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'[OT]:: How can I most easily cut a Coke can into t'
2011\06\18@001341 by RussellMc

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Looking for a way to most easily, cheaply, quickly, ... cut
alumin[i]um  softdrink cans (Coke, Pepsi, ...) into two pieces with a
"vertical" cut. ie left with two U shaped pieces when viewed from top.
No specs on amount of deformation or roughness of edge etc. Target -
two half barrels which are not obviously rough edged or deformed.

- Two pieces to be as close to halves as reasonably possible (ignoring
assymetry caused by tab and hole).

- Metal not to be bent or deformed. Clean cut with no need for
smoothing desirable. Minor post cut tidy up OK.

- Ease of cutting probably important. Low cost more important than
speee BUT speed is good. Cottage industry / "appropriate technology"
method preferred although, if a high tech method was very cheap and
very fast it may be OK.

- Both ends ideally left in place.
Opened end may possibly be OK to remove.

LASER cutting an obvious choice.
How much power needed? (focus, conductivity, ...)
Could a properly focused DVD writer LASER be used (bursts balloons but
seems unlikely)
That would be an acceptable "high tech" solution.

Hacksaw or any hand saw tens to be brutal on such a deformable can.

Flame? Hard to be neat or accurate.

EDM - electro erosion. Speed? Would work.

Maybe slipping over a slit mandrel would work with one end removed.
End removable greatly undesired if possible.

Suitable feed to a suitable high speed blade with good support ...?

Blown abrasive cutting?

???


    Russel

2011\06\18@003030 by Gordon Williams

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Dremel tool with thin cutoff blade will go through it like butter, if I
understand what you are doing.

Water jet is other possibility that may or may not work.

Gordon Williams


{Original Message removed}

2011\06\18@005246 by John Gardner

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Abrasive cut-off wheels come in all sizes. I've cut up beaucoup
beer cans for alcohol stoves using a tiny cut-off wheel in a high
speed drill press. Fast, & easy once you get the hang of it.

Lasers have more geek appeal, though..

2011\06\18@005620 by Brent Brown

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On 18 Jun 2011 at 16:13, RussellMc wrote:

> Looking for a way to most easily, cheaply, quickly, ... cut
> alumin[i]um  softdrink cans (Coke, Pepsi, ...) into two pieces with a
> "vertical" cut. ie left with two U shaped pieces when viewed from top.
> No specs on amount of deformation or roughness of edge etc. Target -
> two half barrels which are not obviously rough edged or deformed.

Samurai sword?

Or, fill can with water, freeze, cut with hacksaw/bandsaw?

2011\06\18@011258 by Bob Blick

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On Sat, 18 Jun 2011 16:13 +1200, "RussellMc" wrote:
> Looking for a way to most easily, cheaply, quickly, ... cut
> alumin[i]um  softdrink cans (Coke, Pepsi, ...) into two pieces with a
> "vertical" cut. ie left with two U shaped pieces when viewed from top.
> No specs on amount of deformation or roughness of edge etc. Target -
> two half barrels which are not obviously rough edged or deformed.

> LASER cutting an obvious choice.
> How much power needed? (focus, conductivity, ...)
> Could a properly focused DVD writer LASER be used (bursts balloons but
> seems unlikely)

Lasers are great. A ten watt fiber laser is about minimum for aluminium.
Twenty is much better. Cheap to use, they are pretty efficient. Not so
cheap to buy, but if you are doing thousands of cans...

Single diode laser is not going to cut it.

You can build a CO2 laser for cheap, it's old technology but it works.
Lifespan is OK.

Bob


-- http://www.fastmail.fm - The way an email service should be

2011\06\18@011432 by YES NOPE9

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>
> On Jun 17, 2011, at 11:30 PM, Gordon Williams wrote:
>
> Dremel tool with thin cutoff blade will go through it like butter, if I
> understand what you are doing.
>
> Water jet is other possibility that may or may not work.
>
> Gordon Williams
>
>
> {Original Message removed}

2011\06\18@014055 by YES NOPE9

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{Quote hidden}

What is cheap ?
99guspuppe

2011\06\18@020214 by Bob Blick

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On Fri, 17 Jun 2011 23:40 -0600, "YES NOPE9" <spam_OUTyesTakeThisOuTspamnope9.com> wrote:

> > You can build a CO2 laser for cheap, it's old technology but it works.
> > Lifespan is OK.
> >
>
> What is cheap ?

Say $500 if you are a good shopper and already have a junkbox of
non-laser stuff. Less if you already know what works and what doesn't.

Since you are only cutting a can you can use almost anything to sweep,
you don't need galvos.

Bob

-- http://www.fastmail.fm - Choose from over 50 domains or use your own

2011\06\18@031837 by Tony Smith

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> Lasers are great. A ten watt fiber laser is about minimum for
> aluminium.
> Twenty is much better. Cheap to use, they are pretty efficient. Not so
> cheap to buy, but if you are doing thousands of cans...
>
> Single diode laser is not going to cut it.
>
> You can build a CO2 laser for cheap, it's old technology but it works.
> Lifespan is OK.


You need more CO2 laser than you think to cut aluminium, even thin stuff.
It has a habit of conducting heat well (as does copper).  YAG is a better
choice for metals.

EDM might work.

But... Coke cans have the annoying property of being covered in plastic to
stop the drink eating the alloy.  For amusement value get some sodium
hydroxide / caustic soda / lye / drain cleaner and drop a coke can in it.
(Nasty stuff, will eat you too.)

Any sort of spinning blade will distort the thin walls.  Maybe you can fill
it with wax.  You may be able to cut the top & bottom first (thicker) then
score the walls with a thin knife.

Tony

2011\06\18@044941 by Peter Loron

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The freezing/wax idea seems like it has merit.

My first thought was waterjet.

-Pete
On Jun 17, 2011, at 9:13 PM, RussellMc wrote:

{Quote hidden}

> -

2011\06\18@051022 by IVP

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> - Ease of cutting probably important. Low cost more important
> than speee BUT speed is good. Cottage industry / "appropriate
> technology" method preferred although, if a high tech method was
> very cheap and very fast it may be OK

Laserstream in Rosebank Rd (still ?). They do water jet cutting.
Set-up cost and then piecework after that

A problem I see with anything like a laser or water jet is that it's
going to go through the one side and then what ? It will still have
enough energy to do something interesting to the other side. And
you'll have a can full of water, sand or laser

You need one of those whips like what Vanko had in Iron Man 2

I've a very very fine oxy-acetylene torch which the very skilled
can work aluminium cans with. Don't know how you'd get on
with a plasma cutter

Jo

2011\06\18@053743 by Michael Watterson

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On 18/06/2011 05:13, RussellMc wrote:
> Looking for a way to most easily, cheaply, quickly, ... cut
> alumin[i]um  softdrink cans (Coke, Pepsi, ...) into two pieces with a
> "vertical" cut. ie left with two U shaped pieces when viewed from top.
> No specs on amount of deformation or roughness of edge etc. Target -
> two half barrels which are not obviously rough edged or deformed.

I cut coffee cans to make sheets to solder little screened boxes for electronics.

A stanley or other similar heavy duty craft knife cuts a can easily. I don't know if the distortion is too much. But if a tin-opener removed the lid you could have a grooved/slotted wooden form go inside can and set it in a wooden jig and quickly cut can with knife accurately without distortion.

2011\06\18@090129 by John Ferrell

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On 6/18/2011 12:13 AM, RussellMc wrote:
{Quote hidden}

I rework soft drink cans frequently. My tools of choice are a box cutter knife
and scissors. If it is OK to remove the top it would be nice to be able to
insert a back up block for the box cutter.

--
*John Ferrell W8CCW*

**//**

"In peace, sons bury their fathers. In war, fathers bury their sons."

- Herodotus, Greek historian, 5th century B.C.**

**

2011\06\18@091719 by Michael Watterson

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On 18/06/2011 14:00, John Ferrell wrote:
>> Russell
> I rework soft drink cans frequently. My tools of choice are a box cutter
> knife
> and scissors. If it is OK to remove the top it would be nice to be able to
> insert a back up block for the box cutter.

Exactly what I meant. We call a box cutter a Stanley knife

2011\06\18@091825 by PICdude

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Thinking of something similar, except using expanding foam, then  dissolving the foam with acetone (which should do the trick, but I  haven't actually tested it).

It takes a special laser to cut metal, so that may be costly.  The  dremel cut-off should work well.

Or perhaps tape off all but the thin cut-lines and etch...?

Cheers,
-Neil.



Quoting Brent Brown <.....brent.brownKILLspamspam@spam@clear.net.nz>:

{Quote hidden}

>

2011\06\18@233420 by YES NOPE9

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How about .............
grab the can at the two ends.
Spin the can up to 10,000 RPM.
Can should want to maintain roundness.
Apply a cutter.
Watch for flying debris.

Perhaps spinning can slowly and then slowly lowering a dremel cutter disc ......
I have done this when "rounding" the shaft of a motor.
99guspuppet

> On 18 Jun 2011 at 16:13, RussellMc wrote:
>
>> Looking for a way to most easily, cheaply, quickly, ... cut
>> alumin[i]um  softdrink cans (Coke, Pepsi, ...) into two pieces with a
>> "vertical" cut. ie left with two U shaped pieces when viewed from top.
>> No specs on amount of deformation or roughness of edge etc. Target -
>> two half barrels which are not obviously rough edged or deformed.
>

2011\06\18@233939 by IVP

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> grab the can at the two ends.
> Spin the can up to 10,000 RPM.

I think Russell was wanting to cut the can lengthwise, to make
two trough

2011\06\19@141800 by YES NOPE9

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>
> On Jun 18, 2011, at 9:39 PM, IVP wrote:
>
>> grab the can at the two ends.
>> Spin the can up to 10,000 RPM.
>
> I think Russell was wanting to cut the can lengthwise, to make
> two troughs

Whoop

2011\06\19@142158 by YES NOPE9

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>
> On Jun 18, 2011, at 9:39 PM, IVP wrote:
>
>> grab the can at the two ends.
>> Spin the can up to 10,000 RPM.
>
> I think Russell was wanting to cut the can lengthwise, to make
> two troughs


#1   Use parallel suction ports to hold aluminium wall steady and cut between them with dremel cut-off wheel..
#2   fill can with steel beebees and use magnets to hold aluminium wall steady and cut between them with dremel cut-off wheel..
99guspuppet

2011\06\20@041120 by alan.b.pearce

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> You need more CO2 laser than you think to cut aluminium, even thin stuff.
> It has a habit of conducting heat well (as does copper).  YAG is a better
> choice for metals.

Many years ago I had some dealings with a company that had a laser cutter, we needed some adapter plates made. I suggested aluminium - but that was the one metal they couldn't cut. We ended up with them being cut out of thin stainless steel.
-- Scanned by iCritical.

2011\06\21@185409 by Denny Esterline

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On Fri, Jun 17, 2011 at 9:13 PM, RussellMc <apptechnzspamKILLspamgmail.com> wrote:

{Quote hidden}

Lots of questions abound, quantities? Rate? Number of people doing it?
(likely number of needed devices) First world / third world? (Relative value
of labor vs. mechanisms? Costs / availability of energy?)

Can you "waste" half of the can?
I can imagine a shear of sorts with a half can shaped cutout to receive the
can and a blade that slides / turns to shear the can from the inside. But
the "other" half of the can would be waste.
Even with lever/human power probably 3-5 seconds per cut.


EDM not a horrible choice, has some hurdles to overcome. Speed is fairly
slow, could be improved by cutting multiples in parallel. Needs good ground
connection to part, soda cans often have plastic coating that could be an
issue there. The wire is only used once - hence a consumable - an ongoing
cost per cut.

-Denn

2011\06\21@190311 by YES NOPE9

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Rzzzzzzzzzzzzzzz
Could you give us some some more background into what you are trying to do ?
How many ? For what ?  Does it involve anyone from outer space ?
99guspuppet

2011\06\22@022455 by Ruben Jönsson

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>
> Lots of questions abound, quantities? Rate? Number of people doing it?
> (likely number of needed devices) First world / third world? (Relative value
> of labor vs. mechanisms? Costs / availability of energy?)
>
Yes, and I for one, would also like to know the purpose. What is the can halves going to be used for?

And here is my contribution...

Make a fixture of two parts with a holow half-can space in both. Put the can in one of the fixture part and close it with the other fixture part but use some spacers to just let a circular saw blade go through it at the top and bottom.

Use a high rpm circular saw to saw a slit through the top and bottom. It may be possible that the saw can saw a slit lengthways (top to bottom) in the can also (using another fixture with spacers at top and bottom instead of lengthways). If not, use another tool, some sort of cutter where one blade is thin enoug to go throug the slits in the top and bottom and then cut the can lengthways. Could possibly be done by hand with a pair of scissors.

The fixture halfes could be made with several spaces for cans on a row where the top and bottom of several cans could be slitted at once.

/Ruben



==============================
Ruben Jönsson
AB Liros Electronic
Box 9124, 200 39 Malmö, Sweden
TEL INT +46 40142078
FAX INT +46 40947388
.....rubenKILLspamspam.....pp.sbbs.se
==============================

2011\06\22@040807 by alan.b.pearce

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> What is the can halves going to be used for?

When I first saw Russells request I thought he was making a mini-barbeque, maybe for doing spit roast mouse or something ...

No knowing what he is likely to want to cook, what with all his visits into the Asian region ... ;)))))
-- Scanned by iCritical.

2011\06\22@103431 by Denny Esterline

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>
>
> > What is the can halves going to be used for?
>
> When I first saw Russells request I thought he was making a mini-barbeque,
> maybe for doing spit roast mouse or something ...
>
> No knowing what he is likely to want to cook, what with all his visits into
> the Asian region ... ;)))))
> --
>

Funny, my first thought was a really tiny Savonius Rotor...
http://en.wikipedia.org/wiki/Savonius_wind_turbine


-Denn

2011\06\22@105542 by Michael Watterson

face picon face
On 22/06/2011 09:07, EraseMEalan.b.pearcespam_OUTspamTakeThisOuTstfc.ac.uk wrote:
>> >  What is the can halves going to be used for?
> When I first saw Russells request I thought he was making a mini-barbeque, maybe for doing spit roast mouse or something ...
>

Or a small Barbecue for mice to use

2011\06\22@132706 by RussellMc

face picon face
> > > What is the can halves going to be used for?

> > When I first saw Russells request I thought he was making a mini-barbeque,
> > maybe for doing spit roast mouse or something ...
> >
> > No knowing what he is likely to want to cook, what with all his visits into
> > the Asian region ... ;)))))

Denny  saith:
> Funny, my first thought was a really tiny Savonius Rotor...
> http://en.wikipedia.org/wiki/Savonius_wind_turbine

Denny gets the olive wreath.
Looking for an "appropriate technology" material for micro turbine
where cost is crucial.
While Coke cans may not be as common in some developing country areas
as other materials, they have widespread availability and very
standardised construction.
I thought it worth throwing out the query for input first as,
regardless of how good they prove strength wise, there re definitely
applications for them in this role.


Whether material will be able to be strong enough is tbd.
Will be trying shortly.

Calculations suggest it may do better than may be expected.

Low diameter has two interesting effects.

Low width means that great length is needed for modest area.
Mass can be low and a very long string or rotors using "cord" (wire -
rope -  yak's   wool -  ...) may allow a several meter long rotor to
be utilised. Potential problems multiply with thought :-)

A pure drag WT has a max tip speed to wind speed ratio of 1 and
probably less. Savonius is NOT pure drag and can manage TSR of up to
a.x where x varies with profile and more.
1.2 ish for 1/2 barrels .
1.5 - 2.0 maybe for Benesh airfoil and magic.

At TSR = 1:1 the OD travels at wind speed.
So the smaller the dia and circumference the greater the RPM per wind speed..
A Coke can rotor will be ~~~~= 100 mm dia or 314mm circ or about 3.2
revs/second per m/s of wind speed or 190 rpm per m/s.
Say 200 RPM per m/s
So in a 5 m/s wind you get 1000 RPM at TSR of 1.

High RPM is of great advantage when trying to build small alternators
with a minimum cost on magnetics.

A coke can rotor doing 15 revs per second = 1000 RPM would be a sight
to behold !!! :-).
Centrifugal force gets interesting :-).
A 1 metre length of Savonius should produce 0.5 to 1.5 Watts at 5 m/s

P =~~~~~~ 600 x A x z x (V/10)^3

A area m^2
Z efficiency
V wind speed m/s

1 metre x 0.1m = 0.1 m^2
Z = 0.1 to start. Savoinius can get 0.1 - 0.2 done well.

600 x 0.1 x 0.1 x (5/10)^3 ~= 0.75 Watt.

3 metres in a "string" - pivot at top to guy to tree etc.
Base to ground with "guy" or a weight.
Say 2 Watts at 5 m/s.

Designing it to stall at above some max speed (probably no more than
above) is needed, or else.

Placing 1 metre lengths of these in a frame with appropriate spacing
covers the whole area. You get a rectangular WT :-)
Quite simple frames MAY suffice.

I'll be playing games with PVC and other pipes as well.
NB: Low pressure PVC pipe and much high pressure shatters nastily when
over stressed. Use at high TSR needs careful thought.

Quick BOTE calc
E&OE
Force per metre on one side at 5 m/s ~= 3 Newton = ~300 gram
Mean radiius = 50 mm.
Torque = 0.3 x 0.05 = 0.015 kg.m = 1.5 kg. cm (to mix units)
That's a useful amount of starting torque!
That's on one blade and the other will partially oppose it but still
shows why Savonius is a good self starter.
NB E&OE 5:20am :-)


         Russell



Anon

           Russell



wher

2011\06\22@140252 by Denny Esterline

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>
>
>
> Denny gets the olive wreath.
>

:-) Always wanted one of those.


Placing 1 metre lengths of these in a frame with appropriate spacing
> covers the whole area. You get a rectangular WT :-)
> Quite simple frames MAY suffice.
>
>
Very interesting. What are your thoughts about the multiple shafts?
Gears/chains/belts mechanical connection or multiple generators?
I've spent considerable time lately with small 3-phase brushless motors. At
least at the moment the RC hobby market really seems to be in the lead over
the industrial market in terms of price and energy density. (hint, I think
they'd be very interesting as small permanent magnet generators)

-Denn

2011\06\23@070850 by Justin Richards

face picon face
The solution most appealing to me (if this was my challenge) was using
a vacuum on the outside of 1/2 of the can.

It turns out that the inside diameter of the drive shaft from a Holden
Kingswood (or similiar vintage holden) is just right to take a coke
can, slightest of interference fits (at least the coke cans and Holden
Tail shafts that I am familiar with in Australia).

I suspect one of these could reasonably quickly cut in half length
ways.  Several small 1/8" holes drilled along the length connected to
aluminum or copper tubing connected to a vacuum.  Sponge down the
"half" tail shaft to improve the air seal.

Many cans (perhaps 12) could be placed in the "half" tail shaft ,
vacuum applied then brought into range of a set of very sharp very
fast spinning knives

Not sure how to do the spinning knives bit but I think the drive shaft
with vacuum assist would hold them secure

2011\06\23@071908 by Justin Richards

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On 23 June 2011 19:08, Justin Richards <justin.richardsspamspam_OUTgmail.com> wrote:
> The solution most appealing to me (if this was my challenge) was using
> a vacuum on the outside of 1/2 of the can.
>
As suggested previousl

2011\06\23@104006 by RussellMc

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> The solution most appealing to me (if this was my challenge) was using
> a vacuum on the outside of 1/2 of the can.

If carefully done a vacuum clamp could be low tech and use eg a foot
plunger to apply suction which may be able to be retained for the
duration without power.
A friend in NZ notes that 40mm x 1mm abrasive cutoff blades rated to
run at 10,000 rpm are available here.
Would probably be even more exciting than a Dremel abrasive disk if
loaded sideways while cutting :-).

Holden shaft sounds fun BUT you could probably cast a perfect fit half
shell using a can mold, or using bent plastic. Or ...

Sounds one of the most likely candidates overall so far. I think Gus
was the first to mention suction.

About 800 N / 80 kg clamping force would be availble at 0.5 atmosphere
if most of the half can face could be exposed to suction.
A curved surface with an axial "O ring" seal and a surface of
microchannels to spread pressure well may work nicely.

It's just possible that if each can half was so gripped and a very
small gap left between the two halves, that mechanical stressing could
be used to separate the two halves.
Ultrasonics or just mechanical vibration. Scoring along the thus
exposed line may well make separation clean and easy. Or not.




R
..
On 23 June 2011 23:08, Justin Richards <@spam@justin.richardsKILLspamspamgmail.com> wrote:
{Quote hidden}

> with vacuum assist would hold them secure.

2011\06\23@105959 by John Ferrell

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On 6/22/2011 1:26 PM, RussellMc wrote:
>
> Denny gets the olive wreath.
> Looking for an "appropriate technology" material for micro turbine
> where cost is crucial.
> While Coke cans may not be as common in some developing country areas
> as other materials, they have widespread availability and very
> standardised construction.
> I thought it worth throwing out the query for input first as,
> regardless of how good they prove strength wise, there re definitely
> applications for them in this role.
> where
Interesting!
I just trashed a similar project using plastic soda bottles. My mechanics were just too crude.

I will try again...

--
*John Ferrell W8CCW*

**

*'A man's feet should be planted in his country, but his eyes should survey the world. '*

*George Santayana*

**

2011\06\23@111208 by RussellMc

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> Interesting!
> I just trashed a similar project using plastic soda bottles. My
> mechanics were just too crude.
>
> I will try again...

Do you mean micro wind turbine?
If so, please discuss.
This area is of great interest to me.

Plastic bottles are also "on the agenda" and have their pros and cons.
You need to understand forces and general available power levels and
work accordingly.
Not rocket science but more than meets the eye to do well.

I presently have a plastic $1 bucket based unit running that turns in
the lightest of breezes. Power at low speed is minimal - but I am
especially interested in low wind speed power regardless.

Rule of thumb

Power = 0.6  x A x Z x V^3 Watt

A m^2, Z efficiency 0 - 1, V m/s

Well made Savonius can get perhaps 1 Watt / m^2 at 2 m/s



                 Russel

2011\06\23@132308 by Bob Blick

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On Thu, 23 Jun 2011 10:59 -0400, "John Ferrell"  wrote:

> Interesting!
> I just trashed a similar project using plastic soda bottles. My
> mechanics were just too crude.
>
> I will try again...

Maybe go bigger, this place in my neck of the woods has been a landmark
for me as long as I can remember:

http://www.flickr.com/photos/14696209@N02/4150948998/

Cheers,

Bob

-- http://www.fastmail.fm - Same, same, but different...

2011\06\23@133616 by RussellMc

face picon face
> Maybe go bigger, this place in my neck of the woods has been a landmark
> for me as long as I can remember:
>
> http://www.flickr.com/photos/14696209@N02/4150948998/

Many go bigger or much bigger
My target is very low wind speed, trivial power out  and as big as necessary.

The WT shown would make decent power and have awesome torque given
good wind at that level - not a certainty.

Does it still rotate?.

Easiest way to use that power would be a friction brake or paddle
churn heating water. A very efficient use of a WT's power.



   Russel

2011\06\23@134616 by Bob Blick

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On Fri, 24 Jun 2011 05:32 +1200, "RussellMc" wrote:
> > Maybe go bigger, this place in my neck of the woods has been a landmark
> > for me as long as I can remember:
> >
> > www.flickr.com/photos/14696209@N02/4150948998/
>
> Many go bigger or much bigger
> My target is very low wind speed, trivial power out  and as big as
> necessary.
>
> The WT shown would make decent power and have awesome torque given
> good wind at that level - not a certainty.
>
> Does it still rotate?.

Absolutely. The current owners are maintaining it. It runs even in light
wind.

Bob

-- http://www.fastmail.fm - The way an email service should be

2011\06\23@150949 by William \Chops\ Westfield

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On Jun 23, 2011, at 10:32 AM, RussellMc wrote:

> target is very low wind speed, trivial power out

I want to do something like this.  Some sort of convenient semi- tubular piece of trash mounted on a discarded CD drive spindle motor  (or one at the top an one at the bottom?), perhaps with much of the CD  drive mechanics still intact.  Put it on the roof and measure the  output...

BillW

2011\06\23@164258 by RussellMc

face picon face
>> target is very low wind speed, trivial power out
>
> I want to do something like this.  Some sort of convenient semi-
> tubular piece of trash mounted on a discarded CD drive spindle motor
> (or one at the top an one at the bottom?), perhaps with much of the CD
> drive mechanics still intact.  Put it on the roof and measure the
> output...

See my prior comments.
You'd need advanced Savonius blades to get 1 Watt/ m^2 at 2 m/s. This
increases with cube of wind speed.
ie 125 Watts / m^2 at 10 m/s.
I want something that makes 1 Watt if you can feel the breeze on your face.

Most promising motor so far is 1.44 MB floppy disk as it is low RPM
compared to CD motor.
Good iron and magnetics to play with
Most BLDCMs can be used by bypassing the drive IC. Rewinding for
higher voltage per rpm is often desirable

Main trouble with CD motor and Savonius is speed mismatch.
Savonius as per my recent posts is only TSR ~= 1 so low rpm wrt lift WTs.
That's why the idea of a long and low dia rotor is useful.
~- 200 RPM per m/s at 100 mm dia.

I have a $1 bucket on a metal pie plate on an inline skate bearing as
a demonstrator of 'how low can you go" $ wise.
Extremely low wind speed start up (unloaded). Savonius has good torque
and good startup compared to most alternatives.

Benesh profile blades do not allow use of buckets and barreles (unless
you beat them severely) but is easy and cheap with sheet material and
signifi=cantly superior to bucket style.

Beware the Rahai profile. His results look good for single blades but
are probably inferior to Benesh when in a real machine.

If you use a large diameter alternator with many poles you get better
low speed performance for give magnetics and windings.

Someone asked about gearing etc multiple rotors together. It's doable
but for low powers and with lowish quality designs (non rigid
structures,  plastic gears etc) the power losses can easily exceed the
modest power available. I'm going to try "magnetic drive" coupling.
May not be economic. One advantage of gearboxes is the ability to
increase alternator speed. but unless some form of clutch or careful
magic is used the reflected load often makes startup torques
unacceptable. Even cogging (saliency) in direct drive alternators is
often the limiting factor in startup wind  speed.


              Russell

2011\06\23@233515 by Tony Smith

picon face
> A friend in NZ notes that 40mm x 1mm abrasive cutoff blades rated to
> run at 10,000 rpm are available here.
> Would probably be even more exciting than a Dremel abrasive disk if
> loaded sideways while cutting :-).


When all else fails do the experiment...

I had the same thought with abrasive discs, tried it and the results are
rather good.

The Dremel-ish ones I used were 25 x 0.9mm, these aren't big enough (and the
tool gets in the way) to fully cut the can as I couldn't cut the dome in the
bottom.  That's about 12mm or deep.

And yes, they do shatter if looked at the wrong way.  I only broke one which
I consider an excellent result.

A larger disc would work well, especially if you can set it up table saw
style with a jig for the can.  You've been able to get angle grinder discs
(100-125mm) at 1mm or thinner, eg
http://www.specialabrasives.com/finecut.htm for some time, so that was next..

As expected it made short work of the can, with a slightly poorer edge
finish (clinging swarf etc), but nothing a quick swipe with a file or the
like won't solve.  That could be reduced by slower speeds or a finer grit
disc (which may not exist).

Or you can wait for the magic 1W IR laser.

Tony

2011\06\24@020355 by RussellMc

face picon face
> When all else fails do the experiment...

I knew the Dremel would work - I use them with due care to cut all
sorts of otherwise intractable things.
Apart from blade size (too small as you say)
That plus vaccuum may work even better.

> And yes, they do shatter if looked at the wrong way.  I only broke one which
> I consider an excellent result.

Yes. I hav a large supply. A good idea as they jumpto hyperspace
without warning One moment there, the next an empty arbor.

> Or you can wait for the magic 1W IR laser.

It would be educational to work out the likely energy flow from a near
point source in insulated Al at melting point.
Outer against can can be thermally high resistance.
Can inner could be hot air washed to raise temperatures.
Flow through Al away from point becomes (I think) the main load.
Or, just try it with a DVD LASER.
I have many dead CD drives (another part is of interest).
Ferwer DVDs.
Would be interesting to try.
Can burst green balloons at several metres with some DVD units I am told.
Yet to try.
Do not stare into beam ...

______________

My wife was recently persuaded to stare into the working end of a YAG
LASER with her remaining bad eye recently. I got to watch.
Soft thump as massive well mounted caps somewhere give up their energy.
Operator retargets and repeats. Every few seconds. Maybe a few 120's
of shots, if that.
2.5 minutes go to whoa.
Perfect restoration of had-been-clouding vision - due to opacifying of
lens sac at rear - left over from intraocular lens transplant needed
months after an Epithelial peel.
Marvellous what you can do with a LASER
Hope for cans yet.


       Russell

2011\06\24@033133 by Michael Watterson

face picon face
On 24/06/2011 07:03, RussellMc wrote:
> Do not stare into beam ...
>
with remaining eye,


A knife or dremel style wheel is simplest. I will try my coffee tins/cans (I don't drink coke).
The steel coffee tins are much more robust than an Aluminium drink can and are easily sliced.

8.5mm dia  x 13.5mm tall.The knife (stanley blade/box cutter) cuts the two sides, and across bottom easily, but not the upper and lower rim. A dremel would make quick work of that. My cuts had no jig so not perfectly straight

2011\06\24@053958 by Lee Jones

flavicon
face
> The Dremel-ish ones I used were 25 x 0.9mm, these aren't big enough
> (and the tool gets in the way) to fully cut the can as I couldn't
> cut the dome in the bottom.  That's about 12mm or deep.

Here in the US, Dremel sells an EZ lock mandrel with various 40mm
diameter disks.  One is a fiber reinforced cutoff wheel.  I tried
it and it is more tolerant of side-force than the 25mm wheels.

Dremel also has the EZ544 wood cutting disk; 1-1/2 inch diameter
designed to cut wood up to 1/2" thick.  I expect it would work
quite nicely on aluminum cans, particularly if you had a guide
to ensure the tools was moving in a straight line.

                                               Lee Jone

2011\06\24@124044 by Michael Watterson

face picon face
On 24/06/2011 08:31, Michael Watterson wrote:
> On 24/06/2011 07:03, RussellMc wrote:
>> Do not stare into beam ...
>>
> with remaining eye,
>
>
> A knife or dremel style wheel is simplest. I will try my coffee
> tins/cans (I don't drink coke).
> The steel coffee tins are much more robust than an Aluminium drink can
> and are easily sliced.
>
> 8.5mm dia  x 13.5mm tall.The knife (stanley blade/box cutter) cuts the
> two sides, and across bottom easily, but not the upper and lower rim. A
> dremel would make quick work of that. My cuts had no jig so not
> perfectly straight.

OK

Cut can with knife, no support or jig
cut remaining parts of top & bottom rim with sidecutters (electrician, not electronic ones)
Soldered two halves and punched two holes for  steel rod (knife slot then push in and turn 3mm approx shaft screwdriver)
www.irishwattystuff.com/images/mech/turbine-2046.jpg
www.irishwattystuff.com/images/mech/turbine-2049.jpg
http://www.irishwattystuff.com/images/mech/turbine-2051.jpg

No idea how much they should overlap (in both directions), but it goes round

2011\06\24@130514 by RussellMc

face picon face
Now stack 10 of them with 90 degree offsets between adjacent ones.
Somewhere along the way the bug will bite.
5am - more on overlap another time.

Put it in a mild breeze. REalise why you want balance :-)

2011\06\24@132659 by Michael Watterson

face picon face
On 24/06/2011 18:04, RussellMc wrote:
> Now stack 10 of them with 90 degree offsets between adjacent ones.
> Somewhere along the way the bug will bite.
> 5am - more on overlap another time.
>
> Put it in a mild breeze. REalise why you want balance :-)
>
>   R
10 x 200g cans of expresso ..

Hmm  More coffee eeee  eee Wheeeee! :)

2011\06\24@134108 by RussellMc

face picon face
>> Put it in a mild breeze. Realise why you want balance :-)

> 10 x 200g cans of expresso ..

> Hmm  More coffee eeee  eee Wheeeee! :)


I've used large steel fruit cans. Metal finally tore - but this was
not speed limited and was well exposed.

I specified "Coke"cans as they are liable to be more available than
most raw materials.
A contact tells me that Haiti has many plastic bottles available.
Value of "many" as yet unknown. Bottles also tend to be less standardised.
It's only an exercise by may yet lead to something.
"Real" tests will be with PVC pipe but if available scrap materials
can be realistically used so much the better.
This is not a substitute for purpose designed and built units but a
possible added bonus - as the quality control is lacking and there's
no doubt that the feedstock is delicate.


R

2011\06\24@134626 by John Gardner

picon face
With a rigid spindle for the arbor (like a drill press/milling machine),
a V-block to locate the can, and a fence to guide the V-block, a cut-
off wheel would likely do what you need well enough, fast enough,
and certainly cheap enough.

Scotch-Brite wheels work well for deburring Al cans

2011\06\28@105719 by Walter Banks

picon face
At the risk of re-opening this discussion. Besides coke cans
there is another readily available material that could be used.

For the price of two or three cokes you can buy 10 feet of
tubing used for built in household vacuum cleaners. In Canada
and the US available in most big box hardware stores.

This tubing is thin walled light and easy to work with. (I use it as
replacement tubes on bird feeders) It lasts quite well outside.
Some of the bird feeders are 7 or 8 years old

A few months ago I attended a seminar that Microchip was
running on reference designs for putting power back into the
grid. Three things came out of that seminar.

1) Intermediate storage batteries are a bad idea. They don't
   last very long.

2) Even small amounts of power can be practically fed into
   the grid even through a plug in the wall.

3) The major design problem is a control loop that phase
    locks to the line. The reference designers we mostly
   PIC32 based.


w..

2011\06\28@113743 by Joe Wronski

flavicon
face
 On 6/28/2011 10:58 AM, Walter Banks wrote:
>
> A few months ago I attended a seminar that Microchip was
> running on reference designs for putting power back into the
> grid. Three things came out of that seminar.
>
>
....
> 3) The major design problem is a control loop that phase
>       locks to the line. The reference designers we mostly
>      PIC32 based.
>
The google foo is weak right now, but recently there was an article about the standards for US power generation synchronization being relaxed to make it easier for solar, wind, and what not to add to the grid.  The focus of the article was on how it would effect your mechanical or power line synched electronic clock's accuracy.
Ah, here's a reference with the reasons based more on money than alternate energy.
<http://radiomagonline.com/infrastructure/power/60hz-stability-going-away-0627/>

-- Joe Wronski
Stillwater Embedded Engineering
http://www.stillwatereng.net

2011\06\28@115552 by Denny Esterline

picon face
>
>
> mechanical or power line synched electronic clock's accuracy.
> Ah, here's a reference with the reasons based more on money than
> alternate energy.
> <
> radiomagonline.com/infrastructure/power/60hz-stability-going-away-0627/
> >
>
> --
> Joe Wronski


"clocks could run up to 20 minutes fast over a year"

and

"Turntable enthusiasts for example may experience some fluctuations"

Hmm... 20 minutes / 1 year = 0.0038%
Dang, those audiophiles must have some impressive ears to hear that.

I can see it now.... "Hey, what's wrong with your turntable - Free Bird ran
almost 20 milliseconds too long?"

-Denn

2011\06\28@140533 by John Gardner

picon face
....Even small amounts of power can be practically fed into the grid...

What range of "small" was being discussed?

Jac

2011\06\28@181521 by Walter Banks

picon face
100 - 300 watts was the working definition of "small" smaller than I
thought was even interesting.  The technology in the reference designs
would allow it to work down to a few watts

The goal was to use the grid as a reliable source of power taking from
it as needed and using your own if possible adding power back if there
is any left over.

It was a different approach for small scale solar and wind. For solar
have a separate controller for each 300w solar array and keep it
simple.

w..

John Gardner wrote:

> ...Even small amounts of power can be practically fed into the grid...
>
> What range of "small" was being discussed?
>
>  Jack
>

2011\06\28@224804 by RussellMc

face picon face
> 100 - 300 watts was the working definition of "small" smaller than I
> thought was even interesting.  The technology in the reference designs
> would allow it to work down to a few watts

I'm not overly interested in grid connectivity (although not
uninterested) but am looking at wind power typically in the1 Watt to
10 Watts range.
Highly valuable for some.


    Russell


'[OT]:: How can I most easily cut a Coke can into t'
2011\07\05@124125 by Gerhard Fiedler
picon face
Denny Esterline wrote:

> "clocks could run up to 20 minutes fast over a year"
>
> and
>
> "Turntable enthusiasts for example may experience some fluctuations"
>
> Hmm... 20 minutes / 1 year = 0.0038%
> Dang, those audiophiles must have some impressive ears to hear that.

One thing has nothing to do with the other. 20 min/year is an average
over a year; short-term fluctuations can be much larger. What exactly
would change is not quite clear to me, but this implies that the
frequency control becomes more coarse, resulting in both a larger
short-term fluctuations and a higher long-term average deviation.

> I can see it now.... "Hey, what's wrong with your turntable - Free
> Bird ran almost 20 milliseconds too long?"

What one would hear is not a song being 20 ms too long, but a
fluctuation in the frequency of a tone. Some people have finer ears than
others, though...

Gerhar

2011\07\05@125553 by John Gardner

picon face
Many humans have excellent frequency discrimination.

Back in the day I could whistle the ring tones for Air Force
wideband multiplex systems, and cause the connected phone
to ring.

Not an unusual talent, I should add...

Jac

2011\07\05@165914 by RussellMc

face picon face
> At the risk of re-opening this discussion. Besides coke cans
> there is another readily available material that could be used.

Less of that lying in the streets of Port au Prince than Coke' cans, I
suspect :-)

But:

> For the price of two or three cokes you can buy 10 feet of
> tubing used for built in household vacuum cleaners. In Canada
> and the US available in most big box hardware stores.
>
> This tubing is thin walled light and easy to work with.

I assume that is a plastic material and not metal, yes?
Regardless, any idea of what the material is?

>  (I use it as
> replacement tubes on bird feeders) It lasts quite well outside.
> Some of the bird feeders are 7 or 8 years old

Sounds good.
What location is that in?

Any plastic that maintains mechanical integrity outdoors for 8 years
is respectable.
In NZ the UV is generally more intense than anywhere more 'normal'.
We were most surprised to find that across the Southern US (Ca, Ar,
?Mon) and all Europe and UK at the height of a hot summer we could
literally stay out in the sun all day long for days on end  with no
sun screen and survive OK. In NZ you'd get maybe 2 to 4 hours and be
severely affected.

"Even" in Africa ABS products have a lifetime of "a few years" unless
great care is taken with UV stabilisation. Even visible light is a
significant issue (hence use of eg HALS stabilisers).
So 8 years is a very benign climate, or not ABS or excellent
stabilisation.   Polycarbonate can last 20 years with due care with
stabilisation.

___________

> A few months ago I attended a seminar that Microchip was
> running on reference designs for putting power back into the
> grid. Three things came out of that seminar.
>
> 1) Intermediate storage batteries are a bad idea. They don't
>    last very long.

Depends very much on chemistry, construction (some chemistries), cycle
depth and cell temperatures and magic stuff.
1/Nth of depth in cycling generally gives more than N times cycle extension..

Simplistically:

LiIon is good for 300-500 full cycles plus has a calendar limit but
responds quite well to shaving ends off cycle.

Lead acid construction matters muchly plus magic plate constructions
and formulations help heaps (deep cycle LA magic is much practiced)
and temperature matters. Basic LA is very very poor for cycles (200?)
but can be extended to many thousands with capacity reduction and
magic. ?

LiFePO4 is good for 2000 with minimal care and more with suitable effort.

NimH is very variable. Maybe 300-600 std but out to 2000 with end of
cycle shaving of say 20% of capacity and temperature matters much.

NiCd lower than NimH notionally if abused but with modest care seems
to go forever and ever and ever.

NiFe is unseen almost nowadays (very low energy density) but is said
and seems (N=1)  to take brutal treatment indefinitely. Auld lang syne
we had wooden crated metal bused "prismatic" NiFe with screwed on
joining busbars that had  been rescued from a rubbish dump and that
seemed to withstand continual school-boy over discharge crash
discharge and random charging excesses forever.

But yes, putting a battery in the middle is bad if it can be avoided.
90% in/out transfer efficiency would be commendable and worse to much
worse is easily achieved. Direct solar to end target conversion is
good if viable. (My special interest is lighting where direct use
tends to "not be favoured" :-). Solar to eg cellphone charging direct
is of some interest but even that often tends to be a night time
application.)

> 2) Even small amounts of power can be practically fed into
>    the grid even through a plug in the wall.

Yes. No reason why not.
Main issue at micro power levels is rate of return.
1 Watt continuous is worth about $2 at typical grid electricity charges.
If grid is localised and/or high cost per kWh it may be economically justified.

> 3) The major design problem is a control loop that phase
>     locks to the line. The reference designers we mostly
>    PIC32 based.

I know people here whose specialty is energy recovery back o mains in
systems often in the sub kW range.



   Russell McMahon

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