VIDEO UPDATE:
Here's the video I just shot with my iPhone and uploaded to YT. The engine had been running for over three hours this afternoon when I shot this. I am quite pleased, but still want to polish and smooth out a few things. This is as hot as I ever plan on running this engine.
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http://www.youtube.com/watch?v=VgpmHj9vvpA
[youtube]
http://www.youtube.com/watch?v=PPVB9qSm0gg[/youtube]
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Now for some details of the engine, and the building process.
As I'm currently on a glass kick, and am fascinated by some of the properties thereof. Besides being just flat out cool to look at the guts of an engine running. The Coleman® camping lantern globe was the heart of the build. I bought that from wally world, and the hunk of floral foam too. I found the "Miracle Thaw" plate in our storage, and my wife told me she never used it anymore, so that's the top and bottom plates. All it is is a 1/4 thick plate of aluminum. I clamped them together and drilled the holes for the allthread. I eyeballed the center and drilled the displacer gland and power piston holes in the designated cool plate.
The power cylinder, which I had to cut down to accommodate the stoke length, broke. I rushed the job with my Dremel and it broke into about 5 pieces. I carefully reassembled the pieces with the superglue, let it sit for 3 or 4 days, and gently honed the inside with Mothers® aluminum polish. I still slides as smooth as ever! I doubt it will last but it's working now. It's a set that I got from Airpot several years ago. It was a snubber, I think, and had a threaded fitting on the end. The trouble was this fitting constricted air flow. I was afraid to attempt to enlarge the hole, lest I break the glass. Oh, the irony.
The displacer gland and rod are a combination of parts I had lying around. The core of it is a short piece of glass tubing, Pyrex from a Sodium Vapor lamp innards. I had a extensible antenna from a old dead CD/FM box. One section of that was a perfect match for the glass. I had the little brass fitting left over from a brake line redo and it accepted the glass perfectly. One drop of SG (superglue) fixed these two parts. I used the high temp silicone to fix that to the cool plate.
Since the rod (antenna) was hollow I found that my stiff steel wire fit loosely into the bore. I affixed my bearing rods/connections so that an excess could be inserted into the tube. When I was assured that the top of the stoke from the crank agreed with the upper connection I disassembled the displacer rod, and with my Dremel I made a slight groove in the connecting rod end, and crimped the displacer tube ever so slightly to index the mounting point. I matched this in the displacer by passing a stiff steel wire up into this tube, also with an indexing groove. When these were all fitted I SG'ed the mounting points as indexed by the grooves.
I used a simple "L" shaped wire to pass through the displacer foam, which I did nothing to alter in any way from the retail condition in which I bought it. I made sure it was square in two directions, as best I could. A jig would be handy here. I allied both SG, and after that cured, a very thin dab of the silicone was applied.
The crank is a shaft from a long dead hard drive, as are all the bearings, and all the other crank and rod bearings. The displacer throw is the body of the drive motor reversed on its mounting point and a set screw passed through into a cut down shaft. When I was absolutely sure the engine was in time I applied a very tiny drop of SG to the exterior of that tiny little screw head. The power piston side is the platter side of another HD and one disc. Yet another HD motor shaft is screwed backwards through the little mounting ring to a SG'ed out facing screw. To this platter I SG'ed the masonry blade circular saw blade. Two 1/2" flat washers (6-8 grams?) SG'ed opposite the displacer seem to balance the little beast nicely.
The main crank passes through two bearings and is affixed to the power side via SG. The two main bearings reside opposite each other on a steel plate with a slightly over sized hole bored therein. I roughed the surfaces of both bearings and the plate, passed a small bolt through them and clamped them in place to assure no interference. Then these bearings were SG'ed in place to the plate and a couple days were allowed for curing. The main crank was then passed through the bearings and plate, and allthread used to mount this plate to the 1" aluminum 90* angle sitting at 90* to the displacer/power piston. This allthread is all 1/4" common thread used throughout.
When the power piston side was set to allow as close to square running as possible I set the stoke length by allowing slack in the stiff steel wire, again by being longer than needed. The Airpot unit has a ball wrist pin arrangement that is as smooth as the rest of the part, I simply wrapped this around the steel wire and set the upper and lower limits according to the little working glass left in the repaired cylinder, and then one drop of SG at this wrap set the length. When this was satisfactory I locked the main crank in place with a tiny little drop of SG on the removable displacer side where the inner race of the exposed bearing meets the crank. This stopped any side to side runout between the two offsets for the two throws of the gamma crank.
I made a hole in the crank bracket mount so that the set screw for the displacer timing could be accessed after assembly. This allowed fine adjustment in squaring and straightening the upper assembly. When the engine was running as smooth as possible I made fine measurements and cut old aluminum hunting arrows into spacers for the uprights (allthread) and everywhere exposed. This not only cleans up the look it allowed me to set the upper framework square in both directions with the cool plate. This keeps the bearings all running true. When all these little spacers were locked into position, and the engine was running as well as possible (I tightened that screw just enough to keep from slipping on its own, but could be turned a little this way or that, and when I got the best results one tiny drop of SG was applied.
The flywheel is too large to allow a straight connection between both sides of the engine (via the allthread). The required me to cut two hunks of the aluminum 90* take out one side, bend 45* on both ends so that they matched up with the main aluminum cross braces. I just used 1/4" bolts, nuts and a lock washer on all four corners when I was sure I had things square plumb and straight. I just used vice grips as clamps, drilled the corners and done. In conjunction with the arrow based spacers the whole works from the cool plate up is one very stiff arrangement.
I affixed the displacer glass by inverting the crank in the trash can by my desk with the displacer in place. I centered the glass around the foam with a consistent gap. The glass is 4" in diameter and 4" tall. The foam is 2" thick and 3.75" in dia. When I was sure things were right I used 3 drops of SG to set this position. When the SG cured I ran a small bead of high temp red silicone around the out side of the glass. I allow that to cure. With the engine still inverted in the trash can and the glass adhered to the cool plate I applied a 1/8"-1/4" bead of the same silicone along the hot end edge of the glass. I didn't mush the hot plate. I just let gravity do its thing. I used those holes I drilled in the beginning to align the two plates. It worked pretty well (note: make sure the displacer is rotated
away from the hot end while the silicone is fresh {don't ask me how I know this} )
Sorry to be so windy, I just invite anyone to make a copy if they can scrounge around.
R