Pocket Rocket.

David's picture

"Come on Little Darlin', lets go try this out!" That's what I told Phoenix when I finished building the pocket rocket. And I don't know about her, but I was stoked about stoking this little contraption. So we jammed our feet in our boots, I grabbed all the parts to the rocket, and we headed out to the cob studio. Overall, the pocket rocket was a very easy project to build and took less than a day to put it all together. It was so easy, but yet I still managed to make a mistake.

The hardest part of the pocket rocket was finding a metal bucket with lid. The only ones I know of are used for containing roofing tar, and I wasn't about to buy any just to use the bucket. Reminds me of when a child gets a cool toy, but plays with the box it came in instead. Anyway, a fella down the road had a few of the buckets laying around. Both had tar in them but one was just about empty. So I took the nearly empty bucket and placed it above the wood stove for a bit so that the tar would loosen up. I then scooped it out until all that was left was a thin coat of tar on the walls of the bucket. Next came the firing.

I lit the bucket on fire first. I put a few bits of scrap wood inside and lit it on fire. It didn't take long for the fire to do it's job, nor did it take a second helping of wood. After the fire died down all that was left was soot. Next was the lid. I suppose I could have put the lid on the bucket to burn the tar off of it, but the lid had the stuff on both sides and I didn't think it was worth fussing with to insure a complete burn. So I brought out my handy washing machine drum and lit another fire inside of it. Then I simply tossed the lid in and let the flames do the work. Once the bucket and lid were cooled (which doesn't take long on a brisk afternoon in northern Canada in the middle of January), I brought them in to scrub off the soot.

One clean bucket, and I was ready to build. Next is where I made my first mistake. It's recommended not to use galvanized ductwork because the high heat will cause nasty fumes to leach off the pipes. So I searched for stove pipe. I needed 6" and 4" diameters. The 6" was no problem as it is a common size among wood stoves. The 4", on the other hand, is probably right up there with Big Foot and the Loch Ness. The two hardware stores in town didn't carry the stuff, and the clerks even gave me weird looks when I asked for it. Well, in one of the stores I just so happened to turn around and low and behold, some non-galvanized 4" ducting. Aluminum to be exact. Apparently the excitement I had in finding 4" pipe overwhelmed my common horse sense because without batting an eye, I paid for the lengths I needed and went on home (mistake #1). Luckily, just before I modified any of the piping it finally donned on me that my choice of piping is not going to work. The thin walled aluminum ducting will most definitely melt with the heat I'm going to be putting through it. So back to the store I went.

I ended up exchanging the aluminum for 6" stove pipe. Sure it's not 4", but I was sure I could fix that. And fix it I did. I simply rolled the pipe into a 4" diameter and screwed it together. I also went ahead and trimmed off one of the edge cleats to that it would lay flat against itself when I screwed it down. Hindsight, I probably should have went ahead and trimmed both edges. Nonetheless, I had my 4" diameter pipe.

I then marked the lid for the locations of the two pipes and cut out the holes. I cut a 5" hole for the 'feed tube', and a 3" hole for the chimney stack. And in them holes I made several 1" slits, to make tabs, to bend down, so that I'd have some way of attaching the pipes to the lid. I ended up with a 6" and 4" hole with tabs. I then went on to attaching the pipes to the lid.

The 6" feed tube went in first. And with a few small adjustments to the hole, the pipe was in. I made sure the pipe was going to be about two inches above the bottom of the bucket when the lid was on, and then screwed it in. The 4" pipe only had to be about an inch inside the bucket, and with another few minor adjustments, it too, went in nicely. (In comes mistake #2) Now all I had to do was put the lid, with piping, onto the bucket and recrimp the sides to seal it up. I went around the entire bucket with a hammer and screwdriver making sure all the crimps were nice and tightly tucked into the groove of the bucket. So what was mistake #2? Well just after crimping the entire lid, I realized my 4" pipe was installed upside down. I know how stove pipe fits together, and which end is supposed to be tapered. I just installed it wrong. The tapered end was inside the bucket. To turn it right side up, I needed to take the screws out, and of course this requires access to the inside of the lid. So there I go pulling out all the crimps I had just finished beating in.

Eventually I had finished product, and it was finally ready for it's first firing. Phoenix and I set it up inside the cob studio. I attached a few elbows and a couple more lengths of pipe so that the smoke would go outside. Now, to light the stove it is said to be done by dropping wads of crumpled paper down the stack, lighting the last one, and then dropping it down as well. This ensures that the draft goes in the right directions and you don't end up with a room full of smoke. This method is assuming you don't have any elbows in your stack. Well, not only did my stack have elbows, but I also couldn't see myself going outside whenever I needed to light my fire. Surely it could be done another way. So what I did was, going through the feed tube I stuffed some birch bark through the 2" gap so that it was directly under the stack. I then lit it from there. The best thing about birch bark is how easy it lights and how quickly it flares up. 10x's better than paper. That intense burst of heat was enough to push up the stack, causing a correct draft. I then tossed in some kindling and sticks of wood, and away it went.

You could see the fire down in the feed tube being pulled into the bucket' so there were no flames shooting out of the bucket. It was running like a champ. But Phoenix and I couldn't really enjoy it because I only had enough pipe to get it just outside the window. It was so close, in fact, that the small breeze going on outside, was enough to push the smoke coming out of the pipe, back inside the building through the window.

Overall it was a great build, with great results. Now that I know it works, I'll look into getting more pipe so that I can exhaust it properly. The holes I made in the lid and the joint from my modified 4" pipe leaked a bit of smoke as the fire started, but once everything warmed up, and the draft was pulling strong, the unit quit smoking. I figure I can seal these joints if I wanted, but I'm not so sure I will. You see, after I found out that it worked, I did some more reading on it. I found a couple people saying that they don't last very long. That the the high temperature it produces will actually turn the bucket into a crisp after a few hard burns. I watched a video of a pocket rocket and noticed the bottom of the bucket gets most of the heat. Maybe I can lay some dirt on the bottom of the bucket to help insulate it a bit. I only have the one bucket, and I'd hate to only get a couple uses out of it.

Anyway, there you have it. A heating unit that's small, inexpensive, easy to build, and puts out loads of heat with minimal fuel. Pictures? Hopefully I'll have some up by this weekend.


Rick's picture

Pictures - definitely pictures. That sounds pretty amazing - take some with and without fire if you could!

By Rick
Criddles's picture

Visuals....WE need Visuals!!!! LOL!!!!

By Criddles