Gas Bottle Hot Smoker

For several years I have wanted a large (by British standards) hot smoker. High prices put me off but and in the end I decided the only way I was going to afford one was to make my own. I opted to make mine out of a couple of old gas bottles.

Neither myself or my friends who helped are professional welders but with a little time we managed to come up with some thing pretty solid.

Edit: I have since been informed that using gas bottles may not be legal in some countries, as they remain the property of the gas supplier. If you are in such a location another option would be to use the air receiver off an old compressor or some other suitable tank.

By far the hardest part of building the smoker is getting the valve out of the gas bottle. Before attempting to remove the valve, I made sure all the gas had been used up and then left the valve open outside for a couple of days. You may be lucky and be able to getaway with a pipe wrench, this did not work for me and ended up rounding off the valve nut. Some definitely come out easier than others, in this casein the end I had to resort to building a large box spanner with a 6 foot cheater bar to unscrew it whilst it was attached to a work bench with ratchet straps to stop it spinning.

Once you have the valve removed, fill the cylinder with water to displace any remaining gas. To ensure all the gas is displaced and no bubbles were remaining I emptied and re filled the tank three times. As the tank full of water is very heavy I syphoned the water out between fills to make life easier.

The next stage is to cut the necessary opening for the flue and two join the two bottles together. I used a holesaw. To keep it centred with valve holes I turned a bushing to guide the pilot bit. Drilling the hole was really tough going as a holesaw that large has a tendency to snatch. If I was to make another I would most likely cut it with a plasma cutter or if one was not available a jigsaw.

As I have a plasma cutter I used it to cut the door openings. For the cuts along the length I used angle iron as a guide for the ends a strip of steel, held in place by a ratchet strap. If you don't have access to a plasma cutter you could cut the opening with an angle grinder or maybe a jigsaw with a suitable blade.

We need a way of regulating the air / smoke flow through the smoker. We came up with the idea of a pair of plates with triangular holes. One welded to the chimney and one to a short pipe attached to the top of the main smoke chamber. They rotate around a bolt which causes the holes to either align or not. We added a cowl from a narrow boat fire but unless you intend to smoke in the rain this is just for appearance.

As I was having some laser cutting done for another project I opted to have these laser cut at the same time, along with the grills, which can also be seen in the picture. These could of course of been fabricated from bar stock instead.

We also created a similar regulator mounted to the smoke box door to control the amount of air getting to the fire.

I added a small length of 125mm steel pipe between the fire box and the smoker main chamber. This along with a raise baffle help stop flames reaching the smoke box but my main reason was to give enough space to fit my Mig torch.

We welded a 35mm steel strip around the edge of each door so that when closed it overlaps the edge providing a sealing surface. We had intended to add a gasket to help seal the smoke box but this proved unnecessary, although as I had already purchased it I may add it in the future.

The hinges were simply fabricated from steel bar drilled to accept a bolt as the hinge pin. They were welded to the steel strip and the body of the smoker. The door latches were fabricated and of a simple leaver design once again made of bits and pieces from the scrap bin.

One improvement I will probably make in the in the future would be some form of insulation on the handle as it gets rather hot in use. Perhaps using the handle of a spring handled welders chipping hammer.

As I intend the smoker to live outside year round it required painting. Due to the heat produced during operation the existing paint all had to be removed prior. I did this with a combination of an angle grinder fitted with a flap disc and a random orbit sander.

I welded small pieces of angle iron 120 degrees apart to support the grills. I added enough to support up to four grills in the smoke box and one in the firebox to act as a grate. Prior to painting I lightly sanded and degreased the smoker with paint thinner. If you are going to paint your smoke you will need to use a high temperature paint. I chose to only paint the exterior and used one formulated for BBQ's and its seems to of held up well.

So far I have only had chance to us it a few times, but I am calling it a successful project. It only takes a very small fire and it seems to last for ages which is good. A few lessons I learnt early on are as follows

1. Put a tray in the bottom raise up, to stop fat dripping onto the fire.
2. As you would expect its hotter at the bottom than the top, so you need to take it into account when cooking many of the same thing.
3. The handle get really hot!
4. It might be worth making a wider base to improve stability, although I am yet to have any issues.

All in all very happy with it and I am looking forward to the summer so I can use it again!