forums energies: society, ecology and clean technologies

Before (re) launching our small paddle wheel (see here https://www.econologie.com/forums/tambour-de ... t6303.html for newcomers), I would like to improve the surface and the penetration of the blades in the water.

Specifications:
- material: pallet recovery (or at "worst", boards to buy but hey ...)
- material: fir wood / pine
- easy to cut (the less cutting, the better!)
- simple to assemble (screwing)
- simple to ... improve if necessary.

For the moment I have a simple 10 cm by 40 cm slat like on this photo:



purpose:

a) Multiply the work surface by about 2 (ideally 3)
b) "Increase" the Cx. It was estimated to be 0.7 - 0.8. I would like to upgrade it to 1.2-1.3 (let's be crazy!).
c) Energy gain recoverable in the modification: 2 * 1.25 / 0.75 = 3.3 ...

Does anyone have any suggestion of "shape"? For the moment the most probable solution I have in mind is that of the "hollow and elongated trapezoid" ... mechanical excavator bucket style!

ps: about the species of wood: does anyone know what wood the "real" watermills are made of if ever I ever have to change? It is necessarily a local essence ...

Hello,

I would see a dawn made of a half PVC tube (yuck ) or more better stainless .......
You will have at least the choice of dimensions without too many problems


Obelix

Christophe wrote:ps: about the species of wood: does anyone know what wood the "real" watermills are made of if ever I ever have to change? It is necessarily a local essence ...

With us there are glutinous alder.

Hello

agree with obelix

Well sorry guys, I don't agree with this for several reasons:

a) I have already used a lot of PVC and I have nothing left over there ...

b) 2 plugs (or 2 * 1/2 plug) will be required for each dawn: at 1 € the plug the bill will be high ...

c) will need to be glued = mechanical resistance over time?

c) these blades will not stand alone: ​​a structure (in wood) must be made behind in all cases ...

d) it's frankly "ugly" (WHAT? WHAT? ) and probably more fragile than wood (possible shocks?)

e) no flexibility for improvement if that is not enough (or vice versa, are we crazy if there is too much torque?)

f) choice of limited dimensions!

In short, I want to make "bucket" out of pallet fir ...

ps: glutinous alder?

Hello
I think that oak and a wood adapt well enough to stay in the water for long periods.
after all there are all exotic woods with high density ..

Ok for oak, I retain the info!

But I do not want exotic wood: our ancestors did not use it and their mills lasted for decades! (maybe more than a modern steel equivalent?)

For the moment I am going to do everything in pallet wood for the "proto" and finding the best shape will suffice! The blades which have already turned for 10 days already have a pain in the micro-algae on their surface but no trace of "rot" ...

I estimated that 1 false Euro pallet = 4 blades as I would like to do them

Bonjour Christophe

The PVC tube cut on a table saw will be more efficient and easy to fix.



Naturally you must put more tube in it than on the photo which is only for information.

Thank you Alain but I think that your diagram will not go without reinforcements: there should be "struts" behind each blade. The fixing screw will work way too ...

But leave concrete, I don't want any more PVC, I would use reclaimed wood slats! If it is not enough for an X or Y reason then I would consider using PVC ...

Too easy PVC, I know I'm a little maso!

Well I dismantled the temporary blades but there I dry (in the rain): in fact I do not know how to attack the rest ... I fear that the shape of a bucket or spoon is counter productive in low pressure blades!

Indeed, when the dawn comes out of the water, there is no risk of having a "suction cup" effect, therefore of creating a counter torque?

So I did some research and I came across 2 interesting sites:

A) http://www.moulinsdefrance.org/old/roue_aubes.html




1) We already have the answer for the choice of wood species: oak, azobé (hu?) Or beech + alder.

2) The shape of the blades is really simple: flat as for the hotton mill, on the other hand they are slightly inclined but the attack of the water is not at all the same as in my case: there is nothing to left"...

B) More interesting in my case: http://clients.newel.net/particulier/am ... leroue.htm

I think my wheel is between a "bottom wheel" and "a flowing wheel". These are the last 2 cases on the page.

WHEEL BELOW



A simple idea from the start of the mills was to attack blades by the mere force of water

The general diagram of this principle is shown on the figure which is also that of a Poncelet

For a long time it was believed that all of the energy was recoverable in this way
In fact it is not
To understand what is happening, refer in the form to the action of a jet on a surface.

In fact the efficiency of these wheels is much lower than that of the wheels above
This question will be treated in more detail with an example in a specific page

WHEEL OVER THE WATER

Who has not mounted on 2 forks a split branch with 4 "blades" that we let turn driven by. the current of the little river?

It is a very mediocre wheel than the wheel over water. (maiiieuh !! )

We must first know what type of flow we are in
Are we in torrential regime or in river regime?
In the first case it is better to turn the page: we are in fact with a type wheel from below, I refer you to it!
We are therefore in river mode. Are we entitled to the entire width and height of the canal, or only part of it?

We can only calculate in the case of the first hypothesis.
There, things are simple.
Between upstream and downstream, there is a difference in height.
This is where we fall and nothing else.
Our wheel, in fact, is a dam. Stopped and well sealed, the water only passes through the "cracks".
In motion, it lets water pass, its linear speed is less than that of current, it opposes resistance and thus recovers energy
It is on this principle that the Sagebien wheel works, a slow, enormous wheel, but one with good performance.

To optimize the design of the blades, I will potash: http://clients.newel.net/particulier/am ... %20dessous
http://clients.newel.net/particulier/am ... %20L%20EAU

Apparently "closed" buckets (buckets is the right term) are not necessary in my case and slightly inclined blades would suffice? The performance will not be good, so I have an interest in taking the maximum possible working surface!