Constructing the Martin Lewis Little Engines Northern Tender

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Carrdo
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Re: Constructing the Martin Lewis Little Engines Northern Te

Post by Carrdo » Wed Mar 30, 2016 10:38 am

Completing some misc. fittings on the tender underframe.

End rounding the drawbar and the safety bar between the engine and the tender.
Attachments
337 End Rounding the Drawbar and the Safety Bar.jpg

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Carrdo
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Re: Constructing the Martin Lewis Little Engines Northern Te

Post by Carrdo » Fri Apr 01, 2016 1:05 pm

A little further on.
Attachments
338 Partially Finished Drawbar and Safety Bar.jpg

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Carrdo
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Re: Constructing the Martin Lewis Little Engines Northern Te

Post by Carrdo » Mon Apr 04, 2016 1:20 pm

I am not going to say too much about this as it is a work in progress which has been on and off (mostly off) for the last 20 years.

The rear coupler for the Northern tender underframe (and all of the other 3/4" scale locomotives here).

These 3/4" scale couplers are top of the line in terms of detail and the way they function. They may be my one and only production item as the special fixtures/tooling/templates/gauges needed to have the necessary quality control to build these couplers are endless.

The aim here is to be able to go from collett to fixture and back again for each and every single operation undertaken.

The internal pocket on the coupler bodies has to be precisely machined (not cast in); hence the need to split the coupler body into an upper and lower section which, when finished, the coupler halves are then either soft or silver soldered together.

The photo shows only some of the parts and fixtures made as much more has yet to be done. And the tooling is something else.
Attachments
339 A Work in Progress Coupler Fixtures, Parts.jpg

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Carrdo
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Re: Constructing the Martin Lewis Little Engines Northern Te

Post by Carrdo » Wed Apr 13, 2016 2:22 pm

Lets do things the most difficult way - again.

For certain internal milling operations on the production couplers, I needed to use both milling machine table stops and in addition, a stop on the mill knee/cross slide which I didn't have.

So, time to make a proper one (in the past I have come up with some flung together make do things when needed).

The body on the stop required a 1" wide by 1.5" deep cutout so I started to mill it out without really thinking about it.

Now that it is nearly done - there is a much easier and better way to do this without going through all of that end milling.

At each bottom corner of the cutout, drill a 5/16" cross hole which ends up being 1/16" inside each corner (to allow for drill runout). Then bandsaw down each side of the cutout to intersect each corner hole which will allow a 1/4" wide bandsaw blade to be turned 90 degrees to enable a cut along the bottom surface of the cutout. The rough cutout could then have been finished to size by milling.

Could have saved hours of milling doing it this way but then ....
Attachments
190 Milling Machine Knee Cross Slide Stop Body.jpg
191 Getting There.jpg

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Carrdo
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Re: Constructing the Martin Lewis Little Engines Northern Te

Post by Carrdo » Fri Apr 15, 2016 2:37 pm

The finished stop and how it is employed on the mill.

There are 4, 5/16-18 socket head set screws located on the bottom leg of the cutout which are tightened to grip the cast underside of the knee/cross slide way. This allows for a strong firm grip. Also, the top leg of the stop, which sits on the finished way, has a layer of masking tape applied to protect the surface of the way. The cast bottom surface and finished top surface of the way on the Millrite were found to be remarkably parallel.

The photo of the new toolmakers clamp was what was formerly used as a stop in a pinch and I kept one clamp to be used for this purpose only.

There is even a way to have a type of micrometer stop if one has adjustable parallels. As seen in the last photo, the adjustable parallel is set between the stop and the table to produce a variable and precise gap.

Thinking outside of the box, if one has a mill which can't take advantage of the way the Millrite is constructed, one could use a strong magnetic base to sit on your cross slide way as a stop. I tried the one I had here but the magnet proved not to be strong enough to not slip but if one had one of these new super strong (176 lbs. pull) magnetic bases, it might work.

Of course if one has a multi axis digital readout all of this nonsense can be avoided entirely but as you are very aware by now, I employ manual machining methods and mostly mechanical devices which were common usage 70 years ago.

At least I can now get back to the machining of the production coupler internals.
Attachments
193 The Finished Stop Body.jpg
194 The Stop Installed on the Mill's Knee-Crosslide.jpg
195 Employing a New Toolmakers Clamp as a Crosslide Stop in a Pinch.jpg
196 Employing an Adjustable Parallel Together with the Crosslide Stop.jpg

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Carrdo
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Re: Constructing the Martin Lewis Little Engines Northern Te

Post by Carrdo » Wed Apr 27, 2016 9:14 pm

Finally finished some needed workshop upgrades and progressed a little further on the coupler fixtures and tooling.

Can now do some further coupler machining.

The first operation was to counterbore the bottom coupler half which ultimately will be one half of the cutout for the head of the knuckle. Photo 341.

After that the coupler half internal pocket was milled. Photo 342.

The double sided fixture which was designed for the above operations (as well as many others) worked very well but one always learns something new when one does something for the very first time.

The head of the half coupler casting definitely needs to be supported as shown. Even though a brand new piloted counterbore was used, it took quite a bit of downward pressure to keep the tool cutting. I guess the counterbore was designed to cut steel rather than bronze. Also, the counterbore shank was not any collet size which surprised me so I had to use a drill chuck to hold it. And this is one of the best American tool brands.

The depth plug gauge worked well but it took quite a lot of cleaning to get all of the chips out from the deep hole. I don't use compressed air to blow chips all over the place so one has to fiddle to get all of the chips out before using the depth plug gauge.

The internal pocket milling operation was controlled by both the table and knee/cross slide stops and one needs these. Once the stops are set, it is just slow careful work with a very sharp end mill.

The bronze used in the casting had a tendency to raise a lot of burrs which can be annoying.
Attachments
341 Counterboring Coupler Bottom Half.jpg
342 Pocket Milling Coupler Bottom Half.jpg

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Carrdo
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Re: Constructing the Martin Lewis Little Engines Northern Te

Post by Carrdo » Thu Apr 28, 2016 9:52 am

Coupler bottom half internal machining complete. Now I have to do exactly the same internal machining on the coupler top half.
Attachments
343 Coupler Bottom Half Internal Machining Complete.jpg

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Carrdo
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Re: Constructing the Martin Lewis Little Engines Northern Te

Post by Carrdo » Fri Apr 29, 2016 12:08 pm

Not a very good photo but both half coupler castings are now internally machined.

Just have to machine a second top half coupler casting to complete a pair of coupler bodies. Lots of work in these couplers.
Attachments
344 Both Coupler Half Castings Internally Machined.jpg

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Carrdo
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Re: Constructing the Martin Lewis Little Engines Northern Te

Post by Carrdo » Sat Apr 30, 2016 12:14 pm

And a knuckle fits perfectly in the machined half coupler castings. As it should.

Still many interesting operations remaining.
Attachments
345 A Knuckle Mated to the Machined Half Coupler Castings.jpg

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Carrdo
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Re: Constructing the Martin Lewis Little Engines Northern Te

Post by Carrdo » Thu May 05, 2016 2:18 pm

The internal machining on two new coupler bodies (4 half bodies) is now complete.

Each new operation throws up its little twists and problems which cannot be readily anticipated but so far it has just made for a better and stronger outcome.

More tooling and fixtures made. Virtually every operation is now rigidly controlled.
Attachments
346 Two Coupler Bodies with Internal Machining Finished jpg.jpg

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slhdsnet@dsuper.net
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Re: Constructing the Martin Lewis Little Engines Northern Te

Post by slhdsnet@dsuper.net » Fri May 13, 2016 8:43 am

Wow and as always, absolutely superb work of yours !! Indeed, very well done couplers.

Any progress on the Josslin boiler and/or Hudson loco ?

Cheers,
Stephane :-)

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Carrdo
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Re: Constructing the Martin Lewis Little Engines Northern Te

Post by Carrdo » Tue May 17, 2016 9:30 pm

Some silver soldering of a new knuckle head and tailpiece using the new holding fixture made for this purpose.

The silver soldered joint was excellent except that when I installed the completed knuckle assembly in a machined coupler, I found that the tailpiece was rotated about 30 degrees from where it should be because I didn't check this using the original coupler parts!

Even in this case, the coupler sort of worked but sort of isn't good enough. Oh well, I can re-silver solder.

I have to modify the holding fixture a bit to ensure this doesn't happen again but I now know that the made up holding fixture will do the job as intended.

I'm telling you, with this coupler design, all of the made up fixtures and coupler parts have to be just about perfect for these couplers to work.
Attachments
347 Cooling Knuckle Head and Tailpiece After Silver Soldering.jpg
348 Silver Soldered Knuckle Assembly.jpg

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