** Build you own TV
* Second Installment *
time we will consider one of the more difficult parts for the average constructor
to fabricate. This part is very important to achieve a smooth operating system.
I'm referring to the axle or bearing for the scanning disk. This device needs
to be even more precise than the scanning disk and good machining of the parts
is a must. Lucky for us, there is a way, where 90% of the quality machining is
already done. Here's how you do it.
Materials you will need for this
* "Junk" VCR
You need to find yourself a "junk" VCR. One that's being
thrown out because it's not worth the cost of repair. Any kind of VHS machine
will do. Sometimes, you may have to pay a few dollars for it, but seldom more
You only want one part out of the VCR. Its usually called the
"drum and drive motor assembly". This is the part that has the rotating
heads that read the signals on the tape. You need to get this assembly separated
and out of the VCR. Just cut any wires that are connected to it. Do whatever you
want with the rest of the VCR.
need to remove the rotating head and driving motor parts from the assembly you've
just removed. In the photo to the right, the upper arrow points to the rotating
head and the lower arrow points to the bearing support after all of the electrical
and mechanical motor parts have been removed and discarded. Finally, remove and
discard the rotating head. You are left with the part that actually supported
all of this material when it was still mounted in the VCR. It contains two precision
ball bearings , a 6mm shaft and possibly a collar on one or both ends of the shaft.
This will be the axle for your scanning disk.
Now here comes the hard
part... You need to saw, file or machine the bearing support until it looks something
like one of the other three items in the photo. This is actually a job best done
on a lathe. But it's up to you as to how you do it. Here is a better photo of
a finished unit. When you are finished, there may be a number of extra holes present that
will not affect its operation. You may even want to add one or more holes, better
located to suit your mounting. If the extra holes should bother you, you can fill
them with epoxy and paint the support with a flat black paint, as I do.
far, so good. But you still need two more things. You need something to hold the
scanning disk on to the shaft, (a hub) and a grooved pulley on the other end of
the shaft. Both of these are lathe jobs, but maybe you can find something in a
hobby shop or in your own "junk box". Here's your chance to be creative.
I said earlier, I will also be building a monitor as we go along, so you can see
how I am making the various parts for myself. To save time and trouble, I'm using
an 11.75" scanning disk from a previous project. It was made of .060"
engraving stock with a .75 center hole and a set of scanning holes for a horizontally
scanned image. I filled the holes with black epoxy, then drilled a new spiral
of 32 scanning holes and a second set of 32 larger (.062") synchronizing
holes, just inside the scanning holes. This time the spiral of holes were set
up for a vertically scanned image.
The disk is shown in the photo here, to the left. The holes that are readily visible
are the synchronizing holes.
I have also made up a simple one piece hub
to mount the disk on the bearing shaft. A set screw holds the hub fast to the
shaft and three or four 4x40 screws hold the disk to the hub. The photo shows
four hubs. From the left, the first three are two piece hubs that clamp onto the
disk. Only the center hole is needed in the disk with this hub. The fourth hub
is a one piece unit, for which three additional holes, around the center hole
in the disk, are required to bolt the disk to the hub. The next photo shows the
diskhub on the right,
made for this project. It is approximately 1.5" in diameter and its size
is not critical. Only the bore is critical. The item in the center is a pulley
that fits on the other end of the bearing shaft. It is about 1" diameter
and not critical either. All of these parts are made of aluminum.
is another view of the same parts, from a slightly different angle. ====>>>>>
here's a view of the parts as assembled. The pulley is at the bottom and the disk
hub is at the top.
Here is a view showing the hub.
Note: this hub has three holes for the screws that pass through the disc, clamping
it to this hub. Four screws can also be used. The disc for this hub has a 3/4"
center hole. The parts that I supply come set up with four mounting holes and/or
screws for the disk.
I recognize that this can be somewhat difficult
for someone without the usual tools for this kind of work. But I have seen numerous
cases where parts that accomplish the same purpose as these, have been built with
nothing more elaborate than a drill press. And in some rare cases, without any
power tools at all. At least try!
I am offering for sale, the hardware discussed in this installment. It consists
of a disk hub, belt pulley and the ball bearing shaft assembly made from a VCR
tape head/motor unit, just as described in this installment. All of the precision
work is done. The hub will fit disks with .375" , .500" or .750"
center holes. You will need to drill four #33 drill size holes in your disk to
mount the disk to the hub with 4 X 40 X 3/8" screws and nuts.
price of this assembly is $87 plus $.50 shipping in the USA. Order it directly
Email me at:
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