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 Te

Post by Carrdo » Wed May 18, 2016 7:16 pm

Two new silver soldered knuckle assemblies with an original part in the center all oriented as they should be. I tried the new assemblies in a new machined body and now they work well.

One of the new assemblies is the re-silver soldered one.

Also, the slightly modified holding fixture can be seen in the the photo.

Some machining and final fitting still to do on the new parts.
Attachments
349 Two New Silver Soldered Knuckle Assemblies with an Original Part in the Center.jpg

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Carrdo
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Re: Constructing the Martin Lewis Little Engines Northern Te

Post by Carrdo » Sun May 22, 2016 8:31 am

Richard also is making some of these fine 3/4" scale couplers but his method is to employ his CNC mill wherever possible. In the first photo, the long tube with the spring ends is the start of the lateral motion or centering device on the Big Boy.

The second photo shows his bench CNC machine generating the coupler knuckle head profile from a stick blank. On paper, the CAD drawings look fantastic, so we will soon see some actual parts.

And we are both discussing what would be involved in the making of a 3/4" scale cross compound. What the heck, at the worst we can only fail.
Attachments
Untitled.jpg
Untitled1.jpg

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Carrdo
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Re: Constructing the Martin Lewis Little Engines Northern Te

Post by Carrdo » Tue May 24, 2016 3:14 pm

Manual machining of a knuckle head from start to finish.
Attachments
350 Knuckle Head Production Stages.jpg

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Carrdo
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Re: Constructing the Martin Lewis Little Engines Northern Te

Post by Carrdo » Tue May 24, 2016 3:57 pm

And the knuckle tailpiece machining.
Attachments
132 Machining a Knuckle Tail Piece from Bar Stock.jpg
135 Tail Piece Double Profile Gauge with Partially Machined Tail Pieces.jpg

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Carrdo
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Re: Constructing the Martin Lewis Little Engines Northern Te

Post by Carrdo » Wed Jun 01, 2016 10:33 pm

The accumulation of small parts, plug/locating gauges, templates and drills employed as each new coupler half is machined.
Attachments
351 Accumulated Small Parts, Plug Gauges, Drills, etc. Employed in Coupler Production to Date.jpg

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Carrdo
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Re: Constructing the Martin Lewis Little Engines Northern Te

Post by Carrdo » Thu Jun 02, 2016 2:09 pm

Some miniature machining on three new coupler lifting pins.

The work involves turning one end of the lifting pin round and dead concentric from 1/8" square stock, them milling a 1/16" thick flat on the circular end of the pin and then cross drilling the end for a 1/32" (#67 drill) clevis rivet.

The above operations can all be successfully performed if the proper procedures are followed.

See the attached photos for the procedures used to accomplish this.
Attachments
352 Start Lifting Pin Machining.jpg
353 Milling Flats on the End of the Lifting Pin.jpg
354 A Closer View of How Lifting Pin is Secured to Mill Flats on End.jpg

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Carrdo
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Re: Constructing the Martin Lewis Little Engines Northern Te

Post by Carrdo » Thu Jun 02, 2016 2:11 pm

The last three photos.
Attachments
355 Cross Drilling End of Lifting Pin for the Shackle Rivet.jpg
356 After Cross Drilling.jpg
357 Three New Semi-finished Lifting Pins with Two New Finished Lifting Pin Assemblies.jpg

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Carrdo
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Re: Constructing the Martin Lewis Little Engines Northern Te

Post by Carrdo » Sat Jun 04, 2016 2:58 pm

To slot the lifting pin through which the knuckle tailpiece passes, I employed a tilting angle vise with swivel base as the slot is tapered 15 degrees on its leading edge.

The angle vise came with a slotted swivel base which allowed the vise base to be set dead parallel with one of the mill's tee slots. Also, in the past, I added a bronze pointer which can just be seen in the first and second photos at the bottom of the vise side plate on the vise body to allow easy aligning of the body of the vise to the swivel base. It is these little modifications which make all of your accessories so much more useful.

To machine the slot, the vise was tilted up 45 degrees and a custom made spacer just thinner than the 1/8" square lifting pin and just high enough so that the top of the lifting pin was as shade higher than the top of the vise jaws. Note that the spacer piece extends beyond the end of the vise jaws right to the end of the square section to fully support the lifting pin. Ensure the rigidity of all components on this setup, as any looseness will cause the end mill to break. Also, carefully check the slot position in relation to the milled clevis lifting pin flats on the end of the lifting pin as it is easy to machine the cross slot 90 degrees out of position.

A 1/8" end mill was then used to produce the basic square angled slot.

To machine the 15 degree leading edge on the slot, the front of the angle vise body was swivelled 15 degrees (towards you) as seen in photo 359. The end mill was then re-positiond so that it just entered the start of the square slot at the required angle (without cutting into the rear wall) and then, very carefully in one pass, the 15 degree leading edge was cut (full slot depth).

It is all about the setup. The actual machining time was only about a minute or two per lifting pin.
Attachments
358 Slotting the Knuckle Release Pin.jpg
61 Tilting Vise Settings to Produce Angled Cross Slot.jpg
359 Angle Vise Swivelled To Mill the Slot Leading Edge.jpg
360 Three Completed New Lifting Pins .jpg

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Carrdo
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Re: Constructing the Martin Lewis Little Engines Northern Te

Post by Carrdo » Sat Jun 04, 2016 3:17 pm

To complete the lifting pin assembly, there is the lifting pin compression spring and the miniature lifting pin clevis.

At one point, I was even winding my own springs but I soon said to he-l with that and found some commercial ones. Only thing to say here is they are just under 3/16" OD by 5/16" long and are made from 0.012" spring wire and ID wise they just slip over the round end of the lifting pin.

The miniature lifting pin clevis was probably one of the most interesting parts to make in the entire coupler project but one of the most difficult to look correct aesthetically.

I actually came up with four different methods of how to make them but will only describe one here.

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Carrdo
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Re: Constructing the Martin Lewis Little Engines Northern Te

Post by Carrdo » Sun Jun 05, 2016 10:13 pm

The coupler lifting pin clevis starts as a roll of 18 gauge (0.048") soft iron bailing wire or the soft iron binding wire used to tie reinforcing steel together in reinforced concrete.

Snip lengths off the roll in slightly longer than 1/2" increments and then the clipped ends are belt sanded down to leave the blank 1/2" long. The wire blanks are then straightened as far as possible on a piece of flat steel using a soft faced hammer. See the first and second photo for these operations.

Both ends of the blank are then crimped down in the vise of the mill which has smooth jaws. It is probably best if the top edges of the vise jaws are very slightly rounded.

Set the blank in the vise jaws so that both crimped ends of the blank are in line as far as possible. After crimping, you will have what is shown in the last photo.

If the wire is set down about 3/32" from the top of the vise jaw surface and strong, but not excessive clamping force is exerted on the vise handle, the soft wire ends will have crimped down to about 0.018" - 0.020" thickness.
Attachments
361 Clevis Wire and a Cutoff Piece.jpg
362 Straightening and Crimping a Cutoff in the Vise Jaws.jpg
363 After Crimping Both Ends.jpg
Last edited by Carrdo on Fri Jul 01, 2016 8:24 am, edited 1 time in total.

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Carrdo
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Re: Constructing the Martin Lewis Little Engines Northern Te

Post by Carrdo » Wed Jun 08, 2016 12:14 pm

To form the "U" end of the clevis, I came up with the fixtures shown in the first photo for my bench arbor press.

I suppose I like complication but this was the first method of all the forming methods used to date and has been the subject of the most experimentation and changes.

Even with the most recent changes made this week, I was not totally happy with the result so the forming procedure was slightly altered (again).

Finally, I achieved the results I was looking for.

The last photo is of the various shackles made following the latest changes.
Attachments
66 Fixtures Used to Form Shackle Body U End.jpg
67 Pressing Shackle Body U End.jpg
70 Some Formed Shackle Bodies.jpg

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Carrdo
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Re: Constructing the Martin Lewis Little Engines Northern Te

Post by Carrdo » Wed Jun 08, 2016 6:30 pm

The final operation on these miniature shackles is to drill a #67 drill hole through the shackle eyes.

The easiest method is to hold a shackle body by its circular end lightly clamped at the edge of the mill's vise jaws and then adjust the shackle body until the crimped or swaged end is as level as possible. Then, using your smallest center drill and best small drill chuck, adjust the point of the center drill until it is on the eye center. Then carefully dimple this position with the tip of the center drill.

Follow with the #67 drill, drilling very carefully and slowly. Have as little drill extension as possible.

Reverse the shackle body in the vise and locate, dimple and drill the other shackle eye as previously.

Excellent lighting must be employed with the above procedure.

It looks difficult but it is quite easy to do if proper methods are followed.

There is enough play such that the 1/32" brass rivet will pass through both eyes even if they have been drilled slightly misaligned.

This completes the entire lifting pin assembly.
Attachments
71 Dimpling a Shackle Eye with my Smallest Center Drill .jpg
72 Drilling Through a Shackle Eye with a # 67 Dill.jpg
73 The # 67 Drill Passes Through Both Shackle Eyes.jpg

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