In a message dated 6/19/00 5:50:02 AM Eastern Daylight Time, 
danieo@............ writes:

<< Amateur constructors need not be daunted at the prospect of
 having to buy expensive penmotors.  An adequate substitute
 can be made, based on a loud speaker moving coil assembly.
 The cone can provide the necessary restoring force  >>

Hi Danie,
    First I want to make a correction to my instructions how to make a drum 
for one millimeter per second writing speed. Make those spacers 3-inches long 
instead of three and one half.
    I like the idea of making a radio speaker into a pen motor. Except for 
the drive motors the whole drum recorder can then be homemade. On some, maybe 
most, radio speakers, the cone does not center and support the voice coil. 
Instead there is an inner diaphragm about the diameter of the speaker's 
magnet that supports the voice coil and can provide the restoring force. This 
means the cone and its frame can be removed completely to make a pen motor 
the diameter of the speaker's magnet. This much smaller pen motor is much 
easier to mount on a traveling penmotor carriage.
    Danie and I have used various pens; ball point, felt tip, draftsmen's 
drawing pens and syphon pens but they all have a bad habit of quitting and 
leaving a blank recording now and then. Sean-Thomas solves this problem by 
writing with a hot styles on thermal fax paper. This is a good idea. I 
checked Best Buy and they a have plentiful supply of thermal fax paper that 
comes in 100-foot rolls so this is the way to go if you can find a hot stylus.
Best regards,
Cap
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