1” USRA Light Mikado

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AnthonyDuarte
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1” USRA Light Mikado

Post by AnthonyDuarte »

Those of you that follow Eccentric Engineer’s Facebook or Instagram pages may have seen this already, and some of you have seen it in person, but just over 2 years ago I started scratch building a 1” scale USRA light mikado.

I really went to town on it for 3-4 weeks and haven’t touched it since. Just been too busy. One of my goals for 2021 was to set aside one day a week for my own projects (out of a 6 day work week).

So far I’ve been working on a gauge 1 scratch build, but recently I got back onto the 1” Mikado. So why not start a build log?? Maybe it’ll help me stick with it.

I’ll follow this up with some pictures of how I machined some of the components.

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AnthonyDuarte
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Re: 1” USRA Light Mikado

Post by AnthonyDuarte »

The side frames were machined from 1/2” precision ground O1 tool steel. To my delight they did not warp at all during machining. My mill didn’t have enough X travel to get the whole thing in one shot, so I had to machine it in 3 sections. All the pedestal openings and everything in between was machined in one shot, then scooted to the left and to the right to get the front and back.

The pedestal binders interface with the frame on the tapered sides just like the prototype. I used a 4° per side tapered endmill to cut the walls which worked out very well.

In my impatience I machined the toe clamps out of a chunk of aluminum bronze I had in the scrap bin. Those clamps still come in handy!

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AnthonyDuarte
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Re: 1” USRA Light Mikado

Post by AnthonyDuarte »

The front bumper bracket was machined from a solid chunk of steel. This one took a long time since it was mostly finished with a 1/16” long reach corner radius endmill. Now that I’m older and wiser (not really) I’d probably go with a slightly larger than scale radius so I could use bigger tools. Realistically it would still look just a nice, and most of this gets covered anyway.

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Everything looks better bead blasted!
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AnthonyDuarte
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Re: 1” USRA Light Mikado

Post by AnthonyDuarte »

Here is a bit on the crosshead guide yokes and link hangers. There’s were really fun to make! I think I posted the link hangers on a CNC thread a while back.

These were both machined with similar strategies. The guide yoke stock was machined flat and square, then roughed on both sides, then finished on both sides, leaving thoughtfully placed tabs to hold the finished part. Then the tabs were carefully cut away on size with a small tool. This leaves just a small burr that is easily filed off.

The link hangers similarly were squared up first as nicely as possible. Roughed from all 4 sides then finished from all 4 sides rotating the block. With this technique the sizing of the material isn’t too critical. What matters is it’s truly square, parallel, and the same dimension in both directions. From there I can program everything off of the center of the material using a stop to locate the material on the X.
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AnthonyDuarte
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Re: 1” USRA Light Mikado

Post by AnthonyDuarte »

The cylinder heads were also quite fun to make. They were done primarily on the mill believe it or not. The mating side was finished on the lathe.


All the dark brown “casting” are the sintered bronze material from shapeways. I might have the rear steam head (valve guide) redone in lost wax bronze.

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AnthonyDuarte
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Re: 1” USRA Light Mikado

Post by AnthonyDuarte »

I’m not happy with the cylinders. They were coming along fine but I got ahold of much better information after the fact. These may also end up as lost wax castings, made identical to the prototype as much as possible.

Nonetheless, I think it’s worth sharing what I did on them so far.

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AnthonyDuarte
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Re: 1” USRA Light Mikado

Post by AnthonyDuarte »

Most of the crossties were pretty straightforward to machine, but the one that really made me scratch my head was the front crosstie. This houses the pin to which the lead truck attaches, and also serves as the fulcrum to transfer the force of the brake cylinders to the break rigging.

I machined one side as well as I could, then mounted it to an aluminum plate using pins to locate off the drilled holes from the now machined side. From here I could go off the plate to machine it to proper thickness, and use my XY cordinates of the holes in the plate to locate the holes on the flip side. Those bronze clamps came in handy here!

Sorry some of these pictures are coming out sideways...

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AnthonyDuarte
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Re: 1” USRA Light Mikado

Post by AnthonyDuarte »

Here’s a few shots of some of the other parts I’ve made. That pretty much brings the project up to date!

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NP317
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Re: 1” USRA Light Mikado

Post by NP317 »

Sorry Anthony, but you are not allowed to post more Build Blog.
Several of us will get more depressed looking at the quality of your work!

:lol: :roll:
RussN
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Greg_Lewis
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Re: 1” USRA Light Mikado

Post by Greg_Lewis »

NP317 wrote: Fri Mar 19, 2021 9:02 pm Sorry Anthony, but you are not allowed to post more Build Blog.
Several of us will get more depressed looking at the quality of your work!

:lol: :roll:
RussN

I'm tossing all my trains and tools in the bin and taking up stamp collecting. :shock:
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kcameron
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Re: 1” USRA Light Mikado

Post by kcameron »

Knowing how Anthony works, I have to look twice to see if something is a photo or a computer image. They both look just so perfect either way. His wiz at the CAD programs shows by what he is able to produce.
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UPsteamfan
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Re: 1” USRA Light Mikado

Post by UPsteamfan »

Man i can only hope that my work can look that nice. If I ever get started.
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