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VandegraffMotor Mounting &
Bottom Electrode
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 | 1 @ electrical motor 12 - 240 volt. |
Depending
on the motor you chose you can have from a 12V ac/dc all the way up to
mains powered 240Vac motor to run on your vandegraff generator. The motor
you choose is your choice and won't make a lot of difference to the
operations of the machine. I used a variable 240Vac motor from an old
vacuum cleaner.  The motor chosen was a series
wound motor, an is far too fast for the VG machine. This motor will blow
the belt and rollers apart if it where left to run out to full speed. If
you get a series would motor be sure to limit the maximum speed of the
motor. Caution: if you are not sure about wiring a mains powered motor
then have some one with electrical experience help you wire the motor from
the mains. There is no set mounting instructions or key dimensions for
mounting the motor. Just try to centre the bottom roller over the mid
point of the main centre tube. View down through the top of the tube to be
certain you have the bottom roller centre most under the tube. You may
have to build a special mounting frame or add packing under the motor to
get the required distance from the back panel to the roller centre
position. You may also move the actual wooden back panel location in
further toward the centre to better mount the motor. I have mounted my
motor from on the back panel because this allows for more adjustment to
the belt. If I break the belt I can join it again and move the motor up to
accommodate the loss in belt length. |
You may decide to mount the
motor down on the bottom panel. That is quite ok, but you will have to add
packing under the motor to get the belt tension correct. The top roller
will only adjust to a set length. So you will need to move the motor to
get any additional adjustment to the belt tension. Once you have your
motor mounted, your vandegraff unit may look something like figure 25.
Bottom Comb/ElectrodeThe bottom comb/electrode construction is very similar to the top
electrode. Once again construct the comb/electrode from 25mm x 25mm x 0.1
shim steel. Cut sharp points into the shim steel. Pop rivet the shim steel
electrode onto a 30mm x 60mm piece of tin. You can then pop rivet this
piece of tin an electrode onto the main motor or motor mount. (see figure
26) You can then manually bend the tin in an out to allow for close
proximity adjustments and fine tuning to the belt electrode distance. Only
trial and error can get this adjustment to the best position. Remember the
closer you get the comb/electrode to the belt, the better the possible
potential available to the sphere condenser. I chose to mount the
comb/electrode directly onto the motor. By doing this you eliminate the
need to supply an earth or ground wire to the electrode. |
[Alternative
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Alternative
If you choose to mount the
electrode from the bottom of the wooden frame then you will need to add a
wire to supply the ground potential to the electrode. You can terminate
this ground wire back onto the motor if you so choose.