Re: THERABAND VDG BELTS?????????/ (fwd)

["High Voltage list" <hvlist@xxxxxxxxxx>]

Original poster: Steven Roys <sroys@xxxxxxxxxx>



---------- Forwarded message ----------
Date: Sat, 26 May 2007 15:05:24 -0700
From: Ed Phillips <evp@xxxxxxxxxxx>
To: High Voltage list <hvlist@xxxxxxxxxx>
Subject: Re: THERABAND VDG BELTS?????????/ (fwd)

High Voltage list wrote:

Original poster: Steven Roys <sroys@xxxxxxxxxx>



---------- Forwarded message ----------
Date: Thu, 24 May 2007 08:00:22 -0600 (MDT)
From: Chip Atkinson <chip@xxxxxxxxxx>
To: hvlist@xxxxxxxxxx
Cc: acmdq@xxxxxxxxxx
Subject: Re: THERABAND VDG BELTS?????????/ (fwd)

I'm forwarding this for Dr. de Queiroz since he got dropped.  I
re-subscribed him so he should be able to get replies to the list.

Chip
  

    Thanks - been wanting to contact him but had lost his email address. 
He's always been a great source of good reading and beautiful pictures of
beautiful things he has built!!!!

---------- Forwarded message ----------
Date: Wed, 23 May 2007 20:27:01 -0300
From: Antonio Carlos M. de Queiroz <acmdq@xxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: THERABAND VDG BELTS?????????/ (fwd)

Tesla list wrote:
  

Original poster: List moderator <mod1@xxxxxxxxxx>

This should probably be taken to the HV list.
  
    

Does this list still exist? I didn't receive anything from it in the 
last years. I don't even know if I
am on it...
  

    Do any of you have experience with cutting VDG belts from thin 
material like Theraband?  I have just made a couple of narrow 
replacement belts using serrated barber's shears and am unhappy with the 
usual jagged edges.  Anybody have a better way?
  
    

I use sharp straight shears, marking first a line with a pen to follow, 
cleaning the ink with alcohol afterwards.
It's really difficult to make a perfect cut. Maybe it's possible to use 
a very sharp blade and a ruler,
with the ruler firmly fixed with C clamps on a table (with something 
below to protect the table).
My last attempt to use Theraband for this purpose failed. The band now 
has a side with a partially
conductive material, with logos printed on it. Difficult to remove.

Antonio Carlos M. de Queiroz

    Thanks for your note.  A lot of people have answered my original
question and I want to thank them too for all of the suggestions which
covered lots of things I've tried and a couple (particularly the of the
use of a big paper cutter which I don't have available) which I haven't. 
After sorting through all of them I decided that, as usual, there's no
free lunch!  What finally worked best here is the use of sharp shears as
several suggested, and EXTREME PATIENCE which is pretty tough for me.  I
just cut a couple of very good looking belts from the blue THERABAND and
cemented them with paper cement (not using Bestest but what I have works
just fine).  I get around the curling problem when the cement is applied
by sticking the material to a thick card with double-sided carpet tape on
top.  Even if it does start to curl the stuff can be stuck back down with
a sharp point.  That's easiest to do when the cement is completely dry. 
These are tiny belts by the way, only about 5/8" wide which makes even
small rough edges look bad.  I should mention that I tested the paper
cement scheme on the THERABAND by joining a couple of pieces and putting
the joint under considerable tension for several months without any
evidence of the edges peeling so decided to use it.

    I had an unpleasant surprise when I was joining one of these new
belts.  My wife came in to ask what I was doing and while paying
attention to her and not what I was doing I managed to make a Mobius
strip out of the one I was working on!!!  Didn't try it of course by just
cut it and rejoined the ends losing about an inch due to the diagonal lap
- the pulley spacing is 14" center to center so small differences in belt
length aren't important.  Other one came out fine and I'll try them both
when I think they're dry enough.

    My best belts for the various machines I've built over the years
(largest uses a 3" belt) has been what appears to be natural rubber,
slightly gray in color and 0.032" thick.  Many years ago I was in C&H
Surplus and saw rolls of the stuff for sale for peanuts.  4" wide by 25'
long.  They had come out of boxes marked "cable splicing kits" and I
found a couple of boxes with the original cement can in them.  This stuff
is called "GooGum" and is (rather was) made by an outfit in St. Louis. 
Naptha or benzol solvent, water thin, and works beautifully to make a
permanent joint.  The stuff is painted on (I use a couple of coats) and
allowed to dry completely before the edges are joined under pressure. 
Seems to stick pretty well that way but I've gone the additional step of
baking the resultant belt in the oven at 300° F for an hour.  Doesn't
seem to hurt the rubber and the final joint appears to be welded
perfectly.  I have one little 4 ounce can of the stuff and it still works
fine after at least 35 or 40 years.

    This is a pretty long post so I'll close it with the question I
wanted to ask Antonio.  Some time back you mentioned a rule of thumb for
estimating the maximum current which could be obtained from a VDG, given
the belt speed and area.  Could you sent that again?  I'm curious to see
how this little machine is performing.  The belt speed is about 780 feet
per minute and the belt width is 5/8".  I get about 3 microamps current
which seems pretty good for such a small and simple machine.

Regards to all,

Ed