The Hamlet of Rock Creek holds a Fall Fest each year at about harvest time (September or October) and part of the celebration is to decorate a “pumpkin” The pumpkins are about 18” by 18” and participants are invited to do whatever they feel like - I feel like making an egg timer.
The blank is purchased from the event organizers and from there on - you’re on your own
A little fun graphic will form the background for the timer.
My new 24” CNC will cut gears of even a larger diameter than this 17” one but that’s for another project
For this project this 17” gear is a little too big so I’ll try again so that it doesn’t stick out so much
This gear has the same 140 teeth but has been reduced to 14” diameter to fit the “pumpkin” better. Also one spoke shows the background better.
The escape is a Pin Type. With 34 pins and a 1/2 second pendulum a one half revolution will give an eight minute timing.
The arms on the first attempt at the pallets were too big (wide) and interfered with the drive so I shortened the arms.
I wanted to install the pallets on the “inside” of the movement to keep things compact so I rebuilt the pallets with the arch on the left leg instead of the right one.
The ratchet assembly is not on the great wheel which instead has a fixed drum and the ratchet is on the escape wheel instead.
The ratchet mechanism ramps up and over the stops. With both the stops and the ratchet wheel is also “ramped” the movement is very smooth - but a bit noisy.
It makes for a compact unit and a ball point pen spring holds a light tension on the pall gear.
This is all there is to it - a drive gear with a weight drum, a 6 leaf pinion attached to the ratchet, a 34 pin escape and a 1/2 sec pendulum.
180º on the drive wheel is done in 8 minutes - good for all but seriously hard boiled eggs!
I designed the pallets so that a pin rests on the “slope” of the pallet at rest and when the timer is wound the movement starts automatically
To “wind” the timer you simply turn the big wheel clockwise until the number of minutes appears in the hole, a stand for the timer allows it to stand free.
There are still a couple items to complete the unit like nicer weights and a bell or chime that will ring when the time is up. That’s next.
The pendulum rod may be pretty special - actually its a left over but the bob should follow the theme so its an
The “bell” is a piece of copper tubing and the hammer is driven off the main wheel hub through a hinged lifting rod.
A pin extends from the hub of the big wheel and is ready to catch the hammer lifter.
The lifter rod has a notch to engage the pin and will stay engaged until the hub pushes on the rod and forces the pin to disengage - bong!!
The timer in action is actually very accurate and you can count on the egg the way you want it.