For a long time I have heard about how taking the trier out disturbs the settings of the roast: it changes the airflow because air comes in from the open hole.
But I hadn’t got a hands-on feeling of it … how much … So I did the trick with holding a flame from a lighter in front of it.
Very illustrative. Air is clearly being sucked into the roaster, see video IMG_1741
Next thing to consider: how is your roaster build ? This is the Bullet R1. The flow is driven by an opening right over the trier. Same place as the bean chute. This is in the front of the drum. Normally the air is coming from the back of the drum: so it goes through the beans and then up the channel next to the bean chute – driven by the fan in the back.
But when the trier is taken out and air comes in here in the front, less air will flow through the beans. So suddenly you get much less (if any?) airflow through your beans.
The Loring roaster (from 15 kilo and up) has a nice detail. When you take out the trier a little door closes from the inside. Exactly with the purpose to keep the intended airflow in the roasting chamber.