Last modified: 2023-11-20 21:41:24
< 2023-11-19 2023-11-21 >I'm printing the escape wheel on a 2-layer raft, to see if it works any better.
The pinion sheared off while drilling it out again. Now I'm reprinting it with flow rate bumped from 95% to 98%.
I've assembled these parts:
The pivots on the balance wheel are very stiff, and the shaft is too long, which means I can't screw the balance cock down properly, and also the pallet fork hits the end of the pivot that sticks out the top.
Need to:
Even with flow rate increased you can see the spokes are not fully solid:
However I have managed to drill it without shearing the pinion, so that is good.
And all assembled!
It looks like it might work if not for the balance wheel pivot issues. And the barrel successfully turns the escape wheel! Incredible.
I shortened the shaft on the lathe. It seemed to be working better today, leaving a better finish, a sharper shoulder, and being less likely to break the insert. I was using 2500 rpm instead of 2000, maybe that makes all the difference.
OK, got it all assembled. The balance wheel is still a bit sticky, and I think it wants some weight on it, but the spring is very weak so adding weight would just make it tick very slowly. So I probably want to take a few turns off the spring and add some weights.
It is almost feeling like it will tick, but not quite doing it. The balance wheel sometimes gets kicked by the impulse face and then swings back, which is very satisfying, but it doesn't swing back hard enough to unlock. So the balance wheel needs more energy and less friction.
I'll try just adding the ball bearings... it has helped a bit, I got it to unlock a couple of times, but it still keeps getting stuck. Too much friction. Also I noticed the impulse pin is quite tight at the end of the slot, maybe some elephant's foot on the pallet fork needs cleaning up.
I also think the coils on the spring are binding together, so I definitely want to lose some of the coils. Well I cut a couple of coils off, but I think the problem was actually that the balance wheel was on wonky and some of the balls were scraping the underside of the balance cock? Maybe?
OK, there is progress! I wound some string around the barrel, held the movement in the vice, and pulled on the string, and got it to tick back and forth multiple times. But I had to pull pretty hard and it stopped working very quickly.
It's definitely tight in the slot. I cleaned it up with a knife but evidently not enough.
Also the impulse pin is very much rubbing on the underside of the top edge of the slot. What is up with that? Why doesn't it do that in CAD?
I hung a weight on the string (a Leatherman) and flicked the wheel back and forth, and it actually is almost working:
https://www.youtube.com/watch?v=_NVsvdUncnI
I need to remember that powering these with a weight provides much more consistent torque than my finger can, so even if it doesn't work with my finger, it might work with a weight.
Obvious remaining problems include:
I modeled this:
It uses 2x 10mm neodymium magnets to stick to the bed, one to stick to the carriage, and 2x M3 countersunk screws through the jaws to hold the Vernier caliper on. It also has some teeth on the part that attaches to the bed to stop it from sliding, but maybe that is a bad idea, because:
I did the CAD on the milling machine PC, very convenient because it is right next to the lathe. Would be more convenient with network access.
Great success! I used it to discover that 1 turn of the handwheel moves the carriage 3/4 of an inch.
I've removed the threading dial because it crashes into the plastic, but I could cut a notch out of the plastic if I really want to use both at the same time.
I have a number of ideas for FreeCAD improvements:
FCStd file I'm exporting,
or at least the last place I exported an STL from the current project, rather than the directory of the last place
I exported any STL.The Digi-Key parts have arrived. I should do my CAD updates and then start building the other clocks.
I have found a piece of bamboo chopping board for one and some birch (beech?) to use for the other.
I have some A4 sheets of 8mm plywood, might be nice to make the Scotch Yoke clock out of these.
I'm imagining the frame, gears, and pendulum top made out of this plywood. The roller would be a 105ZZ bearing as at the moment. The pendulum rod would be a dowel, thinner than at present, and would have a M6 rod at the bottom to hold the bob, with adjustment nut.
In principle I want the clock to run for as long as possible on a single winding, but given this will be my first actual clock driven by a falling weight, maybe I shouldn't be too ambitious. Maybe just target 1 day of runtime and see how much weight it ends up needing, and then I can think about being more ambitious for the next one.
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