2023-12-27

Last modified: 2023-12-27 19:58:36

Planar verge escapement

What about having 2 escape wheels geared together to turn in opposite directions at the same speed, and both pressing against a shared "flag" on the balance shaft?

Like this:

Obviously make the flag shorter and move the balance shaft closer than in that diagram.

That might work just like a normal verge escapement, including allowing amplitudes up to almost 90 degrees?

So an improvement compared to my previous "planar verge" escapement, and also probably less sliding friction.

Here's another version of a planar verge: https://www.youtube.com/watch?v=Ab5CN5rSlTo

I think the one in my drawing is probably better because it is easier to make and maintains symmetry. Although it is true that the "secondary" escape wheel in my drawing will be floating free in the backlash while the "primary" escape wheel is engaged with the flag. But probably we don't care.

You could even imagine separating the escape wheels further and having them work against 2 separate pallets. The secondary escape wheel can be driven off an idler from whatever drives the primary.

Well I tried to draw the version where the two are geared together directly:

This is planar-verge-18teeth.FCStd.

Laid out like that, we can achieve an escaping amplitude of 28 degrees, i.e. 14 degrees either side. The real amplitude will be higher because of the recoil. It doesn't get "banked" (?) until the amplitude exceeds 100 degrees.

(When I say "banked" I mean the pallet escapes the wheel in the wrong direction (e.g. in the pic above it keeps turning anti-clockwise until it no longer engages the tooth).

Can we do better than 28 degrees escaping amplitude? What if there were fewer teeth on the escape wheel and deeper engagement?

planar-verge-10teeth.FCStd. The tooth form is exactly the same here, just with only 10 of them, so it reveals the base circle in the gaps between teeth.

This now has an escaping amplitude of 52 degrees, and gets banked at 144 degrees amplitude.

I should build a model of this and see how it performs, both with and without a balance spring. The reason I am attracted to this sort of escapement is it seems a lot less finnicky than lever escapements.