0-6-0 diesel yard switcher

[Glenn Brooks]

0-6-0 ‘s seem to all have fixed drivers, set into the loco frame. How do they get around tight radius turns?

I assume the middle driver is blind. Are there any other design tricks?

I have an old yard goat that needs restoration. One option is converting it to 0-6-0, and adding a heavier, maybe longer underframe for more traction and work ability.

Thanks,
Glenn

[Bob D.]

Lateral play in the axles. Blind center drivers if the overall wheelbase is large. It is the distance between the outer axle centers that determines the radius limit for the most part.

[rkcarguy]

The switch engine that uses the single three axle truck under it is called the TP-56, apparently it's quite new (2016). They are commonly radio controlled and used in ports for shuffling containers.
I was batting around the 4 vs. 6 wheels in my head last night, and it's difficult to say if the 6 would actually be any better without a really good weight distribution setup that is going to evenly load the 6 wheels in various track conditions.
On the tight radius issues, that's a bit of a tough one. Take into account that 1/87 scale HO scale trains can negotiate a minimum 22" radius with 6-axle diesels, that would equate to 160' radius in full size(which is about half of what the minimum radius really is on real RR's) or a 40' radius in 1/4 scale if you built in similar lateral play in the axles.

[Glenn Brooks]

So the big question is how to build in lateral play? I see several examples of 0-6-0 and 0-4-0 switchers in the live steam world, nut no explanation how the builders made it happen...

G

[rkcarguy]

For a diesel, I think it's as simple as having a loose fit on the axle to the bearings with some end play and let it walk back and forth. A chain drive isn't going to mind +/- 1/4" of misalignment. If you are wanting to have linkage like that little British 0-6-0 then things start getting complicated, because it's going to want to bind when that center wheelset gets out of alignment with the others. I've been drawing up linkage for my maybe-far-in-the-future 0-6-0 steamer and have been stuck with that same problem, because I'll need that center wheelset able to "walk" without the linkage binding up. Do you simply make the pins on that wheelset long and let the rods float around on them with no thrust bearings?

[Pontiacguy1]

You always fix the rotating member to the bearing, and a loose fitting axle is not what you want to do unless it is the outside diameter that is being spun. You press fit the axles into the bore of the bearing so that they do not move relative to each other. For example, if you have an idler pulley, you would press fit the OD of the bearing, and the ID could be loose. For an axle you want the ID to be pressed and the OD can be loose. You then make it so that your bearing can slide side-to-side inside of the axle boxes on their OD, and have a loose enough bore to do so. That's how you get your side play in a locomotive. You can also make the middle drive wheel set have a thinner flange if you use steel tires or wheels, or no flange at all.

Also: The typical radial-type ball bearing can absorb 30% of its rated load in thrust, so there is no need for thrust washers or anything like that if you use a ball bearing in your application and fix your axle boxes so that the thrust goes through the bearing.

[Erskine Tramway]

On Milwaukee Zoo's Pacific, I made the center driver axlebox wider than the end ones. The FMC roller bearing cartridge can slide sideways a little for curve flexibility. In that case the bearing cartridge is 'keyed' against rotation by a bushing that holds the grease fitting.

If you're going to have a side-rod 'diesel', you could use the Heywood style center axle. The wheels are mounted on a sleeve that surrounds the axle proper. They are keyed to the axle, so they can slide sideways.

Mike

[NP317]

Blind center drivers seem the simplest method for allowing tight radius operation.
A very prototype solution, and relatively easy to fabricate.
Then you have all the advantages of an 0-4-0 with the added traction of an 0-6-0.

Downside? Your switch frogs cannot have integral flange guards.
RussN

[rkcarguy]

Blind center drivers seem the simplest method for allowing tight radius operation.
A very prototype solution, and relatively easy to fabricate.
Then you have all the advantages of an 0-4-0 with the added traction of an 0-6-0.

Downside? Your switch frogs cannot have integral flange guards.
RussN

Is this the only way to deal with the linkage on steamers? (i.e. you don't, and have the middle drivers blind). Seems like it wouldn't tolerate much end play and the linkage would bind unless self-aligning bearings were used on the center wheelset's drive pins. Even then the sideways motion would be limited to the side play in the rod bearing driving the center wheelset.

[Dick_Morris]

Then you have all the advantages of an 0-4-0 with the added traction of an 0-6-0.

Everything I've read says the weight on the drivers is primarily what affects traction. Adding wheels without adding weight shouldn't make a significant difference.

[rkcarguy]

Then you have all the advantages of an 0-4-0 with the added traction of an 0-6-0.

Everything I've read says the weight on the drivers is primarily what affects traction. Adding wheels without adding weight shouldn't make a significant difference.

Makes sense, provided the suspension on the locomotive is working correctly so the wheels get +/- equal weight in varying track conditions.

On that note Glenn, maybe just redo the yard goat in a larger 4 wheel setup in an Athearn "Hustler" style and put it to work? If you "geared" for around 3mph top speed (half size your pump), you could use one of the Horrible Freight $120 212cc predators and a single hydraulic pump/motor setup that would make plenty of torque at the wheels.

[NP317]

If weight on the drivers was the only criteria for traction, there would be no 3-coupled or more locomotives.
Every wheel provides additional contact with the rails, which provides opportunity for more traction.
Surface area of contact is part of the traction equations. More contact = more traction is possible.
That's in part what sanding the rails does. Increases contact area. Also of course it changes the coefficient of friction.
RussN