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Discussion Starter · #1 · (Edited)
Hello all,

It's been quite a few years since I've frequented this board, but I recently picked up an Aster/Accucraft Light Mikado kit and I'd like to document the build here.

It will receive an almost entirely new chassis (saving only the driver wheelsets), a coal fired boiler, and a number of detail upgrades. The objective is to make it appear as close as possible to an as-built Texas & Pacific 800 class Mikado.

These Mikes were eventually heavily modernized, which I considered modeling, but due to limited time for my own personal projects I decided to keep it as-built. The modernized version would require a completely new tender and a significant number of detail and structural changes to the locomotive.


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I've begun laying out the new chassis in CAD and modeled up some new check valves for the locomotive, which I had 3D printed from shapeways. I've opened up a shop there so any detail parts I make for this project can be used by others. Eccentric Engineer by ARDuarte - Shapeways Shops

The name Eccentric Engineer might be familiar to you if you're involved in the ride-on scales. It's my primary business which focusses on manufacturing injectors and other steam related accessories in 1:16 to 1:4.8 scales. www.EccentricEngineer.com

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Looking forward to sharing more in the near future.
Anthony
 

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Discussion Starter · #3 ·
Thanks Russell.

Here's a few screenshots of the CAD model still in progress. It's quite a departure from Aster's original chassis design. This model will have 'real' cylinders with piston valves, with some alterations to suit Aster's piping. I have a nice collection of full sized USRA mikado blueprints from the New York Central System Historical Society. The NYC H-6 Mikados were of the USRA design.

I nearly forgot about the axle pump... It's unfortunately very much in the way of the prototype crossties, so I shortened the pump's rod significantly from 2.7" to .75" so the whole assembly fits between two drivers. One of the crossties has been converted into the axle pump body.

Anthony



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Looks awesome
Will you be designing a working injector in 1/32 scale?
What CAD program are you using
what ring material will you be using for the valve pistons? Will the timing mark be at the piston edge or the ring edge?
Where did you find that big quarter
Thanks for posting. looking forward to the build.
 

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Discussion Starter · #5 ·
Hi Bill,

I seriously considered making a working 1/32 Nathan injector for it... but after calculating how small the nozzles would be I decided to keep my sanity. I’ll have some injectors and starter valves printed to go on as detail parts though.

The timing events are to the edges of the ring, which will be Teflon. The piston is a smaller diameter than the ring so it won’t interfere with the events.
CAD work is done in SolidWorks.
Anthony
 

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That SolidWorks is nice. My friend Rob was using it but switched to Fusion 360. He is building a coal fired Uintah and the cad work he is doing is fabulous. I just started CAD and am just stumbling through 2D. I made a 1/32 bell this week from a pencil and paper drawing that took almost a day to complete so I am thinking I need to get into 3D and get these things printed.
I'll be interested to see the decorative injectors.
I fooled around with piston valves early on and didn't use rings so I had some blowby. I also was using under performing boilers so the slight blowby was unacceptable. I understand that Aster uses the piston for the valve events and the rulon rings are set back and just prevent blowby.
 

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Discussion Starter · #7 ·
Took quite a bit of time to get the rear cradle and trailing truck drawn out. I don't have a proper drawing for the cradle, so I had to rely on two elevation drawings and a several dozen photographs I took of the cradle on GTW 4070 at the Midwest Railway Preservation Society. The cradle was widened to 1.125" from Aster's .785" so it will no longer make the recommended 7' minimum radius. It will definitely make 9', and may possibly squeeze around 8'.

The trailing truck will have all the equalization parts attached to it, but it won't actually be equalized to the drivers. At least that's the plan for now.
I was pleasantly surprised to see how close the back of the prototype cradle lined up with the back of Aster's frame. I had to shorten it by only .05" to match them up.

I would be cutting parts already, but my shop is currently down waiting for a new spindle for the CNC mill. Looking forward to getting the frame and equalization cut out so I can get the engine on its feet.

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Discussion Starter · #8 ·
The chassis design is complete minus a few details, some of which don't need to be drawn out.
CNC mill is getting fixed tomorrow, so hopefully there'll be an update soon with some actual parts.

Springs are hidden in the pilot and trailing trucks, so even with the chassis flipped over they can't be seen. Ought to be very hard to see that they're not equalized with the drivers.

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Discussion Starter · #9 · (Edited)
Mill is back up and running today, so I decided to put the repair to the test by cutting new journal boxes for the mikado. I was planning on keeping the originals, but I was concerned about how some things were going to work with the equalization, so I went ahead and made some journal boxes that resemble the prototype.

This meant cutting out the original journals, which was a little hair raising, but it worked out quite nicely. Left a .005” web on both sides which made it easy to break them apart with a pair of wrenches.

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The new journals were cut in pairs. The rear set was a little bit different to allow more lateral movement. The side slots were cut with a key cutter to ensure they’re perfectly centered with the bearing surfaces.

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New journal test fitted on the left, old on the right.

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The bottom piece, which somewhat resembles a grease cellar, is held on with 00-90 screws. The new frame rails will be 3/16” wide, which is why the test fit with side rods looks a little sloppy. Rolls very nicely though!

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Discussion Starter · #10 ·
Started on the smaller crosstie and the axle pump. There were supposed to be 2 small identical crossties, but one of them ended up becoming the axle pump body.
These were fun to make!

The material for the pump body was first made as square and parallel as possible, then rotated 4 times in the vice to machine as many features as possible. After cutting it off in the bandsaw the two holes for the ball checks were machined. I did this after cutoff because I was able to drill with a more rigid setup. It was a bit flimsy hanging out the end of the vise.
And lastly the cylinder for the ram was put in along with the detail webs. The end of the cylinder is threaded 5/16”-40 to receive a packing nut.

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Discussion Starter · #11 ·
Managed to get the side frames cut out of 303 stainless steel, 3/16” thick. Drilled the holes out first then bolted it down to an aluminum plate to machine out the profile. It really warped like a banana when I unbolted it! Nothing a little love in the press couldn’t fix... I checked progress by measuring the distance between the outer edges of the bosses that locate the pedestal binders. Knowing exactly how far apart they should be, I straightened out the frames until they hit that number.

You might notice one side has a few extra holes on top... that’s due to me remembering to locate the edge of the frame and completely forgetting to compensate for my edge finder’s diameter! Oh well... I still had enough room to put the holes in the right spot, and they won’t be seen.

Still have to square up the corners of the slot that holds the cylinders and put a cosmetic relief on the front, but that’ll have to wait.

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Discussion Starter · #12 ·
Here are a few shots of the top crossties. Still need to make the front crosstie which has the pin for the lead truck... that one will be tricky.
The front crosstie holds a bar that supports the crosshead guide yoke. The little “knees” (as they’re called on the drawing) hold a bar that support the back of the link hangers. And lastly the back holds a piece of sheet metal that gives a little extra support to the boiler.

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Discussion Starter · #13 ·
Got started on the equalization and also made the front bracket that will allow the cylinders to be screwed in. Not how it was done on the prototype, but it’ll make installing the cylinder block very easy.
The cap screws are temporary just to hold the leaf springs in place for the picture.

I made a bunch of stainless #0-80 hex head screws in multiple lengths for this build. They’ll be used where the bolts on the real engine were more easily visible. Had to make my own socket drive to secure them since they’re so close to the crosstie walls.

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I see that you made your cap screws out of stainless. Micro fasteners has brass ones in various sizes and stainless in longer lengths which can be cut down. I am just curious why you didn't use brass screws for the brackets.
 

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Discussion Starter · #15 ·
I didn’t make the cap screws, just the hex head screws. I made my own because #0-80’s typically come with a 3/32” head and I needed 5/64” for them to fit. Making my own also allowed me to make them with a shoulder so only the end is threaded as much as needed. I suppose I could have made them out of brass, but I had plenty of stainless bar and it’s quite a bit stronger.

I don’t see any hex head screws from Micro Fasteners? J.I.Morris is my go-to. J.I Morris Company | Miniature Screws & Fasteners Manufacturer
 

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Discussion Starter · #16 ·
Got the brake hangers machined today. These hold the brake levers and also support the equalization. The brake hanger in the middle is a little different since it doesn’t have any equalization going through it. Expecting a number of items from shapeways this week!

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Discussion Starter · #17 ·
The mikado is standing on its own feet now. Watched the equalization as I rolled the chassis over a piece of .02” wire. Seems to work well.

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Discussion Starter · #18 ·
Goodies from shapeways arrived today! The front coupler pocket and Nathan 1918A injectors will be available on my shapeways store.

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Discussion Starter · #20 ·
Thank you Bill! I’m having quite a bit of fun with it.

I added 2% shrinkage to all the shapeways parts which is what I usually do for my lost wax bronze parts for EE. Everything came out right on size except for the the link hangers. They’re exactly 2% larger than they should be. Doesn’t sound like much but it’s enough to make them unusable. Unfortunately those will have to be redone.
I machined up the front bumper bracket, which turned out to be quite tricky to hold. A couple years ago I machined the same part from a solid block of steel in 1” scale, and since all the surfaces were machined holding it was pretty easy. Getting the sides of this cast 1:32 version to come out parallel and on size took some patience.

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Also felt like taking on the trailing truck. Had to do some light machining on the journals to allow clearance for the bearings, and had to tap a couple holes on the bottom to accept the bearing retainer. These were a bit easier to hold in the vise so it all went pretty smoothly.
After machining, the 4 pieces were soldered together and bead blasted. The blasting really brought out the detail (at least I think so).

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