cases the actual counter weight varies with the weight of the supported
rods, greatest at the main driver and least at the leading and trailing drivers.
With the 120 degree version, the weight is adjusted by varying the thickness,
without altering the shape, at least in BLW practice. In all cases an excess
counter weight is added to offset the fore and aft inertia of the main rod's
little end, crosshead, piston rod and piston. This excess is usually
distributed over all of the drivers, so is not obvious.
ALCo practice for outside framed engines retained plain cranks for all but the
main driver, with an outside counterweight for the main rod's big end's
revolving weight, with this arrangement possibly limited to larger engines. The
K-28s and the Oahu's four copies show this arrangement. One notable variation
were the ten 30" gauge 2-6-6-2s built for the Serbian Government in 1915, which
had a full circle counterweight on both main drivers, and plain cranks
elsewhere. But the other half of that order, ten 30" gauge C-21 equivalent
2-8-0s, retained plain cranks all around.
As for thicknesses, I once found a set of drivers for a 2-8-0 outside at the
Silver Plume Shops. My approximate recollection is that the cranks and hubs
were about 4" thick, the main counterweight nearly this thick, the end
counterweights about 2" thick, and the intermediate counterweight about halfway
between. The outside face of all were in the same plain, with excess materiel
removed from the backs. Plain cranks would run 3-5" thick at hub and pin,
depending on the size of the engine, and are generally much smaller diameter at
hub and pin, than on commercial models.
Regarding availability of near HO scale outside counter weighted cranks, MDC had
plain cranks and the narrow K-27 style counter weighted cranks. Keith Wiseman
has offered, as part of his old PIA stock, sets of K-36 cranks that look to be
much closer to prototype than those on most commercial models. These are brass
castings intended for 44" drivers and 22" stroke, but could be reduced. I do
not recall anything in the PSC catalog. English sources should also be
investigated. Sharman Wheels, also now long gone, once offered both 15 and 120
degree counter weighted, and plain cranks, of about 5mm stroke. These were
molded in nylon with integral 1mm steel crankpins for use with 1.5mm bearings,
and intended for 2mm axles. It is possible that one of the OO9 or 3mm suppliers
has continued these. Alan Gibson Models offers some 4mm scale outside cranks of
similar specification, but I have not inspected these, and AGM do not give their
- So, basically all K-27, K-36 counter weights on all models from all manufacturers are not to scale. Apparently, this highly visible part of the monkey motion just isn't that important to be scale thickness at all. If that's the case, maybe we could even get by the round wire connecting rods, too.
This issue always struck me as a ridiculous and obvious oversight based on the real loco's obviously very thick counter weights. For my part, the most obvious moving parts visible on the above models, when in motion, are just found to be little flat pieces of sheet metal.
- Could this be related to the fact that our models need to be able to run on much tighter curves than the originals? There must surely be more lateral play for the axles. Thus prototypical thickness of the counter weights would result in models that have the rods sticking out too much. and that would be more of an optical problem than the too thin counter weights. That's just a thought.
> So, basically all K-27, K-36 counter weights on all models from all manufacturers are not to scale.
- Also because the frame is much wider than the prototype because the wheel
thread is much wider than scale. And the cylinders are wider than than
scale. Its a cascade effect. A truly scale model would look quite differant.
- Thanks to all who answered my query. So, in spite of all our best efforts at scale decaling, painting, and scratch building, etc. Our engines are pretty far out of scale dimensionally in order to allow for proper curve negotiation and general overall esthetic appearances. I guess we just have to grin and bear it.