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| Brass_Machine:
--- Quote from: johnbaz on November 12, 2010, 08:42:37 PM --- --- Quote from: Rob.Wilson on November 12, 2010, 06:40:29 PM ---Looking forward to watching this build :thumbup: Rob --- End quote --- +1 :clap: Cheers, John :thumbup: --- End quote --- +2 Gonna like this one! Eric |
| Bogstandard:
Olli, My little B&D bandsaw has been the backbone of my workshop for the last 25 years. I did make a pair of roller blade guides for it instead of the plastic ones, and it cuts all my non ferrous stuff without complaint, no matter how large. Just give it a new blade every so often and away it goes. I am really going to enjoy this build. Bogs |
| madjackghengis:
Hi Olli, I've always wanted to build a Stirling with a glass tube for the displacer, I believe this will be the motivator to get me going on one. I'm looking forward to watching this build, and and gaining some insight into some of the things it entails. You're certainly off to a good start. mad jack |
| cidrontmg:
Not much done today. Drilled the 16x16 mm bar that will serve as the bearing support. I cut the bar intentionally too long, I wasnīt sure how to make the seats for the ball bearings. Thereīs now an extra hole that will be cut away later, and thereīs still more than enough of it left... The idea is to mount the bearings to the two sides of the 16x16, so it would be necessary for the seats to be in line, otherwise the crankshaft will not be at 90o to the rest of the engine. I first tried to use a 5 mm counterbore drill. It supposedly leaves a 10 mm counterbore (the bearings are 10x6x3 mm). Well, the hole was actually 10.30 mm. Thatīs way too much slack to fill with Loctite. Next attempt was with a 10 mm end mill. A lot better. The hole is 10.15 mm. Just about the ticket. These small ball bearings (and anything even smaller, of course) are best treated with like a babyīs eye. Consider that the bearing thickness is just (10-6)/2 = 2 mm (0.0785"). In that space, there are the balls and the outer and inner races. The races are 0.5 mm (0.019") at their thickest. It doesnīt take much force to distort them. Especially the inner race is very easy to expand if the shaft is too thick or irregular. Itīs a very good idea to use silver steel (drill rod), but to my surprise I couldnīt find any 6 mm stock :bang: OK, next best(?) would be stainless rod, itīs also reasonably even in thickness. As the Germans (from Joachim Steinkeīs page) say "Eine Passung, die nicht geschliffen ist, ist keine Passung", or, a fit that has not been ground, is not a fit. The shaft must be ground (with 800-1000 grit emery paper) to slide with very little force through the bearings. Not to drop through, of course. But if you rotate the shaft in the bearing, and it feels "gritty", itīs no good. Not because the bearing will be destroyed prematurely, as it will, but because these small engines donīt develop much power, and itīs silly to waste a lot of the little in the bearings. It can mean the difference between a good runner, and a non-runner. I made a flywheel, ali, 70 mm dia and 16 mm wide. When mounted temporarily to the shaft, and given a hefty push (by a finger), it should turn for at the very least 10 sec. 15 sec is all OK, the engine wonīt be a non-runner because of the bearing losses. 20 sec and over is quite achievable. The more, the merrier. I had another bronze flywheel, also 70 mm and 13.5 mm wide, made for an an engine for which it was too small. That much heavier flywheel will turn for over 30 sec. But itīs probably too heavy, for high revs. Worth experimenting, though. Thanks for watching! :wave: |
| madjackghengis:
Hi Olli, I enjoyed the bit of German lesson, I have immense respect for lots of aspects of German engineering and that quote is a good one. I was wondering what sort of aluminum you are going to be using for the power cylinder, assuming you will be using the graphite for the power piston. I have a kit for a single cylinder Stirling with power piston and displacer operating in the same cylinder, and Jerry Howell advises lining the aluminum with brass or using steel for the power cylinder, even with the graphite for a piston. My flame sucker has a habit of scoring the cylinder every half hour or so of running, requiring lapping out the cylinder, lapping the o.d. of the bronze piston with 600 grit paper, and lapping both the outside of the cylinder valve face, and the valve. I don't mind so much, but it tends to stick when I'm showing it to someone. I'm considering making a graphite piston and valve for it, but don't want to waste the time or the graphite if it's just going to be longer intervals, and still gall up. I've made two replacement cylinders, as the old ones get out of round, and tapered, along with a couple two or three replacement pistons as well, just to keep the little engine running in its original form. Have you run graphite as a piston in aluminum before? Always looking for more knowledge :poke: mad jack |
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