Re: Synchronome contacts pitted
In the picture you sent with your first post, the movement that you have looks to be an interesting and early example. It does not have an overthrow damper for the gravity arm and it has the early type of latch. These early clocks did not have the later standardised impulse pallet, they had a much shorter curve which was less efficient. It probably does not matter exactly which curve you make for your clock so long as the contacts close before the roller reaches the end of the curve.
However, it would be interesting to know the serial number of your clock. This is stamped into the bottom of the NRA plate. I can make out a 0 in the number but I cannot see the exact number. If the number is very low this could be an interesting movement historically and it would be good if you could let us know the serial number. We might then be able to tell you which design of impulse pallet match the date of your clock
From: firstname.lastname@example.org <email@example.com> On Behalf Of Stephen Hibbs via groups.io
Sent: 19 February 2021 20:51
Subject: Re: [synchronomeelectricclock] Synchronome contacts pitted
I can’t seem to get Norman’s .jpg to download. Wish I could see it. But as a mechanical engineer who has designed thousands of parts for manufacturing, I have some comments about the .pdf from bailey.services that might simplify its fabrication with no loss of functionality.
1. The curved ramp is shown as a segment of the developed surface of a toroid. Again, this could be simplified. If it was simply the surface of a cylinder instead, it could be generated by the simple motion of a milling cutter instead of a complex motion, if you follow me. The roller on the Synchronome’s gravity arm won’t know the difference if it is truly rolling instead of sliding (which it might do if its pivots aren’t sufficiently lubricated). There might be a very slight tendency to twist the pendulum if it rolls down either edge rather than the surface, but I think that would be negligible. If the correct suspension spring is used, it has considerable torsional stiffness and the pendulum bob has huge torsional inertia.
And I still suspect a straight ramp is as good as a curved one. If I were making this part, I’d make the flat ramp long enough that the roller would land below the top of the ramp and be lifted off before reaching the bottom. This is what Gents’ does and it extracts all the potential energy available in the time the roller and pallet are in contact with each other.
2. I believe the 45-degree facets are intended to act as elastic hinges where thin material embraces the pendulum rod. But they are so long that I’m not convinced that a single 4-40NC screw in brass will be able to generate adequate clamping force around the rod. And the effort to generate enough clamping force will likely strip the female thread, leaving you with no clamping force at all. The safe way out is two screws, though there is still risk of stripping one of the female threads if they are tightened unevenly.
You’ll likely be starting with .50-inch thick stock, or maybe the nearest metric equivalent. There’s really no need to machine it down to .44 inch thick, nor is there a functional need to machine the two 45-degree facets on the end opposite the ramp; only an aesthetic one. Nor is there a need for the counterbore if those facets are omitted.
3. The .035 dia. thru hole gives the gathering arm a place to be, but I don’t see what keeps it there unless the 2-56NC hole below it is part of a retaining scheme not shown. The original pallet part, of course, has an elegant but complex retaining scheme machined into it that was wisely avoided in this design.
4. The .38 radius on the underside can actually be any radius that’s convenient. It does happen to match the specified radius of the ramp.
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