The Operation and Maintenance of a Traditional Wooden Water Wheel
There are two basic schools of thought on how to start a water mill. The one method is to start the mill with the millstones together and then open the control gate letting the water flow from the sluice box over the chute and onto the water wheel. Once you hear the water crashing over filling the buckets you gently lift the runner stone that will cause the millstone, gears (belting), and water wheel to turn. Once the millstone seems like it is up to operating speed you then tenter the millstones. The other method of starting the mills is to have the runner stone raised at the full height of its linkage. Then you open the control gate letting the water flow from the sluice box over the chute and onto the water wheel. The water wheel will begin to turn when the weight over takes the balance of the water wheel. When the millstone begins to pick up speed you then gently lower the runner millstone to tenter the two stones. Both methods work equally as well. The main object is not to over speed the gearing and cause harm to it. Another concern is not to allow a huge accumulation of unground grain to accumulate between the two millstones. Then they will have to work through that amount of grain before the millstones they can be properly tentered. If the millstones were cleaned out the last time the mill operated (between the stones and around the cribbing under the vat) the millstones will have to grind about 25 pounds (depending upon the diameter of the millstones) before meal (chop) is flowing at its normal rate down the chute. At with many things there are also two basic schools of thought on how to stop a water mill. One method is to simply close the control gate of the water wheel and gently allow the entire mill to stop. The mill will basically stop in mid grind or it will grind to a halt. This means there is still grain in various stages of being ground between the millstones and there still may be water in the wheel. The problem with this method is the fact that there still may be water in the buckets of the water wheel, and if the runner stone is lifted up with the millstone crane to clean between then you would be in for a sudden terrifying surprise once you slightly lifted the runner stone. The other method involves closing the control gate as you slowly raise the runner stone. The motion of the mill and the millstones will continue until all of the water is exited the water wheel and the balance of the water wheel is once again equalized. The problem with the second method is that if someone, something is caught in the machinery, or there is a problem with the mill, it will continue to turn for several minutes causing in some cases more harm or damage. The third method of quickly stopping the mill could be employed. This involves taking a handful of grain from the shoe and quickly pushing it into the eye of the millstones. This will begin to choke down the millstones like an automobile gets too much gas and stalls. Once the millstones have begun to choke down you then lower the runner stone onto the accumulated bed of grain that now lies between the two millstones. The weight of the two millstones becomes one and over takes the weight of the water flowing onto the water wheel. This acts as an emergency brake. Since water mills do not have brakes like wind mills. The problem with this method is that it puts strain on the gears. If the gear teeth are worn too thin they may break like match sticks, but if someone is caught in the machinery you take that risk. To start the mill again just simply raise the runner millstone until the system starts moving again until it gets back up to speed and then gradually work through the extra grain and then tenter the millstones. This method generally does not work for millstones that are belt driven, they leather belt with snap or jump off of the pulleys. If you constantly have to tenter the millstones, then something is out of whack. This usually means the millstones need to be leveled and balanced. The millstones once properly tentered should stay that way and grind constantly all day unless one of the other factors are changed. A mill is like a machine in a machine shop. You have "speed," the flow of water more or less. The more speed or water this would mean the faster the mill should go and then grind more grain. Then you have "feed," this is the flow of grain into the millstones, more or less. Then you have "cut," this is the distance between the millstones that regulate the grinding of the millstones. The closer the millstone the finer the grind and the farther apart the millstones the coarser the grind. The miller or the mill operator determines the settings for how much he wants to grind and what type of product he wants to produce. He may want to grind 50 pounds in 10 minutes. or if he was demonstrating the process of milling to the public then the may want to adjust the mill to grind that 50 pounds in an hour or more. The factor that compounds this is how much moisture is in the grain. Too much or too little and the grain won't grind or bolt properly. It is much easier for the miller to add more moisture to temper and condition the wheat than to eliminate moisture from the grain. This then arises the problem with grinding grains in the United Kingdom, it is too damp there most of the time and it makes it difficult to grind and bolt meal. One solution is to mix grain with the opposite amount of moisture together and then grind them together. One time of wheat that may have too much moisture may be soft wheat mixed with hard wheat which tends to be too dry, once mixed together in equal amounts produces all-purpose flour. Another important issue facing many restored mills is "to idle," or "not to idle." In other words it could be taken to mean, "to die a slow death," or "live to grind another day." In many grist mills open to the public they cannot operate continuously like a real mill, so many have taken to idling the water wheel when not grinding to show some motion of the machinery. The average traditional wooden water wheel weights 4 thousand pounds (you add water and moisture then it can weigh up to 10 thousand pounds), and that water wheel is mean or designed to be pulling about the equal weight inside of the mill. If the water wheel is allowed to turn with out the load and the process of grinding, then the water wheel will use is energy to destroy itself. A water wheel is designed for one propose to grind grain. If it is not used for that propose then the energy it creates will be used to slowly destroy itself over time. Some historic mills I have observed the policy that they idle the water wheel with the runner millstone raised on the spindle. Never raise the millstones and idle the water wheel in this manor. This is not a good policy or activity. The entire weight of the upper runner millstone is on the bottom millstone spindle bearing. This bearing is not meant to take the weight of the millstone and it will die within about a year or less. When the millstones are grinding grain the weight of the upper millstone is transferred to the action of grinding. The turning millstone is floating on a moving sheet of grain and there is no weight upon the bottom bearing. The millstone spindle bearing of properly cared for (kept fill of oil, clean of debris such as wood chips and metal shavings) if the babbitting is good there is no reason it should not last over a hundred years or more. Also with no grain flowing into a turning millstones this invites a visitor to toss something in between the millstones when he is not looking like metal coins. This could severely damage the millstones, create sparks which could blow up the mill or cause the runner millstone to jump the spindle.
This one was rebuilt by the foundry in Fredrick, Maryland, after one installed originally by the Fitz Water Wheel Companies restoration of Peirce Mill during the 1930's. The bearing mounts in the center of the water wheel on a shelf underneath the water wheel and on the inboard side of the mill wall. Behind the bearing is one half of the main vertical bearing that mounts on a cross beam just above the great spur wheel. Inside of the bearing journal is a coupling where the basment shaft is coupled to the shaft on the first floor. The same sort of coupling is inside of the journals bearing on the second and attic floors. A traditional wooden water wheel has two bearings, the outside or "outboard" bearing and the one inside of the mill, the "inboard" bearing. The inboard bearing usually give no problems even if it is flooded by the stream once and a while. It is the outboard is the one that offers problems because it is exposed to more wetting by the water wheel. The wall behind the water wheel or its wet shadow should be either stone or covered with waterproof material such as tin sheeting. Because of the turning motion and the weight of the water wheel the water wheel wants to turn in one direction, and because of the weight or the resistance effect of the grinding machinery, it wants to drag backwards. This sometimes causes strains in the center of the water wheel shaft in about the location of where it passes through the wall of the mill. This problems can be helped by building a water wheel shaft carriage bearing. An iron band is wedged in place above the bearing around the water wheel shaft and made to run on three rollers at three separate points. For a drawing of this bearing see my drawings of the water wheel. A welding shop can easily fabricate one of these bearings. The roller bearings should be made adjustable so they can be made to move in and out so they make contact with the iron band around the water wheel shaft. The three bearings can be easily aligned and should be heavily greased. Another band outside of the wall is sometimes helpful to stop the flow of water along the shaft and damaging this bearing. The minute one of the rollers lock up it means trouble, but if properly cared for it will gives years of service. A metal water wheel can have problems and its shafts can become twisted also. A wooden and even a metal water wheel can suffer from balance problems. Some have said that millwrights would design a mill so the water wheel would be on the side of the building that faces the moving path of the sun. Why? So during the winter months the sun would melt the ice buildup on the water wheel. If a water wheel is allowed to stand in the sun, the sun will try out the side and faces the sun while the part that remains in shadow remains water logged. This will cause the water wheel to become out of balance by several thousand pounds. To lessen this effect of the sun a water line can be placed under the sluice box and chute with a series of holes to allow a sprays of water to cover the water wheel. This is a good practice for the summer months but should be shut off during the winter months at about the same times as when ice would form on puddles around the mill. If a water wheel becomes out of balance by the sun it should be locked down in place by the weight of the two millstones together and run water over the dry side of the water wheel until the wheel becomes equalized. A metal water wheel has to be balanced like an automobile tire with the adding of metal weights. If water is directed upon a water wheel not in the direction the water wheel rotates a phenomenon will develop known as "shock" which will retard and in many cases the water wheel to stop from turning especially with a water wheels that is out of balance. Generally only wooden water wheels suffer for being out of balance but rebuilt metal wheels sometimes also have this problem. The balance of the water wheel will greatly effect if ability of the wheel to rotate properly. An out of balance water wheel will not rotate properly and cause more strain on the gears. If shock is effecting a wooden water wheel it will sit there for hours without turning unless it is given a "kick" start. An out of balance water wheel will slow in its rotation when it reaches an imbalance point. When you stop the mill you can also see that the water wheel may be out of balance wheel with out an internal load will sometimes it may begin to turn backwards and seesaw back and forth until it stops with the heavy end of the water wheel downward. This can also create a problem when pulling one millstone out of gear to engage another one. A simple solution is to engage the other millstone (with the two stones together) before disengaging the first one so you always have the weight of one pair of millstones stopping the out of balance from turning the wheel wildly. An out of balance water wheel will cause strain on the bearing, gear teeth and gear faces, and become hazardous when pulling stone nut gears out of mesh or lifting the runner stone for dressing. Ice build up on a wooden water wheel can create operation problems in the winter months. I have operated a traditional wooden water wheel through many a winter with no ice buildup. Some winters I have operated a water wheel with an even coating of ice with no problems while other winters the ice has prevented me from operating the water wheel for months. When the water wheel becomes covered in ice the trick is to test it first (like during the summer months) find a place that you can turn the water wheel to check it for balance. If the wheel is in balance operate you can operate the mill. You know that the wheel is in balance when you turn it and stop the wheel it will not continue to turn in either direction. If a wheel is out of balance the thing to do is lock it down with the weight of the millstones and run water over the water wheel. This is the best means of removing ice buildup on a water wheel is to run ice over the wheel. An ax, pick, and other tools can damage the wood of the water wheel besides where you are standing may be covered with ice there is an additional danger factor. Not to mention standing of ladders propped against the water wheel or siting on an ice covered surface. Too much water in the stream can be a bad thing when the stream floods. The first parts effected seem to be the rising waters in the tail race. If a mill is operated regularly the mud and silt should be kept flushed out of the tail race. It may be helpful to have a screen or trash rack across the mouth of the tail race to prevent floating debris from coming back up the tail race and damage the water wheel. I have operated a wooden water wheel with the lower one third of the water wheel covered with back water. You can hear the sounds of water being sucked and trapped in the buckets. The water wheel will reach the point that you can not put enough water onto the wheel to make it turn. The best policy is not to operate the water wheel when the stream is flooding to keep silt and small debris from damaging the water wheel. Operating a wheel in back water you can suck in logs into the wheel and damage and destroy the buckets. Also not to mention loosing loose bucket fronts in the rising water. An overshot water wheel suffers more from the problem of back water because it is turning in an opposite direction to that of the rising water against the wheel. A breast water wheel has much less problems because it is turning in the same direction as the water is moving out of the water wheel. One solution is to vent your water wheel. A metal water wheel will have holes in the buckets to vent out air or allow all of the water to drain out of of the wheel when it is stopped. A wooden water wheel may sometimes have round holes with leather flaps that open and close to allow air to escape when the buckets are filling.
Every day the mill is operated the inboard and outboard bearings should be lubricated along with the wooden gears mounted on the inboard end of the shaft in the mill's basement. Hey it is a wooden water wheel, once built nothing should be done with it until it needs replacement? Wrong assumption. A wooden water wheel needs regular maintenance to increase its life time. The average wooden water wheel will last 10 to 20 years and possibly 30 years or more. To keep a water wheel in long years of service means that it should be regularly maintained. This means crawling into the water wheel to check the wedges that hold the arms tight in the water wheel. As the water wheel rotates a water wheel will tends to pull itself out of round. This will in time cause the arms of the water wheel to become loose and move in and out of their sockets. The wedges should be regularly checked and tightened. If the water wheel wedges become split or water logged they should be replaced with new wedges. A wooden pounding block should be used to pound in the wedges and directly by the head of a hammer. The bolts that hold the sandwich sections of the cant and rim boards should be tightened. The rods that pass through one side to the other side should be replace when rusted and broken. It these rods suddenly begin to break on their own they you know you have movement in the wheel. The rim plate or shroud plate the outer covering of the sandwiched sections of the felloe, cant and shroud boards should be kept in place and tight. A piece of either wooden or metal plate molding that cover the outer edges to protect the wood and its layers from damage by water and ice. This covering is either screwed down or bolted down tight against the circumference of both rims of the water wheel. This covering also keeps the front bucket board in place. The bucket boards should be kept nailed down and square nails work best (if driven in the proper direction) to prevent the wood from splitting. The old saying goes something like: "The old wheels creak the most," but they don't have to. When a water wheel starts making a creaking sounds this means that there is something wrong with the wheel and it is trying to tell you something, "like fix me." The water wheel that creaks the most is the one that is not properly maintained, and age has nothing to do with it. I worked in one mill where when I began working there I picked up a bushel basket of wedges from the gear pit in the mills basement. The old miller just was not able to climb down and pick up wedges. It was easier for him to constantly add now ones. Wedges and bucket boards that fall out of a water wheel tend to get carried down stream by the tail water and disappear. You need to put on your coveralls and climb into the water wheel if need be. Always lock down the machinery with the millstones. A board or planks can be placed on one side of the arms if a platform needs to be created. The bearings should be regularly maintained and the shaft of the water wheel should be checked once and a while to check it for level and trueness. If you have to lift or move a water wheel shaft a hydraulic jack should be used with a piston separate from the pump crank by a long hose. This will save lives and limbs if the jack pumping action does not take place under the heavy shaft in case if falls. If you buy a mill or go to work in a mill this should be one of your first purchases and the second should be a grease gun. The first thing you should check is the condition of the millstone crane. This means take off the iron hardware and walk the crane out of its foot pad and head plate and check the crane's top and bottom post pins for rot. A water wheel really needs less maintenance and attention than other parts of the mill but that does not mean it should be ignored. The water wheel should be locked down at night to prevent turning. As soon as you go home people and kids will come along and climb into the inside of the water wheel or onto the buckets to have their picture taken. Signs and fences don't really matter if someone is hurt, killed or injured this will lead to a court case. The best preventive means is to lock down the water wheel when it is not turning operating the mill. If you let a water wheel turn or idle during the time in which the mill is closed people will come along and stick boards into the turning wheel just to see what would happen. If you spend 50 or 100 thousand dollars on car you don't let it sit there with the doors unlocked and the key in the ignition to let someone go out and wreck it and get killed. There is a lot of power behind water and it does not discriminate between grinding grain or grinding up people. Inspect the shaft, water wheel and attached master or greater face gear from time to time. If you see mold growing on the wood that means the roots of the mold on the surfaces is effecting the wood you do not see. A pocket knife is a good tool to check the condition of the wood. Open the knife and try and stick the point of the blade into the wood. If it sinks in the the wood like butter you have problems with the condition of the wood. Also watch for water running out of cracks in the shaft and socket openings for the greater face gear. If you have water coming out that means you have rot on the interior of the water wheel shaft. Wooden water wheel shafts can presents some interesting problems but a wooden water wheel bolted down to an iron hub on an iron shaft will present even greater problems. Wood is a living and breathing thing. It does not matter that is no longer a tree. It is still a living thing and effected by the seasonal and climatic conditions or changes. You may not have a calendar or date book the mill will tell you when the calendar changes and it becomes winter or spring. There are some times of the year that every time you turn around the wedges are always falling out of gears and arms on shafts, and there are other times of the year that (the wood is so swelled up) the wedges could not be pulled out if your life depends upon it. I should mention water wheel shaft gudgeons. Their installation is discussed on another page, "The Construction of a Wooden Water Wheel." If the gudgeons were not installed properly they will cause you to have maintenance problems before too long. They should be inspected. Gudgeons should be installed with the wedges pounded in a saw cut one inch way from the saw cut made for the wings of the gudgeons. This will then press the wood of the shaft tight against the wings and hold the gudgeon in place. Problems arise when the gudgeons and there wedges are placed in the same slot. The wedges become water logged and they will slide across the metal plate surface of the wing of the gudgeon. I have seen where people have mistaken installed gudgeons incorrectly, had problems with them, and then added a metal plate in the slot with the wedges and wings. Once the wedges become wet or water logged it will act as a roller sliding between the two metal surfaces and the gudgeon will come out for sure. I should say something about wood preservatives. On one of my many mill trips with the late Charles Howell we came across an old wooden overshot water wheel inside of an old mill in Perry County, Pennsylvania. The reason that the old water wheel was in a perfect state of preservations was (1) it was located inside of the mill structure, (2) it was not in contact with the water, (3) and the water wheel had not been used in decades. Later on the same trip we saw an good example of how not to build a water wheel. We came across a wooden water wheel that was built on a Fitz Water Wheel shaft and hubs. The wood was pressure treated (green) lumber. One of the warnings on the label is that the wood should "Never be in contact with water, used on docks, and it is extremely harmful to aquatic life." On another trip later I saw a sluice box that had been also rebuilt with green pressure treated lumber. Don't they realize that the wood is treated with arsenic. That is why they say don't paint it for so many years for the arsenic fumes to be given off. If anyone has ever worked with green lumber they should know that it is a poor grade of fast growing timber with poor quality to the structure of the wood grain. There are a number of wood preservatives that are on the market (that has been approved by the environmental protection agency) that is not harmful to aquatic life. They are available in 5 gallon to 55 gallon drums. "Raw" linseed oil can be used as a wood preservative on water wheels but it does not seem to be long lasting. It needs to be retreated from time to time. It does give off a sheen the first time it becomes in contact with water after the treatment. Maintenance of the water wheel and regular usage is perhaps the best way to preserve a wooden water wheel.
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