2023-11-19

Last modified: 2023-11-19 21:55:25

• 1x plastic escapement
• Garage
• Escapement design
• Next

1x plastic escapement

I'm reprinting the broken parts. The prints don't really look any better, maybe worse. And the elephant's foot is back.

The impulse pin boss sheared off again, this time while I was trying to fit the pin:

But I got the pin in anyway, and even successfully fitted the hairspring.

I also successfully put the escape wheel on its shaft:

But it is not going to work, the elephant's foot is so bad that the escape wheel can't turn because it hits both pallets at the same time.

So there is some progress today, but not a lot. I probably need to reprint the escape wheel with higher Z offset.

Garage

I'm going to start rearranging stuff, in particular I want to get the milling machine into its new position.

I must remember to fix the roof leaks.

OK, I've took all the stuff off the shelf in the back left corner, and dusted off the shelf and moved it next to the pillar drill, dusted off the walls and swept the floor and vacuumed the cobwebs off the ceiling in that corner, and moved the milling machine into its new position.

Control cabinet moved, and everything plugged in and working:

I think the desk is only temporary, because I want it slightly bigger, and I want to be able to sit on a chair and have my legs underneath.

I switched the power wiring over to the other switch, and it has the same problem as the first! So annoying. It switches on but won't switch off. I think the problem is caused by overheating it when soldering the wires on, but I was really careful not to get it too hot this time.

Thinking about the milling machine, I wonder if I would actually get more repeatable results with Z axis backlash compensation turned off, on the basis that once it settles into a cut gravity will do the work of always positioning it in the same place, and it's only the dial indicator that notices the backlash?

Escapement design

The "practical course in horology" book says (page 101) that the escapement should be "banked to the drop", i.e. the limit of motion of the lever should be just beyond what is required to allow the teeth to escape. In my escapement the banking is much further than this, maybe I should remedy that.

Principles it has are:

• banking to the drop
• "a drop lock of 2 to 3 degrees is allowed for wristwatches" - I think this is how much the escape wheel has to recoil to unlock
• "the lever should move an equal distance on either side of the line of centres" - not sure whether this is achievable with my design, hard to think
• "A draw of 12 degrees is considered sufficient by most horologists" - this is the angle that pulls it into the lock, relative to a neutral angle that neither pushes nor pulls
• "the drop should be equal" - by what angle does the escape wheel rotate between unlocking one pallet and landing on the next one? should be the same for both
• "the total angular motion of the lever [is] 10 degrees" which is comprised of 8.5 degrees lift, and 1.5 degrees drop lock (contradicting the previously recommended 2 to 3 degrees of drop lock...)

So let's measure mine (in CAD).

• banking to the drop: the pallet fork is about 4 degrees away from the drop when banked on the receiving pallet and 3 degrees away when banked on the discharging pallet.
• drop lock of 2 to 3 degrees: mine is about 0.6 degrees when unlocking the receiving pallet, and about 0.4 degrees unlocking the discharging pallet.
• draw of 12 degrees: mine looks to be about 21 degrees on the receiving pallet and 21 degrees on the discharging pallet.
• drop should be equal: 5.2 degrees when dropping from the receiving pallet, 3.6 degrees from the discharging pallet.
• total angular motion of the lever is 10 degrees: mine is 18.5 degrees.

So:

• the distance between leaving the impulse face on one pallet and getting fully banked with the other pallet is too far.
• the recoil when unlocking is not enough
• the draw is too much
• the drop is unequal
• the total angular motion of the lever is too much

Possible remedies are:

• make the impulse face steeper (but still leave the impulse face at the same "length", in terms of escape wheel angle), to make it bank closer to the drop
• make the lever longer, or move the impulse pin closer to the centre of the balance wheel, to reduce total angular motion

And I don't know how I can decrease the draw angle but also increase the drop lock. Maybe this is just a geometrical problem with using pins for pallets?

I'm not really inclined to make the impulse face steeper, feels like it will cause more friction. But I think I do want it "banked to the drop". Maybe I just need to increase the size of the escape wheel, but leave all the angles the same?

Next

• reprint 1x escape wheel with higher Z offset
• re-fit escape wheel and pinion on metal escapement
• clamp hairspring to metal escapement frame (maybe get one out of the box instead of using the shit one I made?)
• make spacers and geartrain for Scotch Yoke escapement
• organise garage
• make plastic Vernier caliper DRO