sversimo wrote:If it gives the best result to re-circulate air, I would need to redesign some parts.
Actually it does not.If you do not intend to do more than 500 grams batch the recirculation may not be necessary. Actually recirculation introduces problems of its own and is not desirable if you want to keep it simple. It main advantage is that it reduces the energy requirement. Most if not all small roasters do not use re-circulation because of the problems that it brings.
sversimo wrote:Do you think it's enough to make a hole in the tube going to the vacuum cleaner, and then adjusting the size of the hole, (Its nature to always pick the easiest route)
If you provide a by-pass to the air intake to the vacuum cleaner and have a means to control its effect, it would be sufficient I think.
sversimo wrote:I got one in spare
You have to also plan for chaff dust build-up There is a lot of dust that will collect on your vacuum filter that will change it efficiency. This is just a heads up because it affects all roasters that have fume dust collection, not just you design.
Looking at you latest drawing:Make the vanes bigger!
Seriously the parallel vanes that you show will not empty the drum when you open the exit door. So to properly empty the roaster and terminate the roast evenly for all beans, you will have to tilt the roaster forward. Or you have to incorporate angled vanes. This is more complicated to manufacture of course.
You are showing the trier and the view hole on opposite side of the rotation axis. Be aware that when the drum rotate the beans will be largely on one side of the roaster along with the rotation of the drum. Put the view window as low as possible, in the same direction as the drum rotation, such that you get good movement from the vanes of the beans in front of the window. A lot of roasters have the window in the exit door. This limits the size of the window which in turns limits the usefulness of it. On mine the window is large, with a good light shinning there, it gives a very good feedback of the beans color. But you have to make sure that the beans move.
Put the trier on the same side as the rotation as well. In my opinion, it is useful to be able to catch the beans as they fall off the drum side. These beans, for a conductive roaster, are the hottest most roasted. As well, this way the trier does not impede the movement of the beans to much.
Finally, make sure that you will have enough room to clean under the elements for any chaff and dust that will fall under the drum.