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PM Research #4 - Quarter Horse Vertical Steam Engine

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propforward:
Well, on we go then.

There aren't too many build logs of this engine on the net. Stan Shire did a very nice one on this forum, which you can rest assured I will refer to often because it is excellent.

I have a couple of goals beyond making a working engine on this one - well not beyond it, integral to it.

1. Do not scrap a part (not actually that important, but something to strive for).
2. Make parts individually "by the numbers" rather than transfer punching features. Now - I don't consider transfer punching and drilling "wrong", this is simply a measure for me personally of how well I am understanding the parts, the drawings and the machining process. It should be possible to make parts that fit together by making them individually if the tolerances and methods are understood. One exception - I will likely drill and ream the crank bearings mounted on the base plate.

In my opinion the PMR #4 is not an especially elegant engine, but it is a replica of an actual work horse engine - a full size replica, rated at 1/4 horse power. So the larger physical size made it very intriguing to me when I bought the casting set in 2015, and now it is time to move forward with it.

I suspect that being a bit larger it will be less tolerant of alignment errors and such, but in any case I am determined to put everything I have learned so far into practice (rather than learn the same mistakes again  :facepalm2:).

Here is a look at the supplied parts.



It's quite a lump. Here is the cylinder casting, and I am no waif I can assure you weighing in at (too much) and standing (about this high).







Flywheel is a decent chunk too.



Anyway, the engine itself is actually a fairly straightforward design - but holding the various parts will present some challenges I'm sure. I've had the drawings on the wall of my office at work since the start of the year, so I can peruse them constantly and think through the build a bit, and that has helped me formulate a general approach.

I'm starting with the base. This is because it is a reasonably simple part, but also because the base will go on to become a fixture for machining the bearings in due course.

I started by putting it on a surface plate, and checking flatness and parallelism. It rocked a bit on the surface plate, feeler gauges suggested about 10 thou rock underneath. The top surface was flat within .05", which I think is reasonably good for a raw casting.



Where I didn't do so well on my last engine was not understanding the starting castings well enough. I'm determined to measure and understand the castings better this time so that I can balance the machining and not run out of machining stock, as well as keeping machining balanced on each surface.

I mounted the base on the mill and shimmed it to get it reasonably level.



Then dusted off the top. I didn't completely clean it up, just about 30 thou to get it to sit flat.



Here is the drawing, on my trusty rolly cart. Nice to have it presented so that you can see it clearly without tools piled on top of it.



Anyway, after dusting off the top surface I flipped it over and skimmed the underside.





Had to reset the clamps after milling part of the base.



I checked the top surface for flatness after this step - and it is flat to .0015". I am pretty happy with that to be honest.

Then back on the mill to finish clean up of the top surface.

This time when setting up, I squared the part up using my newly repaired interapid DTI. This is because I'm going to drill and tap the holes in the base as well as do clean up.



I touched off on the front edge first, and got that square (completely square according to my DRO). I do not run the DTI over as cast surfaces - I touch on one spot, set zero, back off and move down, then touch off again. I chose the front edge arbitrarily. Basically, you have to trust SOMETHING on a casting, so I chose the front edge. After squaring the front edge up, I touched off on two positions on the other 3 edges to check them. The right edge was withing .001", the left within .0006" and the back edge within .005". Not far enough out to warrant any balancing acts - this is plenty good.

So I finished tightening the clamps, and skimmed the top surface clean.



And that's where I am.

Next step will be to drill and top the holes in the top surface, then I'll re clamp and drill the holes in the bosses currently being used to clamp the part.

Off and running!  :ThumbsUp:

crueby:
Great start on a big engine. Got a big bowl of popcorn to match!


 :popcornsmall:

MJM460:
Hi Stewart,

Great start on the new engine.  Must be very satisfying to have such a project to prove out your new DRO installations, not to mention the other lathe improvements.

MJM460

Sleddog:
I’ll be 3-4 rows back, sitting comfortable & watching 🍿

tevans9129@charter.net:
This is fascinating, and educational, for a newby, thanks for posting and I am looking forward to the next installment.

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