PF powered steam tank engine

[Dread Pirate Rob]

I love the split piston solution! Is there a technic half width lift arm that long available for side rods? I have never seen one.

[Dutchiedoughnut]

That is looking really sharp (well, that family of locomotives to be more precise). Very clean lines and just a nice looking, well proportioned locomotive. Splitting the cylinders the was you did was brilliant. Is there any chance you can align the cylinder exhaust pipes with the stack? It is hard to do on lego locomotives, but since you've split the cylinders it might be possible.

I'd love to! I will look into moving the cylinders, this requires me to enlarge the wheel base for the leader wheels. I can't do much else as the boiler is built around the battery box...

The details in the cab are nice too. Have you considered using the 1x1 round plate with flower edge for valve handles?

Not yet, but I will. It seems like a perfect piece for the job :).

Looking at the mechanicals, you will probably want to build those up in real brick and test how they work. There is a lot of slack in the rods that could cause problems. It looks like you have a 5 long technic half beam that is only pinned to the front wheel and a 6 long that is pinned to both wheels. Then the connecting rod to the cylinder is held in by either a standard pin or a long pin, but in either case it looks like it is off by half a pin (perhaps sticking half a brick inside the wheel). That will likely cause unnecessary friction. The other end of the connecting rod is not connected to the axle pin, but probably better to use a half pin. All of these seem easy to fix if you build up these details, e.g., you could use an 11 long full technic beam for the connecting rods across the wheels and then test it to make sure there are no problems.

The 5 long and 6 long half beams are merely placeholders, I expect to order custom rods when the drive train proves to work without problem. The wheels are all directly drive by the motor, so I am thinking I won't have too much problems. I will need to play around with the connecting rods for sure!

You will also want to test the clearance on the underside, you have a risk of catching switches or grade crossings with the lowest level of plates. The ball couplers might also prove to be problematic if you run on uneven layouts... still might be fine but probably worth testing to make sure.

Yup. There are some alternatives to the ball couplings so I can change those at will. I'm pretty sure the ball couplings will fail under the load of pulling some carriages.

[Dutchiedoughnut]

Here is my progress :). I've moved the cylinders on both engines. And I've reworked the water tanks on the 2-6-4, and added the coal bunker:

[Redimus]

Yup. There are some alternatives to the ball couplings so I can change those at will. I'm pretty sure the ball couplings will fail under the load of pulling some carriages.

I think the biggest issue you'd have with the direct ball coupling is it won't clear Lego curves. My Q-class uses 2 sets of ball joint connected together. It's never had any issues with disconnecting under loads (certainly no load the loco it's self could actually pull) and fits happily around any curves I try, and on any manner of uneven track (which is particularly important when you risk lifting the conducting wheels off the track with a more rigid coupling).

[Dutchiedoughnut]

Trial and error it is then. The tender uses 2 ball joints and a turntable, the leader wheels use a single ball joint, but they would steer them selves off the track if I use more.

I do use two ball joints for the 4-6-0. The four leader wheels will steer themselves, so they require two joints.

With the 4-6-0, the family is complete :). Its boiler is a bit longer (by two studs) and of course the wheel base is a bit different.

[zephyr1934]

Oh wow, those are looking great. While I usually prefer tender locomotives (and anything is better in dark green), in this case I still think I like the tank engine best. They are both very good though.

[JopieK]

Would love to see a little bit more how you managed that! I a still have some struggles with my 7750 PF Mod to make it not derail.