Just when you think you've seen or heard of everything, even about an essentially dead subject as steam locomotives, something you didn't know turns up. In this case, it's a proposed (but never built) Willamette with 6-wheel trucks:

http://www.mrollins.com/Images/willam2.gif

Of interest is that the trucks seem to have the outer axles articulated, making the wheel arrangement (using Diesel terminology) A-B-B-A.

Sources:

http://www.mrollins.com/willam.html

http://www.mrollins.com/geared.html

Have fun.

Very neat find? Are there any other details about the locomotive?

Almost nothing at all, at least on the web. This is the specific page the drawing is from:

http://www.mrollins.com/willam.html

Wikipedia page on the Willamette, which mentions nothing of this proposal:

http://en.wikipedia.org/wiki/Willamette_locomotive

The page does have a reference to a book titled "The Willamette Locomotive," by Steve Hauff and Jim Gertz, published by Oso Publishing in 1997. That could be the source of the drawing Mr. Rollins has.

It seems an irrelevant design, because was any shay close to exceeding axle load limit?

The drawing does appear on page 53 of the Hauff & Gertz book, although there is no other information other than it was a preliminary design that was quickly shelved.

Fun to think what may have evolved had Willamette entered the geared locomotive manufacturing business just a few years earlier.

Their offerings were pretty limited, 70-3 models, either saturated or superheated, a pair of 50-2 models and four 75 ton machines. These last ones had cylinder bores only a half inch larger than the other 3 truckers, a very modest step up.

Would like to have seen something to rival the 90-3 class Shays, they had a t.e. of 40,400 lbs. At least one that went to Vancouver Island in Canada was rated around 42,000 lbs. account of a boiler pressure increase to 210 lbs. These were really stout pullers for woods work.

I would probably call it (A+B)-(B+A) but then I'm the one who insists that there is no place on a U50 described by a + sign. (I would describe them as (B-B)-(B-B). YMMV.

Steve

This is one of those places Lionel Wiener could be of use.

Part of the issue being how the articulation is handled, part being how the axles are geared. I cannot tell from the posted drawing and don't have the book -- is there shaft drive to those outer axles?

Some of the European notation systems might be closer to what's involved here, for example the Bo convention (I don't have the degree symbol at hand) for uncoupled axles. What you'd have if the outer axles articulate, as it would seem they do, is

Ao'B + B'Ao

showing that the outer 'trucks' are articulated to the sideframe, ut within the common truck wheelbase.

RM- I think you need a higher resolution monitor. The outer axles show pretty clearly as being geared on my monitor.

Any idea of what the intended use of such a stout Willamette was? I'd bet something other than logging- maybe something along the lines of Western Maryland Shay #6? Oddly, the steam feed to the cylinders comes directly from the dome so it would not have been superheated.

Hugh, you could be right about that. Taking another look at the drawing, I just noticed a sloping sheet in the rear tank. That suggests this locomotive, at least as drawn, was intended to be a coal burner.

Now, Willamette was in the Pacific Northwest. All of their engines were built as oil-burners, except for one or two that ran on wood, which is what you would expect for logging engines out there. Oil burners don't normally need or have sloping rear sheets in their bunkers, and neither do the wood-burners I'm familiar with. So, who would they be designing a fairly large saturated coal-burner for?

So far as I know there is only one Willamette built to burn coal, Big Blackfoot Railway #7, built to operate on logging branches of the Anaconda Copper Mining forest products division around Missoula Montana.

The engine survives on static display at the Historical Museum at Fort Missoula in Missoula Montana as the oldest of the six remaining Willamettes. It is a saturated engine.

I have now blown up and enhanced the image, and have some better comments.

The three-axle arrangement is NOT primarily to spread the weight, it's more to give better guiding.

Not only is the 'third axle' geared, it has its own large 'drum' universal like the ones in the main shaft. This tells you the third axle is going to be doing considerable relative motion to the shaft portion on the B truck.

Looking carefully at the drawing, you can see a heavy equalizer running from the center pivot location on the B truck to a point centered over the 'third axle' truck. I could confirm this if I had a front elevation, but it's not really necessary if you know what's going on.

Now it gets more interesting. If you look at the inside of the 'single-axle' truck you will see that it has a Bissel-like radius bar, going to top and bottom of the single-axle frame to keep it from tilting. Presumably this is what translates the torque from the gears into tractive effort.

Those among you with mechanical knowledge are saying 'but isn't that overconstraint?' And the answer would be yes if that equalizer were pinned to the top of the frame, or the radius bar were the 'correct' length (a bit like that for radiating axles). I submit that the arrangement works as follows:

Equalizer is centered and NOT pinned to the forward truck frame -- slides or articulates laterally but slides. See the arrangement on N&W 1218 for an example.

This arrangement allows the third axle to freely cross-articulate on uneven track. It is in its own frame, with springs, and can therefore adopt a considerable twist relative to the frame and axles in that B truck -- you would NOT have this flexibility in a regular three-axle truck.

Radius bar means that the forward axle swivels like a lead truck -- and guides like one, too -- this gives you a first approximation to radial steering too.

If I'm not mistaken, this would guide BETTER than just a B-B arrangement (where the leading axle is essentially pushing into the curves until the frame -- and all the shaftwork and slip joints -- accommodate.

As an 'exercise for the reader', I invite you to tell me exactly what kind of bearings are on the back, front, and frame bolster of this locomotive in order to get it to work. I have been playing with T1 spring rigging so my thoughts are probabluy a bit biased toward high speed... ;-}

This little bitty Mac Air screen is NOT doing my eyes any good.




RME

My best guess is that the center bearing of the 4-wheel truck, and the body bolster bearing of the equalizer (or span bolster?) would be standard spherical or bowl bearings, such as used on freight cars, or whatever the equivalent would be on a Willamette or a Shay. The big question comes with that articulated and powered single axle truck. If it is set up to swing like a leading truck relative to the four-wheel truck, that would suggest a lateral movement device for a lead truck, such as swing links or inclined planes and rollers. This would be required because the distance from the center bearing of the four-wheel truck to the center of the single axle truck will change as the truck swivels. This wouldn't matter if the single axle truck had two axles and could adopt its own position independently, as the trucks at each end of a true span bolster do, but this single axle swivels from a point on the four-wheel truck behind it, and that point doesn't coincide with the center bearing of the four-wheel truck.

Some diesels in Great Britain and some other places had a 1-C-C-1 (or would it be 1-Co-Co-1?) wheel arrangement; these were true trucks at each end of the locomotive, as opposed to a large articulated unit like a GG-1 electric. This arrangement was intended to improve tracking at speed, and was also used to help keep axle loadings down. Those outer axles weren't powered, but I wonder what they used for their articulation or equalization layout.