Thursday, April 9, 2015

A tender behind?

Historically, steam locomotives consumed large quantities of water and fuel.  The nature of the technology - the state-of-the-art in its day - was essentially a giant tea kettle that boiled water to make steam, allowed the steam to build up pressure, used the pressurized steam to perform work, and exhausting the remaining water vapor to the atmosphere.

Light locomotives such as the SCPC 2 or those that operated with limited range may have used a tank to carry extra water.  Thomas the Tank Engine is another example.  Larger locomotives and those requiring greater range used a tender behind the locomotive.  Which brings us to the point of the story: locomotive 924 is under rehabilitation at the Northwest Railway Museum and is receiving a new tender tank.

The lower half of the original tender
tank is worn thin and will no longer
hold water.
A tender tank carries water.  The inside of any tank is almost always wet and will eventually rust from the inside out.  924's tank was constructed in 1899 and today portions of the sides resemble decorative lace, but are made of iron oxide and steel.  Repairing this type of deterioration is time consuming, and often results in additional water leaks just a few years later.  It is difficult to keep ahead of this type of problem and with the price of water in the Northwest, it can get expensive.

New steel parts for a new tender tank
arrived on a trailer from Portland.
924 is expected to operate reliably and a tender tank that does not hold water without measurable loss will never meet that expectation.  So a new tank - an exact copy - is being fabricated inside the Conservation and Restoration Center. The project team thoroughly documented the tender and created a drawing set.  Then, early in February, all the components arrived from a supplier who cut each piece to size and formed shapes such as the radius on the front of the tank.

Rivets are heated and driven with a
pneumatic rivet gun.  The job is
particularly demanding for the person
holding the buck (at left), which backs
up the rivet gun blows.
The heavy work and time-consuming portion of the new tender fabrication is the assembly.  Each piece was moved into position and then lightly tack-welded using an electric welder.  Holes were drilled where rivets were located on the original tender.  Then staff and volunteers applied (or continue to apply) more than 2,000 rivets.

The original tank was removed with a
large excavator and was placed in
long-term storage in the Museum's
Meanwhile, castings, fixtures, and any other part that could be reused from the original tank were carefully removed.  The old tank was unfastened from the deck and frame.  A large excavator was used to lift the tank off the deck and frame and set it aside for long-term storage.

The tank fabrication is nearing
completion, but more rivets are
The tank will remain on the shop floor and many more weeks.  The tender frame requires rehabilitation too, and the tank requires are few more rivets, some hardware, and some paint.  It work continues to progress at the current pace, a fully rehabilitated tender - with new tank - will emerge from the Conservation and Restoration Center in late spring or early summer.  Work will continue on 924 for at least the next 18 months, especially because of the awesome volunteers and staff.  And there is an opportunity for you to help support the project by participating in the Seattle Foundation's Give BIG event on May 5!  Stay tuned for more information.


David said...

Spike, The Northwest Railway Museum certainly has some dedicated and hardworking volunteers! That photo of SCPC #2 is a classic and classy shot... Take Care, Big Daddy Dave

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