A 3 hand clock, powered by a pneumatic engine with a Steampunk design. Include building instructions.
In order to close the clock chapter starting in 2013. I publish my latest clock.
I have developed this clock with one idea : make something different. It is easy, or common, to make clock with escapement system, weight or spring remontoir, with lot of rotating gearing but nothing compare to a clock powered by a pneumatic engine. A little part of history : SteamClock has been widespread in the last century, the steam engine gave the power to lift up the weight which powered the clock. A classic system of escapement gave the time base.
The logical application for this idea was to make the same thing in lego : by using a pneumatic engine also called LPE (Lego pneumatic engine). I have made many pneumatic engines, one of the most efficient was my single pneumatic engine which runs at 100rpm and give 1W of power at 2 bars or pressure.
This engine is composed of a single cylinder, crankshaft, inertia wheel connected with a ratio of 5:1, and a system of switching with connecting rod. The inertia wheel gives inertia to the system, thanks to the weight of the wheel and the multiplication by 5. It enables to pass through the dead point of the switch (the moment when the switch is on the neutral position, and blocks every flows in it). The angular difference between the primary crankshaft and the switching connecting rod (also called ignition timing on thermal engine) is about 15°.
The movement of rotation is then transmitted to the system of escapement thanks to two universal joins. On the final axle, I have placed a system of centrifugal governor watt-regulator using balls on lever which rotate and move away when the speed increases thanks to centrifugal forces. But this system is only for demonstration, nothing which can control the speed of the engine is connected to this fake regulator. On the real steam watt-regulator, the deviation of the two balls is connected to a valve which controls the flow of the steam engine, reducing or increasing consequently the speed.
The final axle of my pneumatic engine drives a friction system composed of a 40 tooth gear with a 3 stud liftarm and a friction pin on it. Like that, the engine can run at every speed, and thanks to the friction movement before the escapement system and the primary shaft, the escapement system is always driven as soon as the engine has been started. This system can be visible on the picture in tan color.
This system is the heart of this creation, in order to not affect the time base by the speed of the engine which is very important.
Then, the friction system is connected to the escapement system which is composed of a simple pendulum on a rotation point below the shaft and on the shaft a propeller with 8 blades. The pendulum is about 30 cm lengthwhich gives a theoretical period of 1.1 second. In reality, it has a period of 1 second because it is not a theoretical purely pendulum with center of gravity on lower point on concentrated mass (here is a boat weigh). The pendulum is design to be very flat and surrounding the clock with the engine.
The last part of this clock is of course the clock system, composed of 3 hands with seconds, minutes and hours by using many gears. It is inspired by the clock gearing of my cuckoo clock with adding a hours hand with a turntable. The clock has a standard minute-hand and second-hand with 1/60 gear ratio composed of worm/24t, 20/20t and 16/40t. The ratio for the hours is of course 1/12 obtained with 1/3 and 1/4 with 8/24t and 14t on turntable (54t).
To finish about the design, I have tried to make as far as possible the steampunk design. That is why I have used a particular color scheme : gray for frame with metal, red for brass and yellow for cooper. I know that is not the most accurate color for brass and cooper but I didn’t have exotic color like that. The best colors will be certainly orange and bright ligh orange for cooper and dark red and dark orange for brass. The metal can be made with metallic silver or a combination with light gray, dark gray and flat silver. Unfortunately, most of these colors are not available for the parts I used but I am sure that some fans will recreate this clock with particular steampunk color scheme !
That is why I have made the building instructions including a bill of material :