2-1/2 x 3 Simple Engine - Cylinder Castings Set

[fredrosse]

Continuing on the milling machine, made the jig to hold the cylinder, no welding, just drilling of a 4 inch heavy channel. Wanted to be sure the casting is not going to move, as that could easily spoil the work. Milling went well, I found a solid Carbide end mill in the toolbox, so so much harder than tool steel.

After milling the valve face, the mill was set 1/8 inch deeper and run around the casting, just to have reference surfaces for future work. Then the steam ports were milled to a depth of 1/8 inch, as it is necessary to have the cutoff and release edges more precise than the casting. Also opened up the exhaust passage a little.

Next steps, to make drilling templates for the valve chest drilling and cylinder flanges.

[Mike Rometer]

Looks well on the way. The only difference between that and mine is that I cut the whole top face in one sweep, being fortunate that my 3" 5 tipped face-cutter was just big enough. As they say round here "The job's a good 'un".

[DetroiTug]

Fred,

Looks good. For a good flat(ter) surface without a surface grinder, a boatstone of about 100 grit is good to use. Just slow controlled flat circular motion with some light oil. That will make the valve seal much better, cut down the wear-in time. Machined surfaces are often not as flat as they appear to be.

-Ron

[barts]

I've also had very good luck w/ 400-800 grit wet/dry sandpaper used wet face up on a granite surface place/piece of plate glass , and using a random orbital pattern of motion of the cylinder placed (of course) valve face down. A poor man's surface grinder; do take care not to 'cock' the cylinder while finishing. Using successively finer grits will help you see where contact is being made, as will using Dyekem or other layout fluid in a thin film.

- Bart

[fredrosse]

Continuing work on the Cylinder Casting. Made a Drilling/Tapping Template for the steam chest, just a small jig welded together for tapping the cylinder, as well as drilling the steam chest and its cover. Did this work on the cylinder casting, as well as the exhaust port (1/2 inch NPT Threads) and the cylinder drains (1/8 inch NPT).

A good idea to keep the cylinder casting on the milling table, assures proper alignment of the tap drills and taps into the cylinder casting.

[fredrosse]

The main boring of the cylinder casting, and facing the cylinder flanges. Fortunately I have a lathe, and 4 jaw chuck, big enough to do this job without the need to mount the cylinder casting on the lathe apron, which I would have had to do if this casting was any larger.

Casting quality is excellent, although I almost ruined the job with the initial setup which was not rigid enough for the first heavy cut. The boring bar started walking to larger and larger cut diameter. I stopped the machine because things did not sound right, and the bore at that point was 2.484 inches diameter. Had the cutter walked just a few thousanths further I would have exceeded the design 2.500 bore and possibly had a ruined casting.

I should probably counterbore the cylinder casting on each end from the flange face to about 1/8 inch past the steam ports. I am thinking about 0.010 inch cut, making the counterbores 2.520 inch diameter. I know this was standard practice a century ago, so the piston rings would not wear the cylinder resulting in a ridge that might make dissassembly difficult.

Does anyone have any experience here? If so please let me know before I unchuck the cylinder. I would think that this problem might easily be remedied without a counterbore. A cylinder hone could knock down any ridge if the engine is rebuilt some time in the future.

Next steps, making the Drilling/Tapping template for the cylinder covers. Perhaps tomorrow.

[Lopez Mike]

Automotive engine rebuilders have, or used to have, a device called a Ring Ridge Remover. I've used one many times but the days of simply removing the ridge and replacing the rings are, I suspect, long gone. Find an older automotive machine shop and ask.

It is turned with a socket wrench and the cutter is arranged such that it will not cut any deeper than the worn part of the bore.

If you decide to counter bore, sharpen your boring bar bit such that there isn't a sharp edge where the bore steps down. It can be hard enough to get rings into a bore without then catching on that step where the ring compressor is of little use.

[Mike Rometer]

When I did mine, I made the counter bore big enough to accept the ring compressor down to the ridge.

[TahoeSteam]

I've disassembled quite a few '60's v8 engines having run 100,000+ miles at a probable average of 2,000 RPM. Their bores never had enough of a ridge to make it more than a quick hit with a rubber mallet to remove the pistons. Keep in mind these bores are at 45* from vertical (weight of piston on cylinder wall) and using taller rings with more tension than today...

I think in a slow moving, vertical cylinder'd engine in a non-industrial application, with moderate ring tension, you and your great grandchilderen will long since be dust before the lack of a counterbore became an issue.

[Lopez Mike]

I would agree that these little steam engines will never get enough hours on them to develop a ridge that you could feel much less measure or need to remove.

I had an old retired milk delivery truck that I used to haul my race bikes around that consumed a lot of oil. Like maybe 200 miles per gallon of oil! Upon pulling the head off, I discovered a .006" ridge above the ring travel. I had to remove the ridge before I could get the pistons out to replace the rings. .012" of bore taper. I should have bored it but was too lazy. With new rings and connecting rod bearings it stopped burning oil and ran for several years before I sold it to some kids to wander and camp.

On a related issue, I have seen some slide valve steam engines where the port surface on the cylinder stood above the rest of the machined side of the cylinder such that the valve travelled slightly beyond the raised area. Thus as the port area wore down there would not develop an edge at the end of normal travel.