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Step 1: Design Constraints
I knew I wanted to build a waterwheel after seeing one on a recent holiday.
I figured it would be a simple matter to set up a small electric pump to circulate water and run the waterwheel - too easy, in fact! My waterwheel is set up at the front of my property , and I wanted people passing by to be able to interact with it. This meant using a hand pump that people could use to fill a bucket and run the wheel for a few minutes.
I am currently renting, so permanent changes to the property such as digging a pond or concreting posts into the ground were out. This meant the waterwheel had to fit into a small footprint, about 1 metre by 2 metres, at the front of the property in a garden bed. It also needed to disassemble easily for removal if necessary.
With these constraints in mind, I decided on a wheel diameter of around 1 meter. I figured that would be an achievable size and if successful I could try a larger one later.
My budget was 'not much', so I used a lot of recycled/second-hand materials and used wood that I had on hand or was on special at the hardware store.
Step 2: Materials
- Pressure-treated rough-cut lumber
- I used around 15 metres of 100mm x 50 mm lumber, mostly in the support frame
- Plywood for reinforcing wheel
- Treated wood boards (150mm x 25mm) and plywood for trough
- EDPM rubber sheet for trough
- A heavy metal pipe or solid bar for the axle
- Vegetable oil (for bearing blocks)
- Screws (various sizes)
- Bolts and nuts
- I used 120 mm M8 and 170 mm M10 galvanised bolts for the frame and bucket stand
- I also used 6 50mm M6 bolts for the axle adjustment blocks
- I used 120 mm M8 and 170 mm M10 galvanised bolts for the frame and bucket stand
- Saw (I used a tablesaw, a circular saw would also work)
- Driver for screws
- Forstner bits to suit your axle
- Spanner, screwdriver, etc.
- Drill press (optional)
- Bandsaw (optional)
- Router table (optional)
I used a lot of woodworking power tools because I have them already, but the woodworking joints involved in this project are very simple and don't need much precision. You could build this waterwheel with a circular saw and a drill.
I was lazy and used ordinary woodworking screws, something more weather resistant like galvanised or stainless steel would probably be better for longevity in wet conditions.
Step 3: Building the Wheel
I cut out two 30cm circles of plywood on the router table and drilled 30mm holes in their centres. I cut some of the 2x4s in half to make the spokes of the wheel. I joined two lengths with a half-lap joint, drilled a hole in the joint (this weakens the joint a LOT) and cut 45 degree angles into the other spokes. I screwed the plywood circles onto the spokes, making sure to line up all the holes and space the spokes out evenly.
The next step was to join the spokes with pieces of wood to form an octagonal wheel. My spokes were not very evenly spaced out and the outside parts of the wheel were all different lengths. I cut simple joints on the bandsaw and screwed the wheel pieces into the spokes. The joints I made were very rough and inaccurate, but this part of the wheel isn't going to see much weight or stress.
Because I used untreated plywood, I had to polyurethane the plywood later. You can avoid this by using treated plywood or something else which will stand up to being wet.
Tip: Keep in mind that the wooden part is only part of your wheel! Adding the buckets makes the wheel much larger - my wheel turned out substantially larger than I had anticipated.
Step 4: Bearing Blocks
Standard ball bearings are expensive and don't work well for a waterwheel, which is a very low-speed application. I found a simple technique for making oil-impregnated bearing blocks out of wood and it worked well.
I used pine for my bearing blocks; a naturally oily hardwood would be better.
My axle is a galvanised pipe 27mm in diameter. I drilled holes slightly larger than the axle in two blocks of wood, then cut them in half on the bandsaw.
I placed the blocks into a pot (it is the same pot which is on the waterwheel) and poured in enough vegetable oil to cover them. I weighed down the blocks with a rock (otherwise they float) and heated the vegetable oil for about an hour, turning the heat down to avoid overheating the oil. The water in the wood turns into steam and is replaced by oil. I left the blocks in the oil overnight to ensure the oil soaked into the wood.
The two halves of the block are bolted together to secure the axle. I drilled a small hole into the top of the block so I could add extra oil to the inside of the bearing if necessary.
I used hose clamps on the axle to keep the waterwheel centered. The axle doesn't seem to wander in normal use, but people might get over-exuberant and push or pull the wheel while it is spinning. If this happens the hose clamps will rub against the bearing block, acting as a brake and slowing the wheel.
Step 5: Axle-adjustment Bolts
I made three blocks of wood with holes to hold an M6 nut and a bolt. These allow you to make fine adjustments to the alignment of the axle relative to the wheel to remove wobble, and also acts to clamp the wheel onto the axle.
I suggest using larger blocks of wood and larger bolts than I have here - these were small and fiddly to work with, and some of my blocks split when I pressed the nuts in on my vice.
Step 6: Choosing Buckets
I tried to choose buckets that were relatively similar sizes and around 1-2 litres in capacity, but also different in type, colour, and material. I had a few of the containers already, and purchased the rest at second-hand shops.
Step 7: Attaching the Buckets
First I weighed all the containers and tried to mount containers of equal weight opposite each other, and alternate heavy and light containers.
The attachment of each container is different. Some could be screwed directly or bolted on to the outside of the wheel; others needed brackets or clips to attach them to the wheel.
I lined up the 'rim' of each container with the center-point of the flat rim piece it was mounted on. I'm not sure how crucial this is, but the containers should probably each be lined up in the same way all the way around the wheel.
I got very lucky with the dump truck - it just happens to dump at exactly the right point in the cycle. It doesn't actually collect much water though.
To mount the glass pyrex bowl I needed to bolt it through the bottom. Turns out tempered glass is impossible to drill through, so I used a small grinding point on a rotary tool to grind a hole instead.
When the buckets were all attached, I found that a certain point would always end up at the bottom of the wheel - it wasn't balanced very well. I added some lead weights to largely correct this.
The waterwheel seems to be very forgiving towards ineffective buckets - the flower pot and the dustpan, for example, don't collect much water at all, but the inertia of the wheel keeps things turning and it isn't an issue.
I screwed a hook into the wheel so it could hang from the ceiling in my garage during construction. This was very convenient as the buckets are too fragile to rest the wheel on the ground.
The final wheel is around 1.4 metres in diameter. The buckets made it much larger than I had anticipated!
Step 8: Building the Stand
The stand is of very straight-forward construction. The joints are all very simple half-lap joints cut on the table saw, or just simple butt joints. All angles are 45 degrees. I used a few bolts with an eye to possibly disassembling things later. When I built the stand, I did not have all the buckets attached to the wheel, so I made the vertical supports taller than necessary and trimmed them later.
Once the stand was complete I was able to trim the axle to the final length with an angle grinder.
Step 9: Testing
When the buckets were all attached, I set it up and tested the wheel with a hose to check how much water would be needed to keep it turning. I found that about 3 litres per minute, or 180 litres an hour, was sufficient to keep the wheel turning at a slow speed. Most fountain pumps can do at least that much, but if you're using a pump, make sure it can handle the head required (about 2 metres).
Step 10: Trough
The trough is very simple, just a wooden box with a plywood bottom screwed together. It is about 1.5 metres long and 50cm wide.
I ordered 2 square metres of EDPM rubber sheet (used to line ponds) to line the trough. This was the most expensive part of the project ($60 NZD) but it is a very high-quality material and easy to work with.
Folding the rubber neatly at the corners took a bit of experimenting and patience but it looks good. I just tacked the rubber to the box with a few tacks on the outside.
Step 11: Pump and Bucket Stand
I wanted people passing by to be able to interact with the waterwheel. This meant a hand pump that people could use to fill a bucket and run the wheel for a few minutes.
I tried building a piston pump from scratch, which almost worked, but I ended up using an old air pump. This needed to be disassembled to fix an out-of-place O-ring. I greased the moving parts, and I had to reinforce some aging plastic parts, but eventually the rebuilt pump did a great job of moving water. Unfortunately it required a LOT of effort to pump. The solution was to mount it with a large lever arm to reduce the amount of force needed. I shaped and painted the handle of the lever to make it nicer to use.
The bucket is just a bucket with a tap (the kind you get for 20 litre water containers) screwed into a hole near the bottom.
The bucket and pump were both mounted on a post which is bolted to the trough along with some angled supports. Again, very simple joints: half-laps, 45-degree supports, screws and bolts.
I used large-diameter clear tubing, and it looks great when pumping. You can see the water sloshing and moving in the tube, with some small bubbles. The large tubing also seemed to make pumping a bit easier (compared to garden hose), possibly due to decreased resistance. I used pipe clips to hold the tubing on the post.
Step 12: Sign
I made a simple sign to let people know that they could pump the water to make the wheel work. Without the sign, most people would hesitate to approach the wheel as it is close to my house.
Step 13: Maintenance
I have only set up the waterwheel in the last few days, but I have noticed that leaves and other debris are already appearing in the trough. I will make a simple cloth filter for the intake hose to prevent these clogging up the hose.
The other issue is keeping the water clear. I am looking into how best to keep the water from going green, without poisoning any animals that drink the water.
With a reasonably small volume of water (about 70 litres) and a permanently attached pump, changing the water completely should be quite straight-forward if necessary.
Step 14: Final Thoughts
This was one of my largest projects to date, and took more than a month to complete (mostly due to getting side-tracked trying to build a pump from scratch). The finished waterwheel turned out MUCH larger than I originally had in mind. But it works great and attracts a lot of attention. The clear tubing in particular is very cool. Any water project with a pump should use clear tubing. :-)
Things which worked: Axle adjustment mechanism, oil-impregnated bearing blocks, lead weights for balancing
Things to avoid: Using untreated plywood for the wheel, using small blocks for axle adjustment blocks
Unplanned successes: Tipping buckets on the dump truck, clear tubing
Final Budget: Around $150 NZD, mostly on the pond liner ($60), screws and bolts ($20), and the clear tubing ($30). I got the majority of the treated wood on sale, marked down to $2 for 2.4 metre lengths, and the containers, buckets and pump were all purchased at second-hand shops.