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CDROM Ball Construction

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Sloted Construction

[photo] There are two syles of CDROM balls I have been making...

The new type (see bottom of the previous page) is cutting slots in the CD's.

Though this requires careful thinking about the final object, and some mathematics. See my page "Studies into Polyhedra", especially the page on mathematical formula and tables , for help in figuring this out.

Construction however is much easier. Just a lot of sawing, slot together and gluing using hotglue in the corners.

I use a jigsaw, after clamping at most 3 CD's between the bench and some plywood. I usually add a fourth CD that has the slots positioned where I want already cut (or just marked for the first cut) in it.

Both the bench and the plywood has an appropriate slot in it. This clamping is important otherwise the CD will shatter and pieces fly everywhere. The cut is made as fast and quickly as possible so the CD plastic doesn't melt, gumming up the blade.

A scroll or band saw may be a lot better as the saw will then only move downward, preventing shattering the CD, and hopefully will not heat up melting the plastic of the CD.


Edge to Edge Construction

[photo] To construct the soccerball like sphere I create a cradle, a cardboard cup if you will, to hold the disks together at the right angles while they are glue together.

The cradle is made by using thick solid cardboard, which were cut into lots of hexagons and pentagons about 2mm larger than the CD's they hold. The extra 2mm is to accomidate the slight thickness of the CDrom as they are held in position. These shapes are then taped together using masking tape. The poldhedral cup, will automatically have the correct angles needed for the sphere you are building. You can see one of these in the photo right.

The cradle is then pinned down to my workbeanch which is multiple layers of thick corrigated cardboard (old fridge box -- look in the bins behind a white good store). The CD's then sit in the cradle, with glass headed pins pushed into the cardboard to stop them sliding out of position.

When ready I use hot glue to make a bridge between the two CD sitting next to each other. Hot glue is a space filling glue -- that is it will fill the angle between the two disks -- and when cool, link them together at the right angle with a small amount of give.

I recommend you rub the first squirt of glue hard onto the disk to make a good bond, then give 3 to four more pumps to fill the angle between the CD's (on the inside of course). Yes you do use a lot of hot glue in a ball! A single sphere will generally use a whole packet of glue sticks (if not more).

I wait a few minutes, to ensure all the glued joints are cool, before lifting the joined CD's out of the cradle. I then rotate them an return them to the cradle so I can join the next couple of CDs.

The ball is generally very floppy until complete, so care is needed, otherwise you will end up with a large distortion in your ball. I often have a stack of old phonebooks on hand to push the sides in, or support the ball while the next few CD's are put into place.

The last CD's are the hardest and just requires care, patience and some luck. I poke the nose of the hot glue gun into the sphere and try to get gravity to deposit the glue in the right spot. Not easy, and the final join is usally the weakest of them all.

For transport I insert dowel through the holes in the CDs to support it and provide good handholds. You can imagine the effect of walking down the road carrying my latest ball to where it is to be displayed!


Ultra Large Balls

[photo] Larger edge-to-edge models, are made more by feel, than anything else.

An inital chain of 12 or 16 CD's is made into a circle, joining them end to end with the correct angle (360 degress divided by the number of CD's to form a circle.

[photo] Then a dome is created with more chains of CD's and the gaps filled by gluing groups of 3 or more CD's together at the same angle, and gluing to fill the holes between the chains.

The whole thing is then supported by dowels, lifted by strings, and some chairs, while more chains are added, to build up the the other half of the sphere.

This is a difficult construction, and requires lots of time, patience, and care to aviod distorting the sphere too much. Even so my final result is not perfectly spherical, though only noticable on close examination.


CD Thrust Bearing

[photo] Using the CD's themselves with some ball bearings a freely spiing support can be made for your CDrom artwork. This spins freely enough that slotted models mounted near a air condintion vent can rotate endlessly.

It is made from 4 CDROMs some dowel which is a bit smaller than the centeral hole in the cdroms, and a lot of 'hot glue'.

Make sure you use the same brand of CDROM for all these,as the groove can variy slightly from brand to brand.

What I did was cut out the central portion 'disk' of three CD's so they they all still have the groove that is built in to all CDs. I used a hot soldering iron to do this. cutting from both sides.

One is the hot glued to the bottom of the dowel, to for a platform on which the whole model will sit. The grovvy, in which the ball barings will run, facing upward. Put lots and lots of glue underneath between this cdrom and the dowel.

The other two as super/crazy glued together, and a hot soldering iron used to melt 6 to 12 holes in centered on the groove, space equally around (roughly). The act of melting holes will also join the two CD's together.

These to CD's act as spacers and hold the ball bearings in place so that the little balls stay put if the model is bumped.

These two were also cut out together, and a little smaller that the platform CD above so as to hide them alittle in the final 'sandwich'.

Put the two spacing CD unit onto the dowel so it rests on the platform, and carfuly insert a ball bearing into each hole.

Now pull the dowel up into the CD built into the model such its groove was facing down, to sandwhich the ball bearings between it and the plaform CD.

To stop the bearing slipping out when you let go of the dowel (and having them rolling everywhere), use a bit of thick wire to make a clip, around the dowel a millimeter or two above the top CD. When it is mouthed this should not touch the top CD, but saves a lot of hassle when working on the model.

If a hole is drilled into the other end of the down you can then use wire (a extra large paper clip, to mount the whole model on the ceiling.


Created: 12 August 2002
Updated: 9 January 2005
Author: Anthony Thyssen, <Anthony.Thyssen@gmail.com>