Constructing the Martin Lewis Little Engines Northern Tender

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Carrdo
Posts: 1444
Joined: Thu Mar 06, 2003 2:20 pm
Location: Toronto, Canada

Re: Constructing the Martin Lewis Little Engines Northern Tender

Post by Carrdo »

Hello Asteamhead,

Yes, the part could be made from two half parts silver soldered together as you have suggested and likely I would do it that way if I ever had to do it again. Some of the square tool bit holder parts in the work head for the Quorn were made that way but as you know I never back down from a machining challenge to do it the most difficult way possible.

As an additional comment, one often has to work with what one has or does not have. I do not have any welding equipment (nor are there any small commercial welding shops here which would undertake such a small job today) and even to heat up two blocks of steel of this size with the silver soldering equipment which I have would be a challenge.

If any replacement casting had been available, I likely would have used it, but they aren't so one has to deal with reality the best one can.
Last edited by Carrdo on Sun Oct 02, 2022 4:30 pm, edited 1 time in total.
Carrdo
Posts: 1444
Joined: Thu Mar 06, 2003 2:20 pm
Location: Toronto, Canada

Re: Constructing the Martin Lewis Little Engines Northern Tender

Post by Carrdo »

Proceeding with some housekeeping items on the bolting in of the side channels to the end of the main frames.

The original constructor did this with commercial nut sizes. In fact, he or she used, commercial nut sizes everywhere. Very ugly, but since they are mostly hidden between the frames, I really don't care but what I do care about is the commercial hex size used (5/16") for a 5-40 NC thread does not allow one to get a box end, socket or an open end wrench in to tighten the threaded fasteners or turn these nuts without interference with one another.

There are 18 of these fasteners in all for the two side frames. So it was off to the spin index as seen in the first photo to reduce the commercial hex nut size to 1/4" over the hex so that now one can get all three of the above mentioned wrenches into this tight space without interference. A 1/4" hex size for a 5-40 NC thread is not a model scale size either (it should be a 3/16" hex size) but I will make a statement here and leave it at that.

I build detailed working locomotives not scale locomotives with the emphasis on working. If something is not practical, my engineering background says change it until it is as everything which I build has to work and work well. I will tend to overbuild on the premise that good engineering allows for much use and even some abuse and from what I have encountered, there is plenty of that out there. American steam locomotives, unlike their UK and European cousins, were worked hard all of their working life and had to stand up with minimal maintenance the railroads gave them. So I try to emulate this principle in all of my working models.
Attachments
520 Reducing the Commercial Nut Hex Size.jpg
521 One Side Bolted In.jpg
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 »

A little further on.
Attachments
522 Drilling the Other Side Frame Bolt Holes.jpg
524 Further On with the Buffer.jpg
Carrdo
Posts: 1444
Joined: Thu Mar 06, 2003 2:20 pm
Location: Toronto, Canada

Re: Constructing the Martin Lewis Little Engines Northern Tender

Post by Carrdo »

The back end now partially assembled. It was a long road to get this far. I had to make two new top and bottom rear frame binders as I found they had been mis drilled to the end of the main frames by the original builder and as a result were set askew on the main frames.

Then, to my horror, I found a snapped off tap deep down in the main frame in one of the top frame binders thread holes. This turned out to be every bit as bad as with the one which had snapped off on one of the valve cover threads on the Uranus. After endless effort, I finally managed to get the broken tap piece out by plunge end milling and then drilling it out with the two small carbide cutters. I then made up a pre drilled and tapped bronze plug which was driven into the oversize hole, the plug being smeared with a little Loctite before being driven home. Everything (on the broken tapped and now oversize hole) had to be exactly the right size and totally straight for this to work.

It was quite a sight as, to do the above, the entire Northern chassis had to be slung up onto the table of the mill, greatly overhanging at one end with the other end being clamped with straps through the tee slots on the mill. Everything had to sit on the table straight and square and not move once clamped. And everything wanted to do just the opposite! I did not take any photos of this as I was too distraught at this point.

In the end, through nerves coupled with desperation/perspiration/luck, it all worked out. Everything now is straight, square and fits perfectly. In fact one would have to view the inserted plug through magnification to know there was a threaded plug there at all.
Attachments
525 The Back End Partly Assembled.jpg
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 »

The setup to bolt the rear side frames to the buffer block. One can see that I am not using scale fasteners here.

A very straight forward operation now that all of the components have been machined correctly. Just avoid breaking any drills or taps.
Attachments
527 The Setup to Drill and Tap One of the Rear Side Frames to the Buffer Block.jpg
528 One Side Bolted In.jpg
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 »

Back to where I thought I was going to start five weeks ago. Now on to new things.

Even in 3/4" scale this locomotive is going to be a monster.
Attachments
529 October 2022.jpg
Carrdo
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Location: Toronto, Canada

Re: Constructing the Martin Lewis Little Engines Northern Tender

Post by Carrdo »

The new parts remaining to be finished on the engine chassis are the 4 wheel trailing truck rockers and the cradle crossbar which the rockers ride on, except they are not rockers, they are rollers as shown on the Martin Lewis prints.

And herein lays an issue as Martin Lewis never really designed them; on the prints they are shown as a general arrangement only. So one is left to figure out the details. And I can sort of see why as there is so little space available for them to be there.

So here are some sketches which I came up with on my own after playing around with the various components needed to make them. I started with the size of the rollers themselves (the absolute minimum size which I figured the rollers needed to be -1/4" dia.) and then worked outwards from there.

But first one has to make the cradle cross bar which contains the two upper roller plates on which the rollers roll against.
Attachments
531 The General Arrangement of the Martin Lewis Trailing Truck Roller Assembly.jpg
532 My Trailing Truck Roller Assembly Sketches.jpg
533 The Martin Lewis Print for the Cradle Cross Bar.jpg
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 »

The cradle crossbar itself is a 1/2" square bar 6.25" long to which the two roller base plates are attached. Martin Lewis shows the roller plates welded to the main body of the crossbar but since I have no welding equipment, I used four 4-40 NC flat head cap screws to hold the roller plates in position on the body of the crossbar.

The main body of the crossbar also has two deep precision slots which fit the cradle side plate girders. These slots need to be a very close hard fit to the cradle side plate girders as one cannot have any slop or movement here at all as this entire assembly is emulating a one piece casting and has to be just as strong and rigid.

Also, as I was trying to obtain as much clearance height as possible, the slots were made 3/8" deep leaving only a 1/8" bridge thickness at each slot necessitating additional design changes which I will detail later. Even with such deep slots in the crossbar, one is only talking about a 5/16" clear vertical space between the top and bottom roller plates. And with the original builder, as made, nothing like this was possible at all.

I have previously described elsewhere how to machine precision slots to the exact size, to truly rectangular geometry and to the exact distance between the slots (similar to machining the axle box openings in the main frames of a locomotive - see the description on the Josslin Hudson main frames) without resorting to any digital aids. Thus, one can produce a close but free fit, a light push fit, a very hard push fit or a tap fit or a true interference fit.
Attachments
534 The Bits and Pieces of the Cradle Cross Bar and the Trailing Truck Roller Assembly.jpg
535 Milling the Precision Slots in the Cradle Cross Bar.jpg
536 The Finished Precision Milled Slots in the Cradle Cross Bar.jpg
537 Further On.jpg
Carrdo
Posts: 1444
Joined: Thu Mar 06, 2003 2:20 pm
Location: Toronto, Canada

Re: Constructing the Martin Lewis Little Engines Northern Tender

Post by Carrdo »

The cradle crossbar itself is a 1/2" square bar 6.25" long to which the two roller base plates are attached. Martin Lewis shows the roller plates welded to the main body of the crossbar but since I have no welding equipment, I used four 4-40 NC flat head cap screws to hold the roller plates in position on the body of the crossbar.

The main body of the crossbar also has two deep precision slots which fit the cradle side plate girders. These slots need to be a very close hard fit to the cradle side plate girders as one cannot have any slop or movement here at all as this entire assembly is emulating a one piece casting and has to be just as strong and rigid.

Also, as I was trying to obtain as much clearance height as possible, the slots were made 3/8" deep leaving only a 1/8" bridge thickness at each slot necessitating additional design changes which I will detail later. Even with such deep slots in the crossbar, one is only talking about a 5/16" clear vertical space between the top and bottom roller plates. And with the original builder, as made, nothing like this was possible at all.

I have previously described elsewhere how to machine precision slots to the exact size, to truly rectangular geometry and to the exact distance between the slots (similar to machining the axle box openings in the main frames of a locomotive - see the description on the Josslin Hudson main frames) without resorting to any digital aids. Thus, one can produce a close but free fit, a light push fit, a very hard push fit or a tap fit or a true interference fit.

Most of the slot material was first removed by band sawing just to the inside of the layout lines with final milling only taking very light shaving cuts to widen the slots. For operations like this, I recommend the use of freshly sharpened undersize end mills as the hot rolled steel cradle side channels are never on size if made from stock hot rolled steel plate.
Berkman
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Joined: Wed Aug 16, 2017 7:55 pm

Re: Constructing the Martin Lewis Little Engines Northern Tender

Post by Berkman »

did you band saw off the angles on the ends of it ? or did you mill this?
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 »

I did both. Bandsaw the bulk of the 45 degree angle material away first and then finish the end angles to the layout line by milling.
Carrdo
Posts: 1444
Joined: Thu Mar 06, 2003 2:20 pm
Location: Toronto, Canada

Re: Constructing the Martin Lewis Little Engines Northern Tender

Post by Carrdo »

The finish machined cradle crossbar and the crossbar set in place on the cradle side frames with the top and bottom roller plates set in position temporarily.

Notice how little vertical roller space there is left between the two roller plates. I can gain a little extra height (1/16") by reducing the top and bottom roller plate thickness down to 3/32" thickness from what is shown on the prints (1/8").

I will not resort to this until the entire roller assembly has been made according to my sketches and tested for what interferences there may be.

As I mentioned before, it is going to be very tight.
Attachments
538 The Finish Machined Cradle Crossbar.jpg
539 The Cradle Crossbar and the Top and Bottom Roller Plates Temporarily Set in Place.jpg
540 The Cradle Crossbar and the Top and Bottom Roller Plates Temporarily Set in Place.jpg
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