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Homeroasters - Home Roasting Coffee Community » BUILDING A ROASTER » Drum Roasters

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Attempting a 5 kg roaster build
simwilldig	#1 Posted on 08/31/2016 2:34 PM
Newbie Posts: 11 Joined: November 26, 2014	Hello, I am attempting to build a 5 kg drum roaster and need some input. I've gathered a lot of helpful information from this form. I'm no roaster expert and I'm only going off my limited experience and pictures and videos I've found online. I have been home roasting for a number of years, most recently on a small stove top "drum" roaster I made. I live in Tanzania and there is plenty of coffee grown here, but the only coffee options in our town are either instant coffee or roasted beans 6 months to 1.5 years old. My idea is to be able to roast for friends and whoever else likes decent coffee. The build has been a bit challenging because of limited tools. Most of it has been done with an angle grinder and welder. It might not be pretty but I hope it will work. I have the major pieces of the roaster completed and did some dry runs with corn to see how the mixing veins are working. Some photos of the progress can be found in this google album. https://goo.gl/ph...bCF179kKk6 The drum is rolled from 6mm thick steel. 400mm long x 398mm diameter. When I had it rolled it turned out a bit uneven but I've cleaned up the face by spinning it against a grinder. It still has a lot of variance up and down but at least it runs true against the face plate. Front and back plate are 8mm. My plan is the put insulation between the inner jacket and the outer. With my current motor it spins about 67 rpm. According to the formula on this forum that is a bit fast. From what I calculated 60 rpm is more what it should be. What issues might a higher rpm cause for roasting? The main issue I am trying to figure out now is the burner setup. I'm planning to make 2 or 3 pipe burners but it has been hard to get what I need. I have found some orifices I can drill out and will experiment to get the right mixture. In comparing to another burner I found, I'll be starting with a 1mm orifice. I'm using LP gas. The normal regulators here for the gas cylinders are rated at 30 milibar which is equivalent to 12 in of water. I have a few questions I'm hoping someone can help me with. I'm going to get someone to bring some parts over from the US for me so I'm trying to figure out what to order. Should I get an adjustable regulator or can I get away with just a needle valve and a fixed regulator? Any suggestions on a needle valve that would be good for this application? I've been trying to find a good pressure gauge for monitoring the heat output. I've seen in some pictures of other roasters a 0-10 in of H2O gauge was being used. Does that seem like the right range to get? I also saw someone suggesting using a flow meter instead. Something like what would be used in a lab for controlling gasses or for oxygen. That seems like a low cost solution but I'm not sure what flow range I would need. There are cheep ones on ebay that come with their own control valve. Has anyone used this type of thing on a roaster? Would 0-3LPM meter be the right range? e.g. http://r.ebay.com/yscEAO I already got a Phidget 1048 for running my thermocouples. While I'm working on the big roaster I've been using it on my stove top roaster with Artisan. I only have one BM thermocouple on the small roaster but it has been fun to play with. So that is my roaster journey so far. I would be happy for input on the burners or any other part of it. Thanks! Simeon Edited by simwilldig on 08/31/2016 2:40 PM


walt_in_hawaii	#2 Posted on 08/31/2016 3:46 PM
1/4 Pounder Posts: 133 Joined: August 24, 2016	Simeon, you are a man after my own heart! that thing's a beast. If for some reason it doesn't work out as a coffee roaster, you can always hire it out to flatten asphalt street construction pours with it! That is huge and very heavy construction... I would think that 6mm, being so thick, would retain a lot of heat and make adjustments to temperature a bit slow since there is so much inertia in that much metal. For comparison, I think the Quest M3 uses 2mm? in its drum. Also the rpms sound a bit high, even though its about the same as the normal sized drum roasters, the normal ones are much smaller diameter. I think you'd have to slow yours down a bit and shoot for the same surface speed of the outer drum skin. Lastly, the drums I have seen are stainless because you're tumbling food in it; I don't think you'll have a problem because the beans produce so much oil as a byproduct, which will season the steel eventually and coat it so it won't rust, but it will need some break in to get the initial rust off, plus I see you've used stick welding, which leaves a flux coating behind, which has to be cleaned out thoroughly as its toxic. aloha, walt


seedlings	#3 Posted on 08/31/2016 4:43 PM
1 1/2 Pounder Posts: 4226 Joined: June 27, 2007	W0W! With higher rpm and larger diameter, just make sure the beans circulate well and are not held to the drum wall. Can you test it with beans before final assembly? CHAD Roaster: CoffeeAir II 2# DIY air roaster Grinder: Vintage Grindmaster 500 Brewers: Vintage Cory DCU DCL, Aeropress, Press, Osaka Titanium pourover


allenb	#4 Posted on 09/02/2016 10:27 AM
Administrator Posts: 3650 Joined: February 23, 2010	Quote simwilldig wrote: The build has been a bit challenging because of limited tools. Most of it has been done with an angle grinder and welder. It might not be pretty but I hope it will work. Welcome to HRO Simeon! You've got a fantastic start on your roaster and I can't believe how nice it looks with the minimal tools you've got. The drum is rolled from 6mm thick steel. 400mm long x 398mm diameter. With the batch size you're shooting for, your drum specs using mild steel will work fine. As Walt mentioned, you'll have a little more hysteresis than typical for this size roaster but will be easily controlled. With my current motor it spins about 67 rpm. According to the formula on this forum that is a bit fast. From what I calculated 60 rpm is more what it should be. What issues might a higher rpm cause for roasting? 67 rpm is well within the usable range for this size drum. But, I always recommend doing a careful analysis of bean trajectory and flow path before installing trier and probe fixtures to be sure you're in the highest density area of flow. The main issue I am trying to figure out now is the burner setup. I'm planning to make 2 or 3 pipe burners but it has been hard to get what I need. I have found some orifices I can drill out and will experiment to get the right mixture. In comparing to another burner I found, I'll be starting with a 1mm orifice. I'm using LP gas. The normal regulators here for the gas cylinders are rated at 30 milibar which is equivalent to 12 in of water. I have a few questions I'm hoping someone can help me with. I'm going to get someone to bring some parts over from the US for me so I'm trying to figure out what to order. You'll want around 40,000 Btu's (=16 cubic feet/hour propane) or (= to 453 liters/hour) for a 5 kilo drum roaster. One burner with a 1 mm orifice at 10" H2O LP gas (adjusted for losses through valve and tubing) will put out around 12,000 BTU's x 3 burners = 36,000 and might be enough depending on ambient temp in your roasting shop. If you end up needing a little more fire power then drill them a couple of thousandths larger. Should I get an adjustable regulator or can I get away with just a needle valve and a fixed regulator? Fixed should be fine. Any suggestions on a needle valve that would be good for this application? I've been trying to find a good pressure gauge for monitoring the heat output. I've seen in some pictures of other roasters a 0-10 in of H2O gauge was being used. Does that seem like the right range to get? I also saw someone suggesting using a flow meter instead. Something like what would be used in a lab for controlling gasses or for oxygen. That seems like a low cost solution but I'm not sure what flow range I would need. There are cheep ones on ebay that come with their own control valve. Has anyone used this type of thing on a roaster? Would 0-3LPM meter be the right range? e.g. http://r.ebay.com/yscEAO You'll want a needle valve with a CV value of around .35 at a few turns open to give you smooth control at this flow rate. Here's a Generant valve ( the one with 3/16" orifice) that would be a good fit: http://www.genera...3000.shtml To me, there's not really any benefit in using a flow meter versus a good "H2O pressure gauge. All we're looking for is to be able to view a value that we can relate to heat output and except in laboratory usage it doesn't provide superior feedback. Keep the progress reports (and photos!) coming. Allen Simeon Edited by allenb on 09/02/2016 11:02 AM 1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana


allenb	#5 Posted on 09/02/2016 10:45 AM
Administrator Posts: 3650 Joined: February 23, 2010	Are you planning on including a burner safety valve/pilot in your burner design? I would highly recommend it unless the roaster will be located outdoors and far away from anyone else! Allen 1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana


simwilldig	#6 Posted on 09/04/2016 2:36 PM
Newbie Posts: 11 Joined: November 26, 2014	Thank you guys for the replies and information. That is very helpful! I did do some testing to see how the beans will be mixing. I used corn for the test, but I think it is similar to how coffee will behave. At 67rpm the corn was still tumbling well and not sticking to the outside. I found what I think is a good spot for the trier, but I'm not sure about the BM thermocouple. Thanks Allen for the input on the burners. That is just the information I was looking for. I did some test with making a pipe burner this weekend. The 1mm orifice worked well. I may be able to widen it a bit to squeak out a few more BTUs. It will be a bit tight to fit in three burners but I don't really have any other burner options. I don't have a safety valve/pilot system. I'll start with out one but I agree it is important. The interesting thing is that even our gas oven in the kitchen doesn't have a safety cut off! Just light it with a match and make sure the burner doesn't go out. There is something to be said for all the safety regulations in the US. I've found a motor to run my fan and I have a guy helping me to make the fan. I'm hoping by next weekend I'll be able to bring the roaster home and start working on all the small details.


allenb	#7 Posted on 09/04/2016 9:06 PM
Administrator Posts: 3650 Joined: February 23, 2010	Quote simwilldig wrote: I found what I think is a good spot for the trier, but I'm not sure about the BM thermocouple. I don't have a safety valve/pilot system. I'll start with out one but I agree it is important. The interesting thing is that even our gas oven in the kitchen doesn't have a safety cut off! Just light it with a match and make sure the burner doesn't go out. There is something to be said for all the safety regulations in the US. A good spot for the bean probe tip for a drum the diameter as yours is usually best somewhere between 6 and 9 oclock if your turning clockwise otherwise between 3 and 6 oclock for CC. Without using a clear plastic front for experimentation it's hard to know where the biggest gathering of beans is on the upward trip of the beans. You'll want to have the probe sheath protrude through the front face plate at least 3/4" into the drum area and then make a 90 degree bend down toward the drum wall but stopping 1 to 1.5" from the drum wall. Make sure you have at least 3/4" between the edge of the sheath and the front leading edge of you vanes or there will be occasional lodging of beans in between vane and probe with a noticeable thump. The reason for going in and turning a 90 is to allow adequate insertion of the sheath so it's not affected by ambient air on the outside of the front face plate which can give a false temp read. If you get a chance, shoot us the make and model of your kitchen oven. Just curious as to how the burner is designed. So, you have to use a match to light the stove top and oven section?' Allen 1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana


simwilldig	#8 Posted on 09/09/2016 2:46 PM
Newbie Posts: 11 Joined: November 26, 2014	Alright, I'm back. I had a busy week coupled with giving my laptop a sip of gin and tonic. It was only a small sip, but the laptop did not like it. After a week of drying out it still won't turn on so tomorrow I'm giving the motherboard a menthol bath to see if that will cure it. Anyway, about our oven. It is not a make I've seen in the States. It is an Oscar 7402 XGI. Just a simple four burner stove. The oven is not thermostatically controlled. Just a nob like you would have for a normal burner that goes from high to low in a quarter turn. You just light it with a match and then turn it high or low to control the temp. No pilot light. The stove top has an electric ignitor for the burners. We couldn't find any gas stove here with a thermostatically controlled oven. Only the electric ovens had thermostats, but the electricity here is not so reliable... I was a bit surprised about no thermostats because in the US even old stoves from the 50's had thermostats on the ovens. For a safety cut off, has anyone tried using a unit off a gas water heater? It seems like that could be a cheap option if you find a junk water heater. They have a pilot light, thermocouple, and safety cut off. I worked on my burner a bit more today. I was trying to see how big of an orifice would work with my pipe burner. I only can a get 1mm or 1.5mm drill bit. I tried 1.5mm but it is just too big. I slowly increased the size of the orifice from 1mm and found what I think is a good max at 1.18mm. However, that is measured with the inaccurate method of using a needle just larger than the hole. I colored the tapered end of the needle with a sharpie and then stuck it in the orifice and spun it around to rub off the sharpie at where it stopped. Then I just I used a micrometer to measure that point on the needle. Not very exact but it seemed I could get pretty close, maybe within a few hundredths of a mm. If I'm reading the orifice chart I found correctly, 1.18mm should give me about 15,000BTU/hr. That means if I put in 3 pipe burners I should be fine for the 40,000btu suggested. I tried both a pipe burner with holes and one with slots. Does anyone know it it makes much of a difference in heat output or efficiency? I added a few pictures of the burners to this album if anyone has any suggestions on them. https://goo.gl/ph...bCF179kKk6 Cheers. Simeon


allenb	#9 Posted on 09/13/2016 4:17 PM
Administrator Posts: 3650 Joined: February 23, 2010	Interesting gas oven design! Make sure you post a HAZCOM NOTICE on the front for safe operation. Stay Safe! Gas hot water heater safety valves usually have the thermostat built into it as an integrated unit. This would work as long as you keep the water probe away from any heat and ambient air didn't reach the usual high setting of around 125 F. Hopefully the gas output to the burner is a female pipe thread so you don't have to do a lot of adapting. I prefer slots for pipe burners as they seem to handle a wide range of firing rates and remain stable. Sounds like you're on the right track with your orifice measurement technique. I'll have to remember that one. Too bad about the laptop! Computers don't make good drinking partners! Allen 1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana


simwilldig	#10 Posted on 09/20/2016 1:45 PM
Newbie Posts: 11 Joined: November 26, 2014	I've have not made much progress lately. I have finished the three pipe burners though. I finally got all three orifices redeemed out to the size I wanted and tested them out. They are working pretty well. Now I'm waiting on someone to bring me a needle valve and pressure gauge (and a used motherboard for my laptop) from the US. I found the valve Allen recommended on ebay for a good price, new. I need to mount the burners on the roster. What is the recommended distance from the drum? Since my drum is 6mm I'm thinking I can get away with having it pretty close and the heat will still be distributed fairly evenly. Would 2.5" - 3" below the lowest point of the drum be alright? simwilldig attached the following images:


seedlings	#11 Posted on 09/22/2016 8:59 AM
1 1/2 Pounder Posts: 4226 Joined: June 27, 2007	Flaming Torches Batman! Wow, that's a serious burner setup! Noice! Looks like good control at low flame too. CHAD Roaster: CoffeeAir II 2# DIY air roaster Grinder: Vintage Grindmaster 500 Brewers: Vintage Cory DCU DCL, Aeropress, Press, Osaka Titanium pourover


allenb	#12 Posted on 09/22/2016 5:45 PM
Administrator Posts: 3650 Joined: February 23, 2010	Quote simwilldig wrote: I need to mount the burners on the roaster. What is the recommended distance from the drum? Since my drum is 6mm I'm thinking I can get away with having it pretty close and the heat will still be distributed fairly evenly. Would 2.5" - 3" below the lowest point of the drum be alright? 3" is fine and if the flame tips hit the drum at high fire it will not cause any problems. Mounting burners too close with flame in constant contact at all firing rates can cause carbon/sooting problems due to lack of complete combustion but what you're aiming for should be fine. Glad to hear you found a suitable valve at a good price! I agree with Chad, nice looking fire! Allen Edited by allenb on 09/23/2016 8:04 AM 1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana


simwilldig	#13 Posted on 10/08/2016 7:17 AM
Newbie Posts: 11 Joined: November 26, 2014	Alright. I have made a bit of progress. I have done two test batches with some cheap local beans to see how it works and season the drum. There were quite a few things to sort out after the first roast, but the second try went better. I really need to learn what to do with the air flow. I've not roasted on a roaster with that variable before. It is going to take some time to figure out how to work this beast. A few things I still need to figure out. Some chaff falls down between the drum and face plate and gets on the burners and the cooling tray. I've not figured out how to fix this or get a shield in the right place. I need to add a fan to the cooling tray and a mixing apparatus. Planning to use a windshield wiper motor for driving the mixer. I've added quite a few more pictures to this album. https://goo.gl/ph...bCF179kKk6 simwilldig attached the following images: Edited by simwilldig on 10/08/2016 7:24 AM


simwilldig	#14 Posted on 10/25/2016 1:38 PM
Newbie Posts: 11 Joined: November 26, 2014	So I have a question I'm wondering if anyone can help me with. I'm having trouble with my fan pulling beans up into the tube going from the front of the roaster to the exhaust fan. I've tried putting in a 3/16" square wire mesh in but it gets plugged with chaff. How do normal roasters keep this happening? Thanks!


dmccallum	#15 Posted on 10/27/2016 8:56 AM
1/4 Pounder Posts: 93 Joined: November 24, 2015	Good question! I've wondered myself just how much air is drawn and asked the question on my thread. I get the idea the actual volume of air drawn varies throughout the roast profile but in general it's lower than you might think. Which had me wondering how well is your cyclone going to work if you're not supplementing its total flow via some sort of by-pass after your damper-valve (and maybe that's the answer for the cyclone question at least). Can anybody expand ?


Ringo	#16 Posted on 10/27/2016 10:34 AM
Pounder Posts: 474 Joined: January 14, 2010	If the problem happen when you drop the batch in, most commercial roaster have a flap that closes off the air inlet when you are dropping the load in drum. this flap holds the beans in the funnel when you are getting ready to roast. it is held shut with a weight on the end of the rod. lift the weight the funnel opens and the air inlet closes after the beans are in close the flapper so the fan can work. I can not believe this is the first time I have seen this roaster it looks great. All you need in life is ignorance and confidence, and then success is sure. Mark Twain


dmccallum	#17 Posted on 10/28/2016 7:32 AM
1/4 Pounder Posts: 93 Joined: November 24, 2015	Just a bit more on this and not meaning to hijack your thread, I've the same question. Attached is a shot of my front plate design showing the draw hole with the dotted line depicting the drum inside diameter. So I'm wondering if this design would suffer the same problem of beans getting sucked out during roast. The obvious thing would be to make the front plate orifice as large as possible to reduce the exiting airflow velocity within close proximity to the beans. Mine seems to be of similar dimensions and position to yours and I've seen other designs like this, but is there any guidance anyone can share? dmccallum attached the following image:


Ringo	#18 Posted on 10/28/2016 4:29 PM
Pounder Posts: 474 Joined: January 14, 2010	You will be fine if you shut the air off when you dump the beans. Every commercial roaster I have used uses the bean dump flapper. The airflow you are planning is how the drum I built works and no problems. You really do not move much air when you are roasting in a drum, I was expecting to use much more. The extra air helps when cooling off the drum as long as you can adjust it down to roast. All you need in life is ignorance and confidence, and then success is sure. Mark Twain

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