Here's a shot (through glass) of an ALCO builders photo of KCS 2-8-0 # 557. I'm wondering about the short extension off the side rod and/or crank pin of the rear driver. I've never seen this used before, and have no idea how it works or what it does. I posted the photos over on "Trainorders" but no one there had a logical answer, and the post is on the down slide now. Maybe some different steam experts on this board can figure it out.

Could it be some sort of speed recorder? The rod going up to the cab could potentially be a drive shaft to an indicator in the cab.

As for the motion, It would seem that the arm on the device would revolve around the center of the device.

Can you post a full photo of the engine? Maybe it is part of some other appliance on the engine.

Per some of the train order comments, the engine clearly has an injector, just to the right of the device in question. I don't think the device has any relation to the grates or ashpan.

Can you give some history on the engine. When was it built?

I'm also guessing here, but suspect it is some sort of speedometer drive. The Smith-Stone speedometers used on "modern" British built steam locomotives are often driven off a return crank on a trailing driving axle, in a position somewhat similar to that in the photo. It looks as though this one is driving a rotating shaft up into the cab, it's interesting to note the slot on the rotating arm to allow for slack and suspension movement. A very interesting question!

P. Hosford

Could be the speedometer drive I guess. Three people have suggested that, but when the wheel rotates 180 degrees, the arm would be at least a foot above the axle center, about in the center of the tapered housing. I think there would be a simpler way to drive a speedometer, but who knows. I just can't see how the thing would function if you imagine the wheel in other positions, or the wheel & rod making a revolution. That might be the reason it didn't become more popular. One revolution and it's twisted scrap. Here's a crappy photo of the engine, real hard to get a decent photo through a glass picture frame.

the rod would revolve. it looks to be on the same center as the crank pins on the axles.

This is the extension when the side rod is in the "down" position. Would really be nice to see a photo with the side rod in the "up" position. Wonder if any such photos might exist?

Les

There should be no need for the linkage to become twisted scrap on the first revolution of the drivers.

It appears the bulbous apparatus on the bracket is simply a right angle gearbox, and rotation of the drivers/ movement of the rods will simply, and reliably, spin it. As noted above, its connection is slotted to accommodate the up-and-down movement resulting from spring action on rough track.

It's actually a nice, simple way to obtain the rotary motion required for a speedometer.

Steve Hunter

Does that extension stay rigidly in line with the main rod? Or does it pivot at the driver pin? Either way, it seems like a lot of motion going into that structure hanging down from above. I can't picture it working, but I am not sure what that hanging structure is capable of doing.

If it is driving a rotating shaft, how does the device convert the reciprocating action into rotary motion?

.

Kelly thanks, I was going to draw that exact illustration!

That helps to see what is going on. I can see the rotation transferring to the angled shaft. How the rod extension passes the gearbox and/or that support frame is still a little confusing. But it is hard to tell what depth those items are in relation to each other.

It looks like the gearbox is set between a pair of supports, and that its crank rod passes between those supports. Yet the rod extension stays outside of the outer support. But that cannot be the case because the outer support would interfere with the crank pin. I guess the whole shaft extends out past the outer support, so the rod extension and the crank lever run outside of the outer support.

...I'm with Kelly on this one... ice cream maker.

For heaven's sake, you can tell the arm doesn't go around in a circle like the countershaft on some versions of Nord salmon-rod drive; there's no clearance at the top. The slot is too long for 'suspension travel', I think it is acting like a Scotch yoke to allow conversion the motion of the drive-extension pin into long-throw swing. I do not think the backward extension has a pivot at all, in fact, I see at least two rather substantial bolts keeping it rigid.

You can also tell that darn 'shaft' is a control linkage to something, either with a lever (if pulled) or a control wheel (if turned) at the top, not a driven rotating output shaft. If it were Bowden cable it wouldn't be so straight. If it were any other sort of drive it would have universals. I think it is a simple push-pull shaft, that engages and disengages a clutch or tumbling mechanism. That it is on the fireman's side suggests something.

If this isn't a grate-shaking apparatus or something like it, I'll be surprised. Surely there are contemporary references to something like this in the literature.

I don't think anybody has suggested that the extension is not rigid with the main rod. I assumed it was rigid due to the appearance of the two bolts you mention. Kelly's diagram assumes that the extension is rigid with the main rod.

Does it have anything to do with the Elvin Mechanical Stoker, or is the inclusion of the connecting rod extension in the description figure coincidence?