Introduction: 12v Car Wheel Forge
Here’s an Instructable for a forge made from a car wheel. I learnt a lot making this and made quite a few mistakes along the way that hopefully you can avoid by reading this. A forge is basically a BBQ with a fan, so actually it wasn’t that hard to make. It did however end up taking longer than I thought, proved that I need to practice my welding skills, and remember to measure twice before you cut.
As I this is only for occasional use I didn’t want to spend any more than I had to, so put this together with stuff I already had, or found around which dictated how it eventually turned out. I originally wanted to make a brake-drum forge, but as I couldn’t find a brake-drum, instead found a car wheel in a skip as they seem to be relatively common cast-off’s (I don’t know if there a bunch of three-wheeled cars out there, but there seem to be a lot of car wheels dumped). I also wanted to be able to use this forge without mains power, so sourced a suitable car blower fan which ran on 12v, which turned out to be cheap and ideal for the job. I’m sure you could produce something better, or more beautiful, but this works and ultimately that’s what matters.
Step 1: Stuff and Tools I Used
- Car wheel – make sure it’s steel, not alloy and if you can, get one without venting holes so you don’t have to fill them.
- Square section steel- I found an old pair of old gate posts rusting in my garden that fitted the bill perfectly, but any hollow steel will do to make legs and the fan/ash conduit.
- Hinge from a kitchen cupboard.
- Car-blower fan- in this case from a Peugeot 807, this cost 12 UK pounds, so was the most expensive item of the build.
- 12v power supply, this could be a car battery, or a suitable 12v PSU if you have one.
- Sheet steel- The heaver the gauge, the better.
- Fire cement.
- Heat resistant paint, look for something suitable for BBQ’s or wood-burners, or just go for a rusty look..
- 12v motor speed controller.
- Small box to house motor controller in.
- Aluminium foil
- Silicone sealant
- Angle grinder with cutting and grinding disks, plus a wire brush attachment.
- MIG welder
- Various files, clamps etc.
Step 2: Planning
I decided to make a forge, there are tons of ideas out there which I looked at and fundamentally a forge is a bowl where stuff gets burnt, speeded up by blowing air into it; so it didn’t seem that hard. I saw some designs for use a car wheel to make a forge and bingo, found one in a skip so that was the basis of the design. Looking around in the garden I found a couple of fence posts, so that was the legs and blower conduit sorted.
I considered using a hair-dryer as a fan as other people have done, but instead decided to use the blower motor from a car for a few reasons. Firstly this would run on 12v allowing the forge to be run using a car battery if needed so I wouldn’t be tied to using mains power. Secondly car-fans are a centrifugal design, this is better at forcing air where there is some resistance than the propeller design used in a hair-dryer. Finally using a car blower-fan would allow me to buy a relatively high-quality fan cheaply that wouldn’t be too noisy. I considered using an air-bed inflator fan which would have run on 12v, but these are so noisy I ended up giving them a miss. When sourcing the fan I had to look hard to find a unit that would work without additional parts of the facia panel, many blower fans are integral to the facia unit so won’t work without the rest. I found a fan which would work on its own without the rest of the panel, mine came from a Peugeot 807, but there are others that will do the job.
Step 3: Getting Started
Firstly I had to get the tyre attached to the wheel off; it was ridiculously tough to cut, I blunted a hack-saw blade and the angle grinder kept getting gummed up in the rubber. In the end I found the most effective way to get the tyre off was to use a knife to cut through the side-walls so the tyre could be taken off the wheel leaving the thin part attached to the hub to be cut with an angle grinder. Once the tyre was off I hammered out a few dents in the rim and it was ready. I left the paint on, but later on found that this was affected by heat so I would recommend stripping the wheel back to bare metal with a wire brush on an angle grinder as it’s much easier to do at this stage than later.
Since we are talking about using a grinder here it’s worth mentioning that these can really badly hurt you, you must wear eye protection, period. I would also recommend gloves and ear defenders as well. During this project I ended up with black snot after a session cutting inside and if it got into my nose it must also have got into my lungs, so I now wear a face mask.
Step 4: Cutting the Wheel to Shape
I cut sections out of the wheel rim to allow the legs to fit in, the height of the legs being determined by the available length of gate-post. This seemed too short, so I added height adjustors comprising of some nuts welded on the bottom over pre-drilled holes to allow bolts to then screw down to some smaller diameter tube which can be slid to the required height then screwed in place. Actually in practice this wasn’t necessary as the height was fine as it was. I was too lazy so set up a jig to ensure the legs were perfectly in place and instead precariously balanced the wheel on the legs and tack-welded them in place one by one. This worked ok, but as you can see it it’s a bit mis-aligned and the perfectionists out there will be able to do something far better.
As you can see the tops of the legs are outside of the rim which allows tongs etc to be slid down them conveniently to hand. An alternative design would have been to weld the legs directly to the bottom of the wheel which would have allowed the bottom flange to be cut off to save weight (it’s pretty heavy to shift around) as the flange doesn’t actually do anything useful.
Step 5: Air Inlet
So, since I now had a wheel for the forge it needed a conduit for the air inlet. For this I used the gatepost. There is a choice here between a side or a bottom air-feed. I chose the bottom feed as it seemed more logical for a wheel shape. I did however make a mistake here as I thought it would be a good idea to make the air-feed off centre to allow some room for un-burnt fuel out of the fire area so I cut a hole in the side that ended up being too far away from the centre. I ended up having to bring this closer to the centre and having to fill in the gap. I the end to work out what it would look like when finished I found put some paper in the wheel could then position the vent without being distracted by the wheel’s shape. I still think the off-centre design is a good idea, but not essential and you could save the hassle of cutting a new hole by using the existing hole in the hub. I cut a circular steel plate using a jigsaw to cover the holes in the wheel and welded this in place on both sides. This project definitely improved my MIG welding skills, which are still not great, but better than they were. A couple of MIG welding points I learnt were to completely remove any trace of rust or grease and to have a fast-enough wire speed, otherwise it’s splatter and bad welds all the way.
Step 6: Air Conduit and Ash Dump
For the air inlet the basic design is pretty universal, a ‘T’ section allows air in and ash to fall past the fan. I used a hinge from a kitchen cupboard to close the ash vent as this is spring-loaded and welded this to a flap. It’s not completely air-tight, but works well enough as the fan gives more than enough air, so a little loss is of no consequence. I welded this together after cutting the fence post to size, the fan tube points slightly upwards which probably helps avoid the chance of ash entering this, I would love to claim this is deliberate, but it’s due to my wonky cutting of the metal. I decided not to weld the vent hinge directly to the tube and instead fixed this with bolts to allow fine adjustment to make it as airtight as possible. If you look at the picture, the hinge is attached so it opens the same side as the fan. In use this means it’s a bit awkward to empty and I should have hinged it the other side from the fan. Once completed this was welded to the wheel in the correct position.. well actually once it was welded in place I changed my mind on how far off centre it should be, so cut it back out and had to fill the gap with another piece of steel.. make sure you get it right first time as this was a pain to fix!
I found a conveniently thick square of steel to use as an ash-filter and drilled some holes in this to keep all but the fine ash particles out of the air inlet.
The fan opening needed modifying to snugly fit the box-section steel, I used a combination of aluminium foil scrunched up with silicon sealant to fix this and fill the gaps which worked better than I thought it would. In the pictures you can see the fan rotated upwards, this was to keep it away from any falling ash but in the end not much ash came down the tube so I rotated it the other way to keep it away from the heat.
Step 7: Fire-cement
I used a 5kg ready-mixed tub of fire cement as I didn’t need much and buying the various ingredients would have been more expensive. The ready-mixed fire cement turned out to be hard to work with as it’s sticky but seems to come apart when applied thickly. The instructions states that it isn’t for outside use, or BBQs as I don’t think it’s water resistant, so far it seems to be ok though. I shaped it to fit making sure the air-inlet was put in place covered in grease-proof paper so it wouldn’t stick in place. I allowed it to dry for a couple of days which I think was a big mistake as when I eventually fired the forge up the fire cement had come apart in places making fairly big holes. I think the best technique here would have been better to have lit a fire as soon as the fire cement was in place, probably using paper and charcoal which are light enough not to leave dents before it’s cured. I was able to fill the cracks and holes with some fire cement I had kept back for the purpose, but I only had just enough to do this and would have cut back the irregularities caused by bubbles/warping had I had more available. I would recommend setting back ¼ of the fire cement for this purpose. The fire cement does provide enough insulation to stop the sides of the forge getting too hot but it’s the aspect of the build I’m least pleased with and may well take this off to start again eventually.
Step 8: Power
I had a 12v power supply unit to hand, it’s a bit big and I will probably replace it with a car battery which frees me from a mains supply. The PSU gives 3 amps which is more than needed and makes the fan blow harder than I wan,t so I needed a way of varying the speed. For this I bought a 12v motor speed controller – I got mine from ebay , search for “DC Motor Speed Switch” They only cost a few pounds, don’t get a reversible one or your motor will suck, not a good idea with a forge! I found an old metal tin to mount this in and pop-riveted this to the leg and used double sided sponge tape to stick the controller in while not making electrical contact.
Step 9: Testing and Final Thoughts
So there you are, after a quick spray with heat resistant paint, the forge was ready. I have used the forge with charcoal and house-coal but I’m trying to get hold of some coke which should be perfect, but seems hard to find in the small quantities I need. It certainly works well, the fan gives more than enough air and doesn’t need to be run anywhere near full-blast so a bit of air leaking out through the ash flap or around the fan is not of consequence. I’m new to blacksmithing, but I have been able to get thick steel hot enough to bend easily so ultimately: job done.
Post script: Since I have been asked how hot this can get, I thought I would add a few pictures of hot metal.. cranking the forge up will get steel white-hot which is about 1200°C I think.
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