"Catherine", a USA "Sweet Pea" engine build

[ironhorseriley]

Ben,

If you stick with the "as designed" SW model, is there no steam dome, just bushed outlets for the safeties, whistle, and manifold? (It does seem like the large area above the fire box seems to serve that purpose) Also as designed, is the SW saturated steam to the cylinders? I like "simple" and wondered if drying or superheating the steam is worth the complications and effort?

Jim

[Benjamin Maggi]

Jim, because the engine is a well proven design in England I don't plan to change much on the mechanical front.

[ironhorseriley]

I am with you on that. But just curious if it is saturated & has no steam dome per say?

[Benjamin Maggi]

The original Sweet William plans called for a piston rod gland which was reamed for the piston rod and then bolted to the rear cylinder cover with three screws. I have seen other engine designs use this and it works, but upon the advice of other live steamers I instead decided to make compression nuts. These are screwed into tapped holes in the rear cylinder covers and can be packed with graphite yarn. And, as long as provision is made to turn the nuts they are easy to install- potentially much easier than the piston glands which requiring screwing them in (and having one or more bolts hidden behind the piston rod).

I looked at my old Gene Allen mogul plans and adapted the compression nuts he used for my engine. Using some 360 brass that my friend had in is shop inventory, I took used a piece that was 1” in diameter and turned down part of it to a diameter of 0.625”. Then, a hole was completely drilled through and then reamed out to a dimension of 3/8” which is what my piston rods are. Threads (5/8-18) were then cut on the portion that was turned down. Then, the piece was cut to length.

Then, part of the compression nut that was still 1” in diameter was drilled four times at 90-degrees apart with a 3/32” drill bit. To make it easier, the nut was mounted in a square collet which was easy to rotate in the drill press vice as I had to do each hole. I tried to take a short cut by drilling through the center of the compression nut and thus making both holes at once, but this didn’t work well. As a result, I got to make another for my trouble and now have 2.5 compression nuts! To tighten them up, a piece of 3/32 steel (or an Allen wrench handle with the same diameter) is inserted in the holes and the nut is slowly worked around. Gene Allen called for 8 holes but we only did 4. If more prove necessary it wouldn’t be all that difficult to add them later.

To take the new compression nuts we had made, I now had to machine the rear cylinder covers accordingly. The piston holes were drilled, bored and finally tapped 5/8-18. The compression nuts went in perfectly.

[Benjamin Maggi]

Next, I had to drill the bolt holes on the rear cylinder covers. Unlike the front ones, the rear ones had to be perfectly aligned with the cylinders so that the top of the rear cylinder cover was perfectly perpendicular to the frame. Otherwise, the slide bar would bolt on out-of-rotation and that would really mess up the valve gear. Though there are probably many ways to accomplish transferring the six holes from the cylinder to the rear cover, we ground down a grub screw into a point which was then screwed into the cylinder. Using squares and a spirit level, we arranged the rear cover on the cylinder just perfectly with the grub screw’s point protruding slightly. Then, a light tap on the rear cylinder cover transferred the mark from the cylinder to the rear cover. This mark was checked by putting the cylinder cover jig on the rear cylinder cover and when it showed the mark was registered properly, the rear cylinder cover was drilled out like before. One cover went perfect but one might require elongating a bolt hole or two when the final fitting comes. Since the bolts holes are clearance anyway, it shouldn’t be a problem. Unfortunately, I left my camera at home and didn’t get any.

Then, the protrusions/lugs of the rear cylinder covers were drilled and tapped to take the slide bar. This nearly completes my work on the cylinders. I will still need to cosmetically machine the lower edges to shape them from square blocks into rounded cylinders. Later details include drilling/tapping for the drain cocks and the outer cladding. In all, it went a lot easier than expected by this was mostly due to the experience of my mentor.

The slide bars were made from O2 tool steel, with bronze slippers on the bearing surface. This was based on advice I received here on the Chaski forum (http://www.chaski.org/homemachinist/vie ... 8&t=100326). I first ordered some square 1/2" O2 steel from my local Metal Supermarket but when it came in I discovered that they had sawed a piece out of a 1/2" plate. This left ragged edges and it was quickly decided to put this into my stock bin for something in the future. Instead, I ordered a replacement from MSC and it came perfectly ground and square. It is tough stuff and the band saw struggled with it (though over the course of this project I think I have worn down the blade. I will owe a replacement to my friend!) So, I finished it with a hacksaw.

The ends were measured to perfectly fit into the rear cylinder covers, and then bolt mounting holes were drilled and tapped for 10-32 hardware. I made sure not to drill too far and break into the passage holes where the pistons will go. When everything was bolted together for testing, it all fit perfectly. I am glad that I can now begin to move on other parts of the engine: the pistons and rods.

[Benjamin Maggi]

After laying out the bolt holes, they were drilled and tapped 1/4-20. Though I am using square-head bolts on other parts of the engine, here I plan to use socket-head cap screws for strength.

[Benjamin Maggi]

Finally... after exactly one year the cylinders are to the point where I could bolt them on to the engine. Last March, when in York I purchased the Durabar cast iron and last week I finally had them to a point where they could be mounted to the frame. It wasn't a quick process... working once a week on them for only a couple of hours doesn't allow for rapid progress. However, we didn't break a single drill bit or tap, damage any casting, and I only had to remake one cover and one compression nut. The cylinders aren't close to being done by any means but I feel as though we have accomplished a lot.

After drilling and tapping all 20 of the mounting holes, the cylinders were held to the frames and it was discovered that not all of the holes in the frame perfectly lined up with the cylinders themselves. This resulted in some filing and Dremel-tool grinding away until everything was perfect. I suspect my drill press skills were lacking when I started the project and drilled the holes in the frames three years ago. However, the cylinders went on.

And then they promptly came off! Having secured a container of Kerosene (which isn't readily available outside the winter heating seasons in the Albany area except at select Hess gas stations) we proceeded to hone the cylinders. In fact, the hone itself took trips to several automotive stores to find one that carried it (or even knew what it was!) To hold the 43-cents worth of Kerosene I picked up a canning jar.

After soaking the hone, it was mounted in the drill press and run up and down the length of the bore for several minutes. At the same time, the inside was constantly being flushed with kerosene. The process must have done something because a pool of black sludge dripped out the bottom of the cylinder.

[Benjamin Maggi]

I am not sure what I expected... perhaps it to be perfectly smooth and shiny like stainless steel plating, but it looks better than before.

[Benjamin Maggi]

The tops of the cylinder ports were then finely polished with a stone. I have heard that this surface will still need to be lapped but that can wait for another day.

[Benjamin Maggi]

I need to still drill and tap the holes on the bottom for the drain cocks, and also eventually do the holes for the cladding. The next daunting task for the cylinders will be putting them through the band saw to transform them from cubes to the profiled, rounded shapes that they must become.

[Harold_V]

I am not sure what I expected... perhaps it to be perfectly smooth and shiny like stainless steel plating, but it looks better than before.

By its nature, cast iron typically doesn't yield a great surface finish, although it can if the stones employed are fine enough. If they're on the coarse side, you can expect the finish to reflect the size of the abrasive. It will generally be better than a machined surface, just not shiny.

Prolonged honing with such a hone can be a mistake. They have a way of creating a bell mouthed condition, especially if you don't stroke properly. That's due to the design, which doesn't keep the stones parallel, nor does that type have any guides, which help prevent unevenness in the bore. For that reason, they are generally used to break glaze, not to size bores.

All in all, if the bores aren't tapered or bell mouthed, they really look good! Well done.

Harold

[Marty_Knox]

You don't want the surface to be smooth and shiny. It should have a crosshatch pattern in it, and a certain amount of roughness for the rings to eat in.
Harold, I'm going to disagree with you about honing - it IS used to precisely size bores. But you can't do it with a hand held hone. Go to a good automotive machine shop and see if they have a Sunnen Cylinder King. It's an amazing machine that can hone a cylinder to the exact size and finish you want.