Author Topic: Ralphs Water Wheel 2011 (Read 12674 times)

12AX7 · « **Reply #33 on:** April 16, 2011, 12:04:38 AM »

I certainly didn't mean to imply that there were mega watts to be harvested.

I was just trying to point out that given the right alternator design, gearing up may not be needed. Or that the gear ratio could be greatly (less wear, less stress) reduced, and in turn improve on overall efficiently.

ax7

Madscientist267 · « **Reply #34 on:** April 16, 2011, 12:36:11 AM »

Understood, and definitely agreeable.

Trick is, really, where are the losses and what's the best way to get rid of them:

Transmission, definitely a loss. Can be compensated by using a large ring as a rotor rather than gearing up a small rotor.

Too many buckets in the water at once and/or the wrong time/place, likely. Semi-trivial to resolve. Ok, maybe less than 'semi'.

Shape of the buckets, possibly. From what I gather, round buckets are more efficient in an undershot than other shapes.

Alternator matching, another good possibility. Air gap, wye/delta/IRP, system voltage, etc.

Just a few things that came to mind when I gave it more than a few seconds of thought...

Steve

damian · « **Reply #35 on:** April 16, 2011, 02:23:31 AM »

I feel like I've just walked into a very exclusive club without my smoking jacket. Oh well. Anyone else ever play with one of the little bicycle generators that is held against the tire with a little overcenter/spring mechanism? You've already got the "bicycle wheel" (water wheel). So rather than taking power off of the central shaft a la a mill for grinding grain, or putting magnets around the perimeter of the water wheel, why not take power off via a much smaller wheel held in contact with the rim of the water wheel? Twenty five to one gearing with a ten foot diameter wheel would imply a friction driven wheel of just under five inches diameter.

Damian

Madscientist267 · « **Reply #36 on:** April 16, 2011, 08:02:12 AM »

Only problem I see with friction drive is, well, the friction.

Water, while generally considered a poor lubricant, is also a less-than-optimal 'friction transfer' medium.

Geared maybe. But then you're back to the 25:1 loss amplification from bearings, etc. So kinda square one.

Steve

REdiculous · « **Reply #37 on:** April 16, 2011, 01:20:12 PM »

Ideally there's no real friction/slip between the wheel and the roller. Tire wear doesn't seem to be a big concern on 1kw+ friction drive ebikes, but in wet conditions they can have problems with slip/friction.

If it was applied here you'd want to rough up the contact area somehow. The only thing that comes immediately to mind is spray on truck liner. Even then your roller would have to press against the wheel with a bit of force to minimize slipping.

It's not the worst idea ever but I think you'd just be trading one set of problems for a different set. $:-\$

taylorp035 · « **Reply #38 on:** April 16, 2011, 03:24:05 PM »

I don't like the friction drive idea either. Too many problems that could become headaches. And I guess the magnet idea was a bad one too...

Could a giant v-belt work on the outside of it? They make custom length belts that can be put together like chains. My local amusement park used them on some of their older rides. I'm not sure how the v- groove on the water wheel would be made, but the alternator end would be easy. The force would be rather high (300+ lbs). Maybe a serpentine belt like a car engine would have would be easier.

12AX7 · « **Reply #39 on:** April 16, 2011, 04:41:35 PM »

A number of years ago I wanted to take on a similar project, where the water wheel would "float". I had thought that I'd keep the alternator on shore and connect the two with a couple of universal joints and a long drive shaft. This would enable the alternator to be heavier (a large motor conversion). Zubbly suggested that with the relative constant torque of the water wheel cogging of the alternator wouldn't be an issue.

If one would make a large cradle on shore, a large diameter alternator wouldn't have to be partially emersed in the river.

This may go against the "KISS" principle but if one can do away with a complicated gear box it might be a wash?

ax7

REdiculous · « **Reply #40 on:** April 16, 2011, 05:03:22 PM »

On DirtyJobs Mike was visiting a tanning factory that had large drums driven w/ 3 belts (iirc). The drums were probably 8ft dia or so and half-full of hides and water so they were probably quite heavy. You'd probably want to keep the belts out of the water but even then they'd still be exposed to the elements and custom length belts probably aren't cheap. I dunno.

The more I think about it, the more I think that the magnet idea is likely to be the cheapest, easiest and most reliable retrofit. Who's gonna do the math to figure out how many magnets it would take assuming an 8ft diameter? Not it!

Madscientist267 · « **Reply #41 on:** April 16, 2011, 05:22:32 PM »

Probably a fair amount, but there's a fringe benefit to rolling this way too -

The alternator 'caliper' could be designed in 3 phase modules, that could be added/removed to dial in that sweet spot for optimal loading of the wheel.

I'd think it would also be fairly trivial to switch and swap stators... Might not even have to stop the wheel!

That's always a plus!

Steve

taylorp035 · « **Reply #42 on:** April 16, 2011, 07:44:04 PM »

I have a hard time believing that the air gap could be held steady enough.

REdiculous · « **Reply #43 on:** April 16, 2011, 08:05:21 PM »

It looks like 150, 2" wide magnets will form something close to an 8' circle.

I'm pretty bad at math though.

The wheel looks really well made so maybe the airgap wouldn't vary that much. $:-\$

Madscientist267 · « **Reply #44 on:** April 16, 2011, 08:51:52 PM »

And even if it does, the solution I see would be to have the gap fairly wide, and compensate with more turns/coil or just more coils.

Might be on to something here. Who's gonna build it to find out?

Steve

taylorp035 · « **Reply #45 on:** April 16, 2011, 09:10:54 PM »

How many coils?

Madscientist267 · « **Reply #46 on:** April 17, 2011, 09:41:12 AM »

I'm thinking maybe 9... 12 if the oversize gap warrants it.

Steve

mitcamp · « **Reply #47 on:** April 17, 2011, 11:34:04 AM »

REdiculous

150 2 in. wide magnets is just going to happen

taylor035

a giant v belt, really.

Madscientist267

alternator caliper, WHAT ARE YOU GUYS, SMOKIN

Mitcamp

REdiculous · « **Reply #48 on:** April 17, 2011, 02:31:17 PM »

mitcamp, we were just doing a little thinking on what might work instead of a gearbox that's likely to fall apart (again). I'll be the first to admit I'm an idiot and at no point should anyone listen to anything I say.

Madscientist267 · « **Reply #49 on:** April 17, 2011, 03:33:23 PM »

Quote

WHAT ARE YOU GUYS, SMOKIN

Oh it's on now.

LMAO

Who's gonna build it!?

hahaha

Steve

taylorp035 · « **Reply #50 on:** April 17, 2011, 05:04:26 PM »

I haven't heard any better ideas yet. This is a rather hard problem to solve.

EDIT:

http://www.fennerdrives.com/high_performance_composite_vbelts/apps/nut/nut_big_drives.asp

12AX7 · « **Reply #51 on:** April 17, 2011, 05:22:56 PM »

Mitcamp, any chance of more pictures?

Close up of the paddles? Before and after the modifications?
A few more of the river, and the wheels location?

A video would be great!

I haven't been smoking anything, but I'll not turn down a cold beer.
ax7

REdiculous · « **Reply #52 on:** April 17, 2011, 08:50:12 PM »

A pic of one of the gearbox's internals would be nice too, if ya got 'em still.

Madscientist267 · « **Reply #53 on:** April 17, 2011, 09:58:02 PM »

Taylor -

The belt idea isn't all that bad of an idea, but still screams 'friction' at me.

Between losses in the belt from 'shearing' friction with the pulleys and slippage due to water contamination, I can't see it.

So far, hate to say it mitcamp, but the 'caliper alternator' is really the most plausible simply because there are no moving parts involved in implementing it, and it solves a string of problems that are apparently plaguing the current design.

I'd try it myself except for three reasons:

1 - I don't have the resources to build a wheel of that size from scratch

2 - I live near a river, but it flows so slowly that the thing would have to be gigantitanimagnanimous to get anything out of it

3 - The town I live in would have a cow if I tried to throw such a wheel in the river

I really would like to see it conceptually built by someone however, because I believe it is a very viable solution to several issues.

Maybe even a small scale version to illustrate the concepts. I can certainly envision it's operation in my mind, there's no question. Trick is, actually being able to put it to the test.

I think that if it's done right, one might even be able to cut down on the number of magnets needed by using some form of magnetic distribution. A car alternator comes to mind; there's actually only one 'magnet', but the stator 'sees' several poles because of the way it is distributed in the rotor.

Any losses could then be made up by adding to the 'caliper', more coils, turns per coil, etc etc.

Very viable if I say so myself.

Just remember, the wright brothers were 'nuts' too...

Steve

12AX7 · « **Reply #54 on:** April 17, 2011, 10:50:49 PM »

I think it's a bit early to say that this project is suffering from a "plague of problems".
I believe that this is the first problem that has occurred?
Most everyone who has built a wind turbine has taken it down for "rework" and that's WITH lots documentation available.

Those who have done the initial work, have given thought to what the problem was and have taken a course of action.
I'm not sure how many others have built a floating water wheel of this size, it's the first one like this I've seen (and very impressed by it). My opinion is that this group of people are "breaking new ground" and I'm looking forward to ALL follow up posts.

I do have a question about the shaft that twisted. Was this failure related to the load that the alternator put on the chain drive?
What was/is the RPM of the wheel with and with out a load on the alternator?

Love to see more pictures!

Madscientist267 · « **Reply #55 on:** April 17, 2011, 11:04:06 PM »

Don't get me wrong; I don't mean to imply that it's "doomed from the start" or anything... I hope that nobody infers that from anything I've said.

Just the building of the wheel itself is quite the undertaking I'm sure, and as I said (I think in my first response to all this) - It's a very impressive piece of hardware given that it is of the homebrew variety.

I just see a way to kill a small handful of birds with one stone.

I think you're right, it's just a new way of solving the same old problem. I'm with you there. That's what I love about this board - many very intelligent people, and a good chunk of them thinking outside the box.

Steve

taylorp035 · « **Reply #56 on:** April 17, 2011, 11:28:41 PM »

From a fundamental stand point, the lever arm needs to be bigger than a 2 5/16" shaft (radius of 2.3125/2 "). If this can be increased, using a large alternator, a multi-piece gear/sprocket/pulley/timing pulley/ worm gear/ect... then the main problem will have been fixed.

REdiculous · « **Reply #57 on:** April 17, 2011, 11:38:20 PM »

How many gearbox has this thing torn apart, 4? The axle broke on the 5th(?) one so the gearbox is getting changed again...number 6?

Not trying to be mean or overly negative but that sounds like a "plague of problems" to me.

It can't be cheap having to pull it out and ship it to the shop to get parts replaced...it's good that they haven't given up.

damian · « **Reply #58 on:** April 18, 2011, 10:47:43 AM »

I'd like to suggest that Taylorp035 was on the right track in trying to quantify the torque on the failed shaft. The shaft broke. Why? And how can one keep it from breaking again?

So, the gearbox input shaft needs to transmit what torque?

Lets say 400 w = ~ 0.5 HP and wheel to watts efficiency is ~ 50%. Others who have better numbers to plug in please adjust accordingly.

So the gearbox input shaft sees ~1 HP at 6 RPM.

1 HP = 550 ft. lbs./sec.

So 1 HP at 6 RPM = 5,500 ft. lbs. at the gearbox input shaft.

5,500 ft. lbs. seems like enough to twist off a 2.3125" shaft.

Maybe it's not. Maybe it could actually handle that, but at some point the shaft was asked to do more than it could.

Now I'm not so up on the realities of alternator output vs. RPM but I imagine there's someone here who is.

As RPM goes up, does alternator output go up in such a way that shaft loading is also increased?

If so would it be possible to regulate the alternator output so that it did not exceed the capabilities of the shaft?

Damian

mitcamp · « **Reply #59 on:** April 18, 2011, 11:42:55 AM »

Udate 18/04/2011

A inspection has been perfomed on the Waterwheel and the cause was the pillowblock bearing failure (on the transmission side) was lack of grease. This in turn caused damage to the waterwheel axle shaft.
We will go with the 12 paddles on the water wheel, instead of the 16 paddles. I will wait until the waterwheel gets back in the water, so I can observe the R.P.M. Then I will wind a stator to match the output R.P.M of the transmission.

Mitcamp

taylorp035 · « **Reply #60 on:** April 18, 2011, 11:59:24 AM »

Good, we found a / the problem. Bearings that seize are never good. I once saw a crankshaft in a locomotive engine (~10-12" diameter) be sheared off when the bearing went bad. It's also a good idea to see the rpm (measure it accurately), because the difference between 4 and 8 rpm will make a huge difference in the calculations.

I'm kinda surprised that it wasn't because of the torque.

Thanks for the update! Can't wait to see some pictures.

News:

Author Topic: Ralphs Water Wheel 2011 (Read 12674 times)