A Real Dirty Job

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Carrdo
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Location: Toronto, Canada

Re: A Real Dirty Job

Post by Carrdo » Tue Jul 23, 2019 2:51 pm

Not to say that I have had enough "punishment" making the heart shaped links on the Josslin Hudson lead truck but now I am basically going to repeat the process all over again to machine the brake shoes on the Langworthy/Yankee Shop Hudson lead truck.

Normally, one would have had castings for these parts where much of the forming work is already embodied in the casting but since I have none, I will be making them completely from cast iron blocks. Again, lots of forming/profiling involved.

Since the model drawings assume castings to start with, all of the dimensions necessary to make them from scratch are not shown but there is enough information on the drawings to produce the parts from scratch. So, the first job was to produce a layout drawing where all of the additional machining information needed is shown.
Attachments
328 The Brake Shoe Layout Drawing.jpg

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Carrdo
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Re: A Real Dirty Job

Post by Carrdo » Wed Aug 14, 2019 11:11 am

The start of the lead truck brake shoe machining.

As indicated many times before I start by " rectangularizing" the CI brake shoe blanks to the best of my ability often using the surface grinder.

As I have machined Hudson brake shoes before, I have some fixtures already made to do this but, as usual, each individual model Hudson design shows slightly different forms of brake shoes to be made.

The first operation on the blanks was to machine the front shoe radius conforming to the diameter of the truck wheels which in this case is 2-1/4" which gives a brake shoe radius of 1-1/8" as per the Langworthy print.

Fortunately, my rotary table has a central tee slot which allows easy radial positioning and holding of the brake shoe fixture made and the blank itself.
Attachments
329 The CI Brake Shoe Blanks.jpg
330 Brake Shoe Blank First Machining Operation Radiusing.jpg
331 The Brake Shoe Blank Holding  Fixture.jpg
332 The Fixture Underside.jpg

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Carrdo
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Re: A Real Dirty Job

Post by Carrdo » Wed Aug 14, 2019 12:19 pm

The next machining operation on the blank is not so easy at all and I really had to think about it for a while and to be a bit inventive. I tried to keep it as simple as possible but it didn't quite end up that way as what I came up with is a bit of a Rube Goldberg.

The large central plug fits both the centre plug hole in the rotary table and its upper portion is the diameter of the lead truck wheel. It is there to keep the brake blank truly radial on the rotary table. The side angle clamp pieces are tapered on the ends both horizontally and vertically to exert both a clamping and slight downward force on the brake blank piece. The large toolmakers clamp gives an extra clamping force.

Not seen is a support spacer under the brake blank piece itself to keep it from tipping as the blank, in the position it is in is right over the intersection of two tee slots in the rotary table, has to be supported here.

You will see why everything needs to be this way with the next machining operation.
Attachments
334 The Brake Shoe Blank Second Machining Operation Setup.jpg

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Carrdo
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Re: A Real Dirty Job

Post by Carrdo » Thu Aug 15, 2019 3:08 pm

Machining, machining, and finally a roughed out brake shoe blank.

Nothing moved at all with this setup but I did take light DOC's (0.005" increments). I thought it wouldn't but this operation really took it out of me.
Attachments
336 Machining.jpg
337 Machining.jpg
338 And Finally a Roughed Out Brake Shoe Blank.jpg

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Carrdo
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Re: A Real Dirty Job

Post by Carrdo » Thu Aug 29, 2019 6:04 pm

If you like rotary milling, I have just the job for you. Endless...

Am finishing the last brake shoe blank face (the 8th). I have changed cutters several times as you really need to have razor sharp end mill cutting edges for this job.

I don't particularly recommend the setup seen in the first and last photos but here I am only taking finishing shaving cuts to keep the two rotary milled opposite faces parallel to 0.001" which is a lot more difficult to achieve than it seems. The clamping force here is quite low as I found that a higher clamping force as threw the rotary milled faces badly out of parallel in both directions. If I didn't have the type of rotary table which I do and the table tee slots configured as they are, I would never have been able to do the job this way.

Even as it is, to achieve this parallelism, part of the the blank is located in the middle of a tee slot intersection (which necessitates it resting on a precision ground spacer) while the remaining body rests completely flat against the top of the rotary table. Also, the periphery of the centre plug has to project into the tee slot intersection just far enough to abut tight up against the milled circular end of the blank to keep the part both radial and square. If the lead truck wheel had been any other diameter than 2-1/4", this would not have been possible.

For the rough rotary milling operation, the blank was given an additional clamping force with the toolmakers clamp as seen and was set on shims but this also threw things badly out of parallel (0.005"- 0.006" taper on the rotary milled opposite faces was the best I ever managed to achieve with this setup).
Attachments
339 Rotary Table Milling the Remaining Brake Shoe Blanks.jpg
340 Rotary Table Milling the Remaining Brake Shoe Blanks.jpg
341 Rotary Table Milling the Remaining Brake Shoe Blanks.jpg

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Carrdo
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Re: A Real Dirty Job

Post by Carrdo » Fri Aug 30, 2019 1:13 pm

It doesn't look like much but this is the end of the rotary milling operation.
Attachments
342 The End of the Rotary Milling Operation.jpg

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Carrdo
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Re: A Real Dirty Job

Post by Carrdo » Sun Sep 01, 2019 3:26 pm

The brake parts as of today.

But there is a problem.

The brake shoes are machined wrong. They should have been slotted 1/8" wide where I machined them with a central tab 1/8" thick. All of the work which took so long with all of the setup and machining problems involved has to be re-done. AAUGHHHhh!!!

Now that I have got past my senior moment, I can say that on the Langworthy drawings, one of the views of the brake shoes is both misleading and wrong - the other views are correct but guess which view I choose to use.

Stay tuned for round 2 but first I have to obtain a special cutter as I am about to go at it again the hard way as usual!
Attachments
343 The Lead Truck Brake Parts as of Sept. 2019.jpg

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Carrdo
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Re: A Real Dirty Job

Post by Carrdo » Thu Nov 07, 2019 4:48 pm

Round two on the machining of the Langworthy/Yankee Shop lead truck brake shoes.

I am stuck for the moment on finishing the Josslin lead truck as I had to order a couple of different sizes and thickness of blue tempered spring steel strip which is on order and back ordered from MSC. They have by far the best selection of this material in the sizes which are useful, they will deal with Canadians, they have been very accommodating to me and they will ship via the USPS to Canada where no one else will. And to say that any local supplier here (in the GTA) is "useless" when it comes to ordering small quantities of spring steel is using a mild word.

As I have oft repeated, start by "rectangularizing" the four CI shoe blanks. After that, the blanks are radiused on a long side of the blank to the diameter of a lead truck wheel using the rotary table setup shown. The fixtures and setup used to achieve this are exactly as described previously in the first go round.

Notice that the blank has been clamped in the radiusing fixture on all three sides after the first blank was ripped out of the fixture when it was only held with a single clamp. After that very light cuts were employed per pass (0.001-0.002" DOC). Very slow but safe.

The "dummy wheel blank" shown in the last photo is really a setting gauge which enables one to quickly position the brake shoe blank in the holding fixture and also to give the correct radius for the cutter to follow.
Attachments
336 First Stage Rotary Table Milling of the New Lead Truck Brake Shoe Blanks.jpg
337 Checking a Couple of Radiused Brake Shoe Blanks Against a Dummy Lead Truck Wheel.jpg

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Carrdo
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Re: A Real Dirty Job

Post by Carrdo » Sat Nov 16, 2019 6:35 pm

My method of machining the 1/8" wide central brake shoe slots in the brake shoe blanks to be true and on size. By "true" I mean that the bottom of the slot will be curved as per the front surface of the brake shoe blank and 3/16" from it.

I may be all out to lunch on this but this is what I do.

First layout the slots on one side of the blanks. As they are 1/8" wide finished width, I first scribed the layout lines 0.110" apart. Then carefully bandsaw away all of the material between the layout lines as shown in the first photo. The reason for doing this is to remove as much metal as possible first so that the sawing operation to finish the slot with the side tooth milling saw is more or less just a shaving operation i.e there is no real cutting force on the saw which might tend to deflect it. Also, of importance is the saw should be sharp on all of its cutting edges and use a high quality arbor to hold the saw so there is absolutely no arbor induced saw wobble.

The setup seen in the second photo to accomplish the above is all about rigidity. This was the most rigid way to hold a blank by its curved, not slotted brake shoe face that I could think of. The saw was run very slowly (approx. 60 rpm) with no lubrication (with cast iron).

The above will produce a flat bottomed saw cut.

To get the bottom slot curvature, I came up with what is seen in the last photo. I haven't done it yet so it will either be a success or a disaster.

One needs to use the special large diameter Woodruff cutter here as nothing can project beyond the bottom edge of the cutter as we are working so close to the top of the rotary table. The threaded rod piece sticking out from the front rotary table slot is an expanding aluminum (made up) slotted arbor whose only purpose is to hold the brake shoe blank curved face against the central dummy wheel plug to ensure everything stays truly radial.

A real Rube Goldberg.
Attachments
338 Bandsawing a Brake Blank Slot.jpg
339 Milling a Brake Blank Slot .jpg
340 The Proposed Setup to Finish The Brake Blank Slot.jpg

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Carrdo
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Re: A Real Dirty Job

Post by Carrdo » Tue Nov 19, 2019 5:18 pm

The next operation was to rough profile the brake shoe blanks so they conform to my drawing.

On the first blank (which I planned to use as a template for the remaining blanks) carefully lay out the outer profile, bandsaw away the surplus metal outside of the layout lines and then mill the blank to nearly the finish profile. Very straight forward or so I thought.

Only now, after doing the above, the curved profile of the shoe blank did not conform to my drawing but the rest of the blank did! I have no Idea how this came about but...

In desperation, I recut the wheel profile with the setup shown in the first photo as luckily I still had some extra metal to work with. I do not recommend such a setup as the blank is now not rectangular and it cannot be very securely held in the vise, setting the cutter radius is not very precise, and the only way to be really certain about what is going on is to take the blank out of the vise as the operation progresses and check it against the drawing and the wheel blank (with no guarantee that anything will go back in the vise in the same position as before). But when conditions become pressing...

I got it but simply due to luck more than anything.

Lesson to be learned, if I ever have to do something like this again, make a paper cutout from the drawing and paste it to the blank which is to be used as the template for the remaining parts. It has to be correct to the drawing if everything is machined to the paper cutout profile.
Attachments
341 Re-cutting the Brake Shoe to the Wheel Curve.jpg
342 It Now Conforms to the Drawing.jpg
343 All the Brake Shoe Blanks Rough Profiled.jpg

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Carrdo
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Re: A Real Dirty Job

Post by Carrdo » Wed Nov 20, 2019 9:10 pm

The next operation was the layout and the drilling/reaming of the two 1/8" dia. holes in the brake shoes as shown on the Langworthy print.

The layout was rather complicated as it involved first locating a point external to the brake shoe itself. How this was done is seen in the first photo. The brake shoe had to be aligned so that one leg of the divider followed the wheel curvature face with the other leg set in the external punch mark located on the top of the inked metal strip piece. Then, two arcs were scribed on the top of the brake shoe as per the print radii.

To find the hole centreline intersection points, the entire assembly was then taken out of the vise and set square and vertical on its free side on a flat surface. A vernier height gauge was employed to find the other hole centrelines as these dimensions were given on the print.

The setup for the actual drilling/reaming operation is seen in the second photo. I had another adventure here which I won't go into other than to say be very careful with the drilling operation (don't be aggressive with the drill feed and use a sharp drill) and be certain that nothing can move. I was lucky again that I only ended up with a bent drill and not a destroyed part.

The one drilled brake shoe shown in the last photo will be used as a template to drill the remaining brake shoe holes.
Attachments
344 Laying Out the Two Drilled Holes in a Brake Shoe.jpg
345 The Setup for Drilling A Brake Shoe.jpg
346 After Drilling and Reaming.jpg

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Carrdo
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Re: A Real Dirty Job

Post by Carrdo » Fri Nov 22, 2019 3:37 pm

These brake shoes are giving me no end of trouble for some reason.

The latest machining operations.

Picking up the spotting points was just a case of very good lighting and my well used eye loupe together with the smallest # 000 centre drill held in the drill chuck.

The latest misadventure was I drilled one of the brake shoes backwards which is very easy to do as the shoes appear to be, but are not quite, symmetrical. I plugged the mismatched holes and re-drilled - one can hardly see where they were now.

I still have to employ my dreaded Rube Goldberg setup but I will modify it again. On the net there are many ingenious low profile tee slot clamp designs for use in the home shop which will keep things much more secure than what I came up with.

Stay tuned.
Attachments
347 Spotting Through.jpg
348 The Drill Hole Spotting Points to be Picked Up.jpg
350 The Matched Pairs of Brake Shoes.jpg

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