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The Construction of a Wooden Water Wheel

The Construction of a Wooden Water Wheel
Theodore R. Hazen

Please Note: Today (Monday, 22, April 2002) I had a main storage drive crash. I had over 900 MB of stuff, and was the last back up for my computer that crashed last October. I lost the only copy of every mill and related mill site (that I have ever visited on the internet with all of the text and images); scanned images and artwork; HABS-HAER mill files; 30 years of manuscripts, writing projects and restoration reports; future web page material and business records. The follow is a "draft only copy" of the original intended article. When I recover from loosing heart and hating computer technology a bit less, perhaps I may issue a revised "final edition copy" with intended images and artwork. Thank you, T. R. Hazen.

The Construction of a Wooden Water Wheel

First of all to construct a wooden water wheel you need to make a set of plans. But before you can go out and order lumber and begin cutting out the various pieces, you need to draw out a section of it full size. One section from one arm to another arm, and then make sure that when you cut out all of the pieces they fit together all the way around and form a perfect circle. All of the pieces fit together and all of the angles are cut properly. This way you will finally know for sure how wide of a board you will need to cut the curved sections of the water wheel. You will also need to plan into your lumber order a percentage of loss due to warping and splitting.

The tools you need to build a water wheel are basic: a wide surface planer (planning machine), a band saw (with a wide neck or throat), a table saw, router, hand saws, chisels, drill (hand or press), wrenches, and a tap and die set (to thread the ends of iron rods). Along with various minor tools that most people have. A lot of hand work is involved to construct the water wheel. You will then spend time cutting out all of the various parts. The wood should be completely seasoned to the point at which is will no longer dry and shrink any more. It it does you will then be in trouble. Remember you have to allow the shaft to be long enough inside the mill's basement to also accommodate the interlocking arms of the greater face gear. The arms of some greater face gears can be 12 to 18 inches wide. So that is several feet of slots and good wedging.

A chain saw and large heavy hand drill are needed to construct the water wheel shaft. This all takes years of planning in advance. You need to first find a larger diameter tree and cut it down. Then you need to remove the bark and band it at regular intervals. The type of metal shipping packing banding will do, and then store the tree off the ground and under cover or roof for about 7 years to season. A proper traditional millwrights yard would have a number of water wheel shafts in the process of seasoning. There is a formula for thickness or board feet to time to allow for proper air drying. The water wheel needs to be first constructed where your shop is located so you need to build two pilings to represent the water wheel columns that can hold the bearing journals. First you find the two opposite centers of the water wheel shaft. You layout the circle of the gudgeon pin center and the wings, and the wedge slots one inch away from the surface of the gudgeon wings (see drawings). Then you drill out the round center hole of the gudgeon pin. Once this is done you then cut out the two wings of the gudgeon and cut the wedge slots. Then you round only the outside if the ends of the shaft to a length that the gudgeon is seated into the shaft. This will allow two or three bands to be driven onto the shaft that holds the gudgeon in place. Many people make the mistake of placing wedges against the surface of the gudgeon in its wings slot. This is incorrect. Another cut should be made back into the wood one inch away from the wing slot on both side of each one of the four wings of the gudgeon. If the wings wedges are placed in the same slot of the wings when the wedges become water logged or begin to rot the gudgeon will slide out. The wedges will become water logged and the wet metal surface of the wings they will slide. The wedges should be only placed into the wood, this way it pushes the wood of the shaft against the surfaces of the wings. The iron bands are bolted into the end surface of the wings and into to the wood between the wings.

An Old Type of Small Diameter Wooden Water Wheel: Original Drawings & Plans Adopted from the Fitz Water Wheel Company.

Once the gudgeons are in place the shaft can be lifted up and sit in bearings on the temporary water wheel bearing columns. This way the shaft can be then rotated and the outer surface marked out to cut the shaft to its multiple sides. Once the shaft is cut to have 8 or however many surfaces the slots of the water wheel arms can be cut out. If the water wheel is to have 8 arms projecting out of the shaft, this means that two arms are the length of the diameter of the water wheel and are interlocked together within side of the shaft. So these two arm slots are wider than any other to allow the arms to pass each other and then come together within side of the shaft. These arms are wedged in place with wedges as wide as the arms (usually 3 inches) and a bit longer (30 inches for a 24 inch shaft) that the diameter of the water wheel shaft The remaining 4 arms are fitted into dead sockets. The dead socket holes in the direction that the water wheel will rotate is under cut with a bottom forward angle. This matches the angle cut of the same side of the end of the water wheel arm. So once the arm is place in the dead socket hole it is moved forward and the two angles match. The back surface is left at a 90 degree surface and the two opposite angles are held tightly in place by two wedges driven into the back side.

Then if the water wheel is to have 12 arms projecting out of the shaft, this means that three arms are the length of the diameter of the water wheel and are interlocked together within side of the shaft. So these two arm slots are wider than any other to allow the arms to pass each other and then come together within side of the shaft. This would mean then that 6 arms are wedged into dead holes between the ones that go all the way through the water wheel shaft.

I have known of one water wheel that was constructed with a iron shaft straight through the wooden shaft with gudgeons wings on each end. It keeps the gudgeons from coming out but none of the arms of the water wheel shaft can go through the water wheel for added strength. A traditional was water wheels were not constructed in that manner. Another new thing it the use of an all fiberglass shaft in place of the traditional wooden shaft. I am not sure what the long term effects of having fiberglass up against the wooden arms of the wheel would be. It would almost have to be build up as if it was reinforced concrete to take the weight of the wooden water logged wheel. I have seen all fiberglass (perhaps with some metal inside) that look like they are made out of real wood or a metal wheel. I guess as long as visitors would never touch the wheel no one world ever know. I always thought that the weight of the water wheel on the outside should be about equal to the weight of the machinery on the inside or you would end up with problems.

The ends of the water wheel arms have an "L" cut that faces inward to hold the rim and cant boards. It the water wheel has a center arm that one would then have a "U" square cut to hold the sandwich of cant, rim and cant boards. There are 3 holes drilled in the vertical part of the "L." The top hole holds a bolt, the center one holds a rod that goes all the way through to the other side of the water wheel and the bottom one holds another bolt. The bolts only hold the sandwich of the upper end of the arm, the rim and the cant boards together. The nut heads (and washers) of the two bolts and rod are on the outside of the water. Then there are 7 other bolts that hold the rim and cant boards together between the two arms. The nuts are located on the inside bucket compartment areas. The problem with this rust on the treads and nuts (and washers) if they need tightening you often have to cut them off and replace them. The rounded bolt heads are pulled into the wood on the outside and then covered with the felloe board plate nailed between the water wheel arms to cover the bolt heads. If the bolts and treads become rusted you can use a nut splitter or a cutting torch as long at the wheel is wet and dump water onto the area before the wood catches fire. The wheel catching afire should not be a real problem as long as it is water logged.

Various kinds of timber was used for the construction of wooden water wheels. Most water wheels were constructed entirely of white oak. Some water wheels had white oak shafts but arms, soling and buckets were made from other kinds of wood. Pine of only certain types was found to be fairly long lasting in some water wheels. Generally common grades of pine will only last for 2 years at the most in a wooden water wheel. Cypress is the best rot-resisting wood discovered for water wheel construction. Water wheel are exposed to water, ice, snow and sun. This along with the water wheels maintenance or lack of it contribute to shortened active life of the wood and repairs become a frequently necessary. In a period of five or ten years, almost every part of a wooden water wheel with the exception of the main shaft would have to be repaired or replaced. This would include things like wedges, bolts, rods, and some bucket boards.

The traditional material that was used for the shafts of water wheels is white oak. It is often made from the trunk of a single tree that holds the water wheel. A shaft for a grist mill was usually 18 to 24 inches in diameter that was dressed circular, polygonal, or square in form. This often becomes a job that will take many months of searching for the perhaps proper tree that would make a good water wheel shaft. It should be clear and straight from defects and branches often for a section of 20 to 30 feet. Once found the tree is cut down. The trunk is them moved to a place of storage. The bark of the tree should be removed to prevent bugs and worms for damaging the wood. The trunk should be banded tightly at close intervals and stored under cover from the elements and above ground. This process is part of a long term planning project of water wheel construction because it can take up to 7 years to season a single white oak trunk to make a water wheel shaft. It is also not uncommon for a new water wheel to be constructed and in operation for only several months when some hidden defect will cause the shaft to split and need replacement. This is why in a traditional millwright's yard there would be many white oak tree trunks lined up in rows seasoning with new ones always being added. Needless to say this becomes like a search for the National Christmas tree that you won't know for 7 years if it looks good decorated or not.

The wood of the water wheel constructed out of both seasoned white oak or cypress the material alone would be 5 to 10 thousand dollars. Then there is the 7 years it would take to season out the wooden water wheel shaft. The wooden water wheel would take about a month to make all of the wooden parts and construct the final water wheel. The final price tag for a wooden water wheel is 50 to 75 thousand dollars, and possibly as high as 125 thousand dollars or more. The same numbers would hold true for a similar metal type of water wheel. The reason for the numbers is the time and labor it cost to construct and build a water wheel.

The depth of the felloes, shroud or rim boards, and cants sometimes varied but usually it was from 9 to 15 inches wide. The problem is finding a wide enough board to be able to cut out the curve of the section. The arms of a water wheel usually is 3 inches thick by 6 inches wide. The bucket boards and drum boards are usually cut out of 1 inch thick boards. The spacing of the buckets around the drum is usually anywhere from 10.5 inches to 11.5 inches depending upon the circumference of the drum and the diameter of the water wheel. The spacing measurement is made form center board of were the bottom board meets the drum.

The drawings for a 10 1/2 foot diameter by 6 foot wide wooden water wheel. The only thing not really shown in the drawings is the rim or shroud plate. That is a 1 inch thick piece of wood that is wide enough to cover the section of the rim boards (the felloe, shroud or rim and the cant boards). This keeps out the water and ice from damaging the water wheel. In later mills this would have been bands of iron wrapped around and bolted the the rim boards. This plate also holds in the front bucket board.

The water wheel is made out of season white oak (only) and cypress can be used for the bucket boards. The finished diameter of the water wheel shaft is 2 feet or 24 inches. The arms are 3 inches by 6 inches. On each set of arms (2) arms are the length of the diameter of the water wheel and are wedged with wedges longer than the diameter of the water wheel. They go into larger slots so they can interlock inside of the shaft. The other four are called "starts," they are mortised into dead holes. The interlocking arms help take the torque of the turning wheel. The felloe boards are 1 inch wide. Shroud or rim boards are 2 1/2 half inches wide and the cant boards are the same thickness. The bearings are either wood, stone or brass inserts. The bearing blocks sit and are wedged into a 12 by 12. The bucket boards and the drum boards are 1 inch thick. The drum boards seams should be covered with batten. The buckets are spaced between 10.5 to 11.5 inches from center to center where the bottom board attaches to the drum boards. There is 48 buckets around the water wheel.

An Old Type of Small Diameter Wooden Water Wheel: 10 Feet in Diameter.

A used Fitz Water Wheel when sold at auction or in the trading post section of Old Mill News would usually sell for 3 to 4 thousand dollars. Generally it then costs 10 to 15 thousand dollars to have a welding shop rebuild the buckets and drum boards sections. There would be the cost of renting a crane to lift the water wheel out of place and the cost of moving the water wheel. Fitz Water Wheels can be lifted out of place with a crane.

The basic water wheel has the following parts: the hub, arms, shroud or rim board, felloe plate, and the collar or spine that would slide over a wooden water wheel shaft. To have a hub casting pattern made for this wheel it would cost 5 to 10 thousand dollars. The foundry casting two hubs of the wheel to be replace would be approximately 5 thousand dollars. A final cost for casting would only be determined when the weight final pattern casting is known. A replacement steel shaft would cost 700 to 900 dollars depending upon the length of the shaft used. Machine work to the ends of the shaft, cutting the key ways into the shaft, and the inside of the collars or spines, making proper thrust collars, bearings and babbitting would run approximately 2,500 to 5 thousand dollars.

One of the basic problems with wooden water wheels is that that anyone with basic carpenter skills or knowledge of woodworking somehow things they can constructed a wooden water wheel. I have seen at least one water wheel that was constructed by a farmer. The water wheel turned for many years but was only operated by a pump and a plastic pipe. The water wheel would have never been able to pull the load of the grinding machinery inside of the mill. It was a breast water wheel without the benefit of a breast or apron behind the water wheel. The plastic pipe was only directed to fill the buckets at the proper point. Over the years I have seen many of good water wheel that was constructed far short of the traditional millwright construction. For want of a better classification for them they appear to be like the "garden" variety of water wheel.

I have known many who just don't seem to understand the proper method for installing gudgeons into water wheel shafts. That was one thing that my grandfather made sure I would understand at an early age. "If you are going to to it then do it right or don't do it at all," he often said. Then there are those who think that you construct water wheel and water wheel shaft out of "green" lumber. This is the craziest thing I have ever heard of. They have made a science of constructing water wheel using so-called "green" or unseasoned lumber. They have methods of wrapping the parts with wet rags and then covering and sealing them with wax so the wood would not season. Moisture gauges are used to maintain the wood at a proper level of moisture so it would hopefully never begin to season. Some who they think if the wood is always wet there is no need for seasoned lumber. Then when the water wheel begins to slowly season it will develop cracks and the joints will open up causing poor fits on what was once good fitting seams. I knew someone years ago who was building a water wheel and winter set in before they could get the water wheel assembled. They tried to carefully store the parts but when spring came the water wheel parts would no longer fit together because the wood had begin to season. Still good intentions sometimes does not take the place of proper understanding or knowledge. Some years ago, a park that has an operating flour mill, they needed a new water wheel. So the problems with the old water wheel were recorded and identified. All of the paper work done and sent through the chain of bureaucracy. Some good meaning soul through the chain of command when they saw the paper work for a "new white oak" water wheel at a price tag of 50 or 75 thousand dollars (I forget the exact price over time), but they said that will never do. They crossed out the words, "white oak," and penciled in the words, "red oak." It is much cheaper. And somehow a "new red oak water wheel" was constructed. Then someone came along who know something about building water wheels and they said that will never do. Because red oak does not have the structural strength of white oak and it rots very quickly. If you look at the end grain of a piece of white oak and of red oak you will notice that the cell structure of the wood is very different. Red oak is fine for building something like small furniture but is best serves as firewood.

The arms are installed through slots cut into the flat hexagonal surfaces of the shaft. Every other arm would then go all the way through the shaft and it would interlock within side of the shaft. These arms would be wedged into place with longer wooden wedges also made out of white oak in combination with shorter wedges, also made out of white oak. The in between arms ware fitted into dead pockets or slots. The direction in which the water wheel turns that side of the leading slot is undercut with an angle that matches the angle on the leading end of the arm. Then placed in the slot the arm rests and matches up with that angle. The back side of the of the slot is cut with a square right angle and there is enough room to place in two wedges in reverse to each other. The arms are just snugged into place and the wedges should not be tightly put into place. A pounding block should be used, made out of the same material as the rest of the wood. This will prevent the breaking over or splitting the wedges. If need be a wooden handle can be placed in the center of the pounding block so it can be safely held in place.

To install the sides of the water wheel, place together to sections of cant boards with the diagonal ends butted together. Then place over them in the center a rim or shroud board. The bolts can then be placed into the bolt holes on the sides of the diagonal ends that are butted together. The washers and nuts go on the inside or bucket compartment of the water wheel. You then hold the three sections with the lap joint to a water wheel arm and then add the next section of rim board. Then you add sections alternatively until the entire side is completed. One method is to add the mirror opposite side as you go around the water wheel. Remember the wheel will become heavy and tend to rotate as up add sections or weight to the water wheel. Once all of the sides are installed the will should be free to rotate by hand once again. Then the center rods can be placed through the side at the arms.

Now it is time to install the front bucket boards. You slide one bucket board down from the top and then insert a bucket bottom in through the back so the lap joints will mesh together. The buckets could not be nailed together from the front with cut nails. Clap will have to be placed around the sides holding the back of the bucket board bottom so they can be nailed together. Once all of the bucket boards are in place, the drum boards and batten can be install around the inside of the water wheel. The next step is to install the fellow boards between the water wheel arms covering up the bolt heads on the rim boards. Now all bolts can be tightened and the rim plate can be install around both rims of the water wheel thus locking in place the front bucket board. Now the wedges that hold the arms in place can be tightened for one last time. After the new wheel is run for a day tighten all bolts and nuts, and wedges. Then again after a week of operation. Then again in a months time and then a year after that, and each year afterwards.

A Hybrid Water Wheel at a Saw Mill in Chester County, Pennsylvania.
This is a combination wood and metal water wheel. The parts of this Up & Down Saw Mill
was incorporated into a poplar Smithsonian exhibit, which is now lost in museum storage.
This water wheel has all of the hallmarks of a transitional I-X-L Fitz Water Wheel.

Now see: "The Operation and Maintenance of a Traditional Wooden Water Wheel.," for future maintenance of the water wheel

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Copyright 2001 by T. R. Hazen