Home Made Venturi Smoke Generators
Home made smoke generators are easy to build from ready to make components which are available from Home Depot. To our surprise it has performed incredibly well and it was very easy to make.
The system consists of three parts:
- Air pump, connecting tubing and an air injecting nozzle.
- Smokebox - a container where wood burns and and smoke is produced.
- A pipe that connects smoke box with a smokehouse.
A nozzle that injects air may be located inside of the connecting pipe or inside of the firebox.
The air pump can have a fixed air pressure output or it can have an adjustable volume control. An adjustable volume air pump permits to control the amount of smoke that is generated. In most cases a small 3.5 W adjustable air pump is all that is needed. Do not expect much air pressure coming out from a typical air pump. It is hardly noticeable, but surprisingly it is all that is needed to do the job. A higher pressure adjustable air pump (4.5 W, 4 psi) can be used for making a higher output smoke generator.
Single outlet pump nozzle.
Double outlet pump nozzle. A T-adapter is added to create a single output line.
Inside hot areas plastic tubing will curl and melt. To prevent that, the end of the tubing is inserted on a 1/4” metal tube which then becomes the injection nozzle.
For ease of installation copper 1/4" plumbing tube was used as it can be bent with hands only.
Plastic tubing connects pump with copper nozzle.
The middle (flattened) and the right nozzles end in smaller diameters than the one on the left.
Barbed brass splicers come in different sizes. The right side of the lower splicer was filed down to enter the brass tube. Once it is coated with contact cement it makes a permanent joint creating an efficient injector nozzle.
From the top: 3/4" T-plumbing connector, PVC plastic bushing and the wooden dovel in which 1/4" hole was drilled. The brass splicer is cemented to the tube.
Decreasing nozzle diameter should theoretically increase the air speed and induce a stronger vacuum. However, in our tests we did not observe any significant difference, most likely due to very low air pressure that the air pump supplies. In our opinion the extra work involved in decreasing the diameter of the nozzle is hardly worth an effort.
The fully assembled injector.
A plastic PVC adapter bushing screws into the T connector. Then a wooden plug fits snugly inside. After 12 smoking sessions, both the adapter and plug were fine. However, a metal bushing can be used instead. It is shown in this picture on the right.
The 3/4" pipe nipple on the left connects injector to the smoke box. The nozzle in the middle delivers air from the pump and sends it to the right tube. This creates enough vacuum to suck in the smoke from the left nipple pipe and to send it to the right nipple pipe and into the smokehouse.
This can be any type of a metal box or a pipe. They range from 2.5” (64 mm) diameter and up. If you make it yourself our recommendation is to go with 3.5” (89 mm). This diameter allows insertion of a hand inside in case some assembly is required. A metal container can be assembled from thin metal sheets, corner brackets, little bolts and nuts. Those fireboxes usually average about 6-10“ (15-25 cm) in height.
Aviation snipes can easily cut 20 guage sheet metal.
Aluminium brackets provide rigidness.
Sides get attached to brackets.
3/8" holes are drilled on three sides to supply fresh air and to start the fire.
We made our own box, but it was time consuming. A better solution is to visit a local machine shop. They will have round tubes, square tubes and they can cut, drill, and weld them the way you like. You can also look around for a suitable container, even a large metal can will do the job. What may change is the way the connecting pipe and nozzle are secured.
Low nozzle design.
The screen is made from a thin sheet metal to prevent wood chips from getting inside the pipe.
Plastic tubing is inserted on the brass tube. Metal bushing with the screen inside secured the pipe to the smoke box on the inside.
Another way for blocking chips is to cut diagonally the nipple pipe which will prevent falling down chips from getting inside. An electrical conduit nut secures the pipe inside the smoke box.
This smoke delivery system is very solid and works great. Screw all connections just finger tight so they can be easily disassembled for cleaning.
By flipping the smoke box 180° , the design changes from low to high nozzle configuration. Of course, you can make a fixed high nozzle generator.
Smoke generator - high nozzle configuration.
The fire is usually started with a lighter, but inserting wooden toothpicks into the fresh air holes is sometimes of great help.
Venturi smoke generators are small units and can get easily dirty. It is recommended to clean them well after each use. Those units can be used outdoors as well as there are many inexpensive battery operated aquarium air pumps. They usually operate on two D size batteries and last up to 48 hours.
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