Base+ColumnAssembly/Base+ColumnAssembly.html
(photos) Base+Column.pdf (drawings) |
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UpperTerminalSection/UpperTerminalConstruction.html
(photos) UpperTerminalFramework.pdf (drawings) |
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MakingTheBeltRollers.html
(photos) RollerDrawings.pdf (drawings) |
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Belts/BeltMaking.html | ||
LowerBearing&BrushHolder.html
(photos) Bearing+Brush_Supports.pdf (drawings, lower and upper) |
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Brushes.html ( photos) | ||
Provisional
Brush Power Supply (photos) |
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SparkSystem.html (photos) SparkSystem.pdf (drawings) |
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MotorAssembly.html (photos) Custom_motor_shroud.pdf (drawing) Gear_safety_shield.pdf (drawing) |
Photo of the complete prototype Van de Graaff generator
(VDG)
in front of a garage door. Visible are the 14" upper
terminal,
one of two 6" wide belts, a simple control panel, and an electric drill
driving automotive breaker points for a prototype 25kV lower brush
supply. The crease in the vinyl belt is due to a "double cone" profile of only 0.5 degrees on the upper roller. The bottom roller has a flat profile. Belt tracking and adjustment were satisfactory. |
Here the double roller system and the two belts can be
seen. The bottom rollers are PVC. The gears
are barely visible in the back. The lower pulley is driven by an AC/DC
"universal" chain
saw motor. Violent starts are softened with two NTC thermistors (8
amp; Honeywell ICL2210008-01)
connected in series with the power line. The accessory equipment post
stands upright on the right. At the base, is the housing for the
ignition coil. This setup is very noisy during operation due to the AC/DC chain saw motor and the gears. An alternative would be to use an AC induction motor with a 2:1 or 3:1 (?) step-up pulley ratio. The gears could be replaced by a figure 8 belt and two pulleys of equal size |
MotorAssembly.html (photos) Custom_motor_shroud.pdf (drawing) Gear_safety_shield.pdf (drawing)MotorAssembly.html (photos) Custom_motor_shroud.pdf (drawing) Gear_safety_shield.pdf (drawing) |
Corona control rings were later added to the van de Graaff |
Another side view shows the gearbox cover. This machine has no bottom terminal. It is not intended to produce sparks. The voltage and current produced are sent elsewhere to a test cell where the relation between gravity and high voltage, pulsed, monopolar, rotating fields can be systematically investigated. See: ElectromagneticTestCells.html In actual operation the column is wrapped in layers of plastic food wrap film, and the terminal is covered with a clear plastic trash bag, all to reduce corona. The lower brushes are presently connected to the power line safety ground, instead of the 25kV supply. The main use of the equipment post is to hold the magnetic spark gap system: |