Constructing the Martin Lewis Little Engines Northern Tender

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Carrdo
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Location: Toronto, Canada

Re: Constructing the Martin Lewis Little Engines Northern Tender

Post by Carrdo » Thu May 24, 2018 12:33 am

The bane of my existence is trying to finish these couplers.

Yes, I have two new pairs of matched couplers which fit together perfectly but the knuckles do not snap open or closed until I have machined the special lead in on each knuckle tailpiece. I made a special fixture to machine this lead in as shown in previous photos (as the originals were hand filed).

Here is the actual machining operation using the special fixture. Everything went well.
Attachments
384 Using the Special Fixture to Machine the Lead in on a Knuckle Tailpiece.jpg
385 A Finished Knuckle Now with Tailpiece Lead in.jpg

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NP317
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Location: Northern Oregon

Re: Constructing the Martin Lewis Little Engines Northern Tender

Post by NP317 » Thu May 24, 2018 9:20 am

SOOO much effort with fixturing!!
But that's how we get repeatable results.
Nicely done.
~RN

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Carrdo
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Re: Constructing the Martin Lewis Little Engines Northern Tender

Post by Carrdo » Fri May 25, 2018 8:13 pm

As shown before but now the paired couplers snap open and closed.

I am not out of the woods yet - I have three final operations yet to do.

The first is to silver solder the bronze coupler body halves together. Will use 0.005" thick strip silver solder for this and take them over to Richards to use his heat treating furnace. I will wrap the coupler bodies with soft iron bailing wire to put a slight compression force on both coupler body halves. I hope this will work as planned although I have not done something like this before. One never knows though. Then back to the belt and/or drum sander to give a quick cleanup around the coupler shank outer contour.

The second last operation is to mill out the dummy hollows as seen in the front RH coupler. Another template to make as seen in the photo.

The last final operation is to close the 1/32" brass rivets holding the lifting pin shackles to the lifting pin. I made a miniature press forming piece to do this but will try it first on a test piece.

I will also have to slightly modify my sketch of the coupler tailpiece from what I have just learned.
Attachments
386 Now They Snap Open and Closed.jpg

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Carrdo
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Re: Constructing the Martin Lewis Little Engines Northern Tender

Post by Carrdo » Sat Jun 09, 2018 10:24 am

Richard silver soldering the coupler body halves together. He gets all of the tricky things to do although he made short work of it.

He "pre-tinned" one flat mating face surface first and then the body halves were silver soldered together. Two locating pins were used to ensure alignment of the two coupler body halves. The brass locating/aligning pin located in the coupler shank was permanently fixed after silver soldering.

After cooling and soaking overnight in water to dissolve all of the remaining flux, the steel knuckle assembly and lifting pin hardware were reassembled into the couplers. Everything did fit together but some parts were now tight. I will need to acid wash the units to remove the surface oxidation which is causing this issue as everything is such a precision fit.

Looking at the new couplers and the originals now, I think that the original ones, the half bodies, were only soft soldered together but it is a bit hard to tell.
Attachments
164 Richard Heating One Coupler Half Body.jpg
166 Heating Another Coupler Body Half.jpg
167 A Really Hot Coupler Body After Silver Soldereing.jpg
169 Orange Hot at Silver Soldering Temperature.jpg
177 After Silver Soldering.jpg

Harold_V
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Re: Constructing the Martin Lewis Little Engines Northern Tender

Post by Harold_V » Sun Jun 10, 2018 1:22 am

Carrdo wrote:
Sat Jun 09, 2018 10:24 am
I will need to acid wash the units to remove the surface oxidation which is causing this issue as everything is such a precision fit.
Something to consider. :idea:
If you are so inclined, you might explore a small blast cabinet. They're very useful for projects like we do, and provide a service that is hard to beat. I use aluminum oxide and glass bead in mine, and I don't know how I'd get along without it. It does an excellent job at removing surface problems, including rust. The resulting surfaces, especially when blasted with glass bead, are quite attractive, with tool marks and other surface irregularities blended away. The process removes little metal, although it can be more aggressive when aluminum oxide is employed. The couplers you showed would clean up beautifully, with a very nice patina.

The one real negative to having a cabinet, even a small one, is that a respectable air supply is required. I run a 5 horse Quincy, which can provide right at 20 cubic feet of air @175 psi per minute. It's enough to run the cabinet, and allows the compressor to stay caught up, although it runs about 85% of the time.

H
Wise people talk because they have something to say. Fools talk because they have to say something.

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Carrdo
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Re: Constructing the Martin Lewis Little Engines Northern Tender

Post by Carrdo » Sun Jun 10, 2018 8:05 pm

Laying out the coupler body cavities with the cavity template set in place. The body of the coupler has been inked to facilitate this operation.

Yes, Richard has a small bead blast cabinet but we have never used it. I will see if there is enough air available to be able to use it effectively.

Harold, thank you for pointing this out.
Attachments
175 The Side Cavity Template in Position.jpg

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Carrdo
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Re: Constructing the Martin Lewis Little Engines Northern Tender

Post by Carrdo » Mon Jun 11, 2018 2:52 pm

The machining of the coupler body dummy cavities. Different size adjustable parallels were used to machine the upper and lower cavities on the curved body.

In the last photo, something the original builder never added to his couplers but I think intended to do so. One can see the miniature letter stamps and a numbers of tiny brass shim pieces stamped AAR. To be glued on the top of each coupler in front of the lifting pin.
Attachments
176 Machining the Coupler Body Cavities.jpg
178 AAR Stamped Brass Letters.jpg

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Carrdo
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Re: Constructing the Martin Lewis Little Engines Northern Tender

Post by Carrdo » Tue Jun 12, 2018 8:31 pm

Nearly there. But I have said that before haven't I.
Attachments
180 The Couplers - June 12, 2018.jpg

pollockmarine
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Location: New zealand, Wellington

Re: Constructing the Martin Lewis Little Engines Northern Tender

Post by pollockmarine » Wed Jun 13, 2018 4:09 pm

Hi is this a 1" scale Northen

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LVRR2095
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Re: Constructing the Martin Lewis Little Engines Northern Tender

Post by LVRR2095 » Wed Jun 13, 2018 4:19 pm

No.....3/4” scale 3& 1/2” gauge

pollockmarine
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Re: Constructing the Martin Lewis Little Engines Northern Tender

Post by pollockmarine » Wed Jun 13, 2018 7:59 pm

Who supplies the castings for this engine

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Carrdo
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Re: Constructing the Martin Lewis Little Engines Northern Tender

Post by Carrdo » Wed Jun 13, 2018 10:01 pm

Nobody at the moment I think. I have had this locomotive waiting to be completed for decades.

Partially built or completed Martin Lewis Little Engine Northern locomotives sometimes come up from time to time on ebay and/or Discover Live Steam.

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