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Old September 4th, 2005, 05:46 AM   #1
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New method for spinning real Ground Glass

OK, starting a new thread on this as its not related to hard drives anymore.

I am just getting ready to buy the tools required to build this spinning glass adapter. Below is what I intend to use:

1:A plastic project box to house everything in. size - MB5 145 x 95 x 575 (mm):
http://www.maplin.co.uk/Module.aspx?...rldID=&doy=3m9

2:1 Circular glass cutter like here:
http://cgi.ebay.co.uk/ws/eBayISAPI.d...MEWA%3AIT&rd=1

3:Pack of 1mm Diamond drill bits like here:
http://cgi.ebay.co.uk/ws/eBayISAPI.d...MEWA%3AIT&rd=1

4:Coolermaster 80mm Tri-Blade Silent Fan:
http://cgi.ebay.co.uk/ws/eBayISAPI.d...MEWA%3AIT&rd=1


Firstly ill cut the fan blades off and the outer body. Ill then drill 3 holes in the centre of a 5x6" glass from a photoframe using the 1mm diamond drill bit, the 3 holes will form a triangle shape to mount to the pc fan.

i will then place the glass in top of the pc fan where it should be mounted as accuratly as I can, then mark 3 holes on the fan. Ill then drill the holes on the fan ready to take 1mm screws to hole the glass to the fan. Ill use rubber grommets/washers, as to prent the screws from cracking the glass when they are tightened.

With the glass mounted, Ill start the glass spinning slowly, then using a perminant marker pen, touch the surface of the glass exactly 45mm from centre (90mm diameter glass), keeping the pen very steady. This will result in a line in the perfect position in relation to the axis of the motor.

Unmount the glass from the fan, then using the circular glass cutter, cut the 90mm diameter glass disk exactly on the line.

Once cut, you can then grind the glass with aluminium oxide (maybe its best to grind before hand?)

Remount the glass and you have it. The glass should be centred perfectly in relation to the centre axis of the motor.


There are 2 possible problems with this method. 1: Any inaccuracy when trying to cut on the line with the cicular glass cutter and 2:making sure the glass mounts to the fan in the EXACT same position each time.

Anyway, im going to buy the tools next week and give this a go. the 90mm diameter disk is the smallest possible while being able to use a 36x24mm frame area. The smaller the diameter of the glass, the less gyro effect i beleive. Ill let you all know how I get on.

Thanks
Wayne.
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Old September 4th, 2005, 06:55 AM   #2
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Ill see if I can make some drawn diagrams today to demonstrate my method, hopefully I can post them later.

Wayne.
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Old September 4th, 2005, 07:19 AM   #3
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Howdy, using a computer cooling fan is a good idea, I wanted to do this not too long ago. However I couldn't power the fan, they require 12V which is quite a lot.

I'm interested to know how are you going to power the fan?

Thanks.
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Old September 4th, 2005, 07:27 AM   #4
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Good question,

According to Keith Wakeham, the brushless fan will have the same effect to varying voltage as a brushed motor, less voltage=slower, higher voltage=faster.

This is something I will have to look into, but I dont think it will require the full 12v as this will spin too fast. There are a few options as far as battery power is concerned. high capacity AA batteries is an option, 8 of them would give 9.6v.

maybe 1 high capacity 9v square battery would work? Others have sujested the use of camcorder batteries.

1 more expensive option is to use a 3 cell lithium polymer pack. these come in very high capacity and supply 11.1v. They do require a special charger, though.

Anybody have any other ideas?

Thanks,
Wayne.
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Old September 4th, 2005, 08:03 AM   #5
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I've been looking at high voltage batteries. Here is a good reatiler:

http://www.maplin.co.uk/family.aspx?menu=77&doy=4m9

They have quite a large selection.
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Old September 4th, 2005, 08:08 AM   #6
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Thanks.

Im popping into maplins tomorrow to buy the project box, so ill have a little look while im there.

Im half way trough drawing these diagrams, ill post later.

Wayne.
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Old September 4th, 2005, 12:53 PM   #7
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Ok,
Here are 10 images illustrating my method a little more clearly:

http://homepage.ntlworld.com/wayne.k...inal/glass.htm

Glen hurd came up with an idea that could be added as a last step to the aobe method:
Quote:
Originally Posted by Glen Hurd
Another possibility to creating a perfectly balanced glass disk, is to spin it on the motor slow enough (100 rpm perhaps) that any vibration doesn't pose a danger, and use a fine sharpening stone with lots of oil. Mount the motor on something solid, and raise the stone to where it's just barely rubbing the glass. You may be able to grind it to a perfect circle that is perfectly centered on its mount. That would be better than going with a coupling approach.
You may have good luck, and get a perfect cut on a perfect center. I'm just trying to come up with solutions for the off-chance that you experience results more like mine tend to be :)

G

Anyway, any coments would be great

Thanks,
Wayne
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Old September 4th, 2005, 07:10 PM   #8
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I think i will try this method as well, as you described it very well and I already have all the supplies. Please keep us posted with how your test goes
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Old September 4th, 2005, 07:32 PM   #9
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Jeff,
Im glad to see your giving it ago as well, im not alone!!! I'll certainly keep everyone posted as to how I get on, if you could also do the same.

I feel i should judt say "BE CAREFULL", as this method can be dangerous. Sorry, had to say it.

Wayne.
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Old September 4th, 2005, 10:51 PM   #10
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Looks good wayne

Going to have to watch out for a few things with the fan.

Little difficult to get the spinning part dissasembled from the rest, sometimes the bearings are pressed in.

Also your likely going to run into a little bit of a clearance issue with bolts through the plastic so best to dissasemble the fan first to see how much room you have under the hub. It might not be much so might be best to have some countersunk bolts go through the plastic side and the nuts on the glass side.

And just to confirm, I've been running some of my 80mm computer fans rated at 12v at 7v for a while know and they spin (slower) without a problem. Less noise too.
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Old September 5th, 2005, 05:56 AM   #11
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Hi Keith,
I have a fan laying around, in this particular case, I could screw in the screws about 3mm with no problems. It maybe difference with other fans though. Im not sure how to take it apart?

Thanks for again confirming the operation at lower voltage, just what we need.

I have been talking to a friend who works with glass, we are trying to improve the method so the glass can be bolted to the fan once and not taken off again then cutting, getting rid of the possibility of it shifting.

I'll keep you all posted,
Wayne.
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Old September 5th, 2005, 08:29 AM   #12
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The biggest problem is "9:Cut the glass exactly on the line with a circular glass cutter."

There's no way to truly center the cutter.

Perhaps a better idea is to do what is done in all forms of manufacturing to produce balanced rotating assemblies: People do not try to cut something in such a way as to be on-center both in terms of concentricity and center of mass. Instead we just get the thing as concentric as possible, then take the rotating assembly to a balancing shop. Look in the yellow pages. (I assume they are yellow in Europe ;-) ).

If all you can find is a manufacturer, try them. Most balancing machine manufacturers perform it as a service for about $35 for something like yours.

Worst case you could call Turbo Technics in England, explain that your disc is non-automotive and spins only a few hundred rpm, and ask them to steer you toward even just a shop with a non-VSR balancer.

I am sure you will find it easy to get it balanced FAR better than a person could ever achieve by eyeballing it.

And grind the surface first, before balancing, not after!

P.S., One would hate to see you go to this trouble and then crush or break the disc upon tightening. You may want to use rubber washers on both sides of the fasteners through the disc.

And were it me, I would make sure the motor spins counterclockwise (by reversing the polarity sent to the motor, if needed) so there's no tendency for the bolts to loosen over time.
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Old September 5th, 2005, 10:06 AM   #13
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Thanks for your tip Bill. Ill certainly think about that if I fail.

Quote:
Originally Posted by Bill Porter
P.S., One would hate to see you go to this trouble and then crush or break the disc upon tightening. You may want to use rubber washers on both sides of the fasteners through the disc.
Yeah, I was thinking the same thing, this will 'dampen' the pressure in the glass surface. Thanks.


Quote:
Originally Posted by Bill Porter
And were it me, I would make sure the motor spins counterclockwise (by reversing the polarity sent to the motor, if needed) so there's no tendency for the bolts to loosen over time.
I would have never thought of that. Something I will do. Thanks again.

Wayne.
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Old September 5th, 2005, 10:44 AM   #14
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Bought the project box today, here are 2 pics of it (sorry a bit over exposed):

http://homepage.ntlworld.com/wayne.kinney/DSCI0074.JPG

http://homepage.ntlworld.com/wayne.kinney/DSCI0075.JPG

Outer dimensions are: 150x100x60mm

Inner dimensions are: 145x95x57mm

The box was 4.29 at maplin electronics store (UK version of radio shack)

Wayne.
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Old September 7th, 2005, 10:12 AM   #15
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OK peeps,

I have received the PC fan, as stripped it down as per my tutorial here:

http://homepage.ntlworld.com/wayne.k...inal/glass.htm


Here are some pictures of the fan:

http://homepage.ntlworld.com/wayne.k.../DSCI0082a.jpg

http://homepage.ntlworld.com/wayne.k.../DSCI0083a.jpg

http://homepage.ntlworld.com/wayne.k.../DSCI0085a.jpg

The fan is very quite indeed. Good thing is it already had marks on top where the screws will go which was handy.

Just waiting for my diamond drill bits and glass cutter now. I'll keep you all posted.

Thanks,
Wayne.
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