Baldwin Unitah 2-6-6-T Superstructure Mods

This engine is being bashed from a Roundhouse Outside Frame 2-8-0 kit and a Roundhouse 3 in 1 kit.  The superstructure will primarily be made up of components from the 2-8-0 kit.  This superstructure project will have us doing the following:

  • Extending the 2-8-0 boiler.
  • Relocating domes.
  • Scratch building side tanks.
  • Bashing the cab to add a side door, shorten its length and add a bunker.
  • Extending the front pilot deck.
  • Detailing with brass parts.

Here is a Jon Davis drawing of a Unitah 2-6-6-2 articulated locomotive.

Unitah Mallet Davis Drawing

Extending the Boiler

Note that the front of the smoke box falls at about the midpoint of the front cylinders.  The following photo of the Roundhouse boiler shows the extent to which the boiler needs to be extended so that the smokebox falls in the right place.  By my calculations, the boiler needs to be extended by 0.8″.

2-6-6-2 Unitah Boiler Ext

A consideration in the boiler modifications needs to be that the underside if the boiler needs to be open to handle the drive train that will be powering both sets of drivers.  This image shows the underside of the boiler.  The drive train slot works fine for a 2-8-0.  Not so much for an articulated 2-6-6-2.  Note that the weight (silver object) is held in place by rivets.

2-6-6-2 Boiler Underside

The logical places to make the cuts to extend the boiler is shown in the following image.  One potential cut spot is right behind the smokebox (right cut line).  The problem with this location is that the splice will be fairly visible.  Another potential cut place is behind the right dome.  That cut/splice would push the dome closer to the front of the engine but the splice would be less visible as it would be hidden between the saddle tanks.

2-6-6-2 Boiler Cuts

In either case, the cut would be through the weight.  I’m considering relocating the weights to the saddle tanks, freeing up space under the boiler for the drive train.  At this point I prefer the right cut point as engine smoke boxes are often a slightly different diameter than the boiler because of the lagging applied to the boiler.  In addition, the splice may be far enough forward that the underside doesn’t need to be open to accommodate the drive train.

Plastruct makes tubing that is available in a variety of different diameters including 0.75 inches, the measured diameter of the Roundhouse boiler.  The Plastruct tube walls are 1/16 inch thick.  The next smallest tube (0.625″) slides tightly inside the 0.75″ tube allowing very solid support of the splice.  I may have to either taper a bit or shim a bit on the roundhouse sides of the splice depending on the thickness of the Roundhouse boiler casting.

So I cut the boiler at the right cut line and ended up with this.

2-6-6-2 Cut Boiller

All I have to do is make this work is:

  1. Remove the weights from both cut sides – doesn’t look easy.
  2. Cut a 0.8″ piece of the Plastruct tube and order the next smaller size so I can splice the three pieces together.
  3. Slot the bottom to clear the drive train.
  4. Cut off and relocate the domes.
  5. Whatever else is needed to make this work.

Or I could replace the entire boiler with Plastruct tube.  I would need to:

  1. Slot the bottom to clear the drive train.
  2. Place the domes where I need them – brass domes on order from Wiseman.
  3. Add a smoke box cover – on order from Wiseman.
  4. Fabricate a fire box – would need to be scratch built.
  5. Put bands on the new boiler – some styrene strips.
  6. Whatever else I need to do to make this work.

Somehow the latter sounds easier than the former so that is what we’ll do.

Saddle Tanks

Support of the saddle tanks is already cast into the Roundhouse boiler in the form of running boards. Or I will need to add supports to the new Plastruct boiler.  The saddle tanks will be scratch built from styrene.  Th hollow space inside the running boards will be filled with sufficient strip weights to more than offset the loss of weight inside the boiler.

Bashing the Cab

Not counting the bunker, the cab on the 2-6-6-2 is shorter than the Roundhouse cab.  With the bunker on the rear, there is no rear access to the cab so doors or door openings need to be added.  A consideration in bashing the cab and adding a bunker is that DCC and sound are anticipated. So the cab/bunker will need to accommodate a speaker and provide a space for the Soundtraxx Ecomomi DCC unit and sound circuit board.

Extending the Front Pilot Deck

Logging articulated engines had relatively long front pilot decks.  That was certainly true of the Unitah 2-6-6-2T.  There are a number of options for extending the depth of the pilot deck and putting a more prototypical front beam on the unit.

Detailing with Brass Parts

Wiseman just released an array of detail parts for HOn3.  I have a representative sampling coming to me.  Some of the parts are going to be used to give my engines a family feel.  Others are very specific to the Unitah Mallet including a deck mounted headlight, a potential front deck, Unitah front trucks, etc.  Check the Roundhouse Kits Detail Parts post for more details.

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