Lead and trailing trucks on prototype steam locomotives versus models

[trailrider]

Compared to prototype curves, the ones on our models are much more severe. Our model steam locomotives have the two-wheel lead and trailing trucks connected to the frame with a link that permits radial movement. Likewise 4-wheel trailing trucks, while four-wheel lead truck pivot on a mount generally under the cylinder block.
Do prototype steamers (fixed wheelbase) work the same way, or do the 2-wheel trucks slide transversely, with their bearings attached to the frame by some sort of link arrangement? How about four-wheel trailing trucks? Four-wheel lead trucks? I have books that show the trucks, with different names, but no details on how they work. The Delta-B trailing trucks look like they might pivot like those on a model, but I'm not sure.
Just curious.

 

[kjd]

Even though you're off the Christmas card list after the "awful BN green and black" comment on Sunday, I found this link showing the attachment point of a lead truck for CNW 1385, a 4-6-0

It looks to me very similar to how our models are constructed. Here is another drawing from Alamy but it's not clear what the truck is off of. It looks like there is some mechanism for allowing lateral motion, more elaborate than a slotted screw hole.

Trailing trucks seem to be attached on the models similar to how they are attached on the prototype, with a pivot behind the rear driving axle. I couldn't find a quick photo but I've looked at the engines at the Oregon Railway Heritage Center in Portland, OR. As a sidenote, UP, and maybe SP, often installed booster engines on the trailing trucks. They were used for starting out and shut off when the Johnson bar was moved from the corner, ie, the engine was not trying to muster as much tractive effort as possible. Google "Franklin Booster Engine" for one example.

 

[trailrider]

Thanks, kjd! The Q (C.B.&Q) also used boosters on some, but not all of their trailing trucks. I'll check on your link when I have more time. As far as the BN pain scheme is concerned, I like the BNSF scheme for their "motors" (diesel engines) much better, as it is similar to the old GN one, which is great!

 

[Iron Horseman]

I like the BNSF scheme, as it is similar to the old GN one, which is great!

So you are a pumpkin patch kind of guy? I can handle the paint scheme ok, definitely not my favorite, but what I can't handle is the Wedgie logo.

To the topic of the thread, the leading truck has to have some mount that allows lateral movement while at the same time has to be stiff enough to "nudge" the locomotive in the direction it is traveling. I mean that is the whole point of a pilot, is to guide the way. Hey locomotive wheels behind me we are turning THIS way, follow me. I have only 1 model loco that does that, and it is one I modified with a piano wire "spring" going from the pilot truck back to the frame of the loco.

Trailing trucks are just there to support the weight of the firebox. That is the one I have a hard time understanding because as you say there is a pivot that almost just looks like an elaborate permanent trailer hitch. How does that support weight directly above it. Or is is like the trailer load distribution hitches. Holds up the back of the locomotive like a wheel barrow?

 

[kjd]

More like the stinger on a heavy haul lowboy instead of a trailer hitch.

The models are different there since it would actually be better to not take any weight off the drivers. A steamer should be balanced on the drivers so, while the model lead and trailing trucks attach in a way similar to the prototype, they don’t need to function the same.

 

[KriegslokBR52]

So you are a pumpkin patch kind of guy? I can handle the paint scheme ok, definitely not my favorite, but what I can't handle is the Wedgie logo.

To the topic of the thread, the leading truck has to have some mount that allows lateral movement while at the same time has to be stiff enough to "nudge" the locomotive in the direction it is traveling. I mean that is the whole point of a pilot, is to guide the way. Hey locomotive wheels behind me we are turning THIS way, follow me. I have only 1 model loco that does that, and it is one I modified with a piano wire "spring" going from the pilot truck back to the frame of the loco.

Trailing trucks are just there to support the weight of the firebox. That is the one I have a hard time understanding because as you say there is a pivot that almost just looks like an elaborate permanent trailer hitch. How does that support weight directly above it. Or is is like the trailer load distribution hitches. Holds up the back of the locomotive like a wheel barrow?

Trailing trucks on real steam have in fact support pivots right under the fire box which work on sliding motion (friction bearings) and need to be greased. The suspension linkages (equalizer bars) are adjusted accordingly to either put more, or less weight on trailing trucks. For pulling power the equalizer bars are designed to put less weight on trailing trucks. Interestingly i've overheard a conversation between older gentlemen, that in order to incure less labor costs, steam locomotives of the Reading Railroad, the T1s were designed to carry more weight on the trailing trucks than normally. Apparently the engineers were being paid by the tonnage they pulled with their steam locomotives, so less tonage=less pay. This lack of friction bearings on model steam locomotives is what i don't like about models, there is empty space on models between trailing truck and main frame, when in reality that space is filled by slide pivots. On one model which i worked on, i made sure there is no empty space:

You can see the friction bearing on this Pennsy M1b just ahead of that trailing truck wheel:

 

[Iron Horseman]

Apparently the engineers were being paid by the tonnage they pulled with their steam locomotives, so less tonage=less pay.

They still are indirectly. My software has a function for a "weight on drivers" differential that the engine craft gets.

This lack of friction bearings on model steam locomotives is what i don't like about models, there is empty space on models between trailing truck and main frame,

Agree. Have never liked that huge vacant space one can see when looking directly "side on" the models.