Last modified: 2023-11-07 21:13:41
< 2023-11-06 2023-11-08 >It has stalled again. This time caused by neither the hook (which isn't there any more) nor the ratchet. It has just stopped in the middle of its rotation, and all of the gears have play in them, so I think it's not at a tight spot.
I turned it off and on again and it is going again.
Maybe this motor just can't run continuously on 12v AC without stopping.
Maybe I need to use an actual synchronous motor instead.
With a https://en.wikipedia.org/wiki/Lavet-type_stepping_motor it wouldn't even need the anti-reverse feature.
I made up a little collet (breaking only 2 of the PCB drills in the process).
With great difficulty I bent up a bit of a hairspring, and fitted the collet & hairspring to the balance wheel shaft.
I noticed that the balance wheel is a bit loose on its shaft, and also the escape wheel is a bit loose on its shaft as well. They probably want bosses at the centres, or I need a better method of fitting things to shafts.
But I've put this together:
So now I need some way to hold the spring to the frame.
What I've learnt so far is that this scale is too small. I need to be working at a larger scale than this. Maybe I make a "2-layer" design, where one layer has the train and the other layer has the balance and escapement?
By holding the spring in place by hand, and turning the escape wheel by hand, it is kind of working! I mean, not working enough to actually work, but the spring is returning the balance wheel to the centre, which is its job.
I think the balance frequency is way too high, which means this spring is too stiff. Also the amplitude is really low.
The neutral position has the pallets never touching the locking faces, so this is not really good enough.
But actually, looking at the CAD, it looks the same there as well? Have I made a blunder?
Doesn't that look like the pallet pins are both on the impulse face? By rotating the escape wheel in CAD, I discover that yes, indeed, at the neutral position both of the pins hit the impulse face. Is that OK?
Maybe the idea was that by the time one pin unlocks, the other pin is lined up with the locking face, and the issue is simply that the balance frequency is way too high, so the pallets are returned to centre before the escapement has a chance to lock.
If it is determined that the pallets should have a tighter angle between them, then it seems likely that I would be able to bend the existing pallet fork and not have to make a new one.
Things I've learnt from this escapement prototype
I could:
It's always easy and tempting to to CAD work instead of making things, so I think I should err on the side of making things, and look at making the barrel next.
Great success:
I don't know what steel this is, but it was very hard.
I think this is worth doing even if this escapement never works, because it is good practice at making some of these parts, and in particular at making tiny gears work together.
Ugh, the gear got flicked off the superglue arbor while I was cutting the teeth:
Frustrating. I can try to centre it on the superglue arbor again using a 3mm (or 2.9mm?) drill to reference the centre, and then use the dial indicator to counteract any remaining eccentricity, and then reduce the depth of cut. This was 0.4mm depth of cut, of 0.9mm total to do.
Yesterday I picked up a big book on "Science", of which Adam Hart-Davis was Editor-in-Chief. It has this picture of a clock:
How many things are wrong?