Inside the 3 kg Mill City Roaster (drum speed analysis, 400 g batch)

400 g batch with varying drum speeds (OFF, 0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100). The roaster drum speed setting shown in upper left hand corner. Actual RPM is approx. 5 units lower than roaster setting (e.g. if setting = 60, then actual RPM is approx. 55).

This is a follow up to the previous "Another look into the 3.0 kg Mill City Roaster" series (see https://www.youtube.com/watch?v=SKfCH.... Previously, the point of view was through the face plate using a modified clear plastic door. This allows us to see what is happening with bean action at the bottom of the drum, and in particular, where the bean probe is in relation to the bean mass at various drum speeds.

In this video/series, the camera is placed through the hopper chute and positioned looking into the drum (a top down view), whereby we can now see how the beans move above the bean mass. In order to visualize this, lights are placed inside the oven behind the drum (you can clearly see the lit up perforated end cap of the drum) and through the looking glass of the face plate.

The objective of this video to understand bean action at various speeds and batch sizes. Some experts have suggested setting the drum speed at the highest possible setting, so long as beans are not being sucked through the exhaust or being centrifuged (clinging to the drum) - in order to maximize convection (heat exchange from the hot air to the beans) and minimize conduction (heat exchange from the hot drum to the beans).

Unfortunately, with larger batches (e.g. 3.0 kg), the bean mass blocks the light at the face plate, making it difficult to see bean action. However, as drum speed increases, light does begin to permeate the bean mass, allowing some bean action to be observed. Nevertheless, the overall lack of light makes the video a bit grainy. Perhaps in another series, a light can be placed along with the camera at the drum exit to the hopper chute/exhaust.