Jan Ridders Bobber Stirling Engine

[substandard]

Not much to post, I had some nice "action" shots of the milling, but the computer died taking the pictures with them.

I started with the engine base, made out of .5" (12.7mm) aluminum. Used a flycutter to even out the flat surfaces, and then squared the edges with an end mill. Being clever I bought a metric square making it a lot easier to layout the parts. Converting from metric to inch repeatedly was just begging for a math error sooner or later. (Sooner than later to tell the truth).

The base then went into the mill vise and out came the edgefinder, the inch edgefinder with the .20" diameter tip : Yeah, I was soooo clever buying the metric square and eliminating the conversions. So production was stopped for a few minutes while I considered my options. Then I had the DUH moment! My DRO was set to metric, all I had to do was switch back to inch, locate the X,Y edges, move in .10", rezero, and then switch the DRO back to metric.

The holes were drilled and counterbored, the drawing calls for four mounting holes in each corner. I omitted these for now, until I decide exactly how I want to mount the base. I used a edge rounding end mill to radius the edges, and that is when the trouble started. You can see in the one picture where the cutter dug in. Nothing major should clean up during final polish.

 

[RobWilson]

Looks an interesting engine substandard , keep the photos coming ;D
Rob

 

[substandard]

Yet another rather disappointing post Not much progress to report and no really interesting photos.

The engine plans call for a Pyrex glass test tube 16mm OD x 75mm length, the problem is the standard length of a 16mm OD tube is 100mm. I searched Ebay, and the internet and only found the 100mm long tubes, but I was able to buy 27 of the 100mm tubes for only $15. I figured it would give me plenty extra, as I was bound to break one or two when cutting them to length.... :

Tried the standard glass cutter from the hardware store, I mounted the cutter in my Q/C tool holder. I then placed a bronze mandrel in the lathe's 3 jaw chuck. (The lathe was NOT plugged in during this). The plan was to slide the tube over the mandrel, bring the tool post up to the proper position, turn the tube by hand. The mandrel kept the tube straight and the tool post held the cutter perpendicular to the tube... Didn't work. The cutter barely made a scratch on the Pyrex.

Went to the tool chest and got out my handy trust worthy carbide scribe. Placed the scribe in the Q/C tool holder and brought the scribe up to the tube and mandrel. After repeatedly turning the tube, I was able to scratch a line into the tube deep enough to be able to feel it with a fingernail. I took the tube outside gave it a tap to break it on the score line and...the &*$#% thing shattered.

Back to the Internet, and I found a glass tube cutter that was rated for Pyrex . So another $20 down the drain and yesterday I receive the "Knife For Cutting Glass Tube" at least that is what the label on the box called it. Tried to cut three different tubes and it was a miserable failure. I seriously thought that this project was doomed. I decided to try the local glass shop and see if they could tell me anything. The owner was real nice and helpful, said he would grind it ??? Why not, I had nothing to lose...

I heard him grinding away in back for a couple of minutes and out he came with a nice 75mm long tube.. asked him what did I owe and it was free! Now you can't beat a deal like that. The end of the tube isn't a square, but for free I won't complain and the engine design should be able to compensate for the uneven edge.

So now I have that problem solved and the trash truck came by this morning taking away the shattered remains of 10 or so tubes. Hopefully I will now actually make some real progress..