Pin Pallet Clock Escapement

Design of a Pin Pallet escapement

I want to try a new escapemnt on a clock, I liked the way the escapement that I made for the Roskopf watch worked out and wanted to do something similat for this clock.

I found that PLA on PLA friction is a magnet for dust and is source of increased friction over time.

This escapement with the friction of a steel against PLA shoud work quite well

At this time the pin pallets are on the anchor, with a 3D printed escape wheel, I might try a pin wheel escapement in the future with 30 pins on the escape wheel

This prototype below run with the weight of M6 nut to the string, that is 2,5 gramm

The design

Setting some numbers

One rotation per minute of the escape wheel and 1 second period achieved with a 1 meter pendulum

Escape wheel will have 30 teeth with a wheel diameter of 60 mm

With 30 teeth, the angle between teeth is 12 degree

The opening of the anchor need to be: n teeth angle PLUS 1/2 teeth angle (n x 12 + 6)

Options are 90, 102, 114, 126... I went with 114, that is (9 x 12) + 6 = 114

The wider the angle, the smaller the swing of the pendulum

With a 60 mm escape wheel , the design below gives me a distance of 55.08 between the escape wheel center and the pivot of the anchor

I choose a diameter of 1 mm for the pins, small but not too small, a 1mm pin on the circonference represent 1.91 degree

This sketch below gives me all the critical dimensions for the pin anchor

The white ligne on right represent the angle of the escape wheel pallet

The escape wheel pallets

There is 30 teeth 360/30 is 12 degree, but each osiliation is only half of that, 6 degree

Those 6 degree must "contain"

The exit pin, actually half of it
The pallet
The Entry pin, again half
Some drop/play

The 1 mm pin located on a 60 mm circle covers 1.91 degree alone, so I went with the following value:

Pallet width = 6 degree - ( 0.5 degree drop + 1.9 (2x half the pin). = 6 - (0.5 + 1.9) = 3.6 degree

That gives me a pallet width of 1.91 mm

The look face is straight, this is not a perfect dead beat escapement but very close

To be, the entry pallet would need to be concave, the exit convex, that is not possible, so straight it is!

Time for testing the design

I designed a simple anchor based on the dimensions of the first sketch, placing the pivot of the anchor at the origin

I then move the anchor body on the Y axis to get the distance anchor escapement of 55.08 mm

Next I design the escape wheel, at the origin, starting with a disk, adding one tooth based on the design above, finishing with a polar pattern

The spokes give a better visual of the motion

By changing the angle property of the anchor and of the escape wheel, I can study the interaction

It may look like the pallet is hittig the thooth very deep after the drop, this because of the manufacturibng process

Because I am doing 3D printing, there will be a radius at the transition of faces, since I am using a 0.4 mm nozzle, the minimum radius would be 0.2 mm, at the tip, I have to go even bigger to avoid bulging

0.2 mm radius caused some bulging at tip and a dip in face of pallet 0.65 mm radius make it flat and round

The very minimum swing of the anchor is 2.5 degree, the safe range is 4 to 6 degree

The final design of the escapement

Shorter teeth, with with a radius on the back side, just for the look

There is a slot on the anchor at the pin location, this to make for a more more precise printing of the location of pins

Making a precise 1 mm hole with a 0.4 nozzle can be a challenge, this way it is a one shoot perimeter

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