One of the greatest things about doing the woodwork I do is seeing people enjoy it. I have made wooden mugs in vast numbers and can recognize my work from a distance away. One of the other joys is working to create other peoples visions. In 2019 I was approached about making a table and bellows for a historic glass bead making furnace by the lovely people at “My Ancient Musing“.
I was given some idea of what was needed and a picture of some examples of set ups other people had done and asked to do my best. The result came out pretty well I think.
The idea behind this was to create a portable setup to demonstrate the use of historic tools to produce glass beads. The information I was given was for a pair of single action bellows that would be worked in sequence to provide a steady air flow.
To start the bellows, I looked around for information on how they are currently constructed, and then began to look for older models. One big difference seemed to be that double action bellows are more modern. On a single action bellows air is drawn in to the chamber from a simple valve on the bottom when the handle is raised, and then forced out the nozzle when the internal pressure forces the valve closed on the downward push. A double action bellows has two valves that allow air to forced through the nozzle both when the handle is raised, and when it is lowered.
The bellows consist of a solid top, a solid bottom, an internal frame, a solid front that the nozzle connects to, a handle, and the bag. For this project I used plywood for the frame, a block of solid wood for the front, and a lightweight leather for the bag.
First off was to determine the height of the table based on the needs of the user. Once we had a good working height I planed out the rest of the dimensions for the breakdown portion of the table. The tray that the furnace would be in needed to be sturdy as it would have a layer of fire brick and sand in it that the furnace would sit on to contain the heat.
For the bellows it was a lot of guess work on the construction. Trying to figure out the size of the bellows to produce enough air to properly feed the flames in the furnace, when the entire setup was an experiment was a bit frustrating. Ultimately I ended up basing my dimensions on the materials I had on hand. The length of the bellows was dictated by a combination of how much room was left on the table in the wood I was using and trying to keep the bellow short enough to not be awkward for transportation. The width of the table was dictated by the width of the tray for the furnace and provided the width of the bellows.
Now that I had some rough dimensions to work with I began laying out my plan. Many examples of bellows I have seen depicted favor a spade shape and are used two handed, usually being for use in the home at the fire place. For a bead furnace the bellows needed to provide a larger amount of air steadily and consistently. The simplest solution was to stick with a spade shape but split it length wise in to two separate pieces.
The top plate and bottom plate create a stable platform to force the air to the go where directed, while a perforated rib in the center allowed the air to travel freely through the bellows and kept the sides from merely bowing out. The front block is attached to the bottom plate solidly, while dowels extending up from the bottom plate fit into grooves in the rib to keep it aligned. The top plate is hinged to the front block. There is a hole cut into the bottom plate, centered in the back third of the bellows, that has a simple gasket. A piece of leather is attached to the inside of the bellows, with a block of wood attached to it. When the bellows is lifted, the air pulls the wood up and inflates the bag, when depressed the internal pressure forces the gasket closed so the air goes out the front.
Once all of these pieces were cut and dry fitted together to ensure smooth motion and no binding I could cut the leather for the bag and begin nailing it in place. I really didn’t try to lay out the leather for the bag to precisely, I measured the length from the block, around the back, and to the other side of the block, then to the height I wanted the bellows to go to and cut my leather. I added a bit of extra so I could double the edge under to act as a simple form of gasket to keep pressure in. Once I had that cut I tacked down the leather to the bottom, then put a single tack to the top center, and a single tack to the rib in the back. Once I was happy the distance was even at full extension I fully tacked down the leather all around the bellows.
At this point I duplicated the process for the other side and began preparing a simple handle. I noticed I had some air leakage around the front block and decided to add some extra leather around it to keep as much air out of the nozzle as possible. The hardware for connecting the bellows to the furnace was being made by others so based on the finished bellows and the finished furnace but at this point I was pretty much done except for the delivery.
I enjoy working with wood and creating things, working with others to created their ideas is even better. Projects like this one are truly special, being involved in creating tools to showcase skills and techniques from ages past is a singular pleasure that I hope to do more of in the future.
Sawdust and Shavings 