Author Topic: Making stuff in a roast drum move back and forth?  (Read 1912 times)

Offline CrazyModder

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Making stuff in a roast drum move back and forth?
« on: December 19, 2017, 08:22:38 AM »
I roast my coffee myself, in a rotating steel drum heated by gas. Everything works great, except for whatever hard to change reason the drum is not being heated quite evenly.

Right now, I have to occasionally tip the whole contraption forwards/backwards during the roast, to shift the mass of beans around and get a more even roast. This is no problem, the thing is hinged anyway to get the beans out at the end. But it is a little more effort than I'd like, and not completely sufficient to get them even.

I already have long "fins" inside the drum that grab the beans and avoid some of them being in contact with the metal of the drum all the time. But I have had suggested that it is also possible to rotate the bean mass axially by some clever contraption. Unfortunately, I have never seen how that would work, and my imagination seems not to be enough to figure it out.

Does anyone of you have experience with such a thing, and better yet, photos/images?

Offline mcostello

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Re: Making stuff in a roast drum move back and forth?
« Reply #1 on: December 19, 2017, 01:32:50 PM »
A small gear box with an eccentric arm could tip the drum on it's axis.
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Offline ddmckee54

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Re: Making stuff in a roast drum move back and forth?
« Reply #2 on: December 19, 2017, 03:04:04 PM »
It sounds like you currently have a straight sided cylindrical roasting drum with flat scraper/s running longitudinally inside the drum.  It also sounds like one end of the drum is probably sealed and the other is hinged to allow you to add/remove the beans.  What's the possibility of replacing the straight scrapers with spiral scrapers that are pitched to return the beans to  the sealed end of the drum?  If you could reverse the rotation of the drum, you might even be able to unload the beans just by turning the drum in the opposite direction.

Don

Never-mind, I just realized that a spiral scraper probably would not work.  You'd need spiral flights fixed to the rotating drum to get proper mixing.  Like in a redi-mix concrete mixer drum.
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Offline CrazyModder

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Re: Making stuff in a roast drum move back and forth?
« Reply #3 on: December 20, 2017, 05:13:29 AM »
Don, your guesses are correct, and I firmly believe that I once saw a configuration of fins/scrapers/flights that would kind of move the beans on the one side of the drum to the back, and those on the other side to the front. Very hard to explain not being a native speaker (and probably as hard if I were one :D ).

The concrete mixer drums I just googled are a good inspiration - not exactly what I had in mind, but then they seem to be good at keeping stuff at a certain (axial) area inside the drum, and the mixing capability is obviously supreme. I'll see if I can cobble something up with that, thanks so far.

A small gear box with an eccentric arm could tip the drum on it's axis.

Yes, that would be a solution (and I could just run another belt to the drive which rotates the drum), but I would prefer not to have the whole setup tip around all the time (all is fine when doing that manually, but having a sizable, hot, gas-connected device walk on its own is not my idea of fun :) ).

Offline ddmckee54

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Re: Making stuff in a roast drum move back and forth?
« Reply #4 on: December 20, 2017, 03:28:37 PM »
How big of a drum are we talking about here, and what is it made out of?  A bigger drum makes it easier to install things into it, but a smaller drum makes cobbling the parts together a little easier.  Also how willing are you to mutilate the drum?  For instance, like drilling holes through it so you can mount something to the drum.

What you are talking about doing is not that different than the coating/blending processes used in the food plant where I work.

Don
Too many irons, not enough fire.

Offline CrazyModder

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Re: Making stuff in a roast drum move back and forth?
« Reply #5 on: December 21, 2017, 01:58:15 AM »
How big of a drum are we talking about here, and what is it made out of? ...  Also how willing are you to mutilate the drum?  For instance, like drilling holes through it so you can mount something to the drum. ... What you are talking about doing is not that different than the coating/blending processes used in the food plant where I work.

It is a steel drum, 25cm long, with a radius of 14cm. Wall thickness is 4mm. Mutilating the drum is fine with me.