Now the model of the current UP excursion train water tenders is all finished in N scale, I turned my attention to the Pre-Rebuilt version.

My original thoughts were that this would be an easy design, as I had already drawn the main components, all that I would need to do is remove the embellishments, adjust the shape and print.  I was very wrong.  Although the two designs were built from the same tender they went through a lot of changes to get from old to new.

Here are two of the tenders in their 1955-2007 configuration.

(Photo by Richard Wrede: UP 3985 In Dunsmuir,Ca. taken in 2005)

And here is one in it’s 2007-present configuration, and yes they are the same type of tender.

The obvious details that where different from the new 2007-present tender such as the grab rail on the top and the chamfered ends would be fairly easy to do.  The main challenge I encountered was the actual shape if the tender body.  The Pre-Rebuilt body is wider, and longer.  Not because it is bigger inside but because the whole tender was insulated and clad with a second metal skin.  These tenders were ‘hand me downs’ form the large 8500 class Gas Turbines, this cladding covered the heating equipment and insulation which was used to heat the Bunker C fuel oil.  Remembering we are working in N scale at 1:160 I pondered about not changing the body width, that would mean all I had to do was remove the rivet detail from the sides.  But I just could not bring myself to do it so I widened and lengthened the bodies.  This in turn meant both ends had to be remodeled as the radius intersections where the curved areas meet the sides all moved.

With new body modeled in, I could then start adding the detail.  Service holes on the sides are shown below.

End pipe work and electrical ports.

And side piping.

This cars had a lot of piping and from the reference material I could find, it varied from car to car.  The two most common differences I could find, mainly with the pair UP have been using with the heritage fleet, was one had piping running over the top to the service hatch and one did not.  Here is the pipe work going to the hatch.

Using the reference material I was able to mostly work out where the pipes went, some just seemed to go nowhere.  Putting them in over the curved end was the trickiest part as this surface curves in two directions and the pipes don’t run in a straight line.  The piping on the model is not actually round, to give it strength it is curved on top and squared down to the body, making it into an elevated detail rather than a separate object.  This is almost impossible to see in N scale and gives the look of piping running over the body, plus it makes it strong.

Next came the top area, and this car it is covered with an open grill mesh.  This is very hard to do, not that it can’t be printed but because it would either look way too chunky or be so fragile it is unlikely to survive the cleaning and handling process.  To overcome this, the piping which runs along the side of the body between the grill mesh and the top of the body has been closed off as shown below forming a solid object.

The grill has then been drawn as a recessed detail which now forms the top of the car.

The end ladders are also different on this tender, plus they had steps made from the same grill mesh.  This made them fairly quick to model, plus this time all four are the same.

As for the grab rails along the top, once again they would either look way too chunky or be too fragile so I have not included them in the print, however we will cover them in a later post.

The final details to add such as the tool box came last.  The trucks and chassis where used from the previous water tender model, although I couldn’t help my self and did some improvements on those too.

And here is the finished 3D model.

And you can get them here.

So not the quick turnaround I first considered, but I think well worth the extra effort.  The model is sized correctly and I think it will look fantastic.  In a later post I will show how it came out.

The Union Pacific railroad heritage fleet currently runs two of their preserved steam locomotives on regular excursion trips and, with the very much anticipated Bigboy No. 4014 re-entering service in the next few years, the modelling of the excursion train will become even more popular. With Athearn’s new N scale Challenger and Bigboy locomotives, or even the former Rivarossi models, and the Kato ‘City of Los Angeles’ cars, this can easily be done. The one important thing missing is the extra water tenders now always used for the long trips.

Ever since the switch from steam power to diesel the supply of water along the railroad has all but dried up; often you can see local fire department filling the excursion train locomotives water tanks with their pumping equipment at stops along the way. To combat this UP have created auxiliary water tenders which hold more water than the engine’s own capacity and greatly increases the range of the excursion trips. Currently, my understanding is, the UP has four auxiliary tenders in the heritage fleet.

Here is UP 844 in Oakland, California in 2009, accompanied by one of the auxiliary tenders whilst on an excursion trip stopover.

These tenders started life as regular coal and water tenders for the 800-class steam engines until the engines where decommissioned due to the new diesels. However when the new 8500 class gas turbine locomotives, built by General Electric, started being used by the UP, the need for tenders to hold their bunker C fuel oil was created and the old 800-class tenders where recycled for this purpose. Because the bunker C fuel oil needed to be kept warm so it could be pumped as a fluid, the tenders were fitted with a heating system and a second metal skin for insulation and to cover the system. When the UP retired the 8500 Gas Turbines the tenders remained in storage until the heritage fleet commandeered them for the excursion trains. The heritage fleet used the tenders in this configuration until 2007 when two were rebuilt removing the heating system and the second skin. This increased the water capacity by 3000 gallons to 28,000 gallons. These two tenders were christened UPP 809 Jim Adams and UPP 814 Joe Jordan after two retired steam fitters from the UP repair shop.

I wanted to produce models of both versions of the tenders so I could replicate both periods (pre and post 2007). I decided to start with the newest incarnation and set about producing a 3D computer model.

I used a mixture of images and drawings from the internet and books to get the correct dimensions.  There’s a 8500 gas turbine and tender at the Illinois Railway Museum and they have lots of good pictures, as do Wasatch Railroad Contractors, who did the conversion on water car UPP 814.

Some elements were simply too small to be reproduced in N scale, such as the handrails that run along the top and up the ladders.  I decided that it would be best to add these using brass wire at a later stage.

To make this easier to paint I separated some of the detail parts from the main model body.  The ladders, roof tool boxes, headlights and flag plates are all loose parts, as are the trucks, chassis and bolster pins.  Here are the parts laid out ready for the first test print.

The body has been designed to take Micro-Trains body mount couplers.  The bolster pin that holds the trucks to the chassis has also been positioned off centre, unlike the prototype, so that the trucks can be removed without removing the wheel sets.

In the next post I will show you how it came out and what improvements needed to be made before it was ready for the final print.