I know a few of you out there reading may have asked yourselves “should I wear this near fire?”. Well, this post will help you decided that. Lets start at the top (of your body) and go from there.
Your brain is the most important safety tool you have. It will often warn you something bad is about to happen (like in that question above) and it can be easily upgraded (by educating yourselves on what not to do). Use it first and always! That also means no playing in fire if your brain isn't fully functioning. Be it drink, cold medicine, a lack of sleep or just feeling off, if you aren't on your game, save forge work for another time.
Eye-wear is the single most essential safety item. Period. Why? Simple, a blind blacksmith doesn't know how hot his steel is, where to hit or if he is done. So much of the craft is visual, and most education to further your craft is visual. Good quality safety glasses, furnace glasses or some kind of impact rated goggle is a bare minimum. And they don't work on top of your head – WEAR THEM.
Hearing protection is a pretty close second. Hearing damage occurs over time, and by the time you finally realize there is a problem, it is way too late. And I can tell you first hand, it sucks. Ear plugs, shooting cans or a combination work well and aren't that hard to get used to. Sure, you might not look all that cool, but damn! You have hot metal and a hammer in your hands! That offsets any non cool look right there.
The constant ringing of the anvil, sharp noises from steel being dropped and other sounds can quickly damage hearing, but other sounds over time can as well. Things like a grinder, sander or even the blower can, over time, damage your hearing. Wear cans or plugs.
Next up is your torso. Sure, working bare chested is pretty cool, but a burned nipple will definitely screw up your day. And not just hot steel burns your skin. The infrared heat coming off the forge or a large, hot bar of steel can also cause surface burns pretty easily. If you will be doing any arc welding, these also can cause surface burns. Wear either a leather apron, or a heavy shirt made from natural fibers.
Here is a big thing on clothing to remember; natural fibers ONLY. No polyester, rayon or other synthetics, as these will turn to dripping napalm if they do catch fire. Natural fibers will not melt to your skin, and extinguish fairly easily or on their own (good quality wool in particular). Cotton and linen are also good choices, and many commonly available garments are 100 percent cotton (things like denim jeans for example). Also remember, you are going to sweat. Natural fibers will wick sweat away from your skin to help cool you. Thicker clothing will insulate some heat away from you as much as it holds your heat in.
On your legs, jeans are a good way to go, see notes above on natural fibers though.
On your hands... here is where it gets interesting. We generally don't wear gloves for forging or grinding, but do for welding. Gloves can get caught in rotating machines (that's bad by the way) and may allow things you are holding to slip. Often, you get a lot of physical feedback up through a set of tongs that can warn you a hot piece of steel is about to go on its own way that gloves will prevent you from feeling. Gloves can also give you a false sense of security, and if they get hot can be hard to get off in a hurry. That said, a lot of guys do wear tight fitting gloves with great success.
Gloves are one you are going to have to decide on for yourselves.
Boots or shoes; here is one we see a lot. People forging in tennis shoes. Uh... no. We prefer leather engineer boots, as they protect the feet from falling hot scale, bounced off bits of hot metal and other minor hazards, as well as supporting the ankle. Boots or shoes made of synthetics are just asking for trouble. Remember that bit about molten, burning plastic sticking to your arms and torso? It hurts more on your ankles and arch of your foot. Wear sturdy leather here, K? And steel toes are up to you. We usually aren't moving large, heavy objects, so the worse thing that falls on our feet is a dropped hammer or tongs. Sure steel toes would prevent some loud, bad words. But you get quick about moving when hammers fall.
So that covers the basics of what to wear when forging. We might do some more detailed posts later, who knows?
Have fun, be safe. Wear your safety gear!
Showing posts with label how to. Show all posts
Showing posts with label how to. Show all posts
21 January 2011
Bellows update
I posted a bit on building bellows a while back, and had planned to get photos up of the build process. Well, that tanked. Something went awry and I seem to have lost all the photos, so I am in the process of trying to make a few drawings up to better explain the process, then when we build another set I will photograph the process and reshoot (hopefully we will also do video at the same time for our upcoming DVDs). So, keep an eye open here for new bellows images - hopefully soon!
(see the orginal post here: Bellows)
Until then, these pics will probably help:
In this pic, we see all three boards hanging in space, one over the other. This is how the bellows would be arranged if the nozzle (with hinges) and lung were mounted, and both chambers were fully open (ie, full of air). The valve boards are shown in violet (without their leather hinges in place), the top and bottom are shown as edge joined boards and the center as chip board. This is only done to make the image easier to understand, please see the main post on what to make these parts from.
This image shows the rough shape and proportions of the boards from the top. Yours does not have to be exact, roughly this shape and these ratios will work just fine.
This image shows the midboard, with the notch at the front for the nozzle to be mounted in, the hanging pins and the holes for the valves. The bottom board has the same valve holes, but does not have the hanging pins or notch at the front.
The top board is the same size and has no holes.
The lung of the bellows will wrap from the front (narrow) edge all the way around the curved rear of the bellows to the opposite front edge.
I will see about getting the nozzle image up asap.
(see the orginal post here: Bellows)
Until then, these pics will probably help:
In this pic, we see all three boards hanging in space, one over the other. This is how the bellows would be arranged if the nozzle (with hinges) and lung were mounted, and both chambers were fully open (ie, full of air). The valve boards are shown in violet (without their leather hinges in place), the top and bottom are shown as edge joined boards and the center as chip board. This is only done to make the image easier to understand, please see the main post on what to make these parts from.
This image shows the rough shape and proportions of the boards from the top. Yours does not have to be exact, roughly this shape and these ratios will work just fine.
This image shows the midboard, with the notch at the front for the nozzle to be mounted in, the hanging pins and the holes for the valves. The bottom board has the same valve holes, but does not have the hanging pins or notch at the front.
The top board is the same size and has no holes.
The lung of the bellows will wrap from the front (narrow) edge all the way around the curved rear of the bellows to the opposite front edge.
I will see about getting the nozzle image up asap.
29 September 2009
Building a set of dual chamber "great" bellows
Blacksmith lessons Building bellows
The next project is a fairly big one, and will be one of the more costly in terms of materials we will cover in this series. This project is building a set of dual chamber bellows to drive air into your forge. It is worth noting that the dual chamber bellows are sometimes called the great bellows as well, and in older texts you will see this name more often.
Of course you can simply use a blower or fan system, as we described in the bucket forge lessons, but there is a certain romance and elegance to the great bellows that a whining shop vac simply can not provide. Another benefit is the bellows are very quiet, and rather efficient. They are a tremendous pleasure to work with, having an almost musical quality to the quiet sounds they make once you get the hang of using them.
This project can be scaled up or down, depending on how much storage space you have. Larger bellows will be easier to work with, though a great deal harder to move and store. If you follow roughly the proportions laid out here, you can scale these up to a set at least 12 feet long or as small as 12 inches and they will still work. The biggest difference between a medium and large sized set of great bellows is the number of pumps they will need to bring a forge up to a given temperature.
First let's have a bit of overview on the pieces of the project and how the great bellows works. This will help you better understand what we are doing, and why somethings are done in the way they are.
The great bellows is made up of two chambers, one on top of the other. In the bellows resting state, the bottom chamber is fully inflated while the top chamber is fully deflated. Pulling up on the handle of the bellows pulls the bottom board upward, driving the air in the lower chamber through the air valves into the upper chamber. This inflates the upper chamber and air begins to be driven out the nozzle of the bellows into the twyre pipe that feeds the forge from underneath. The top chamber is deflated as the top board falls free, driving the valves shut as the pressure from the bottom chamber drops off so the air is only funneled into the forge. The bottom chamber bottom board drops back down as you release the handle, and as it falls the vacuum inside it opens the bottom set of valves and refills the bottom chamber with air. Once it is refilled you can press down on the handle again, refilling the top chamber.
The benefit to having the two chambers in series like this is the bellows produce a steady stream of air blowing into the forge, where a single chamber set of bellows will only blow intermittent puffs, much like using your own lungs and a blow pipe. The linked chambers allows the bellows to “breath in” at the same time the upper chamber is still “breathing out”. There is another, less obvious benefit to this as well. Sometimes, a single chamber set of bellows may draw hot air back out of the forge, which can contain unburned flammable gas. If this gets inside the bellows, it may ignite. While it only very rarely will cause the bellows to catch fire, and probably never explode, the increase in internal pressure may be enough to blow the “lung” off the bellows, making a repair immediately necessary.
For the “lung” section of most old great bellows, a large sheet of leather was generally used. We are going to cheat a little here to help you save money, and if it is done correctly the bellows will still look completely proper for any historical re-enactment. Unless someone touches the actual lung surface, most people will think you spent a fortune on leather to wrap your bellows.
So now that you have a bit better idea of what the bellows do in action, lets begin the process of building them.
The bellows are made up of three “boards”, a nozzle, valves in two of the three boards and a lung. There also needs to be some sort of frame or stand to hold the bellows with enough space for both halves to be fully inflated at once, and a handle with a linkage to the bottom board of the bellows to allow you to operate them. Note that there are many ways to build most of these pieces, but I have used the most common shape and mounting system here, along with the materials that are the easiest to work with and find.
The middle board does not move, and the nozzle will be built attached to the middle board. The frame that holds up the bellows is also connected to the middle board at each outer edge. The top and bottom boards are hinged to the nozzle and supported by the lung around the outer edge. The bottom board will also have a projection at the rear farthest away from the nozzle for the handle to connect to. In larger sets of bellows you may want to add “ribs” along the lung to help it open and close without puffing over the sides of the boards as well.
For our project, I suggest ½ inch plywood for the three “boards”. This is a good compromise between strength and weight and is much easier than trying to carefully laminate planks and cheaper than using pre-cut tongue and groove material. Plywood also is airtight so you don't have to worry about that issue. If you like, you can cover the top board with planks glued on the top to make your bellows look more authentic.
The drawings here will help you get a feel for the proportions that are generally seen, and these evolved over many generations of smiths using the bellows daily. You can change the shape and proportions to suit your needs or materials at hand, but this layout is known to work. You are on your own if you decide to do a giant letter K shaped set of bellows or something of the like. I will interject here that a coffin shaped set of bellows works fairly well. Also, if you scale your bellows to fit width wise between the legs of your wooden forge, the forge legs can be used as the mounting bracket, making the footprint of the whole system much smaller.
Usually, your best bet is to draw a full sized template on a large sheet of cardboard or several sheets of newspaper taped together. This will allow you to layout all three boards so they are the same size. You can also cut out one board and trace that as your pattern. Once you have your pattern, trace it on your plywood with a sharpie pen or something else you can easily see.
You will need some way of cutting these out of the raw sheet of plywood, such as a jigsaw. You can also use a circular saw and cut away all the material outside your layout lines, then use rasps or a surform plane to shave the edges smooth. Do NOT attempt to cut a curved line on a table saw! This will more than likely catch the blade and kick the panel out and more than likely it will hurt you. It could also pull your hand into the saw or outright kill you if a thrown piece hit you in the head with sufficient force. Play smart, anything that cuts wood cuts you better.
Usually, once I have the boards cut out, I clamp them together and smooth the edges with an angle grinder fitted with a sanding disc so the boards are all the same size. You can also use a surform or rasps, and it is not even all that critical that the boards are all the same size, it just makes the final product look a bit better. A clean, square edge does help when it comes time to install the “lung” but is not critical.
The next step is cutting holes for the valves. A very large hole saw would work, but drilling a hole large enough to pass the jigsaw blade and jigsawing the hole to size will work just as well. If all you have is a skill saw, you can plunge cut squares, but these may be fairly tricky to do. The holes do not need to be perfectly round either, again it is a purely cosmetic thing, but in this case in a place that will not be seen in normal use. The valves only need to be an inch or so larger than the hole in all directions, and can be made from scraps of the main sheet of plywood. It will help to have one straight edge on the valves to allow you to mount the hinges so the valve opens and closes cleanly and efficiently.
The next part to make is the nozzle. Historically speaking, these are usually shaped into a nice smoothly transitioned shape, but they can be left blocky and square without changing how the bellows work. I usually build up the nozzle out of 2x6 stock with a layer of 1/2” ply across the top. The drawing will help explain the layout. Mostly, you are trying to make the air flow smoothly out of the top chamber into the forge inlet pipe. At times I have made this section more complicated, but this simple version works very well and is much quicker to make than the version that requires cutting through the center board and carving out the bottom board.
Normally, a tapered snout is mounted to the front of the bellows, so it can just be wedged into the inlet pipe. This can be made from sheet steel, or even a can cut down the side and reshaped. This can be fairly complicated to fit up, but a pattern is provided here if you feel you have the sheet metal skills to make this part. Another option is to build a “cheater” adapter mounted to the snout. This is a box with a hole in it mounted to the snout. The hole is the same size as the outside of your inlet pipe and allows the pipe to simply slip in. You will probably want to stuff something like a rag in around the pipe if the fit is not very tight, to get as much air into your forge as possible. Both are illustrated here.
Next comes putting the valves in. Your valves can be square or the tombstone shape shown, no one sees them in use. I like the tombstone shape, as it allows me to more easily get my hand inside the bellows and feel around should something get in there that has to be retrieved. The valves mount on the top side of each board, and are usually covered on their bottom face with some kind of felt or other fuzzy cloth to help them seal somewhat when the valve is closed. An old washcloth can be glued to the face of each valve with decent results. By wrapping the cloth up around the valve and only gluing on the back or top side of each valve, you won't have problems with clumps of glue preventing the valve from sealing.
For the hinge here either a strip of thin leather or vinyl is very easy and fairly fool proof. Simply tack it on as shown, and you could probably even use glue (though put in a few tacks, a failure here is gonna be a pain in the butt to fix later). I usually also add a strap on each valve to prevent the valve from flopping over backwards and staying open or getting caught. Almost anything flexible can be used as a strap, even old shoestrings or a bit of canvas. The valve should be able to open about 30 to 45 degrees, so the board above pushing against it will close it without it catching.
A note on the valves; you do not need two valves in each board, you can have one, or have two holes and one large valve board. I use two out of tradition and have to admit I am not sure why most sets of bellows have two valves. Most likely it is a compromise between getting air into the chamber quickly and the weight of the valve itself. Too heavy of a valve will not open easily and admit air and too small of a hole will make the restricted air move from chamber to chamber very slowly. Having two moderate sized holes is a good compromise. I have seen a few old 18th century sets with three smaller valve holes that appeared to use one large valve board across all three holes.
Once you have the nozzle and valves built and installed, you will need to put the hinged top and bottom boards in place. Again, a flexible strip hinge here is an easy and effective way to hinge the board, and seal up the connection. I generally put the hinge strips on the outside of each assembly for ease of maintenance. A little construction secret here can save you a lot of extra time pumping at the bellows. Put silicone caulk on the face of each piece and the underside of your hinge strap before assembly and let it dry. Once assembled, this silicone will act as a gasket. Don't worry, you will have another use for the rest of it very soon so it won't go to waste.
With the boards in place, now comes the fun part. This is also going to be one of the most costly parts of this project. We are about to put the lung on your bellows, and this can be a very time consuming, frustrating step.
The lung is a flexible, airtight sheet of material that wraps around the outside of the bellows, and is nailed to the boards in each layer to help seal the chambers. Historically, the lung was usually leather and the joints along the edge were sealed with hot pitch a short section at a time as the lung was nailed on. We are going to take a whole bunch of modern short cuts here then dress the whole thing up so it looks like you went to the full effort of doing it right.
Instead of leather, I would suggest finding a mottled brown, leather look cloth backed vinyl. This material can often be found at fabric stores, but be ready for some sticker shock. It is usually about 10 dollars or more a linear yard. Usually it is about 60” wide though, so you may be in luck and only need a single yard if your bellows are small. Using a flexible tape measure, check the distance around your bellows board perimeter. Don't forget to give yourself at least 1 inch of overlap on the ends where the nozzle is. A bit more would be even better.
A less airtight material is canvas, but this can serve fairly well, and if sprayed with something like Thompson's Water Seal, it can be quite serviceable. At our local Field's Fabrics, vinyl remnants can often be had for less than the price of canvas, sometimes as little as 10 dollars for a 60” wide section that is 3 yards (9 feet) long. If you can find these deals, you will save a considerable amount on this project.
Once you have your material laid out and all the wrinkles have been pressed out of it, you can caulk the edges of your boards with silicone. I try to mount my bellows lung with the silicone still wet, so it bonds to the lung material more effectively. You can work in sections if you do not feel comfortable with trying to do this all in one fell swoop. Generally, I fold the edge over at the start and staple it to the side of the nozzle box. Then I work backward around the bellows, stapling to all three boards evenly. Something very important must be taken into consideration here; the bellows must be fully open at this step! This will limit the travel of the bellows and if you make the mistake of having the lungs closed you have just made a very strange coffee table. Usually, I cheat a bit here and staple a strip of heavy cardboard or nail a piece of light scrap wood across the back of the bellows boards to hold the boards open. You have to be sure that the open position is just a bit less than the full width of your lung material, otherwise you wont be able to mount the lung and seal up the bellows. With 60” material, I generally set the open width to 58” outside surface to outside surface but only on a very large set of bellows.
A good rule of thumb is to make the bellows lung as wide as the boards plus or minus a bit. So if you have a set of bellows that are made to fit inside your colonial forge, the width of the board will probably be about 22” so the lung material might be 28” or so. If you are building a narrower set of bellows like this, you have the option to buy half as much material in length. This is then cut into two pieces half as wide and a seam is sewn down the center back of the lung. Many large leather lunged bellows have seams, so this is not uncommon.
Remember; your frame needs to be able to hold the fully expanded height of your bellows. If you opt to hang your smaller bellows underneath your forge, you will have to limit your bellows lung height to just slightly less than the length from the underside of your forge to the ground.
If you have opted to build a larger set of bellows, the full width of the material may be useful (for example, if you have built each board from a single sheet of plywood, so the bellows are 48” wide – note that this is a very large set of bellows and they will be quite heavy to try to move). You will have to adapt these instructions, like many of the other lessons here to meet your needs.
Once the lung is in place and stapled down all the way around, I trim off any excess material, usually leaving about 1inch extra, which I fold under and staple on the top and bottom of the bellows. This will help form a better seal and the folded edge gives the lung a nice, finished look. If you have used canvas, a bit more work may be needed to make the edges look good.
Now you have a couple options to dress the final look. One possible thing to do is outline the edges of the boards with a thin strip of screen door molding, nailed on ever few inches with a dome headed furniture nail. The strip will have to be soaked in water overnight to allow it to flex around the curve of the bellows without breaking. Another option is to simply put a row of nails in the edge of each board to hide the staples somewhat. If appearance is not a concern to you, simply leave the great bellows as they are.
Now that we have completed a set of bellows, our next installment will show you how to mount them in a frame and set everything up to put them to use. We are nearly ready to start forging!
The next project is a fairly big one, and will be one of the more costly in terms of materials we will cover in this series. This project is building a set of dual chamber bellows to drive air into your forge. It is worth noting that the dual chamber bellows are sometimes called the great bellows as well, and in older texts you will see this name more often.
Of course you can simply use a blower or fan system, as we described in the bucket forge lessons, but there is a certain romance and elegance to the great bellows that a whining shop vac simply can not provide. Another benefit is the bellows are very quiet, and rather efficient. They are a tremendous pleasure to work with, having an almost musical quality to the quiet sounds they make once you get the hang of using them.
This project can be scaled up or down, depending on how much storage space you have. Larger bellows will be easier to work with, though a great deal harder to move and store. If you follow roughly the proportions laid out here, you can scale these up to a set at least 12 feet long or as small as 12 inches and they will still work. The biggest difference between a medium and large sized set of great bellows is the number of pumps they will need to bring a forge up to a given temperature.
First let's have a bit of overview on the pieces of the project and how the great bellows works. This will help you better understand what we are doing, and why somethings are done in the way they are.
The great bellows is made up of two chambers, one on top of the other. In the bellows resting state, the bottom chamber is fully inflated while the top chamber is fully deflated. Pulling up on the handle of the bellows pulls the bottom board upward, driving the air in the lower chamber through the air valves into the upper chamber. This inflates the upper chamber and air begins to be driven out the nozzle of the bellows into the twyre pipe that feeds the forge from underneath. The top chamber is deflated as the top board falls free, driving the valves shut as the pressure from the bottom chamber drops off so the air is only funneled into the forge. The bottom chamber bottom board drops back down as you release the handle, and as it falls the vacuum inside it opens the bottom set of valves and refills the bottom chamber with air. Once it is refilled you can press down on the handle again, refilling the top chamber.
The benefit to having the two chambers in series like this is the bellows produce a steady stream of air blowing into the forge, where a single chamber set of bellows will only blow intermittent puffs, much like using your own lungs and a blow pipe. The linked chambers allows the bellows to “breath in” at the same time the upper chamber is still “breathing out”. There is another, less obvious benefit to this as well. Sometimes, a single chamber set of bellows may draw hot air back out of the forge, which can contain unburned flammable gas. If this gets inside the bellows, it may ignite. While it only very rarely will cause the bellows to catch fire, and probably never explode, the increase in internal pressure may be enough to blow the “lung” off the bellows, making a repair immediately necessary.
For the “lung” section of most old great bellows, a large sheet of leather was generally used. We are going to cheat a little here to help you save money, and if it is done correctly the bellows will still look completely proper for any historical re-enactment. Unless someone touches the actual lung surface, most people will think you spent a fortune on leather to wrap your bellows.
So now that you have a bit better idea of what the bellows do in action, lets begin the process of building them.
The bellows are made up of three “boards”, a nozzle, valves in two of the three boards and a lung. There also needs to be some sort of frame or stand to hold the bellows with enough space for both halves to be fully inflated at once, and a handle with a linkage to the bottom board of the bellows to allow you to operate them. Note that there are many ways to build most of these pieces, but I have used the most common shape and mounting system here, along with the materials that are the easiest to work with and find.
The middle board does not move, and the nozzle will be built attached to the middle board. The frame that holds up the bellows is also connected to the middle board at each outer edge. The top and bottom boards are hinged to the nozzle and supported by the lung around the outer edge. The bottom board will also have a projection at the rear farthest away from the nozzle for the handle to connect to. In larger sets of bellows you may want to add “ribs” along the lung to help it open and close without puffing over the sides of the boards as well.
For our project, I suggest ½ inch plywood for the three “boards”. This is a good compromise between strength and weight and is much easier than trying to carefully laminate planks and cheaper than using pre-cut tongue and groove material. Plywood also is airtight so you don't have to worry about that issue. If you like, you can cover the top board with planks glued on the top to make your bellows look more authentic.
The drawings here will help you get a feel for the proportions that are generally seen, and these evolved over many generations of smiths using the bellows daily. You can change the shape and proportions to suit your needs or materials at hand, but this layout is known to work. You are on your own if you decide to do a giant letter K shaped set of bellows or something of the like. I will interject here that a coffin shaped set of bellows works fairly well. Also, if you scale your bellows to fit width wise between the legs of your wooden forge, the forge legs can be used as the mounting bracket, making the footprint of the whole system much smaller.
Usually, your best bet is to draw a full sized template on a large sheet of cardboard or several sheets of newspaper taped together. This will allow you to layout all three boards so they are the same size. You can also cut out one board and trace that as your pattern. Once you have your pattern, trace it on your plywood with a sharpie pen or something else you can easily see.
You will need some way of cutting these out of the raw sheet of plywood, such as a jigsaw. You can also use a circular saw and cut away all the material outside your layout lines, then use rasps or a surform plane to shave the edges smooth. Do NOT attempt to cut a curved line on a table saw! This will more than likely catch the blade and kick the panel out and more than likely it will hurt you. It could also pull your hand into the saw or outright kill you if a thrown piece hit you in the head with sufficient force. Play smart, anything that cuts wood cuts you better.
Usually, once I have the boards cut out, I clamp them together and smooth the edges with an angle grinder fitted with a sanding disc so the boards are all the same size. You can also use a surform or rasps, and it is not even all that critical that the boards are all the same size, it just makes the final product look a bit better. A clean, square edge does help when it comes time to install the “lung” but is not critical.
The next step is cutting holes for the valves. A very large hole saw would work, but drilling a hole large enough to pass the jigsaw blade and jigsawing the hole to size will work just as well. If all you have is a skill saw, you can plunge cut squares, but these may be fairly tricky to do. The holes do not need to be perfectly round either, again it is a purely cosmetic thing, but in this case in a place that will not be seen in normal use. The valves only need to be an inch or so larger than the hole in all directions, and can be made from scraps of the main sheet of plywood. It will help to have one straight edge on the valves to allow you to mount the hinges so the valve opens and closes cleanly and efficiently.
The next part to make is the nozzle. Historically speaking, these are usually shaped into a nice smoothly transitioned shape, but they can be left blocky and square without changing how the bellows work. I usually build up the nozzle out of 2x6 stock with a layer of 1/2” ply across the top. The drawing will help explain the layout. Mostly, you are trying to make the air flow smoothly out of the top chamber into the forge inlet pipe. At times I have made this section more complicated, but this simple version works very well and is much quicker to make than the version that requires cutting through the center board and carving out the bottom board.
Normally, a tapered snout is mounted to the front of the bellows, so it can just be wedged into the inlet pipe. This can be made from sheet steel, or even a can cut down the side and reshaped. This can be fairly complicated to fit up, but a pattern is provided here if you feel you have the sheet metal skills to make this part. Another option is to build a “cheater” adapter mounted to the snout. This is a box with a hole in it mounted to the snout. The hole is the same size as the outside of your inlet pipe and allows the pipe to simply slip in. You will probably want to stuff something like a rag in around the pipe if the fit is not very tight, to get as much air into your forge as possible. Both are illustrated here.
Next comes putting the valves in. Your valves can be square or the tombstone shape shown, no one sees them in use. I like the tombstone shape, as it allows me to more easily get my hand inside the bellows and feel around should something get in there that has to be retrieved. The valves mount on the top side of each board, and are usually covered on their bottom face with some kind of felt or other fuzzy cloth to help them seal somewhat when the valve is closed. An old washcloth can be glued to the face of each valve with decent results. By wrapping the cloth up around the valve and only gluing on the back or top side of each valve, you won't have problems with clumps of glue preventing the valve from sealing.
For the hinge here either a strip of thin leather or vinyl is very easy and fairly fool proof. Simply tack it on as shown, and you could probably even use glue (though put in a few tacks, a failure here is gonna be a pain in the butt to fix later). I usually also add a strap on each valve to prevent the valve from flopping over backwards and staying open or getting caught. Almost anything flexible can be used as a strap, even old shoestrings or a bit of canvas. The valve should be able to open about 30 to 45 degrees, so the board above pushing against it will close it without it catching.
A note on the valves; you do not need two valves in each board, you can have one, or have two holes and one large valve board. I use two out of tradition and have to admit I am not sure why most sets of bellows have two valves. Most likely it is a compromise between getting air into the chamber quickly and the weight of the valve itself. Too heavy of a valve will not open easily and admit air and too small of a hole will make the restricted air move from chamber to chamber very slowly. Having two moderate sized holes is a good compromise. I have seen a few old 18th century sets with three smaller valve holes that appeared to use one large valve board across all three holes.
Once you have the nozzle and valves built and installed, you will need to put the hinged top and bottom boards in place. Again, a flexible strip hinge here is an easy and effective way to hinge the board, and seal up the connection. I generally put the hinge strips on the outside of each assembly for ease of maintenance. A little construction secret here can save you a lot of extra time pumping at the bellows. Put silicone caulk on the face of each piece and the underside of your hinge strap before assembly and let it dry. Once assembled, this silicone will act as a gasket. Don't worry, you will have another use for the rest of it very soon so it won't go to waste.
With the boards in place, now comes the fun part. This is also going to be one of the most costly parts of this project. We are about to put the lung on your bellows, and this can be a very time consuming, frustrating step.
The lung is a flexible, airtight sheet of material that wraps around the outside of the bellows, and is nailed to the boards in each layer to help seal the chambers. Historically, the lung was usually leather and the joints along the edge were sealed with hot pitch a short section at a time as the lung was nailed on. We are going to take a whole bunch of modern short cuts here then dress the whole thing up so it looks like you went to the full effort of doing it right.
Instead of leather, I would suggest finding a mottled brown, leather look cloth backed vinyl. This material can often be found at fabric stores, but be ready for some sticker shock. It is usually about 10 dollars or more a linear yard. Usually it is about 60” wide though, so you may be in luck and only need a single yard if your bellows are small. Using a flexible tape measure, check the distance around your bellows board perimeter. Don't forget to give yourself at least 1 inch of overlap on the ends where the nozzle is. A bit more would be even better.
A less airtight material is canvas, but this can serve fairly well, and if sprayed with something like Thompson's Water Seal, it can be quite serviceable. At our local Field's Fabrics, vinyl remnants can often be had for less than the price of canvas, sometimes as little as 10 dollars for a 60” wide section that is 3 yards (9 feet) long. If you can find these deals, you will save a considerable amount on this project.
Once you have your material laid out and all the wrinkles have been pressed out of it, you can caulk the edges of your boards with silicone. I try to mount my bellows lung with the silicone still wet, so it bonds to the lung material more effectively. You can work in sections if you do not feel comfortable with trying to do this all in one fell swoop. Generally, I fold the edge over at the start and staple it to the side of the nozzle box. Then I work backward around the bellows, stapling to all three boards evenly. Something very important must be taken into consideration here; the bellows must be fully open at this step! This will limit the travel of the bellows and if you make the mistake of having the lungs closed you have just made a very strange coffee table. Usually, I cheat a bit here and staple a strip of heavy cardboard or nail a piece of light scrap wood across the back of the bellows boards to hold the boards open. You have to be sure that the open position is just a bit less than the full width of your lung material, otherwise you wont be able to mount the lung and seal up the bellows. With 60” material, I generally set the open width to 58” outside surface to outside surface but only on a very large set of bellows.
A good rule of thumb is to make the bellows lung as wide as the boards plus or minus a bit. So if you have a set of bellows that are made to fit inside your colonial forge, the width of the board will probably be about 22” so the lung material might be 28” or so. If you are building a narrower set of bellows like this, you have the option to buy half as much material in length. This is then cut into two pieces half as wide and a seam is sewn down the center back of the lung. Many large leather lunged bellows have seams, so this is not uncommon.
Remember; your frame needs to be able to hold the fully expanded height of your bellows. If you opt to hang your smaller bellows underneath your forge, you will have to limit your bellows lung height to just slightly less than the length from the underside of your forge to the ground.
If you have opted to build a larger set of bellows, the full width of the material may be useful (for example, if you have built each board from a single sheet of plywood, so the bellows are 48” wide – note that this is a very large set of bellows and they will be quite heavy to try to move). You will have to adapt these instructions, like many of the other lessons here to meet your needs.
Once the lung is in place and stapled down all the way around, I trim off any excess material, usually leaving about 1inch extra, which I fold under and staple on the top and bottom of the bellows. This will help form a better seal and the folded edge gives the lung a nice, finished look. If you have used canvas, a bit more work may be needed to make the edges look good.
Now you have a couple options to dress the final look. One possible thing to do is outline the edges of the boards with a thin strip of screen door molding, nailed on ever few inches with a dome headed furniture nail. The strip will have to be soaked in water overnight to allow it to flex around the curve of the bellows without breaking. Another option is to simply put a row of nails in the edge of each board to hide the staples somewhat. If appearance is not a concern to you, simply leave the great bellows as they are.
Now that we have completed a set of bellows, our next installment will show you how to mount them in a frame and set everything up to put them to use. We are nearly ready to start forging!
28 August 2009
Basic blacksmithing – building the bucket forge
(Click on the image for a larger view)
Ok, we talked about this very primitive forge in previous posts, and here is the “how to” article to build your own bucket forge. Just so this is very clear, this is not going to be a really incredible forge, and it probably won't be very pretty, but it is simple and dirt cheap (that's a joke son, a joke... it will become apparent in a bit).
This bucket forge has not been covered anywhere else on the internet that I am aware of, but a lot of parallel evolution happens, so it is quite possible. You could think of this as a portable ground forge if you like, so any photos or information you might happen across on a ground forge could apply to this project.
So lets jump right into this then.
First you are going to need a bucket. A metal bucket or pail is certainly fireproof, but because of the way we are building this, any 3 to 5 gallon plastic bucket will work just fine.
Next, you will need some way of getting air into the fire. Here, I really suggest you use a section of steel pipe. Plastic pipe, such as PVC, is definitely going to melt and it won't last longer than it takes to get a good fire going. Copper pipe is going to carry a lot of heat back out of the fire, and could melt the side of your bucket, plus it is pretty expensive. Now for this project, any old hunk of 1 1/2” or larger pipe should suffice, though I wouldn't suggest much beyond about 3 inches in diameter. If it has an elbow or T connector on one end, that's even better. You will need a way to put a hole in the side of your bucket for the pipe to enter, but we will get to that in a bit.
Lastly, you are going to need some fireproof material to fill your bucket and make your bowl. This is where the “dirt cheap” joke comes in. Simple dirt can work just fine, with a layer of clay to make the bowl. And if clay is hard to come by in your area, kitty litter shouldn't be, and it is just pelleted clay. If you opt to go the kitty litter route, make sure it is the non-scented stuff, those scents could emit nasty fumes once they heat up.
Now that we have our materials, we just have to put it all together. The first thing is going to be a hole in the side of the bucket to allow the air pipe to come in under the fire. If your air pipe is just a straight section, it can come in higher up than if it has a T or elbow on it. The proper way to do this is to use a hole saw to cut a properly sized hole in the side of the bucket for the pipe to have a nice close fit. But hole saws are fairly costly, and this thing is to be done on the cheap, so... you will need to heat the section of pipe at one end, and find a means of safely holding the pipe to melt a hole in the side of the bucket. For this a propane torch can work, or a small camp fire. You only need to get the end of the pipe up to about 400 degrees, so even putting it in your grille or oven would work. Now wrapping a wet towel around the pipe might seem like a safe way to hold it, but go with me on this... it's not. If the pipe is long enough, you should be able to hold in with your hands, as long as you check it with the back of your hand first. By that I mean hold the back of your hand near the potentially hot pipe and feel for heat. Then get a bit closer and so on until you can touch it and know for certain it is a comfortable temperature. Why use the back of your hand, you may ask? Because the back of the hand is more sensitive to heat than the palm and fingertips, plus if you do burn yourself, it is in a place that wont cripple your ability to keep working. If the pipe is too short, or the heat moving though it has heated it up, you will need something like a pair of pliers or vice grips to hold the pipe. DO NOT put one end of the pipe in a bucket of water. This can cause the water in the pipe to turn to steam and shoot out the end like a shotgun, and steam is very effective at causing burns.
Once you get your pipe heated up, you simply hold it against the bucket and let it melt the plastic. Be sure to do this outside on a windy day, those fumes can not be good for you. Also be sure there is nothing flammable nearby, like a wooden deck or a bucket of gasoline soaked rags. If the plastic flares up and starts to burn pull the pipe off it and let the pipe cool somewhat, and put the flame out either with water or a hand full of sand. Don't blow on it to put it out though, as that could easily splash molten, burning plastic back into your face.
The objective here is to get a hole that is just about the size of your pipe, about halfway down the bucket. Of course if you have a hole saw, you can use that too, but this is the low dough way.
Now that you have a hole, let the bucket and pipe cool back to air temperature. Next fill the bottom of the bucket with whatever is handy to make up the space up to the level your pipe comes in at. Dirt is just fine, but is rather heavy. Since this area will not be exposed to much heat, it can be filled with wood scraps, a couple empty cool whip containers with lids or what have you. Just fill any air gaps with dirt and make sure you have a few inches of dirt under your pipe for insulation. If you choose to fill the entire bucket with dirt, the forge will be much more stable in use, which is safer, just be careful moving it, as the handles on many of these buckets are not designed for that much weight. Now slide your pipe in through the hole you made so the open part is at the center. If your pipe has and elbow or T, you will have to put the pipe in from the opening at the top of the bucket, on an angle and slide it into position. Now fill the bucket with some more dirt around the outer edge to create a basic bowl shape. Tamp this all down from time to time to make sure the dirt is packed as tightly as you can, so it wont collapse later.
Next comes the final part, making the bowl. If you have river clay, simply press it into place forming a nice bowl shaped depression with the sides packed tightly all the way to the top. If you are using cat litter, you will need to mix a little water into it so it is sticky, and pack it into place. There are illustrations on my blog to better show the shape and layout of this step, and that can be found at http://ironangelforge.blogspot.com/, along with other lessons.
Now you must have some patience, and let the clay dry for several days. Once you have let it dry, check it for cracks, and if some have formed, mix up a little clay and water and patch the up nicely, and let it all dry again. If you have no cracks, congratulations! You just built a bucket forge! You may want to build a small fire of paper and sticks in it to bake the forge bowl, but don't get to gung ho, you are just trying to drive out more of the wetness in the clay, not build a fire that can be seen from space.
Lastly, you will need to find a few nice rocks to put in your pipe to keep the coal from falling down into the pipe. These are easy to come by along side gravel roads and some driveways. Try to steer clear of any rocks that have been in creeks or rivers, they could still contain water and explode or turn to powder under heat. We will cover how to use those rocks in our next installment, which will also cover putting air into your bucket forge.
That's all for now, stay out of trouble til next time.
Blacksmith basics - the forge
Blacksmith basics – the forge
This post will cover more specific details on the forge a blacksmith uses in their craft than our previous post “absolute basics” did. This resource will cover mostly coal forges, with gas forges covered in a later article. I will be leaving out the exotic and semi-exotic heating sources here, such as electric resistance heating systems and solar forges. These other systems are more specialized in their application and generally financially out of the reach for the average hobbyist smith. In later articles we will cover some simple variations of the modern and historical forges that can be built very inexpensively and in short order.
The forge is a place that the smith can contain and control a fire to heat metal up to working range, which is usually hotter than a normal camp fire. The term also often means the building the forge is located inside of, and the term “forging” is something made in a forge. Forgery is not the correct term for making something in a forge though... that would be smithing, which comes from smite; to strike something. You know... blacksmith, a smith who strikes iron, which comes from the ground and fire black, as opposed to gold or silver.
The history of metal smithing is a long and varied one, and forges have undergone many variations and changes over the passage of time. Originally, the forge was a simple hole dug into the ground, and a blowpipe was used to increase the heat of the fire. As time passed, the smiths decided that standing up was a lot more comfortable than crouching down to work in a ground forge, but a few clever smiths dug holes to stand in next to their ground forges, and in a few parts of the world these ground forges are still used today.
The next evolution was to make the forge a roughly waist high table, either of laid stone or brick. This allowed the air-blast to come into the forge from under the fire, instead of from the side or above, which increased efficiency and allowed the smith to get even greater temperatures from his fuel. There are variations during this long age, including forge tables built of wood and covered in clay, side blast forges and long trough forges. For simplicity sake, we will only cover the generic, basic forge here for now though and save the unusual ones for later.
In modern times, the forge is often built as a steel table with a heavy walled cast iron firebowl or firepot at the center of the table to contain the fire. This forge bowl is usually several inches deep and a bit more than a handspan across. This allows a decent amount of fuel to be used, yet is not wasteful. It also allows the solid sides to absorb and reflect some of the infrared heat back into the center of the fire, increasing efficiency.
In all ages, the area around the forge bowl is often used to hold extra fuel and lay out work pieces and tools. Careful fire management will keep the fire contained in the smaller, central pot so as to not waste fuel. Many smiths build special fittings into the table to aid their work. These can be tool racks, special dies for forming or bending, or workpiece supports for long rods of steel.
So why build a large, heavy table for a forge in this day and age? Forges are an efficient means of heating steel compared to other options, such as a simple torch with either a fuel air mix or a fuel-oxidizer mix. The fuel air torches are things like a propane plumbers torch which have only a single gas cylinder. A fuel-oxidizer system like a oxy-acetylene cutting torch, will have a pair of tanks. The problem with using either style of torch is the amount of lost heat that is simply blown into the room and not absorbed by the work piece. The amount of fuel used by either of these torches in medium to heavy blacksmith work will make them prohibitively expensive in short order.
That about covers the basics of the forge, now we need to look at the fuel, air input assembly and the hood or draft system to remove smoke and heat.
Historically, forges burned coal, charcoal or in some rare cases peat moss as fuel. Raw wood is generally not clean burning enough to be used as is, so it was usually rendered down into charcoal, which gave a better heat and was less troublesome. Today, coal is probably the most common, as the amount of charcoal one uses for even simple projects makes it somewhat cost prohibitive in comparison to a coal forge. Coal is somewhat uncommon these days, but not terribly hard to find, and we will cover resources for finding it later on in our article about fire building and management.
For a moment I would like to diverge here to discuss gas forges in passing, just so the reader will have a bit of familiarity with them until we reach that chapter.
Most modern gas forges are a box like object with a pipe or set of pipes on top, so they can easily be put in a number of places like the tail gate of a pickup truck for field work. A gas forge can be built into a table like a coal forge, or sit on a stand or mount at any convenient height for work in a shop. The forge box is lined with a fireproof refractory material, much more resistant to heat than common brick, and this makes these forges rather heavy for their size. The pipes that enter the top of the forge are gas jets, and have a system to mix fuel and air from the room together to produce a clean burning flame inside the forge box. Most gas forges are set up to run on propane, but any flammable gas that can be pressurized can be used (such as hydrogen, methane or natural gas). More on gas forges later though...
Once we have a forge and something to burn in it, we need to consider how to get that fire hotter than normal. This was originally done with a blowpipe. It works, but is pretty tedious and can make you quite light headed very quickly. So some clever smith came up with a way to build an automatic lung, which we today know of as a set of bellows. There were a number of improvements in bellows tech over the years, but in this modern age most smiths use a much smaller mechanical fan system. Heck, you can even use the output from a vacuum cleaner or a hair dryer, but both of these have interesting problems we wont cover here yet. Most of these systems have some way to control either how fast the fan turns or how much air it is allowed to push into the fire to better control the heat in the forge. Too hot can burn the steel and too cold will make many jobs much harder if not impossible.
This air system is connected to the underside of the forge with a section of fireproof pipe, and enters the bottom of the firepot through a specialized part of the bowl, usually called a tuyeer. (There are some variant spellings of this word.) Usually this section of the bowl also has a gate or some kind of door to allow the ash that falls out the bottom of the bowl to be cleared out.
Now that we have air in our forge, we have to do something with the smoke... that's where a stack and hood or some other system comes into play. Now if you are just outside, you can let the smoke drift away, but I have done this a lot, and I can tell you it will often drift right toward you (there really is a scientific reason too – you create turbulence in the air stream passing you, and the smoke can be pulled right to you even if you are up wind of the forge). Building a stack (or chimney) is a more complex process than it may at first look, but I will cover it in great detail later on, so do not fret. Connected to the stack is some kind of metal hood that collects and funnels the smoke, allowing it to leave the building through the stack. There are optimal ratios for the intake area vs the pipe size and stack height, and I will cover them in that article I just mentioned. For now, I just want you to be aware that most smiths use a steel hood over their forge, though some use what is called a sidedraft hood system. This is the system I prefer, and I will have a full article including pictures and plans up here soon as part of the aforementioned article.
That wraps up our lesson for today, and once we get past these most basic lessons we will begin to get into the real meat of it.
Until then, stay out of trouble.
The podcast for this will also be up at http://alonetone.com/ironangel under "albums and playlists - Blacksmith lessons".
This post will cover more specific details on the forge a blacksmith uses in their craft than our previous post “absolute basics” did. This resource will cover mostly coal forges, with gas forges covered in a later article. I will be leaving out the exotic and semi-exotic heating sources here, such as electric resistance heating systems and solar forges. These other systems are more specialized in their application and generally financially out of the reach for the average hobbyist smith. In later articles we will cover some simple variations of the modern and historical forges that can be built very inexpensively and in short order.
The forge is a place that the smith can contain and control a fire to heat metal up to working range, which is usually hotter than a normal camp fire. The term also often means the building the forge is located inside of, and the term “forging” is something made in a forge. Forgery is not the correct term for making something in a forge though... that would be smithing, which comes from smite; to strike something. You know... blacksmith, a smith who strikes iron, which comes from the ground and fire black, as opposed to gold or silver.
The history of metal smithing is a long and varied one, and forges have undergone many variations and changes over the passage of time. Originally, the forge was a simple hole dug into the ground, and a blowpipe was used to increase the heat of the fire. As time passed, the smiths decided that standing up was a lot more comfortable than crouching down to work in a ground forge, but a few clever smiths dug holes to stand in next to their ground forges, and in a few parts of the world these ground forges are still used today.
The next evolution was to make the forge a roughly waist high table, either of laid stone or brick. This allowed the air-blast to come into the forge from under the fire, instead of from the side or above, which increased efficiency and allowed the smith to get even greater temperatures from his fuel. There are variations during this long age, including forge tables built of wood and covered in clay, side blast forges and long trough forges. For simplicity sake, we will only cover the generic, basic forge here for now though and save the unusual ones for later.
In modern times, the forge is often built as a steel table with a heavy walled cast iron firebowl or firepot at the center of the table to contain the fire. This forge bowl is usually several inches deep and a bit more than a handspan across. This allows a decent amount of fuel to be used, yet is not wasteful. It also allows the solid sides to absorb and reflect some of the infrared heat back into the center of the fire, increasing efficiency.
In all ages, the area around the forge bowl is often used to hold extra fuel and lay out work pieces and tools. Careful fire management will keep the fire contained in the smaller, central pot so as to not waste fuel. Many smiths build special fittings into the table to aid their work. These can be tool racks, special dies for forming or bending, or workpiece supports for long rods of steel.
So why build a large, heavy table for a forge in this day and age? Forges are an efficient means of heating steel compared to other options, such as a simple torch with either a fuel air mix or a fuel-oxidizer mix. The fuel air torches are things like a propane plumbers torch which have only a single gas cylinder. A fuel-oxidizer system like a oxy-acetylene cutting torch, will have a pair of tanks. The problem with using either style of torch is the amount of lost heat that is simply blown into the room and not absorbed by the work piece. The amount of fuel used by either of these torches in medium to heavy blacksmith work will make them prohibitively expensive in short order.
That about covers the basics of the forge, now we need to look at the fuel, air input assembly and the hood or draft system to remove smoke and heat.
Historically, forges burned coal, charcoal or in some rare cases peat moss as fuel. Raw wood is generally not clean burning enough to be used as is, so it was usually rendered down into charcoal, which gave a better heat and was less troublesome. Today, coal is probably the most common, as the amount of charcoal one uses for even simple projects makes it somewhat cost prohibitive in comparison to a coal forge. Coal is somewhat uncommon these days, but not terribly hard to find, and we will cover resources for finding it later on in our article about fire building and management.
For a moment I would like to diverge here to discuss gas forges in passing, just so the reader will have a bit of familiarity with them until we reach that chapter.
Most modern gas forges are a box like object with a pipe or set of pipes on top, so they can easily be put in a number of places like the tail gate of a pickup truck for field work. A gas forge can be built into a table like a coal forge, or sit on a stand or mount at any convenient height for work in a shop. The forge box is lined with a fireproof refractory material, much more resistant to heat than common brick, and this makes these forges rather heavy for their size. The pipes that enter the top of the forge are gas jets, and have a system to mix fuel and air from the room together to produce a clean burning flame inside the forge box. Most gas forges are set up to run on propane, but any flammable gas that can be pressurized can be used (such as hydrogen, methane or natural gas). More on gas forges later though...
Once we have a forge and something to burn in it, we need to consider how to get that fire hotter than normal. This was originally done with a blowpipe. It works, but is pretty tedious and can make you quite light headed very quickly. So some clever smith came up with a way to build an automatic lung, which we today know of as a set of bellows. There were a number of improvements in bellows tech over the years, but in this modern age most smiths use a much smaller mechanical fan system. Heck, you can even use the output from a vacuum cleaner or a hair dryer, but both of these have interesting problems we wont cover here yet. Most of these systems have some way to control either how fast the fan turns or how much air it is allowed to push into the fire to better control the heat in the forge. Too hot can burn the steel and too cold will make many jobs much harder if not impossible.
This air system is connected to the underside of the forge with a section of fireproof pipe, and enters the bottom of the firepot through a specialized part of the bowl, usually called a tuyeer. (There are some variant spellings of this word.) Usually this section of the bowl also has a gate or some kind of door to allow the ash that falls out the bottom of the bowl to be cleared out.
Now that we have air in our forge, we have to do something with the smoke... that's where a stack and hood or some other system comes into play. Now if you are just outside, you can let the smoke drift away, but I have done this a lot, and I can tell you it will often drift right toward you (there really is a scientific reason too – you create turbulence in the air stream passing you, and the smoke can be pulled right to you even if you are up wind of the forge). Building a stack (or chimney) is a more complex process than it may at first look, but I will cover it in great detail later on, so do not fret. Connected to the stack is some kind of metal hood that collects and funnels the smoke, allowing it to leave the building through the stack. There are optimal ratios for the intake area vs the pipe size and stack height, and I will cover them in that article I just mentioned. For now, I just want you to be aware that most smiths use a steel hood over their forge, though some use what is called a sidedraft hood system. This is the system I prefer, and I will have a full article including pictures and plans up here soon as part of the aforementioned article.
That wraps up our lesson for today, and once we get past these most basic lessons we will begin to get into the real meat of it.
Until then, stay out of trouble.
The podcast for this will also be up at http://alonetone.com/ironangel under "albums and playlists - Blacksmith lessons".
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