The construction of machines and devices requires that sections of material be attached to each other. This can be accomplished by friction, adhesives, mechanical connections, and welding.
Down-time fastening methods were mostly mechanical. That is the methods depended on adhesion (stuff sticking together) created by means of a device compressing the parts together. Screws, rivets, nuts and bolts, trunnels (tree nails), pegs, lashings, glues, and gravity were all used to hold stuff together. All of the fastening methods described are composed of layers, and so have some inherent weaknesses. While suitable for most construction, the methods described do not provide the strength needed for many things our up-timers want to make.
Of all of the fastening methods described, rivets and glues come closest to being able to provide the strength to weight connections needed.
Rivets involve making a hole through the two (or more) parts to be joined and putting a pin through the holes. Then the ends of the pin are hammered down to form a mushroom shaped head on each side of the parts. This compresses the parts together and holds them firmly in place. Well done riveting can make seams that will hold pressure (as in a boiler), or stand up to great stress. Rivets have problems where the demands of the connection do not allow room for the mechanical process of riveting or space for the rivet heads in the finished application. Countersunk rivets (cone shaped depressions in the plates to be riveted) allow rivets that are flush to the surface, but reduce the strength of the join, thus increasing the number of rivets in the seam or requiring the increase in thickness of the parts.
Glues can form very strong joints, but require that the material glued be porous. Often this limits the utility of the method. Soldering and brazing are a form of gluing, and were known before the ROF, but due to limitations in heating methods were used mostly in smaller applications. Brazing and soldering also need pores in the material connected and can shear under stress or heat.
Welding is the connection of two parts by actually mixing the metal of the two parts so that they form one continuous piece. Welding is also normally done to ferric (iron based) metals. Non ferrous welding is possible but requires care due to the tendency of the metals to oxidize before the parts can be joined into one piece. Welding also allows the rapid fabrication of devices in a fraction of the time needed to make the devices by other methods.
Welding can be accomplished in a number of ways. Down-time welding was most often forge or percussion welding. This weld is made by heating the two pieces until they are soft and plastic, placing flux on them, putting them one on the other and applying force, hammer blows or pressure, causing the metal to fuse into one piece. This is also called hammer welding and can be done manually or by a forging machine like a drop hammer. The flux is usually sand or borax and serves to exclude oxygen and oxides from the join. Hammer welding is most effective with low carbon steels and iron. High carbon steel requires much higher temperatures and this makes the exclusion of oxides harder. Hammer welding is a skill well known by the smithing community of the 1600s and even high carbon steels are with in the ability of a master smith. The greatest limitation of hammer welding is the amount of heat that needs to be applied. Normally the heating time possible with a forge fire means that larger pieces have to be heated over larger areas than are required for just the weld. This slow heating increases the fuel consumed and also increases the difficulty in handling the work.
New to the down-time world are gas, electrical, and chemical welding. Gas welding is accomplished with a torch burning a fuel and an oxidizer, normally acetylene and oxygen. The torch is used to apply heat directly to the point to be welded and cause the material to liquefy and flow together. Often a rod of the same metal is used to control the heat and provide additional material for joining the gap between the two pieces to be fused. Gas welding markedly decreases the amount of time needed to heat a join to welding temperature. Also a weld created with the gas method does not need percussion applied to fuse the metals. However welds heated by a gas torch can run into the same problem, heat traveling, and requiring the heat of large areas before welding heat is available to the join in large pieces.
While at first glance a new gas welding set would seem to be outside of the industrial base available down-time, careful consideration brings to light workarounds that will allow the technology to spread. Hoses can be made from leather tubes wrapped in latex-impregnated cloth with an outside leather case protecting the cloth. The latex is locally available as milkweed sap or dandelion sap and while it is not as pure as rubber tree sap, it was used during WWII as a substitute until the synthetic rubber industry came on line. Gas regulating valves also looked very difficult, but I “bit the bullet” and tore one of my old regulator sets down to see how they were made. To my surprise they are not complicated, and the hardest parts to make will be a large spring that holds the diaphragm against the valve that controls the pressure released from the storage device. The valve bodies are made of brass and the spring and diaphragm can both be made by any smith that can make a knife that will hold an edge. Storage is a little harder as down-time produced tanks are likely to be more cumbersome, probably riveted and seal welded on the seams. All in all, a down-time set will be larger, not as long lasting, but will be possible. That leaves the gas. Welding gasses, normally acetylene and oxygen, need to be produced in quantity. Both will need electric current, oxygen produced by electrolysis, and the acetylene produced by adding water to calcium carbide. The calcium carbide is also produced by applying an electric arc to coke (refined coal not the drink) and limestone. While not explicitly canon, production of calcium carbide is implied in the operation of the mines in Grantville as “carbide lamps” were the industry standard prior to long duration batteries, and I am sure that as the high tech bulbs burn out, that old lamp of dad or grandpa’s will come out of storage.
Electric welding uses a high current electric spark to create the heat needed to fuse the metal and form the joint. Of note, is that the electrode is normally sacrificial and is used to add metal to the joint created. This current may be AC or DC and can be provided by batteries or by a generator set. Variations on “stick” welding include wire-fed inert gas shielded welding where the electrode is a wire fed through the welding handle and is shielded from oxidization by an inert gas fed to the weld site from a tank connected to the “stinger”. Also of note, is that electric welding is an immediate heat in a small area and can be used to weld large sections of material with minimal heat.
The major problems with electrical welding are the need for insulating the cables used and providing flux on the electrodes (welding rods). Lastly because electrical welding heats such a limited area, crystallization of the metal can occur. This can be avoided by experience on the part of the person welding and by annealing the joins made.
Other forms of electrical welding include Spot welding and Roller Seam welding. Spot welders are normally stationary machines with two electrodes mounted on parallel arms. The material to be welded is placed between the electrodes and high current is passed through the material via the electrodes causing the metals to melt into each other. As a welding method it is really fast, and lends itself to sheet metal fabrication especially well. Roller Seam welders are a variation of the spot welder where the material to be welded is placed between roller tipped electrodes and moved so as to continuously weld a seam. A variation of the roller seam welder has the rollers on each side of a seam in a pipe or tube as it comes out of the rolling mill to make sealed seam pipe.
Of all the methods, electrical is probably the easiest to make from scratch. Large batteries can provide the amperage needed to strike an arc and weld. The electrodes can be made from drawn wire. Flux can be applied at the work site by dipping the rod in a bucket of borax and allowing it to dry. The biggest problem will be insulating the cables and the clamp that hold the electrode. After that will be charging the batteries. Insulation is probably possible using dry linen and latex or wax, wrapped in dry leather. The clamps can be fabricated with ceramic handles containing the cable and clamp. Good welds can be made with as little as fifty amperes, or about the capacity of an automotive battery. Heavier joins on large metal will need more amperage. Lead acid batteries can be made with 1600s technology. Glass cases and bronze supports for the plates with sulfuric acid are sufficient to the work. Note that thick glass is harder to break and makes a safer battery. Chargers can be operated by a water wheel or small engine. The system will be bulky, and awkward to use, but will weld like a charm.
Thermite welding is perhaps one of the least known and potentially most useful forms of joining metals. The process is achieved by making a mix of aluminum and iron oxide powder. This mix, oddly enough called thermite, is placed in a container above the metals to be joined, and ignited. Use black powder or potassium permanganate and glycerin. The aluminum during the reaction pulls the oxygen from the iron oxide leaving the iron to flow into the mold around the pieces to be joined. The mix can be “salted” with a number of ingredients to provide the exact grade of steel or iron desired. This was the preferred way to repair large items. These could be anything, like a broken locomotive frame. It can be thermite welded and be restored to full function.
The greatest problem is the powdered aluminum supply, as a limited amount will be available right after the ROF. It is possible to rework the aluminum oxide to aluminum with electricity and heat processing.
Personal protection is another consideration. All welding demands some form of vision protection. Hammer welding is the least damaging to sight and electrical welding is the most damaging. Face-covering helmets with smoked or tinted glass windows are used to protect from spatter and intense light. Leathers are used to protect the body and arms, while gloves are used to protect the hands. Gas welds can often be made with tinted goggles only, and provide sufficient protection for the eyes.
Now we come to the Grantville connection. Who in town knows how to weld? How many sets of welders are sitting around? What does Grantville do when the up-time supplies run out? I have never lived in Mannington, and so am falling back on the town my mother is from. It is a small community in Idaho of some 1800 inhabitants, it has a grain elevator on the UP main line, a small downtown area, a garage, a used car dealership and a Co-Op. Most of the local farmers come into town to shop and resupply as needed, forming most of the economy of the region. Welding is considered a skill essential to the rural life style. Almost every male in town (and most of the ladies too) over the age of twelve can at least stick stuff together. Complex jobs tend to get passed off to a friend who has a better hand.
In Grantville the “good hands” are relatively common, at least four or more at the mine, about the same at the power plant, one or two at each machine shop, and the instructors at the Vo-Tec. Of note is that the Vo-Tec has a comprehensive instruction set up and should be able to pass on welding knowledge with no major problems. The majority of households have an arc welding set with a mask and a box of rods in the old fridge in the garage. Gas sets are a little less common with one household in three having one. Before the ROF, when tanks had to be filled, one would need a trip to the “City”.
Most of the sets are of home quality (think Harbor Freight,or cheap-stuff-from-China grade). Industrial grade sets are more limited, with appropriate businesses having one or two sets each, and the high school having three or four sets for instruction. This adds up to around 200 to 250 arc sets and maybe seventy-five gas setups of secondary quality, leaving fifteen to twenty sets of industrial grade equipment in town. Grantville has a power plant, a mine, and three or four machine shops, so add maybe twenty-five more industrial sets giving forty to forty-five sets of the good stuff (arc and gas) and a whole lot of lighter weight stuff sitting around.
Welding supplies will take a dive after six months to a year, even if there is a welding supply house in town, and arc welders will be down to hand-drawn rod coated with glued-on sand or borax. Specialty rod (like stainless steel rod and high-carbon steel rod) will be hoarded. Gas will run out in a year or so and those sets will be unusable until the calcium carbide works are in operation, and some one is producing oxygen, either by electric means or by pressure distillation. If I had to predict, I would imagine that initially gas will be produced by generators on site, for acetylene, and by large low pressure cylinders, for oxygen. As the steel industry develops, forged steel high pressure tanks will become available for oxygen storage, and acetone will be available to provide higher concentrations (pressures) of acetylene. The acetone is needed as acetylene compressed to more than 15 psi will self ignite in the same way that diesel ignites under compression.
In summary, welding is available for Grantville in the short term (twelve to sixteen months), and is still possible after that time as supplies become more and more common. Dissemination of welding knowledge will happen as fast as the down-time community becomes aware of it. Just the knowledge of the possibility will cause the rapid development of the technology outside of the local Grantville area.
Machinery’s Handbook 11th ed pp.1546-1566 by Erik Oberg and F. D. Jones. The Industrial Press, New York. Copyright 1942.
Manual of Formulas: Recipes, Methods & Secret Processes. Edited by Raymond B. Wailes, B.S. Popular Science Publishing Company, Inc. Copyright 1932