Doxford opposed piston engine model

[ths]

Coming on nicely, Hugh,

Cheers, Hugh.

[bytewise]

I was not satisfied with the fist set of crankshaft parts. The fits of the various pins and cheeks were not good enough. I cut off some pieces and remade them. This time, I bored undersize and took them out to be honed to size. This time the presses of various parts were quite uniform. I am now satisfied with the crank.
I have also completed welding the crankcase parts together.
Attached is a picture of the completed crankshaft. Also, pictures of the crankcase.
Next I will work on the pillars and upper works.
Hugh

[bytewise]

Work on the engine has been slow but continues. Attached is a picture of the engine at this point. I had a serious alignment problem. One pillar was 1/8 inch taller than the other. The angles were also not correct. I had to make several saw cuts and weld things back in proper alignment. The decks are now parallel  to the base and the correct height. So far, there have been no ‘show stoppers’. The problems have been correctable.
Hugh

[smfr]

Very interesting build process, this one, and it looks impressive. What's the purpose of the Al ring around the outside of the bearing?

Simon

[Maryak]

This is going to be a beauty when it's finished 

Best Regards
Bob

[bytewise]

The Al rings on the outside of the main bearings are cups to catch oil and let it drain back to the crankcase.
Hugh

[bytewise]

Attached are two pictures of the setup for milling grooves in a plate. These circular grooves are to locate the walls of the scavenger air pump. At final assembly, the grooves will be filled with a gasket material.
The Dalrae vertical attachment mounted on my B&S mill has a very wide range of speeds. I had trouble getting the collet  to to hold the cutter and adapter sleeve.. The cutter kept spinning in the collet. I finally put a set screw in the sleeve to engage the flat on the cutter and piece of sheet metal in the slot of the collet and sleeve as a key to stop the slip. Finally it all held and accepted a good rate of feed. Two more plates need similar grooves.
Hugh

[bytewise]

Progress has been very slow since my last post. I have had a lot or trouble tapping 6-32 holes in several steel parts. I started with ordinary structural steel (A36). It is very gummy and does not machine well. I then tried 1018 steel. It was not much better and had hard spots in it that broke drills and taps. Next I got some annealed chrome-molly (4130) and drilled the tap hole for only about a 40% thread. I have a long enough thread engagement that this should be strong enough. After all these remakes, I finally have the connecting rod end pieces and caps mated. The caps were made oversize so the sides could be machined flush with the side of the main rod end. Now, on to the rest of the machining on them.
The crosshead slide has some close clearances both inside and outside the U shaped structure. I had to do some rework before I got that right. It is done now and mounted in the frame.
There is a saying I have heard ‘You don’t need to be perfect, just good at recovering'. That certainly applies to me! 
Hugh N.

[bytewise]

I have been working on the connecting rods. There are a lot of precision operations on the end pieces and progress has been very slow. I had a lot of trouble tapping 6-32 holes in steel. The first material I used had very poor machining characteristics. I broke several taps. I then got some better steel and drilled for only a 50% thread rather than 75%. Finally, I got all the pieces made.
The end caps were made oversize and after being bolted together, they were machined to be flush with the body piece. I put a shallow pocket in the end pieces to align the rod. After clamping and aligning the pieces I welded the ends to the rod. I then ground of the lumps to make them prettier.
Attached is a picture of the three rods. One has the babbett cast in ready for finish boring.
Hugh

[bytewise]

Several things have been accomplished. The lower ends of the three rods have been poured and bored to size. I discovered a clearance problem with the center rod. I had to reshape the upper end to clear the crosshead slide. It now runs freely. (picture attached)
I installed an oil line to the crosshead slide. While considering how to oil the pistons, I had to make several revisions to the initial design. I will be installing a pressure oil line to each cylinder. The revisions were still on paper. No parts had to be scrapped!
The cylinders have been bored to size and ports milled. (picture attached) The left one is the lower one with inlet ports. The right one has the exhaust ports .
The second plate has many things mounted to it. A picture is attached showing the setup to jig bore holes and slots needed. Some were on a circular pattern, others in straight line.
Work continues upward, mounting the lower cylinder, water jacket and the combustion zone ring.
Hugh

[fumopuc]

Hi Hugh, that is a very impressive fabrication work you are doing there. Regards Achim

[bytewise]

A bit more progress to show. The cylinders, water jackets, exhaust manafold and various rings have been fitted. They will not be bolted up until several more parts are done.
Hugh N.

[Don1966]

Nice work Hugh some nice fabrication going on here. Still following you bud.

Don

[bytewise]

Progress has been very slow the last several months. My wife broke her hip and has been in a nursing facility some distance from our home. It is a bad break and cannot be repaired. Travel and visiting has taken a lot of my time. We hope to move her back to home soon. I hope then to get more time to work on the model.
On the model, I found that the location of the scavenger drive arm pivot is critical because of clearances and stroke ratio matters. The location I set initially was not good. I have to modify the pillar for the proper location.
Hugh

[bytewise]

My wife is home now in a wheel chair and requires continuous supervision. I have been able to get a little time in the shop.
While fitting the connecting rods and scavenger drive linkage I discovered several clearance problems that had to be corrected. Attached are pictures of the scavenger drive linkage.
The first three show the scavenger drive linkage. The last two show the side connecting rod in place (loose).
Hugh