WM Shay No. 6 was the largest Shay built by Lima, and is standard gauge.  The largest Shay ever was WVP&P (Cass) No. 12.  It was built as a large 3-truck engine, but was rebuilt at Cass as a 4-trucker and tipped the scales at over 200 tons.  Unfortunately, it was scrapped in the late '50's before the state took over the former Mower Lumber Co. operation and turned it into a state park. 

My memory was a bit faulty.  The correct formula is 5,730/degrees of curve = radius.  Therefore, that 36" radius curve is almost a 23 degree curve. 

In railroad engineering, the measurement of curves is based on the number of degrees of arc of a circle subtended by a chord of 100 feet.  The larger the radius, the smaller the angle.  In the prototype world, curves of 10 degrees or more are considered tight.  If I recall rightly, the formula to get radius from degrees of curve is 5,632/degree of curve = radius.   Using this as an example, a 36" radius curve in HO would be about a 22 degree curve.

The B&O B-18 Ten-Wheelers would fill the bill.  There were originally built with slide valves but most if not all were rebuilt with piston vavles and Baker valve gear.  This link shows one still in service in 1953:  http://www.northeast.railfan.net/images/bo2034s.jpg

There have been brass models of these locos done in the past.  Another brass option is the Arkansas and Louisiana Missouri 4-6-0.  I think it may have been a PFM import.  Very similar to a Kishicoqulis Valley RR engine.

When I was a kid, there was a hobby shop that was largely trains about 2 miles from the house.  When I was old enough, I could bike there.  Downtown DC once had three major hobby shops - one was trains exclusively, one was mostly trains but also boats and planes, the other was primarily Lionel.  There was another train shop about 6 miles the other way.  All of them ultimately were lost to various urban redevelopment projects.  Today, aside from the Timonium train shows, the only really decent train stores are Kline's, 45 miles away north of Baltimore and Mainline Hobbies, sixty miles away. 

MDC/Roundhouse once made a metal kit for a Southern Pacific 0-6-0 that is really pretty generic.  If Bachmann were to approach such a project, I would suggest that the model be done in two versions - One with slide valves and inside (Stephenson) valve gear, and one with piston valves and Walscheartes valve gear.  I suspect a lot of the USRA 0-6-0 parts might be adaptable to this. 

I for one would vote for the B&O 2-10-2.  I'm trying to mate a Rivarossi superstructure to an IHC mech, and it's slow going.  I also agree that the Harriman stable has been woefully under-represented.  Re:  The B&O Q-4b, the light Mike mech with a Delta trailing truck is "close enough".  The boiler is sort of half-way between a light and heavy USRA, and the Vandy tender would be a nice new addition.  OTOH, the light Mike is offered in B&O, which is a class Q-3.  I would actually like to see something like the heavy Ma and Pa 2-8-0's.  They would fit in almost anywhere.

Photos are not coming through for me.

Split gears have a long history.  I have a Gem NP 2-8-0 that is at least 40 years old.  The gear split on that loco about 15 years ago.  I have an Athearn/Roundhouse old-time 2-8-0 that I intend to use to put under the old superstructure to solve that problem.  I think that Gem gear is nylon.  NJ Custom Brass diesels were also notorius for splitting gears, even sitting on the shelf.  And the Athearn Genesis USRA light Pacifics and Mikes would also split gears by themselves.  Metal gears would solve a lot of these issues but I guess there is a cost point the manufactures don't want to cross.

With Lee Riley gone, I would not be shocked if that were the case. 

Just a reminder that the Mid-Atlantic Narrow Gauge meet is this Saturday in Kimberton, PA.  Located on the fire company grounds.  Kimberton is near Valley Forge, and just south of Phoenixville.  Dealers, modules in most all scales, lots of knowledgable modelers.  Entry fee is $15.00.

I'm pretty sure that the loco is Little River RR No. 110.  It is the smallest 4-6-2 ever built for a standard gauge U.S. railroad.  I believe it still resides at a museum in Indiana.  It's definitely too modern for the post-Civil War time frame.  There are at least two period-appropriate locos out there - the "Leviathan" and the "York".  Both were built by Kloke as copies of mid-19th Century 4-4-0's and both are operable.  You can take a look at the "York" on the net.  Search for "Steam Into History".

Had a friend come to vist the layout one day.  My O standard gauge includes a drop-down bridge across the entry aisle.  When up, the bridge is locked in place with a door hinge pin.  Well, after he came in I put the bridge up but, being a bit distracted with the conversation I forgot to put the pin in place (it's a snug fit).  Cranked up the Weaver RS-3 with a few cars.  It made it around at least once OK, but when it got the bridge again the bridge dropped as did the loco.  The only good news is that the Weaver model is plastic, not brass, and I managed to repair it enough that it is still servicable.

I think the Jim Garner movie probably post-dated 1981.  I remember watching it, and I think some of it was filmed on the Texas State RR, which is where I believe the Magma engine is now located.  i'm going to guess this was some time in the early '90's. 

Be aware that the axle lengths of the replacment wheelsets need to be the same as the originals.  This length is not standard.  If the replacements are too long they will bind in the truck frames.  If too short they will fall out.