New project

[mike90045]

Holy Cow ! What a beast, I love it.

[mbryner]

Don't know how I missed this thread.   This is awesome!!!

[sailawayrb]

Somehow I missed this thread as well.

I really like the look of waterwheels and I also like that they operate at low RPM (typically 5-15 RPM).  However, while it's clearly true that a waterwheel can exert a lot of torque, their ability to generate power (i.e., their ability to do work over time) is severely limited by this low RPM.

0.000253 x flow rate (in GPM) x waterwheel diameter (in feet) x efficiency (%/100) = mechanical horsepower

The constant (0.000253) is the water weight of 8.35 pounds per gallon divided by 33,000 foot-pounds per minute (i.e., the definition of one horsepower).

So one would estimate an 8' diameter well-designed, over-shot, waterwheel (80% efficient) being fed 30 liters/second (476 GPM) would generate about 0.77 HP (574 watts).  One will likely lose 25-30% converting this mechanical power to electrical power, so one would expect to be able to generate about 400 watts of electricity.  If 6' diameter, one would expect to be able to generate about 300 watts of electricity.

Of course, the aforementioned assumes that the waterwheel can "digest" being fed 30 liters/second (i.e., all the water produced by this flow rate stays in the buckets and goes along for the ride from the top to the bottom at the operational RPM).  So, for a given waterwheel bucket volume and operational RPM, one would expect there to be a maximum flow rate that the waterwheel can digest...beyond which, more flow rate won't produce any more power.  Or worse, one won't obtain the aforementioned power because the waterwheel bucket volume won't be able to digest 30 liters/second.

Lets try to figure this out...  Lets assume the operational RPM is 10 RPM.  The water doing the work only travels half the rotation.

0.5 times 10 RPM divided by 60 seconds per minute equals 0.083 RPS

30 liters/second divided by 0.083 RPS equals 361 liters per rotation

So I am thinking the waterwheel total bucket volume has to be at least 361 liters to digest 30 liters/second.  Or each bucket has to be at least 361 liters divided by the total number of buckets.

Bob B.

[mobile_bob]

what an awesome project!

wow, i am green with envy at having the resource, and the ability to construct such a beast

very cool

bob g

[KeithO]

Thanks for the support guys, I appreciate it a lot. 

Bob B ,Your power numbers stack up with mine though I am being conservative with efficiency to keep my expectations down .
I 'm  looking for 200 - 250 watts for a start as we have quite low electrical usage. ( lpg cooker ,coal boiler)

As far as volume the wheel will handle,  treating each bucket as a straight triangle and ignoring overlap works out to:
15.5 ltrs x 24 buckets =372 ltrs per rpm x 10 rpm = 3720 ltrs /60 = 62 ltrs sec
So 30 lts sec should give a low spill point at 10 rpm, though a higher rpm will work and reduce wear and tear on the drive line.
As usual it will all depend on gearing and generator cut in speed

Cheers
Keith

[sailawayrb]

Hi Keith,

Sounds like you are golden and this should work very well for you indeed.  I am very much looking forward to more photos and perhaps a video when you bring her to life!

BTW, and certainly not critical for this slow RPM project...whenever one builds rotating machinery (e.g., a Banki crossflow turbine), it is best to use a "prime number" of rotating elements whenever practical.  Here are the prime numbers below 100:

2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97

This improves balance and minimizes the potential for harmonic body bending mode combinations that can lead to noise, vibration, and ultimately fatigue failure.

Bob B.

[KeithO]

Progress pics
ratio is 33:1

[bschwartz]

Now THIS is a labor of love!!
Holy cow!!!  That looks like a ton of work (literally) to make 2KW a day.
I love the shape.  I can't wait to see a video of it in work.

[mike90045]

Great, just great,  I now have to clean the keyboard of the other computer that I drooled all over !

[rcavictim]

KeithO,

Is that 'alternator' a modern washing machine pancake motor?  I've only seen a removed stator from one, many poles.  Is the rotating armature a permanent magnet jobby?

That is a terrific project you are tackling there IMO.  I actually saw an exact same type metal reel the other day free for the taking.  I recognized it immediately having followed this thread.  Unfortunately it could not follow me home, too heavy for my car's roof rack. 

[Apogee]

I too think this is an AWESOME project!

One question, not sure about the belt driving the alternator.  With that small pulley, I'm concerned it will slip once a load is put on it.  Just my $.02...

I'd love to have the water resource to build a project like that!

Fantastic job!

Steve

[KeithO]

Cheers guys

Hi RCA
The alternator is a motor from a Fisher and Paykel smart drive washing machine.
That one has 1mm windings (aka 100) but I have a couple of others 0.8 (80)
The grey plastic rotor/cover has permanent magnets on the inside.
The wiring can be reconfigured many different ways
See here http://www.thebackshed.com/Windmill/FPRewire.asp
LG also make a similar one
I know what you mean about the reel , not so easy to move.

Steve
Hopefully the pulleys will do the job , they  were both taken from a water pump that used a motor of about the same size hp as I am hoping to generate , admittedly at a higher speed though , we shall see I guess.

[sailawayrb]

Have you filled the buckets to confirm that you capture enough water weight to create enough torque to overcome the friction, static inertia and gearing so as to be able to get everything turning?

Here's an interesting water wheel website:

http://www.waterwheelplace.com/water_wheel_electricity.html

Bob B.

[KeithO]

Hi Bob B
Good question , no not yet as the buckets aren't sealed .

The cool thing about water wheels is their start torque.
If we apply the water supply it fills the top bucket and the cascading water fills those below it.
I stopped a 4 ft breast shot by hand in the past and received that lesson.

If we assume that the equivalent of a quarter of the wheels buckets fill at standstill we get 93 kg or about 205 lbs of water at roughly  3 ft of leverage , so thats 615 ft/lbs at the shaft.
That  divided by the 33:1 drive ratio gives us 18.6 ft/lbs at the notorious badly cogging smartdrive alternator.
Should be fine.........

I'll look into it though as it is good to have the numbers

Another good calculator for playing with water http://www.calctool.org/CALC/eng/civil/hazen-williams_g

[sailawayrb]

Keith,

What is the status of this project?  Is it alive with perhaps a video to show?

Bob B.