Once you
have the motor mounted you are ready to fit the belt, and glue the centre
tube to the bottom flange. This is the final stage. Place the belt onto
the Top roller and secure the roller into position. Place the
sphere-centre tube assembly down into the bottom flange of the wooden
frame. Now fit the belt around the bottom roller of the motor. Be sure get
this tube positioned square with the belt an the rollers. If you turn the
tube to far one way or the other the belt will fall off the rollers.
Manually hold the tube up with both hands so the tension is on the belt
and both rollers. View down from the top of the centre tube to see you
have the belt running straight an square on the rollers without twists or
bends. Have some one turn the motor by hand so you can turn the tube to
get the belt running square with the top and bottom roller. Do not worry
about the top roller to much, as this can be adjusted by raising or
lowering either side of the roller. Just allow yourself plenty of
adjustment on the top roller. When you have the belt running square with
the rollers you can mark a pencil mark around the flange and the centre
tube. At the intersection of the flange and centre tube place a pencil
mark around the circumference of the tube for the correct vertical
position (tube height). Place a pencil mark vertical on the tube and
flange for the correct horizontal position. Place a pencil mark at the
bottom side of the flange and tube so you know how much glue to apply to
the tube. Remove the belt off the bottom roller and slide the tube upwards
to where you can see the bottom pencil mark. Apply PVC glue to the centre
tube between the upper and lower pencil marks. Slide the centre tube back
down into position and refit the belt onto the bottom roller. Align both
the horizontal and vertical pencils marks.
Hold the centre tube in this positions for about a minute or until the
glue becomes firm. Be sure you get the tube into the original position
aligned with your pencil marks. PVC glue dries very quickly so be sure
about your settings. The final position of your centre tube may be similar
to the dimensions of figure 27.
Adjustments And Fine Tuning
Once you have the vandegraff generator assembled you will need to make
running adjustments and fine tuning. You may need to raise and lower
either side of the top roller so the belt positions itself centre most on
the roller. You may need to raise or lower either side of the motor
slightly to get the belt to position itself centre on the bottom roller.
You may need to adjust the top and bottom comb/electrodes to find the
optimum distance away from the belt while the vandegraff is running. These
adjustments are straight forward but might require a little perseverance.
Get the belt running correctly first before you adjust the top and bottom
comb/electrodes.
You may like to rub the inside surface of the belt with methylated
spirits and a light sand paper to remove any contaminates that were put
there during assembly. Turn the VG machine on and carefully rub a slightly
damp methylated rag on the inside of the belt and rollers. Touch the
inside of the belt with light sand paper to rough the surface and cause
rubber dust on the belt to produce friction on the rollers. Do not
touch the upper or lower rollers with the sand paper. This should only
need to be done once in the life of the vandegraff generator. Keep dirty
oily fingers off the VG belt. Do not wipe the rubber dust off the inside
of belt, leave it there while the belt is new. The rubber dust helps build
static friction until the belt is permanently charged with ions.
Clean the sphere/condenser with methylated spirits and a clean rag.
Tape the bowls together with a complete strip of insulation tape around
the circumference of the two bowls. One and a half circles of insulation
tape will be suffice.
Alternative
Once you
have the motor mounted you are ready to fit the belt, and glue the centre
tube to the bottom flange. This is the final stage. Place the belt onto
the Top roller and secure the roller into position. Place the
sphere-centre tube assembly down into the bottom flange of the wooden
frame. Now fit the belt around the bottom roller of the motor. Be sure get
this tube positioned square with the belt an the rollers. If you turn the
tube to far one way or the other the belt will fall off the rollers.
Manually hold the tube up with both hands so the tension is on the belt
and both rollers. View down from the top of the centre tube to see you
have the belt running straight an square on the rollers without twists or
bends. Have some one turn the motor by hand so you can turn the tube to
get the belt running square with the top and bottom roller. Do not worry
about the top roller to much, as this can be adjusted by raising or
lowering either side of the roller. Just allow yourself plenty of
adjustment on the top roller. When you have the belt running square with
the rollers you can mark a pencil mark around the flange and the centre
tube. At the intersection of the flange and centre tube place a pencil
mark around the circumference of the tube for the correct vertical
position (tube height). Place a pencil mark vertical on the tube and
flange for the correct horizontal position. Place a pencil mark at the
bottom side of the flange and tube so you know how much glue to apply to
the tube. Remove the belt off the bottom roller and slide the tube upwards
to where you can see the bottom pencil mark. Apply PVC glue to the centre
tube between the upper and lower pencil marks. Slide the centre tube back
down into position and refit the belt onto the bottom roller. Align both
the horizontal and vertical pencils marks.