Author Topic: Fitz Waterwheel - Suitable gearing and generator?  (Read 7819 times)

0 Members and 1 Guest are viewing this topic.

Coles

  • Newbie
  • *
  • Posts: 16
Fitz Waterwheel - Suitable gearing and generator?
« on: April 08, 2013, 04:30:44 AM »
Hi folks.

I'm designing a small over-shot waterwheel identical to the old Fitz waterwheel. 

It's a small system with only a 2.5m head, and a design flow of 70 L/s.  The wheel diameter will be 2.25m and it will turn at 15.2 RPM at 70 Ltrs/s and I am expecting the wheel to have a shaft power of 1.4kW.



The sluice at the end of the flume will control the flow of water on to the wheel while maintaining a constant water level.  This should result in good efficencies for part flows.

If the head is maintained at 2.5m and there is a part flow of 30 L/s the wheel should turn at 16.0 RPM with a shaft power of 0.69kW.



Intuitively I would expect the wheel to slow down under part flows and that the wheel would turn at 10-12 RPM, but would this depend on the type of generator? 

Any thoughts on the best transmission system and generator would be greatly appreciated  A grid connection is available, or the power could be used off grid with a battery bank/inverter.

Many thanks.

 

FoolAmI

  • Newbie
  • *
  • Posts: 16
Re: Fitz Waterwheel - Suitable gearing and generator?
« Reply #1 on: May 16, 2013, 10:24:56 PM »
As someone who's built over 400 water wheels and hooked gearing to a few of them for making electricity let me give you a few ideas.      First a formula.    height in feet X flow in gpm X .000253 X efficiency (.55 for wheel and generater set or .80 for a well designed water wheel axle hp) = hp.     so @ 1063 gpm with a 6.9 foot diamater wheel would look like this.
6.9 X 1063 X .000253 X .55 = 1.02 hp electrical output      since a hp equals 746 watts we now go
1.02 X 746 = 761 watt output 24 hours a day.      I've got a calculator on my website to do this for you but I'm not allowed to post it here.       http://www.waterwheelplace.com/water_wheel_electricity.html

With a wheel that size if you spin it much over 20 rpm (depending on bucket design) the centrifical force will sling some of the water out of the buckets reducing efficiency.      With that much water going over a 6.9' wheel spinning at say 15 rpm you will need at least 12" of wheel face (inside bucket width) for every 216 gpm flow so to maximize efficiency the wheel's face needs to be about 48 inches.       If you overfill the buckets you will reduce efficiency some by dropping the water out too early in the wheel's rotation.        This information comes from practical onsite testing with my wheels at customer's sites.     Computer simulations show that about a  65-70 degree paddle angle is best with a J bucket shape for metal wheels or an elbow bucket for wood wheels.

I've found that hooking the wheel's axle to an inline gearbox (use a flex coupling) as the 1st stage gearing works best.       Then a large bely pulley (18") to drive a small pulley on the PMA (altinator) for the second stage.       By using a belt for the final drive you can easily "tune" the PMA's speed to maximize electrical output in varying conditions by using different sizes pullies on the PMA.       Most of the supplies you may need are available @ www.surpluscenter.com .