Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

What a lovely job, so very exciting!  Steaming up next???

I have no idea what you are talking about ;-)

Though it is going to be great to see this little guy running!

Hi Bruce,

The kit that I made my filer from is available here:

https://www.metallatheaccessories.com/category/kits

It's more of a "Cadillac" version than most people really need.

Martin Model sells two "open" versions, though the basic price is roughly the same:

https://www.martinmodel.com/collections/die-filer-casting-set

The Metal Lathe Accessories version has several added-cost upgrades which push the price up considerably.

Here's a short video of a guy using the Metal Lathe Accessories version to file a square hole in a gear:




Also, here is an animation of a half-section of the MLA die filer I made in Solid Edge




Paula

Thanks, Charlie. It's been a fun challenge so far working on this very old engine!

And now, on to the

CRANKSHAFT

As mentioned previously, the crankshaft on this engine had a lot of wear and looseness. I was surprised because it seems to have wide and substantial bearings -- not like the stamped sheet metal bearings on some of the later engines:

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This was kind of deceiving, however, as I found out after disassembling. It turns out that only a small portion of the bearing stanchion was contacting the shaft. This is why the amount of wear was so much greater than expected. Here is a drawing of the original crankshaft configuration (upper view) and the proposed design (lower view) with sintered bronze bushings:

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It's perfectly understandable why they designed the bearings this way. It is much more tolerant of misalignment between the bearings due to routine manufacturing variables. This was a mass-produced item, and at the end of the day, the easier the engines went together, the more engines they could send out. The only downside was a higher susceptibility to wear over the years of use.

In repairing the worn bearings, I've decided to make a new crankshaft, and ream out the bearing stanchions for some Oilite sleeve bushings. In addition to providing considerably more bearing surface, the Oilite bushings are made of an oil-impregnated bronze material, which releases a small amount of lubricant when friction builds up. So, if someone neglects to oil the bearings, it's not such a big issue with the Oilite bearings.

Here's a picture of the original crankshaft. Note the grooved area on the right-hand end. This the crank end, which apparently took most of the radial thrust from the engine:

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The original shaft had a diameter of 4.5 millimeters (0.177"), and I will making the replacement shaft from 3/16 (0.1875") O-1 drill rod. Note that the shaft features a #4-64 threaded extension on one end. This is for attachment of the crank/eccentric assembly. It's kind of a tricky feature to reproduce, given the small diameter and length, so I will be using the threaded end from the original shaft. As shown in the drawing below, the original crank end will be cut from the shaft, the cylindrical end turned down to 0.125", and fitted to a hole in the end of the new shaft:

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The threaded end piece will be secured in the new shaft with Loctite 609. When properly cleaned and fitted, this provides a joint far stronger than press-fitting, and as good as pinned joint, without the need for pinning. The only way to disassemble the joint is with heat from a torch. Below is a picture of the original shaft, the "donated" shaft end, and the new shaft with a hole to accommodate the modified shaft end:

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The opposite end of the shaft is threaded #8-32 for the pulley. This thread could normally be cut with a die mounted in the lathe tailstock, but O-1 tool steel is not the most machinable of materials. I decided instead to single-point the thread on the lathe, taking light successive cuts, frequently checking the fit with the pulley:

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After threading the pulley end, I mounted the shaft in the mill to cut a small flat near the center of the shaft for the flywheel setscrew. Here's the finished shaft, along with what's left of the original shaft:

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Next installment will be reaming out the bearing stanchions, and installing the Oilite sleeve bushings.

(to be continued...)

Mighty fine machining work & sound judgment on the decision to oversize of few things, you really had no other choice.

I appreciate the nice comments, you guys! 

Moving on to the crankshaft bearings...

To make certain that the bearings line up accurately, I thought it best to ream the bushing holes with the bearing supports assembled to the engine base. To mount up the engine base in the lathe, I used the same basic method that I used for the Doll engine (though that engine had both bearings in a single casting.) I made a fixture plate from a piece of aluminum from the scrap box. This fixture will enable the engine base to be attached to the vertical slide of the lathe cross-slide:

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With the engine base secured to the vertical slide, it was aligned with the headstock using a rod sized to fit the existing holes in the bearing supports. Once they were aligned, a 1/4" reamer was used to enlarge the holes to fit the oilite bushings:

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Following this, the bearing supports were removed, and the oilite bushings were pressed into place. The bearing supports were then re-attached to the engine base, still mounted to the lathe. I had previously marked the supports to make sure they got back in their original positions:

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After this, a .1885" reamer was used to size the bearings to .001" over the nominal diameter of the crankshaft. Before removing the engine base assembly from the lathe, the fit and alignment of the bushings were checked with a piece of 3/16" dia. drill rod:

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The engine base was then removed from the fixture, and is seen in this picture sporting its brand-new, sintered bronze, oil-impregnated, sleeve-type bushings (and some seriously cylindrical bearing support screws!):

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With all the parts put back together, here is the engine assembly, including a sleeved crank pin bearing:

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Up next: The smokestack.

LOL, I did a small edit shortly after posting, and maybe you viewed the post while it was being updated? 

I've kind of changed my mind on the smokestack. Probably be modifying the one that I received with the engine. More details soon.

Paula