Constructing the Martin Lewis Little Engines Northern Tender

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Carrdo
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Joined: Thu Mar 06, 2003 2:20 pm
Location: Toronto, Canada

Re: Constructing the Martin Lewis Little Engines Northern Tender

Post by Carrdo »

Well, here I go again, jumping around from project to project but that is what I do.

This time it is rebuilding the cradle on the LE Northern as the original builder obviously didn't have a milling machine (no discredit to him or her) but it doesn't follow the Martin Lewis drawings which results in construction problems later on.

What are we talking about here? See the first photo of the main frame extensions which I need to construct as per the Martin Lewis print.

Martin Lewis says to make these parts out of 7/8" channel and with heat forge one end of the channel flat as shown on the print. Well, maybe he could do it that way but not here. First of all there is no supplier of anything that small in Canada especially if you only want a few feet of it - so it is unobtainium.

Secondly, even if I could get such channel, I do not have the blacksmith equipment or the skill/experience to do it this way.

So, I will make it as I have done before from a solid piece of hot rolled plate, the hard way again, as usual.

By the way, one can make any size miniature structural channel from the solid, the way I am going to show how it is done - it is just a lot of work but...

For these parts I started with a piece of 4" wide by 1/4" thick hot rolled steel plate. Layout and bandsaw the rough outline of the cradle side frames from this plate. This can be a lot of dog work just to do this as one is making multiple cuts of 13.5" in length.

Then use the setup's shown in the remaining photos (or something similar) to machine the side frames straight and square nearly to finish size.

Also, to add to the fun, I found that the original bronze buffer piece casting, as supplied, was totally defective as it was riddled with major blow holes and cavities. So I will make a new buffer piece also from the solid. It can be seen in the last photo - the roughed out hot rolled steel block which the defective casting sits on.
Attachments
479 The Little Engine  Drawing for the Cradle Side Frames.jpg
480 Setup for Machining a New Cradle Side Frame.jpg
481 Machining the Bolt on Section of a Cradle Side Channel.jpg
482 The Part Machined New Cradle Side Frames and the Original One Together with the Bad Bronze Buffer Casting.jpg
Carrdo
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Location: Toronto, Canada

Re: Constructing the Martin Lewis Little Engines Northern Tender

Post by Carrdo »

Moving on to the more interesting machining operations on these parts.

A centre slot was first machined full length. The milling operation itself is just dog work but the setup is a bit different as one has to grip the channel edges on both sides with hardly anything to hang on to so multiple regular and special clamps were needed. As the parts are so long, the edges have to be supported fully along their entire lengths.
Attachments
484 The Edge Clamping Setup Used.jpg
485 A Clamp Insert Within a Clamp Insert as Used in the Clamping Setup.jpg
Carrdo
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Location: Toronto, Canada

Re: Constructing the Martin Lewis Little Engines Northern Tender

Post by Carrdo »

Further work on the side frame to have it look like the heavy duty channel as shown on the Martin Lewis print.

This involved the setup to produce the tapered legs on the channel. Structural channel has the legs tapered 2 in 12 or 16.67 degrees. But on the model no one will notice if the taper is made 15 degrees or 18 degrees.

As these parts are both long and "slender" I went the high horsepower route employing two light "identical" angle vices to hold and angle the side frame blank. On the initial setup I had the two vices acting together, the vices being aligned together using an indicator. The Craftsman vise is really a Palmgren vise as it was made by them and Craftsman only put their label on it. However, the two vices, being purchased (new) decades apart, there are subtle differences between the two which become important.

I used the outer edge of the side frame as a reference as I knew that it had been machined straight and parallel unlike the rough internal slot.

I wanted to have the two angled leg surfaces end up all square and parallel as this is easily seen if they are machined tapered or cocked. But surprise, even with indicating, it didn't work out this way as the two vices are slightly different dimensionally.

The solution to this was to make one vise the master (where the vise is clamped to the milling table and the jaws aligned dead square and the part sits on a parallel to bring the side frame to the correct height for milling) and the other vise the follower (no parallel, the vise is left unclamped on the mill table initially and the part is lightly clamped between the vise jaws). After everything has ben aligned by the master vice, the follower vise is then clamped to the table of the mill. The jaw of the follower vise may have to be released and retightened on the part in order to have it sit dead level between the two vices and to avoid bending it.

The later procedure also involved taking a light angled trial cut, measuring the result and tapping one or both vices as needed until the angled cut gave a true square non tapered edge all along the entire length of the part.

The two setup photos look to be identical but they aren't.

In the end it all worked out fine, just more dog work milling to actually do it.
Attachments
486 The Setup Showing the Two Vise Acting Together.jpg
487 The Setup Showing the Master (Palmgren) and the Follower (Craftsman)Vise.jpg
488 The Roughed Out Channel End.jpg
Carrdo
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Re: Constructing the Martin Lewis Little Engines Northern Tender

Post by Carrdo »

A little further on with some external profiling.
Attachments
489 External Profiling.jpg
490 External Profiling.jpg
491 A Little Further On.jpg
Carrdo
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Re: Constructing the Martin Lewis Little Engines Northern Tender

Post by Carrdo »

The finished cradle side frames. Now, one just has to pick up the existing drilled holes in the rear of the main frames but first...

The radial curved end buffer piece has to be machined.

To do this the block was first rough "rectangularized" and then two of its long length faces (90 degrees to each other) were finish ground on the SG truly square. Also, the block was machined to a specific overall length which I will explain shortly as to why. There are no photos of this as this is basic machining.

I will diverge here for a bit and for those of you who know what radial means, you can bypass this part.

Because nobody ever really explained it to me in detail.

There are some locomotive machining operations which involve radial machining and this is one of them.

To visualize radial in it most basic form is to consider it like the spokes on a bicycle wheel. For something to be truly radial, two conditions have to be met. Theoretically, one end of a radial spoke has to pass through the centre of the wheel or a circle having any radius and secondly, the end point of the spoke must be tangent to the circumference of the wheel or circle where the radial line intersects the circle circumference. See the sketch on photo 493. The line A-B is truly radial as it passes through the centre of the circle and where it intersects the circumference of a circle it is tangent to the circle circumference at that point. By definition, any line which is tangent to this intersection point such as line C-D creates a right angle at that point and only there. Lines E-F and H-G are not radial lines.

Why go through this song and dance? It is due to the fact that the block we are about to machine has to be set up radially. It is easy to draw this on paper but it is not so easy to set up a part radially on a lathe faceplate or on a rotary table without having it skewed in some manner. Fortunately, my rotary table has its table tee slots arranged so that it is easy to do.

See the setup used to achieve this photos 494 and 495. The reason the block was machined to a specific length was so that it was a nice slide fit between the the two parallel tee slots on the rotary table. This centred the block lengthwise. The flat bar piece in the tee slot passing through the centre of the rotary table kept the (centre or centreline of the) block radial and square. Then there was the backup spacer block to set the part outer face to the correct radial radius and a sacrificial spacer block underneath the part to lift it off the rotary table surface. All of these parts had to be custom made to fit the setup. It is a lot of setup work just for one operation but as can be seen in in the second last photo, the two curved faces came out virtually coincident.

After that, I used the bandsaw to remove most of the corner material to try and speed things up. And one needs a very sharp extra long end mill to get at all of this. The clamping system used is just adequate so do not try and take heavy down feed cuts (not more than 0.005" per pass) or climb milling and keep the rotary table clamps finger snug at all times. An end mill like this can yank and grab faster than one can react so...
Attachments
492.The Finished Cradle Side Frames.jpg
493 The Definition of Radial.jpg
494 The Rotary Table Setup to Produce the Outer Radial Curved Face.jpg
495 Another View of the Setup.jpg
496 The Two Radial Curved Faces are Virtually Coincident.jpg
497 After Bandsawing Away the Corners.jpg
Carrdo
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Re: Constructing the Martin Lewis Little Engines Northern Tender

Post by Carrdo »

The next operation is to machine the internal wedge shaped cutout for the coupler. Not an easy operation to do from the solid so it was done in stages.

Here is stage one.

After laying out the wedge shape on the front and rear surfaces of the curved buffer piece block, the blank was set up in the mill as seen in the first photo and the square centre portion of the wedge was carefully chain drilled. This is a very deep drilling operation with a few personal observations on this.

I was drilling a 1-5/16" long series of through holes with a new 3/32" HSS drill; the drilled holes had to be straight and not wander. And this depth of hole was greater than the length of the drill's spiral flutes.

Contrary to what others have said this drill seemed to work better at lower speeds (<700 RPM) with frequent drill chip clearing ((I only fed the drill down to produce chips half way up the spiral flutes (after the first 1/4" depth) then withdrew the drill to clear the chips)). At no point did the drill grab or spin in the drill chuck but I fed the drill into the work quite slowly. The operation required one to cycle the quill of the mill much more than normal but the drill never complained.

I have experienced this with deep drilling before that if one tries to feed the drill too quickly or if it is not sharp or if chips start to pack in the flutes, disaster will follow - the drill will either spin in the drill chuck or it will start to squeal and grab or it will jam in the hole and/or break.

To do the chain drilling here, one also has to precisely maintain the drill set over to leave as little bridge metal as possible between adjacent holes without the drill actually breaking into an adjacent hole. I always use a centre or spotting drill to start each hole in these situations.

One can see in the photos how straight and on location the chain drilled holes are.

After this the remaining bridge material was cut away with a jewellers piercing saw. Again, with this operation, one has to be careful to properly tension the saw blade and to let the saw teeth do the cutting without pushing the saw teeth. Even so, these tiny and fragile blades were never designed to cut through this depth of steel, so I broke a few blades in the process.
Attachments
499 Deep Chain Drilling.jpg
501 After Employing a Jewellers Piercing  Saw to Saw Away the Bridges Between the Chain Drilled Holes.jpg
Last edited by Carrdo on Wed Sep 28, 2022 4:24 pm, edited 1 time in total.
Carrdo
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Location: Toronto, Canada

Re: Constructing the Martin Lewis Little Engines Northern Tender

Post by Carrdo »

On to stage two of the internal wedge cutout. This involves more chain drilling all around the periphery of the layout lines on the curved face of the cutout.

Two lines representing the taper of the cutout were first scribed on the top face of the blank as reference lines for the chain drilling of the large end on the cutout. Chain drilling the ends meant they would intersect the central cutout near the bottom of the blank.

And therein lies a problem which I didn't realize until it bit me. The drilled end holes of the cutout intersect the centre cutout at an angle and when the drill end broke through near the bottom of the part (at an angle) the drill was driven sideways and it snapped off at the end before I realized what was happening.

So what to do as this was now the situation with every remaining hole which needed to be drilled.

For every problem there is usually a workaround if one starts to think about it enough so...

The part was flipped over and rotated in the vise of the mill so that one of the tapered layout lines was vertical. The rough cutout was then pocket milled to a depth of about 3/8". This created a square "ledge" (to the drilled hole) on the opposite end face into which the drill could break into without any sideways deflection. Both ends were done this way. After that, all of the remaining deep drilled end holes were drilled without incident but one still has to take care with the drilling as described previously.

The remaining drilled holes (4 of them) along the long edge of the cutout couldn't be drilled into any ledge so extreme drilling care was taken to just have these holes break into the central square cutout (at an angle also) and to just stop there. These drills were freshly sharpened before drilling so the breakthrough would be as smooth as possible and to stop the drill grabbing.

After all of the cutout holes were drilled, more tedious and careful jewellers piercing saw work (and two more more broken blades) to cut away the tapered end pieces as seen in the last photo.

I think that all of the difficult work is now behind me but I still have to carefully finish profile the cutout (stage 3).
Attachments
502 The Part to be Made.jpg
503 Pocket Milling to Create a Flat Ledge for the Drill to Break Into.jpg
504 Deep Chain Drilling the End Faces on the Front Curved Face of the Internal Wedge Pocket.jpg
506 Perimeter Drilling Complete.jpg
507 The Rough Wedge Cutout.jpg
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NP317
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Re: Constructing the Martin Lewis Little Engines Northern Tender

Post by NP317 »

That challenge makes you appreciate castings!
RussN
Carrdo
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Re: Constructing the Martin Lewis Little Engines Northern Tender

Post by Carrdo »

Switching gears for the moment, I decided to mount one of the new cradle side frames to the rear of one main frame.

This meant transferring all of the 9 bolted connector 1/8" drilled holes to the new side frame.

To do this I used the existing side frame drilled holes as a drilling template to locate and drill the new mounting holes. This is always a risky move as one has to ensure that one can spot through the existing frame bolt hole pattern perfectly so the new drilled holes will align completely with the existing holes drilled in the end of the main frame (all 9 of them having very minimal clearance!). In addition, the two side frames need to be first set together so that the new side frame will end up exactly in the final position where you want it to be.

It is easy to say but a lot more difficult to do. So clamp the two frames together with the old frame outside of the new frame and mount the two on the existing bolts to see where the new frame ends up, check, measure every which way, adjust as necessary, check and check again as one only gets one shot at this.

Yes, it all worked out in the end but it was a very tight fit requiring some tapping to bed in the new side frame. This is not for beginners or for the faint hearted.
Attachments
509 Employing an Existing Cradle Side Frame as a Drilling Template.jpg
510 One Cradle Side Channel Mounted to a Rear Main Fame.jpg
Carrdo
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Re: Constructing the Martin Lewis Little Engines Northern Tender

Post by Carrdo »

On with stage three or the finish milling of the internal wedge shaped cutout.

For this operation one needs an extra long end mill, actually one with a full 1-1/4" depth of cut. Not too many end mills come this long in the diameters which I needed ( 3/16" and 1/4").

But first how was the part set up to successfully undertake this operation?

Initially, my first thought was to set the part radially again on the top of the rotary table and then mount the rotary table to the largest and stiffest angle plate which I had to allow for vertical radial rotary milling. It would have worked but it would have been a nightmare setup (and much too complicated as usual with me). So in the end...

Simply mount the part in the mill vise and tilt it over until one of my scribed end face lines is vertical and mill down through the cavity (one end face and at the same time partly along the front and rear faces). Then, without altering anything, tilt the part over in the opposite direction until the other scribed end face line is vertical and repeat the process working from both end faces towards the centre (or slightly past it). Simple.

Simple, except that one has to be extremely careful with the milling in small depth increments as no end mill which I have will cut a full 1-1/4" DOC except incrementally. Also, I needed to first make roughing passes to remove all of the spikes and half circles left from the chain milling operation and one has to be extremely careful here as well as the end mill wants to snap and grab on these spikes and half circles.

I did not take any photos of the initial rough milling but it was tense.

So, after removing all of the "furries" as Richard likes to call them, I proceeded to finish mill to the layout lines. This presented another issue as, if one wants to produce a finished cutout like that shown on the Martin Lewis print, one has to mill up to the layout lines and no further. And since you can't see what the end mill is doing when it is way down there, one needs all of the milling aids one can think of. This includes carefully setting a table stop to limit the end mill travel at each end of the cutout and a second set to limit the cross slide travel for the front and rear faces of the cutout.

So this sets the stage for the actual milling operation. To be continued.
Attachments
511 The Extra Long HSS End Mill Needed to Mill the Wedge Cutout.jpg
512 Needing the Full Extra Long End Mill Depth of Cut.jpg
513 Plunge Milling All of the Wedge Shaped Cutout Corners Up to the Layout Lines.jpg
514 My Custom Made Milling Machine Cross Slide Stop.jpg
Carrdo
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Re: Constructing the Martin Lewis Little Engines Northern Tender

Post by Carrdo »

To finish machine the cutout, the first operation was to carefully plunge mill down in each of the four corners in small horizontal increments to the layout lines then slowly shave down an end face and part of the longer front and rear faces having the part tilted in one direction and then in the other direction until the two part faces became one. This was done with small depth increments using all of the stops to precisely limit the travel of the end mill to end up with a single face.

If one was patient and didn't rush or push the end mill, one could end up with a continuous and uninterrupted interior cutout as seen in the last photo.

But never again - once was enough.
Attachments
515 Finish Milling the Front Face with the Part Tilted to the Right.jpg
516 Finish Milling the Rear Face with the Part Tilted to the Left to Blend with the Rear Face with the Part Tilted to the Right. jpg.jpg
518 The Wedge Shaped Cutout Finish Machined.jpg
519 The Finish Machined Wedge Cutout.jpg
Asteamhead
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Re: Constructing the Martin Lewis Little Engines Northern Tender

Post by Asteamhead »

Hello Carrdo,

What about making those parts of two halves and weld (or solder) them together? It`s much less risky to mill the open parts rather than milling such deep caverns :!:
Just my two cents
asteamhead
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