Constructing The Josslin NYC Hudson Lead Truck

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Carrdo
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Constructing The Josslin NYC Hudson Lead Truck

Post by Carrdo » Thu Apr 18, 2019 1:43 pm

Nothing like jumping around wildly and not doing what I said I was going to do next but that is just how I operate sometimes.

I have built two and one half of these lead trucks to date.

The first completed lead truck is on the Hoffman Hudson here and it does not have the added on brake lugs.

The second completed lead truck is on the Josslin Hudson and it has the added on brake lugs.

The third lead truck was also described in the Josslin Hudson construction series running here on Chaski but it was only constructed to the finished frame. It also has the added on brake lugs.

All of the Josslin lead trucks are a silver soldered fabricated frame assembly vs the detailed one piece casting as seen on the Langworthy Hudson.

I have never described how to construct all of the remaining parts on a Josslin lead truck beyond the completed frame assembly so here it is now.

There is nothing secret or new here that has not been done or described before. It just consists a lot of correct machining procedures and setups to ensure everything turns out to be square, concentric, parallel and not tapered, inline, etc.

I will start with the lead truck axleboxes. They are of the two piece type with removable cellars. Axleboxes of this type represent a great deal of careful machine work and when finished, they don't look like much has been accomplished.

I use Meehanite iron to make my axleboxes. Meehanite is one of the best materials available to construct axleboxes from but this material may be difficult to obtain in small quantities.

Start by "rectangularizing" the axlebox blanks. Achieving square and flat surfaces will pay dividends later on so do everything to achieve this condition. Make the axlebox blanks about 1/32" larger than the final print size and make all of the blanks exactly the same size. See the last photo.

A lot of boring dog work here.

Recently, I acquired a couple of like new carbide insert facing cutters and this speeded up the sizing operation considerably. As well, since I am very fortunate to have a surface grinder, one side face of each axlebox blank was finished by surface grinding. The surface ground face of each axlebox will be set against the fixed jaw of the milling machine vise with the axlebox itself set on a true ground parallel for further machining.

Of course, indicate the fixed milling machine vise jaw first and make certain that the fixed jaw has no nicks, gouges or scratches which could throw things out of square. Grind or stone the vise jaw as necessary to achieve this condition.
Attachments
538 Third Lead Truck Frame Top View.jpg
539 Third Lead Truck Frame Underside View.jpg
541 Squaring the Meehanite Cast Iron Axlebox Blanks.jpg

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Carrdo
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Re: Constructing The Josslin NYC Hudson Lead Truck

Post by Carrdo » Fri Apr 19, 2019 6:38 pm

The first real operation is to machine the side slots in the axlebox blanks to precisely fit the frame axlebox openings.

Select the surface ground side to be against the solid vise jaw then center the end mill over a side. To do this I use a graduated scale having a drill angle stop, an eye loupe and good lighting. Rotate the end mill to have a tooth just graze the end of the scale when the scale stop is set on each side of the axlebox blank. This can be done very quickly and precisely under magnification. Remember, the blank has been left 1/32" oversize so there is a bit of tolerance to play with here. I do everything mechanically but if you have the digital or CNC equipment, then use it to accomplish the above.

Debur the blank thoroughly then set the axlebox blank on a true parallel which is wider than the axlebox slots which you are going to machine. Take a cut, rotate the blank 180 degrees and without altering anything, slot the opposite face. Remember to lock the mill's cross slide. Since I have a SG face, I can see and feel this surface at all times but if you have milled faces only, it would be best if you marked the face which is set against the solid jaw as the blank orientation is easily lost as all the blank milled surface finishes will look the same. Thoroughly clean the vise and setup of chips after each cut and when rotating the blank 180 degrees as you must keep both side slots dead aligned and the depth of cut on each side must be exactly the same. It is also best to keep everything in roughly the same position in the vise after each 180 degree rotation.

Repeat the above until the slot depth on each side of the axlebox blank approaches the frame opening. The last cuts taken are just shaving cuts. You can remove the blank and test it multiple times in the frame opening as one approaches the final slot depth. Of course a very sharp, on size cutter needs to be used. Everything will always align exactly as it should if the above procedure is employed.

Remember, these side slots as well as all subsequent machining, will only be as good as the initial blank " rectangularization".

For the initial axlebox fitting in a frame opening, I fit very tightly; that is, a very hard push fit or a tap fit as my experience has taught me that it is much easier to remove metal later on than to try and add it back again. Later, I will also relieve the sides of axlebox slots further and show how to do this.

Even with all of the above, each axlebox is individually fitted to an axlebox opening and each axlebox is marked to ensure this condition (see the last photo). Because the frame has been entirely silver soldered together, it may have distorted slightly or acquired surface oxidation and nothing is truly flat or parallel and this has to be taken into account. A little hand fitting with a smooth file and fine wet and dry paper is all that is usually required.
Last edited by Carrdo on Fri Apr 19, 2019 7:06 pm, edited 1 time in total.

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Carrdo
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Re: Constructing The Josslin NYC Hudson Lead Truck

Post by Carrdo » Fri Apr 19, 2019 6:40 pm

The associated photos with the above post.
Attachments
542 The Josslin Lead Truck Axleboxes.jpg
543 Machining the Axlebox Frame Opening Slots.jpg
544 The Initial Fitting of a Pair of Axleboxes.jpg

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Carrdo
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Re: Constructing The Josslin NYC Hudson Lead Truck

Post by Carrdo » Mon Apr 22, 2019 4:01 pm

A little further along.

Now that all of the lead truck axlebox frame opening slots have been machined, the next step is to relieve the side slots.

How I do this is quite interesting.
Attachments
545 A Little Further Along.jpg

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Carrdo
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Re: Constructing The Josslin NYC Hudson Lead Truck

Post by Carrdo » Tue Apr 23, 2019 11:59 am

I normally don't do this here but I am including a couple of photos of the special shaving tool needed to relieve the side slots on the axleboxes.

The semi universal holding fixture was made from a couple of commercial tools which I had. It allows the grinding wheel to relieve the cutter bit in two directions with one pass of the grinding wheel. I sometimes don't know how I would get things done without having a surface grinder.

The setup for shaving the axlebox side slots is shown in the last two photos.

The first question is how large to make the sweep on the cutter bit?

I have never seen anything published on this so I chose to make it 3 times the wheel back to back gauge, that is 3 x 3-9/32" which is slightly less than 10". It is not all that critical and another reason I chose this figure was it was just about the maximum extension I could have of the boring bar in the boring head.

The lower slide portion of the boring head is adjusted central to the body and the tapered cone seen in the photo is set in the central hole of the boring head slide and then the foot long metal scale is used to set the cutter sweep from the point of the cone to the tip of the cutter.

To set the cutter central on the side slot, the boring bar is rotated by hand until the tip of the cutter just grazes the top and bottom edge of the side slot.

DO NOT do any of this under power.The shaving operation itself is done entirely by hand.
Attachments
546 Grinding The Special Axlebox Side Slot Relieving Toobit.jpg
547 The Special Relieving Toolbit.jpg
548 The Setup to Relieve an Axlebox Side Slot.jpg
549 The Setup to Relieve an Axlebox Side Slot.jpg

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Carrdo
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Re: Constructing The Josslin NYC Hudson Lead Truck

Post by Carrdo » Thu Apr 25, 2019 5:04 pm

For completeness, the axlebox side slot shaving operations in photos and a verbal description.

As stated previously, the cutter must only be swung back and forth by hand throughout this operation.

The cutter is operated to shave down a slot wall advancing with 0.001"-0.002" horizontal increments per full slot depth pass and and 0.001"-0.003" depthing increments using the micrometer handwheels on the table and the quill of the milling machine. I advanced the cutter down this way to about 0.010" above the floor of the slot by noting the appropriate micrometer reading on the quill and returning to it to the same reading for each additional horizontal table movement.

One soon develops a continuous fine swinging depthing motion with the above.

Only the ends of the slot were relieved with about a 1/8" long center section left parallel as originally milled.

To set the cutter to the maximum depth in the slot without the cutter actually grooving into the bottom face of the slot, thin cigarette paper was employed as seen in the second photo. The quill was locked when one could just barely pull away the cigarette paper and only then was the table advanced in 0.001" increments to clean up the bottom 0.010" remaining ridge until, under very good lighting conditions and using an eye loupe, the bottom slot edge was seen to be shaved truly square.

Do not be tempted to hurry this operation even though it is quite tedious. I can do only about two slot faces per session so with 2 done and 14 more to go...!!
Attachments
550 Hand Swinging the Relieving Cutter.jpg
551 Setting the Maximum Cutter Depth in the Side Slot.jpg
552 Both Sides of One Side Slot Relieved.jpg

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Carrdo
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Re: Constructing The Josslin NYC Hudson Lead Truck

Post by Carrdo » Thu Apr 25, 2019 5:18 pm

Rob G.

I replied to your request for some additional photos of the fixture but the reply is still sitting in my outbox of the PM after 5 days.

Please email me directly at carrdo66@gmail.com

Don

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Carrdo
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Re: Constructing The Josslin NYC Hudson Lead Truck

Post by Carrdo » Sat Apr 27, 2019 7:57 pm

The next operation is to cut away material from the axlebox body for the cellar piece.

After all of that nice machining, it looks like a butcher job, initially at least.

From the print, carefully layout the cellar location on the partially machined axlebox body. Then bandsaw down the sides of the cellar piece and chain drill along the top edge. Be certain to keep well inside the layout lines as drills can wander. Use the bandsaw fence to assist in cutting a straight line down the sides and let the blade do the cutting - don't force it.

Finally, employ a jewellers fret saw to cut away the bridge metal between the drilled holes.
Attachments
553 Bandsawing and Chain Drilling for the Cellar Piece Cutout.jpg

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Re: Constructing The Josslin NYC Hudson Lead Truck

Post by Carrdo » Sun Apr 28, 2019 6:50 pm

Milling the cellar piece opening to its finished size and a rough milled cellar piece.

All of the above is just the basic unit operation of setup squaring but it has to be done as well as possible. It is a good test of your machining abilities and the condition of your machine and cutter.

The rough machined cellar piece will be finished on the surface grinder dead square and to a very tight slide fit in the axlebox cellar piece opening.
Attachments
554 Milling the Cellar Piece Opening.jpg
555 The Cellar Piece Roughed Out.jpg

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Carrdo
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Re: Constructing The Josslin NYC Hudson Lead Truck

Post by Carrdo » Mon Apr 29, 2019 7:50 pm

After finishing the cellar piece blank, the next operation is to attach it securely to the axlebox body. This is accomplished by drilling, tapping and countersinking each of the axlebox side slots for two short 4-40 NC flat head cap screws. The screws are countersunk to sit just below the bottom of the side slots.

Nothing special here, just careful layout and machine work to locate the screws as shown on the Josslin prints.

I would estimate that the axleboxes are half finished at this point.
Attachments
556 Tapping the Axlebox Body Side Slots for the Cellar Piece Countersunk Flat Head Screws.jpg
557 How the Cellar Piece is Secured to the Axlebox Body.jpg

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Re: Constructing The Josslin NYC Hudson Lead Truck

Post by Carrdo » Tue Apr 30, 2019 10:48 pm

In preparation for the drilling, boring and reaming of an axlebox to accept an axle which is the next major operation, I always first create a matched pair of axleboxes having exactly the same width and height (thickness doesn't matter at this point). This way I can set the matched pair in the milling machine vise against a fixed stop (or whatever) and have the axle opening come out in exactly in the same location on both axleboxes every time.

Of course having a surface grinder allows one to easily achieve the above in terms of geometric accuracy (to be truly square and rectangular) and to be exactly identical. At the same time I ground the axlebox width/height to within 0.005" of the print size.

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Re: Constructing The Josslin NYC Hudson Lead Truck

Post by Carrdo » Tue Apr 30, 2019 10:49 pm

Here is a photo of the above.
Attachments
558 A Now Identical Matched Pair of Axleboxes After Surface Grinding.jpg

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