2025-01-24

Last modified: 2025-01-24 20:10:59

Clock

I've put 2 more M12 bolts on the balance wheel, now has a period of about 7.5 seconds.

I also readjusted the balance pivots and the pallet angles, which were quite badly off.

It would definitely benefit from improved balance pivots that somehow locate more positively. Since they're just located by a screw thread, there is a lot of wobble in them every time you loosen them, so I am pushing it to one side before tightening the nut to adjust the location in X/Y plane, which is not really ideal. It should be positively located in X/Y and the screw should only move it up and down, and there should be a separate adjustment for X/Y (which in the worst case could just be provided by the aluminium extrusion).

7.5 seconds is about 1.4 times 5.25 seconds, so it'll run for another 40% longer on a given amount of drive weight, or the same amount of time on 1/1.4 as much drive weight?

So we're down from 180kg to 128kg.

Shaft rotation periods are:

• balance oscillation: 7.5 seconds
• escape wheel (x37): 277.5 seconds
• winding drum: 46m15s

If the winding drum ratio were 12:1 instead of 10:1 then the winding drum would be very close to 1 rotation per hour, which is your minute hand.

Todo is:

1. new catching-arm, one piece instead of 2
2. new fly, no sharp leading edge
3. another gear reduction stage, 10:1 or 12:1 or something, heavier-duty bearings probably
4. heavier weight, 4kg or 5kg
5. heavier-duty pulley and string hook at top of frame
6. narrower balance shaft, and associated spacers, pallets, etc.
7. balance shaft running on taut wire
8. axial locating features for remontoire input shaft
9. make the escape wheel shaft bearing also have a hook feature to go around the remontoire output gear and hold an end bearing for the remontoire input shaft
10. longer string, longer winding drum
11. get more aluminium extrusion, cut more short pieces
12. find a better type of string (is fishing line good?)

3 requires 4,5,11.

8 and 9 are kind of associated (for example one of the locating features could be the bearing).

1 and 2 are kind of associated (make the new fly at the same time as the new catching-arm).

I'll do the new catching-arm now.

New requirements are:

• make it balanced
• make the pinion integrated instead of a separate piece
• add a groove for the fly to stay in so it can't drift sideways
• more clearance on the pinion
• lose the sharp leading edge on the fly
• make the fly weights attach more convincingly, should be able to fit M5 screws

I actually left the fly the same, the new catching-arm piece is good enough. I've balanced it with some sticky rubber domes.

It still doesn't quite run with only 4 drive weights, but it seems close. In particular if I loosen the screws on one of the adjacent-shaft bearings then it winds a lot more strongly, I think the bearings may be misaligned and binding slightly.

I set the clock going about 20:10, fully wound, will see if it runs all the way down this time, and if so how long it takes.