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Smart Drive Oil Barrel Undershot Waterwheel
bmannz:
As a kid I used to make waterwheels in our tiny creek at the farm out of timber scraps, lego gears and lego motors to drive the massive load of one dim red LED in my bedroom 150m away. I learned a lot more than I realized then about paddle efficiency, balance, torque, bearing wear and watertightness. 30 years on the interest is as strong as ever and having recently brought a piece of land with a large drain running thru it I thought it was time to try it again but this time on a slightly bigger scale.
The drain only runs at around 10-50 lps in the summer but can get to 1000lps in winter. The culvert in the photo is about as deep as Alex is tall and Alex is about 1700mm depending on which gumboots she has on.
bmannz:
I thought I had about 1200mm of fall so after much research on this forum and a few others I decided on a breastshot with poncelet paddles fed from a weir or dam built out of either compacted clay or posts and board - something like the picture below which I sent of to my engineering friend Tracey for her comments.
After a fun afternoon in the drain with Emma, some garden hose & a home made staff and level I discovered my 1200mm was actually 300mm :(
So it was back to the drawing board and the Borsten Engineerings website for some recalculation.
After a few goes with the flow and velocity data I had gathered over several months observation and my newfound 300mm fall information it was clear that the total amount of available energy was somewhere between zero and bugger all, at this point I should probably mention "The Wager"
THE WAGER:
Not long after buying the land I was kicking around the idea of a waterwheel to augment the solar and wind systems we have in place. One sunny afternoon standing on the bridge with a beer in hand I raised this with a friends dad, who for the purposes of this post we will call Rob. Rob is someone very handy on the mechanical side and who's opinion on such things I value. At the end of this discussion he bet me $100 I could not get an average of 50 watts over the course of a year & so the bet was on.
So here I am with both Borsten and Eco Innovations websites among others telling me its not happening & don't waste your time but I know from my childhood there is power there to be had so I completely ignore the advice and power on regardless because I will be dammed if I will lose this bet.
bmannz:
Borsten told me my only hope was 36 paddles, thinking back to some videos I had seen of crossflow turbines and remembering my childhood wheels stalling when the paddle count got low I decided on as high a paddle count as I could manage.
With my fall cut to shreds and my flow already iffy at best I was desperately in need of every % efficiency I could get, the Poncelet curved paddle would be a must have. I considered a design of halved plastic barrels mounted on a complete plastic barrel but the diameter felt wrong. 200L steel drums would be too wide but the 60L drums the mechanics use would be perfect!
Spending a few minutes on Autocad I came up with this design:
Taking a day off work to trawl the mechanics of Auckland I tuned up a shed full of used Castrol 60L barrels that was mine for the taking, trailer load of used oil barrels - check.
bmannz:
Next it was time to figure out how to get the 10RPM I was hoping for from the wheel up to the 90 RPM a smart drive needs to start pushing out the juice.
I am thinking sprockets, big ones.
Now my background is electronics, if its got electrons in it, i'm your man, but when it comes to mechanical stuff the only thing I can tell you about my car is it is black and doesn't like it if you put petrol in the diesel tank.
Luckily I have a friend whos brother races go karts and whos dad Randall builds them along with owning a performance car workshop - Edgell Automotive - AKA sprocket city.
After a chat with Randall and a visit to Matt at Auckland Bearings I came away with a bunch of pillow block bearings and some sprocket chain. Now I know what you are thinking, pillowblocks will sieze as the RPM is too low to keep the bearing lubed and you might be right about this but I have a bunch of mates coming up this weekend and not much time to get the material together, so they'll have to do for now.
Sitting the bits on the floor the transmission looks like this:
One last minute adjustment was the 50mm pipe I had arranged for the axle was slid inside a bigger pipe to enable me to get the wheel on and off the axle to make installation easier - shims would be required to keep the wheel true but my mate Mark pointed out that coke cans are really good for this.
bmannz:
Browsing waterwheel images for hours at a time waaaay too late into the night I found waterwheels with a high paddle count commonly have a steel disc around outside to support the paddles and axle.
My design had two hoops instead made from 32mm galv tube to support the paddles. The thinking behind the hoops was twofold:
One - This would enable me to mount the barrels at whatever angle Mr Poncelet deemed appropriate
Two - I didn't have any steel discs, but I did have a supply of galv tube in the form of a dissassembled commercial glasshouse from our friends across the road - thanks Jackie and Maike!
I spent a happy hour or two in the dark on Thursday night in 3 degree weather grinding off the rollers from the galv tube:
Friday morning I went to see another friend in Whangarei with access to some serious heavy engineering equipment, he found me a pipe bender small enough to handle my 32mm tube. A box of Heineken later and we have four hoops.
Saturday morning with all the gear on site and a bunch of friends arrived to lend a hand it was time to put it all together - first step, weld the spokes to the axle and hoop - one issue - I don't know how to weld, hmm, this could be a problem.
My soldering is pretty good and I brazed some copper pipe one time so I watched a couple of youtube videos with the usual conflicting information about the best way to stick weld galv tube, chose some amperage setting in about the middle and away we went.
After getting the first four spokes welded on I dropped the assembly it on its side to weld the back bits and one of the spokes cracked off the hub - It turns out a couple of passes with the stick does the trick - lesson learnt & further quality control testing (hitting with hammer) proved the welds were pretty good.
A production line formed to cut the barrels, notch the ends & screw them onto the hoops
Big thanks to Ivan, Chris, Phil, Erin & everyone for lending a hand!
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