CNR 3737 :: Pump for Feedwater Heater

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On Friday, Andy Malette and I held another session at his place to work on our CNR S-3-a class 2-8-2s. Having installed the Elesco Feedwater Heater during our previous session, we moved onto the pump that supplies water to this appliance.

The water pump sits ahead of the compressor, under the running board. But before I could install the water pump, I had to make room for it. This involved cutting away part of the running board on the fireman’s side then fabricating a new section of running board.

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Using my fireman’s side photo, I planned the running board modification. I measured and marked the running board, then used a pair of tiny metal shears to cut the running board in two places, from edge to boiler. I then used the resistance soldering iron to remove the isolated midsection. More heat and a wire wheel in a Dremel Tool took care of the lumps of solder left behind on the boiler. I also removed the sand lines, which need to be re-routed.

Before installing the new running board and the water pump, it seemed like a good time to fill the holes left by the model’s check valves.

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(That hole in the boiler, just behind the foremost sand line, is the location of the original check valve. There’s one in the same location on the other side of the boiler, too)

I found a piece of brass rod just larger than the hole, and used an appropriate drill bit to open up the hole to accept the rod. I then tinned the hole and the rod and used plenty of flux and the resistance soldering rig to secure the rod. One it was in place, I used a cut-off disc to carefully cut the rod as close to the boiler as I dared. I then ground down the rod flush with the boiler, and finished up with progressively fine grades of sanding paper.

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(… and the hole is filled. I still need to polish the scratches out of the boiler)

I then fabricated a new running board segment from .020″ brass sheet. I used CA to spot-glue the segment I removed to my piece of brass sheet, with the outside edge flush to a sheet edge. I then used a pin so scribe the inside edge, which needs to follow the shape of the boiler and fit around the boiler bands. I made sure I had extra sheet stock to the left and right of this pattern, then sliced the original running board segment off the brass sheet, sanded off the CA, and cut out the new segment with shears. I then filed the new running board segment to final shape.

The new segment sits above the original running board, with tightly curved ends that meet the running board segments ahead and behind it – hence the need for extra material to each side of the new running board. I located the point at which I needed to make the bends and folded them down using pliers. I then measured the height of each folded down section and used shears to cut off the excess material. There are also various notches along the boiler edge to allow for the passage of piping, so I marked those out and filed away the unneeded material.

With the new section fabricated, I soldered it to the boiler then used photographs to locate the water pump. It’s centred just ahead of the boiler band over the third driver.

I cut and folded an L-shaped bracket for the pump, then soldered the pump to it using the provided mounting post. I trimmed the bracket so it would support the pump in the proper location, then soldered this to the boiler.

I finished up by placing the boiler on the chassis to ensure that the new water pump doesn’t interfere with the valve gear. It barely clears – but it’s sufficient.

Every work session brings this bog-standard USRA Mikado closer to my chosen CNR prototype. Compare the photo above with this photo of the stock model, taken just before we started this project:

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The main reason I’m doing this project with Andy is I did not have the know-how required to tackle it myself. I’m learning more at every session, What’s more, I’m throughly enjoying this project and look forward to what we tackle next!

6 thoughts on “CNR 3737 :: Pump for Feedwater Heater

  1. Nice recap – I really enjoy following along with this project. You mentioned using “tiny metal shears” to cut the running board. Which shears are you using?
    Thanks…gregg

    • Hi Gregg:
      I don’t know the brand. They belong to Andy. They looked like a tool from Micro-Mark or Xuron. I’d check a well-stocked military modelling shop to see what you can come up with.
      Cheers!

  2. Apropos of nothing, when I sorted my storage locker tubs yesterday, I realized that the HO Scale Athearn Genesis CNR Mikado i have is an S-3a as you and Andy are doing in S Scale. Not that I need more projects, but acculturating the model has long been on my maybe someday project list. Maybe I’ll have you use your brass endeavors to motivate me to work on my 3708!

    • Hi Stephen:
      That’s great news – I’m glad that sharing this project on my blog is providing inspiration!
      You’ll probably get your 2-8-2 finished before I get my D-1 completed…
      Cheers!

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