Sam Lombardi

Mechanical Engineer



Wall-Mounted Mechanical Pendulum Clock

I am designing and prototyping it now via a laser cutter and will update this page as I work on this project.

This is the title block for the laser cut sheets to organize the many similar-looking parts.

Power Source = Weight on a string
Gear Train = Plywood laser-cut gears
Escapement = Custom recoil escapement.

The first major step of creating the clock is the escapement. This mechanism advances a fixed amount with each swing of the pendulum. It also maintains the swing of the pendulum via a small push each swing.

I choose a recoil escapement (aka. anchor escapement) with a recoil of 2° -- as the tolerances and precision of my design is not accurate enough yet to lower that number.

The escape wheel was designed specifically for my clock through CAD geometry and trial and error prototyping. I choose an escape wheel with 30 teeth and a 1-1/4 second period due to the desired size of the pendulum and the efficiency of the power source.

With the escapement and pendulum length set, the following gear ratios are easy to find as my only real constraint was space. Making sure the minute and hour hand pass through the same axis was the most difficult part. The initial design has the axels press-fit to the gears, due to their relatively small face size -- I will change this in the next iteration because it is a pain to assemble accurately.

I will continue to work on the clock until it is accurate to ±5 minuets a week.

The second cut is done and assembeled (shown right). There were some major problems with the cut though. First, the drawings of the gears were not perfectly enclosed shapes, and that lead to jagged broken teeth. This was due in part to the conversion from 3D model to 2D drawings, switching between programs and file types. The Second problem was the narrowness of certain parts. The laser settings create slight burn on the middle of the material, which compromises the internal structure of the wood, making is especially weak in key areas.

Once the first iteration was assembled it became painfully obvious that the design was not accurate enough. There is far too much play in the axels and the gears would not mesh properly.

Back to the drawing board.

This page was last updated May 2020; I have the next iteration completely designed in CAD, but due to COVID, I am not able to use the laser at this time.