I was sick of working in a cold workshop and wanted a heater that will last forever without costing the world. Reusing old truck brake drums is a fun, easy and cost effective way to make a potbelly heater that will stand the test of time and perform great giving you heat in the coldest of conditions for years to come. I don’t like wasting anything so by reusing old scrap metal to make a heater proved a great way to repurpose it into something useful.
So this is how to make a potbelly heater from old truck brake drums. No welding to cast necessary.
Note: You can weld to the cast iron drums if you wish but I’ve found keeping it in seperate pieces makes it easier to move if/when needed, as the drums weigh 40kg each.
. Grinder/Cutting & Grinding Discs
. Press or Roller
. Oxy Torch (Not necessary but makes life easier)
. 130x10mm Flat Bar
. Heavy Walled Pipe
. 3x Truck Brake Drums
. 3x Chipping Hammers
. 12mm Round Bar
. 5-10mm Plate
. 7x 3/4” Nut and Bolts
. Exhaust Paint
Be sure to wear all Personal Protective Equipment necessary to complete the job safely. Also keep in mind while grinding the cast iron if it gets too hot the grinder tends to grab so be sure to use extra caution.
Step 1: Finding Brake Drums
Get 3 truck brake drums from your local truck depot or metal recyclers. If you can get them for free awesome, otherwise they should cost between $15-$20 AUD each.
Step 2: Cut Out Ash Door
Cut a hole out of the base drum this is so you will be able to remove the ash and charcoal from your heater. Keep in mind this will also act as the air intake for your heater so don’t make it too small. The opening pictured here is 120mm x 250mm.
Note: Cast iron cuts very poorly with an oxy so it’s best to use a grinder or plasma cutter. While cutting with a grinder may take longer initially it will save you a lot of work in the long run.
Step 3: Weld Grate and Bolt Drums
Bolt the two bottom drums together (four 3/4” or so bolts will be plenty) and weld up a grate. I used some scrap square bar I had lying around.
Step 4: Bend Up Bar for Mid Section Ring
Bend some flat bar for the mid section of the heater. I cut it into three pieces because it was easier to bend short pieces with the shop press (if you have a heavy duty roller it would be perfect as you could roll it in one piece). Follow the curve of the lip on the brake drum. Then weld the 3 pieces back together to make a ring. The flat bar size used here was 130x10mm. The ring should sit nicely over the lip of the bottom brake drum and the top brake drum lip should sit inside it. See pictures for clarification.
Note: You can use any size flat bar depending on the height you want between the drums. I recommend however, going at least 10mm thick as this needs to support a lot of weight while under heat.
Step 5: Ash Drawer
Weld together a drawer to catch the ash. I used some 5mm scrap checker plate and a chipping hammer handle for the handle. Make the drawer as long as possible as this will also act as your air intake for the heater. When pulled out slightly you’ll still want the length in order to catch the falling coals.
Step 6: Cut Out Openings
Now cut out the opening for door and flue. Grinder worked fine just takes a bit of finessing and patience to get it how you want. Also drill a 20mm hole for the door to bolt to.
Note: Keep in mind cast iron cuts very poorly with an oxy torch. Use a grinder or plasma cutter if you have one.
Step 7: Cut Top Plate & Mark Out Flue
Cut top plate using an oxy works best. Cut in half depending on the size you want for your door/flue. I used 10mm scrap plate. Mark out your flue, this will help you see how it will look. I’ve used 6 1/4” heavy walled pipe for the base of the flue but anything 5” and up will be fine.
Step 8: Attach Door
Cut the top off a 3/4” bolt and weld it underneath plate to be bolted to drum. Alternatively you could just use a nut and bolt. Round off the edge near where the bolt is to allow the lid to swivel open.
Step 9: Attach Flue and Door Handle
Weld the flue to the top plate be sure to weld the top and bottom for strength. I used some scrap 6-1/4” heavy walled pipe for the base of the flue. Make sure the hole cut for the flue isn’t restricted in anyway as this will effect performance. Again use a chipping hammer handle for the door.
Step 10: Flue Damper
Weld in a flue damper. I used scrap 5mm checker plate. Run a 12mm round bar with a flanged end through to weld disc to. Also added a spring on the other side to help keep tension when the flue is under draft. Welded chipping hammer handle on also.
Note: The flue damper is the most important part for the heaters operation, this damper controls the temperature as well as aiding shutdown. However, do not stress about tolerances. You’re better to have a bit of play to allow for the heat, soot and rust over the years that may begin to clog it up if you make everything fit too tight.
Step 11: Final Assembly
Assemble everything together make sure your happy with it. Check all parts that they function correctly. If any changes are to be made now is the time.
Step 12: Optional: Prep and Paint
Run over and remove all/any rust with a wire wheel. Wipe down with metho. I used VHT Flameproof Black says it’s good for 704-1093°C. Apply paint and allow to dry for 7 days.
1. Heat to 121°C (250°F) for 30 minutes. Cool for 30 minutes
2. Heat to 204°C (400°F) for 30 minutes. Cool for 30 minutes
3. Heat to 343°C (650°F ) for 30 minutes.
As far as possible try to follow instructions closely for best outcome.
Caution: The first time running the heater there will be fumes while the paint cures. Please be aware of this and run the heater in a well ventilated area.
Step 13: The Performance
Here are some temperature stats that might be of interest. If there’s anything else you’d like to know that you would like covered please comment below.
At normal running the temperatures are as follows:
Flue: 210°C - 320°C (410°F - 608°F)
Top Side of Heater: 365°C - 400°C (689°F - 752°F)
Bottom Side of Heater: 500°C+ (932°F+)
Size of Shed: 6.5m x 7.5m (21.3’ x 24.6’)
Outside Temperature: 3°C (37°F)
Inside Temperature of Shed (Heater Side): 42°C (108°F)
Inside Temperature of Shed (Other Side): 34°C (93°F)
Second Prize in the