Optimal Roaster

[Axel]

What is the optimal commercial roaster?
maybe something that can handle 25-50lbs ..or whatever is an optimal batch size...

By optimal I mean:
consistent high quality roast relatively not effected by external climate while retaining great fine tuning ability.
+size of drum(diameter, length, and wall thickness)
+size of propane burners(BTU's, length, etc..)
+Drum rotation speed(motor/gear specs)
+air circulation(this is probably a loaded question)
+any other relevant specs to build a well balanced roaster...

Thanks!

 

[ellatas]

What are you trying to achieve? What sort of roast profile? How fast do you want to roast? 6min per roast, 12 min, or 20 min? How dark do you want to roast? All these factor into the type and design of roaster.
Do you intend to build your own?
For solid drum roasters, an insulated drum is beneficial since it reduces the impact of conductive heat transfer between the drum and the coffee. The convective heat transfer between the air and the coffee is more dominant which is good since the heat within the air is easy to control by either reducing the air temperature or reducing the air flow. Also, most manufacturers will maintain a ratio between the drum diameter and the drum length. Many consider a critical point is that the thermocouple is in the bean pile to ensure accurate temperature of the bean.
But depending on what flavour profile you're trying to achieve, your optimal roaster may be a fluid bed roaster or a perforated drum roaster.

 

[Axel]

Thanks for responding so quickly ellatas!

I'm very new to roasting and so far have only roasted in my Delonghi convection oven which I have modified to house a perforated stainless drum approximately 9"x12".
its powered by a grinder motor from which I have geared down the rotation using bicycle parts...(I'll add a photo when I have better internet connection speed)
basically very amateur to say the least but since I only spent a few hours building it and the coffee from it has been great(compared to store bought),
I feel ready to invest much more resources into building a roaster I can build a business around.

The final product I am looking for is a roast that highlights as many of the fine qualities of superior quality beans as possible while giving a creamy body that will leave people who usually add dairy to their coffee more than satisfied without.

cold brew or pour over are set to be the first two products, maybe espresso once I save enough money for a machine(did think of building one...lol.

I have already built a 4'x8' CNC plasma/router table so I can manufacture most of the parts.
The drum specifications are what I am most concerned about at this stage of development.

What drum wall thickness should I be aiming for to achieve the best selling roast?
I understand that balancing convection and conduction is one part of a good roast equation.
My questions are probably over simplistic but I guess I have to start somewhere

 

[ellatas]

The trick with building your own drum is more associated with the internal flights. These are designed to ensure the mixing of coffee is achieved as well as moving the coffee back and forth within the drum...which is needed for even roast.
Rather than figure that out, you could make a fluid bed roaster; either modeling it off a popcorn popper in a vertical tube or base it off a Sivetz roaster. You can look at his patents to see how they are designed.

 

[Axel]

from what I understand, the fluid bed roaster is basically an air roaster. and air roasters have the reputation for producing roasts with very little body.
do the fins(flights?) really need to be that precisely positioned as to be a major challenge?

 

[peterjschmidt]

For a BBQ drum, the vanes can simply be welded to the drum, inline, because you remove the drum to dump the beans.

With an actual drum roaster, you not only need the fins/flights to agitate, but move from one end of the drum to the other, so that when the dump door is opened the beans are pushed out.

It can't be rocket science as they've been making these things for a long time and I doubt there's much difference in the positions and angles over the years, but it's not child's play either.

I get the satisfaction of making your own things, and maybe saving some money other than what your time's worth, but when it comes to building a real roaster I wouldn't try to reinvent the wheel and would just plop down some cash - that's me, not saying you should.

You might consider buying a used roaster if there'd be one local, taking measurements and all that, making yours and then selling the other one.

 

[Axel]

Searching for a decently priced machine to buy and then selling it seems like at least two whole projects.. and at a price I could afford, it would probably need to be seriously refurbished before being sold, that's another project.
maybe there are some blue prints to be found?
Maybe for an medium sized probate or diedrich?

seems like the fins against the walls of the drum are traditionally angled to push beans towards the front(opening) of the roaster while the central fins pull the beans back...

what is a good wall thickness for the drum?
if I have a mild steel drum with an 18" diameter that's 24" deep, is 3/16" too thin or too thick for the wall?

 

[ChefDavid]

Don't take my word for it but when I started to look for a Roaster, I was told that the better roasters all use a Cast Iron Drum.

I don't have the Skillset, to try to cast and pour, a Drum large enough to work in a Commercial Coffee Roasting Environment.

I have to agree with Peter and the rest of the Guy's, about looking for a Used Roaster.

If you live near, where the various, Roasters are Manufactured, some take Trade In's, so you may be able to find a Trashed Machine, that you could get cheap and overhaul it yourself. I've heard that there are a few good Rebuilding Companies, already, so maybe you could call one, to just buy an old Roasting Drum.

I have found out that a Few of the Folks on this Board are a Real, Wealth of Knowledge. And a Great Sounding Board for Questions.

You may also try to search "All-Of-Craig's-List", and you may find a Cheap or Rebuild-able, Roaster.

 

[Axel]

I've actually read that thick mild steel is better than cast...?
better heat transfer?
much easier to weld on fins.

 

[sae]

Axel, if you're interested in building your own roaster check out www.homeroasters.org. They have a section dedicated to building roasters

 

[Axel]

sae, a 1lb home-roaster is what I've already built and it works fine. it took a couple of hours to cut up a bicycle and a little welding.

i'm now looking to build a 25-50lb capacity roaster

 

[sae]

Reverse engineering a 12kilo or 24 kilo roaster would not be that difficult if you have one close to you that you can look at. Pretty simply machines.

 

[peterjschmidt]

The cast vs. mild steel debate is ridiculous. If there's any difference between the two metals, I don't believe the beans pay any attention to it.

I think you'd be okay with 3/16 wall thickness, but you'll have to research the dimensions on a 20# drum for the ideal diameter:length ratio.

I wasn't suggesting rebuilding an old roaster... just to buy a used one that you'd be able to sell for what you have in it when you're done.

 

[Axel]

Points noted. Thank you sae and peterjschmidt.
Getting to look at a professionally built roaster(especially in the size range I'm designing) from the inside out with measuring instruments in hand is an amazing thought.
However since I just scraped up barely enough money to buy a Bobcat skid steer for building my house(still have to build the house), buying a roaster is not currently an option.

Does anyone know the drum dimensions(lenth, width, and wall thickness) of a Probate P25? or a P12..?

 

[peterjschmidt]

How soon do you need to have your roaster up and running?