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Upshur Horizontal Farm Engine - Mike's Version

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I'm going to start my build log of my version of a Upshur Farm Engine.  I've already done a good portion of the build, so I'll catch up with the log and photos in the next few days and then will start the more or less real time updates. 

Just to describe my approach for this engine:  I purchased all of Upshur's plans and decided that since I've never built a hit-n-miss type engine, I'd try that.  But to me, the Farm Engine plans were a bit confusing since several different versions were all mixed into the same set of plans.  So, I modeled what I wanted to build in Fusion 360 and then generated a set of 2D drawings to do my build from.

Here are changes that I decided to make on my version of the build:

- My version will be an horizontal air cooled, but will keep Upshur's bore and stroke. 
- Use roller bearings rather than bronze bushing for the crank main bearings.
- Crankshaft will be a built-up fabricated type  rather than turned from solid stock. 
- Add bronze bearing inserts to both ends of the connecting rod.
- Use an o-ring for the piston rather than cast iron rings. 
- Make the crankshaft more easily removable by adding separate bearing blocks that will attach to the frame via cap screws. 
- Use cast iron flywheels from Martin Model, slightly larger than the plans call for.  They'll end up at 4.125" diameter
- Change the gears from 48DP to 32DP. 
- Use an S/S hall effect base ignition system.
- Add a 'Brian Rupnow Design' starter hub.

There are a few other minor changes, but I'll note them as I post the build.

Hopefully this will be enjoyable and maybe even useful to some!


I'll definitely be following along, Mike.
Both the built-up crankshaft and the O-ring piston are shown on my plans. It will be fun to see how your changes compare to my build, which is mostly as drawn, except for some cosmetic changes.

All righty, I'll document the engine frame build as I did that more or less all in one go over a couple of days. 

As all project start, some 1/4 and 5/16 AL stock was chopped off with my small horizontal bandsaw.  Here's the rough cut pieces laid on top of the working drawing I generated from the CAD model I created in Fusion 360.  You can see some of the changes that I made to the frame design to accomodate the removable bearing carriers.  The frame is .25" and the bearing carriers are .313 so they can accommodate 2 flanged, sealed roller bearings, .3125x.500x.1875. 

Just one quick pix of the way I did most of the frame pieces.  I used super glue and mated the rough cut pieces together to minimize all the swapping in the mill vise.  I normally detest super glue as it doesn't hold all that well, but since the surface area is large and I'm gripping it in a Kurt vise anyway, I figured I'd get by with it.

A pix of the last operations on the bearing carriers.  I'd already drilled and reamed them and am drilling thru and putting in a counterbore as those blocks will be attached with some 1" 4-40 shcs.

Here's a shot of the 'main plate' after drilling out most of it then boring to the final size of 875" 

One of the last operations on the side plate, milling a 45 degree angle on the upper rear corners of the side plates, mostly because it looks better.  I set the angle with an angle block under the frame side and tightened the vise down on the plates.

The frame plates and base with work done so far.  The surface finish will be worked on but not until much closer to completion.  The front  main plate still has some detail to be added also.

I didn't show it, but I drilled and tapped a hole in the center top of the main plate 10-40 (same as 3/16-40 as near as I can tell) that will be for a PM Research drip oiler.  Then I made an alignment pin for the center hole of my rotary table, mounted the main plate on a piece of scrap AL and milled the rounded top on the part.  Shown is the mounting operation in progress.  Process involved center the rotary table under the spindle then stepping off in y axis .937" as per Upshur's design and rotating the table until the top was rounded.

I wanted to assure that the bearings would be as close to aligned as possible so I assembled the frame pieces and reamed thru them both with an on size reamer.  I'd left the holes originally just slightly under and my hope was that this would make them as close as i could get them.

I also not so cleverly forgot to drill thru for the camshaft mounting hole and for a tapped 4-40 hole on the other side frame for mounting the hall effect sensor.  Soooo, after I found my omission(s) I located and drilled/tapped those holes.

And that's pretty much it for the frame.  I'll show it assembled with some other pieces as this thread progresses.



So today's post will be on making the cylinder.  This is a  horizontal air cooled engine, so the cylinder for this version is fairly simple.  So, here we go!

I started off with a piece of nominal 1.5" cast iron and centered it up in my 4J chuck as best I could given the surface roughness.  I tend to get material from Hobby Metal Kits out of Watertown, WI.  They normally sell in 1" lengths and their shipping is about as cheap as I've ever seen. 

Then with a carbide insert tool, I turned all the major ODs.  I love the way CI cuts!  Very easy to cut and very nice surface finish typically.

I made the air cooling grooves with a 2mm parting/grooving tool.  I changed the drawing to make it easy for the tool I had, so the grooves are .079 wide and the tops are .079 side (2mm) so it makes it easy with the DRO to space things our properly.  Then I just plunged straight in to .187 deep as per the drawing.  This went quick with the CI and a carbide insert.

Then I center drilled and drilled thru with a smaller drill and then finished with a .11/16" bit.  Again, pretty easy drilling at around 90 rpm.  No lube.

Next was boring to just under the final ID with a carbide boring bar with a carbide insert.  The finish was pretty good after the boring operation but I'm going to lap to the final ID after this.

Ended up at .749" which is right where I wanted to be.

Parting off with the same tool that I used for making the grooves.  I think I had the lathe at 430 and the parting worked well at this rpm.  Again, all the cutting was dry.

Over to the mill.  I mounted the cylinder in a collet block on the 1" diameter and milled the .187" slots on each side for the mounting studs to pass thru from the head to the main frame plate.  The collet block allows easy indexing for the groove on the other side.

Next I mounted the cylinder on the engine frame and drilled thru both pieces 1/16" to create the oil hole in the cylinder.  Then I drilled and tapped 10-40 in the frame only to mount the drip oiler. 

Finally I lapped the cylinder.  I used a brass lap turned at the slowest speed on my lathe.  I used Timesaver compound mixed thick with a little oil.  Just a small amount mixed in a small paper cup works well.  I started with medium grit, then fine, then finished with extra fine.  I held the cylinder by hand and activated the lathe just with the bump button so I could quickly stop the rotation if it became too hard to hold.  It's interesting that you can really feel the lapping progressing.  At first the part is easy to hold and you can almost feel the high spots and you have to tighten the lap quite often.  Later, as you progress to fine and finer grit, the rotation becomes very smooth and it gets harder and harder to hold as the lap is tightened.  After lapping, as close as I could measure it, the cylinder ID ended up at .7505" so I was completely happy with that.

Upshur's plans call for a cylinder liner with pressed on or Loctite on cooling fins.  I'm sure that will work, but I think doing the cylinder for a solid piece of stock is easier and for sure the cooling will be better with a one piece cylinder. 

And that's about it for the cylinder.  Next up is the head, but I'll post that in a separate reply just to keep the process at more clear.



This post will cover making the head for the engine.  I have to preface this by warning "Here Be Dragons".  For details see my other thread about plugging a hole in the head for details.  I'll mention now that I'd do it differently if I ever do it again end up remaking it.  I'll mention why in the body of the post below.

The process starts with a piece of 1.75 Al that I had on hand.  I chucked it up and turned the OD to 1.50" and parted it off at .562" OAL as per the drawing.  Nothing terribly exciting.

The head is illustrated on Upshur's plans on pages 12 and 12a and I was somewhat confused by them as there are a couple of options and some of the drawing details just weren't completely clear, so I carefully modeled the head and generated a drawing to make sure I understood it.  So here's the drawing I generated showing the side entry plug and adding 10-32 threads to all the ports. I did this since on my Webster build, I had some trouble with the exhaust and intake adapters loosening after I ran the engine for an extended time.  I figured the thread with a little Loctite on them would be much more secure.

Then over to the mill, holding the part with some V blocks and AL packing.  Holes were positioned by centering the part under the spindle and stepping off using the DRO and center drilling, then drilling, then reaming as indicated on the drawing.

Now would be a good time to discuss the issue that I ended up having and what I'd do different the next time.  Upshur's plans call for drilling thru the head to insect the spark plug hole and then plugging off the top of it with a small AL plug Loctited in.  That turned out to leak and involved a repair documented in the other thread. 

I'd recommend NOT drilling thru, but turning the head over and drilling ONLY from the bottom side so as to avoid a thru hole.  This will eliminate any chance for leakage.  But you need to maintain orientation and center the work up again.  Also, Upshur's plans call for a thru hole for the rocker mounting post.  That ended up working for me, but it would be better to NOT drill thru, but maybe drill .40" and then shorten the rocker post by the same amount.  This again just eliminates a potential leak point. 

The the alternative is to mount the spark plug thru the face of the head.  But I didn't like how Upshur did this.  I did an alternative design where I moved the location of the spark plug and angled it at 15 degrees so it fully intersects the bore vs in his design, where the spark plug hole is half obscured by the cylinder wall. 

To drill the intake port, I just flipped the part and held it in the mill vise with pins thru the mounting holes and then centering under the spindle.  Then it was just a matter of drilling to intersect the bore from the face and threading 1/4-32.

There are 2 other intersecting holes that need to be drilled.  The exhaust is at 30 degrees from horizontal, but the intake is 39.8 degrees from vertical.  There are several way to do this, but one of the easier ways, at least to me, was to create a a 39.8 degree angle block.  So the following pix show how I did that.

First, recall what your high school trigonometry!!    I did the calculations and then drew it up in CAD to generate xy coordinates.  Then I cut a square block, and it's important to make sure the corner of the resulting block is really 90 degrees.  Then using the DRO, locate each of 2 holes and drill and ream for a .250 pin. 

Then insert 2 accurately sized .250 pins, turn the block so the pins rest on the vice jaws and mill the corner away.

And here's the resulting angle block shown against the drawing.

Showing actually using the block to set the head to the proper angle to drill and tap for the spark plug hole. 

I do want to clearly state that I claim no originality for this procedure.  Many other's have made angle blocks this way but I thought it might be interesting for anyone building this or a similar engine.  So again, this is not my original idea, I just used it to solve the problem I had.

And here's the head completed so far, with the spark plug installed.  That's one of the Rimfire plugs with a 1/4-32 thread.

And a pix of the engine assembled with the parts I've made so far.  The drip oiler is from PM Research.  So far, everything fits together!

That's it for day.




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