Apollo Interval Timer

A replica of the Apollo Interval Timer used during the lunar missions. 

For the mechanism, I used an analog oven timer with 3cm hole spacing (M4 screw holes). 

For the dial, I printed the layout on adhesive paper (the details are too small for 3D printing) to remain as faithful to the original as possible.

The dial photo must be printed with a size of 7cm.

A bit of history:

The Apollo Interval Timer works like a standard kitchen timer, sounding a bell when the selected interval is over. As per Apollo stowage lists, it was provisioned onboard the Command Module & Lunar Module to time short interval events. Timer features two selectable modes of operation (6 and 60 minutes) determined by positioning of a switch on the timer’s face: X1 for 6 minute or X10 for 60 minute timing intervals. To operate, the crew would select the mode and rotate the pointer to the desired time setting. An alarm bell chime is generated at the conclusion of the interval.

Interval timers flown on Apollo 10 through 13 show the part number P/N SEB33100092-301, Apollo 14 through 17 shows the P/N SEB33100092-302. According to the Apollo 13 report, a well-known incident happened on Apollo 13 when an astronaut attempting to use the timer found the knob had fallen off. Originally there was a set screw with locktite used to secure the knob on the shaft. The timer knob/shaft union was redesigned after Apollo 13 by using a compression pin to secure the knob to the shaft. The "-302" on this timer indicates this one was modified and is a second-generation timer. This timer is of the type used on Apollo 14-17.