Instructables

A different water wheel design?

I posted this idea on the makezine forums recently and got 1 answer but it seems I did not explain what I meant too well so I thought I would try here to see what you think.
See the diagram at http://www.nelliott.co.uk/maker/water-wheel.jpg
Would this produce more power than a conventional water wheel?
My theory is as follows:
In the case of a normal wheel each bucket/segment when full of water has the turning power equal to weight of water x length of horizontal line such as the yellow one in the diagram.
That is it's weight exerts a force to turn the wheel according to it's horizontal distance from the centre of the wheel.
If instead of the normal wheel the 3 blue circles represent 3 sprockets.There would be a whole series of buckets attached to the red lines ( which represent a chain ).Water would pour into the buckets as shown, so it would simply propel the buckets vertically down.The turning power of each one of these would be equal to to weight of water x radius of large wheel. So each would have the turning power of the best one such as the line from H to the center of the wheel.
As far as I can see this would mean a large increase in torque over conventional which I hope would easily offset the losses due to the chain drive.
What do you think?

buteman (author) 4 years ago
I received this explanation on makezine which pretty well shows my idea will not work so I thought I would put it here for completeness.
Thanks to all for your input.

Wheelthru said:

"You're exactly right in saying that the turning moment of a bucket on the wheel is much smaller at the top and increases until at the horizontal point it's equal to the contribution of a bucket on the chain. But if you "unwind" the wheel, you can see that while the forces are smaller, the distance the water travels is larger. I believe these cancel each other, resulting in the same amount of work being done with the wheel as with the chain (again except for spillage).

Does that make any sense?"
jeff-o4 years ago
There's a reason they don't use waterwheels to generate power  - turbines are more efficient!  Look into how they work and see if you can improve that design instead.
seandogue4 years ago
I think your gains (if any) would be largely offset by the added work presented by the system you show in the link.
buteman (author)  seandogue4 years ago
Ah well it was just a thought. I suppose that if I could do a cheap small mock up it might be worth doing some actual measurements. Got a lot on at present so not too likely.
As you say, there's no reason not to try it, but I suspect it will only be empirical confirmation.
buteman (author)  seandogue4 years ago
Any idea if I can get maybe plastic chains rather than metal?
Perhaps nylon would be lower friction?
Even better I suppose would be something teflon coated.
There ain't no such thing as a free lunch. A good water wheel will extract kinetic and potential energy from the flow, 

You can't change the total energy that's available from the stream.



Steve
buteman (author)  steveastrouk4 years ago
I agree,I was just hoping the increased turning moment would mean the wheel would start to turn and continue with a lower water flow because of the increased leverage.
+1
Kiteman4 years ago
The losses in the links would be huge.

You'd be better off with a bigger wheel instead, or direct the water through a turbine designed to match the available flow.


buteman (author)  Kiteman4 years ago
Thanks for the reply. As I said to k1illerjackalope I was hoping that the losses would not be that great.
You'd lose more energy that way, if you want to improve a big waterwheel's efficiency by lowering the total mass of it and the friction on the bearings...

Alternatively a turbine would be a reasonable option. 

As for the increase in torque, it'd be the same amount of energy from the water, at best efficiency so really gearing a wheel or turbine would be more efficient overall...
buteman (author)  killerjackalope4 years ago
Thanks, I was hoping that the losses would not be that great.
Hadn't thought about a turbine.