RSG Disk Material

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Steve & Jackie Young by way of Terry Fritz <twftesla-at-uswest-dot-net>" <youngs-at-konnections-dot-com>

Dear RSG builders,
 
I want to know why I shouldn't use GP03 (electrical grade figerglass) instead
of the more expensive G-10 (Garolite)?  As Dan points out below, the G-10 has 4
times the tensile strength, but about 4 times the cost and about two-thirds the
high temp rating.  At what rotor electrode velocity will 10,000 PSI tensile
strength not be adequate to keep the electrodes from becoming projectiles as
the RSG flies apart?  I like the cheaper price of GP03, and being able to cut
it with non-carbide tools.
 
Your thoughts on GP03 vs G-10 will be appreciated.
--Steve
 
Back in April, Dan posted the following (the prices are still the same today):
 
"Here's some material offered by McMaster-Carr I've been thinking about
using for SRSG rotors. 
 
A 1/2" thick, 12" x 12" square is $12.54 

Electrical Grade Fiberglass (GP03)
. Color: Opaque red
. Temp. Range: 0° to 400° F
. Tensile Strength: Excellent
Enhanced electrical insulation properties and a flame-resistant additive
make this material ideal for electrical applications. It is a glass
fiber-reinforced polyester. Material meets UL-94V0 standards.
. Impact Strength: Excellent
. Excellent electrical insulator
. Use indoors
. Easy to machine

Notice that the temperature goes to 400° F, and it's listed as easy to
machine.

Other specifications:

Tensile Strength: 10,000 psi
Impact Strength: 8.2 ft.-lbs./in.
Dielectric Strength: 400 V/mil
Tracking Index: 500 volts
Durometer: Barcol 50
Coefficient of Thermal Expansion: 2.010 -5 in./in./°C
Weather Resistance: Material is not weather resistant. Resin will break
down over long periods of exposure to the outdoors.

Processing--

Machinability: Can be easily machined. Can be cut with a hacksaw, diamond
grit saw blade, and carbide tip saw blade. Holes are easily created using
conventional drill bits and milling bits. A dust mask and gloves should be
worn when working on this material.
Welding: Not recommended.
Scratch Resistance: Moderate.
Chemical Resistance: Use with mild detergents. Do not use with strong acids.

The original GP03 page is at
<http://www.mcmaster-dot-com/pdf/106/3088.pdf>http://www.mcmaster-dot-com/pdf/106/30
88.pdf
The extra specifications are at
<http://www.mcmaster-dot-com/pdf/106/8549KAC1.pdf>http://www.mcmaster-dot-com/pdf/10
6/8549KAC1.pdf

Here's some G-10/FR4 Garolite specs:

A 1/2" thick, 12" x 12" square is $46.87

. Color: Opaque brownish-green (except where noted)
. Temp. Range: 0° to 284° F
. Tensile Strength: Excellent
An outstanding electrical insulator, this continuous-woven glass fabric
lami-nated with an epoxy resin absorbs virtually no water and offers good
dimen-sional stability. Meets UL-94V0 standard for flame resistance unless
noted.
. Impact Strength: Excellent
. Excellent electrical insulator
. Use indoors
. Difficult to machine

Notice that the temperature goes to 284° F, and it's listed as difficult to
machine.

Other specifications:

Meet the following standard: UL94V-0 for flammability and Mil l 24768/27.
Tensile Strength: 40,000 psi
Impact Strength: 7 ft.-lbs./in.
Dielectric Strength: 500 V/mil
Durometer: Rockwell M: 110
Coefficient of Thermal Expansion: 1.8210 -5 cm/cm/°C
Weather Resistance: Material is weather resistant.

Processing--

Machinability: Can be machined using carbide tools.
Welding: Cannot be welded, but can be glued.
Scratch Resistance: Material has good scratch resistance.
Chemical Resistance: Use with dilute acids and some organic solvents. Do
not use with acetone, alkalines, and strong acids.

The original G-10 page is at
<http://www.mcmaster-dot-com/pdf/106/3092.pdf>http://www.mcmaster-dot-com/pdf/106/30
92.pdf
The extra specifications are at
<http://www.mcmaster-dot-com/pdf/106/8667KAC1.pdf>http://www.mcmaster-dot-com/pdf/10
6/8667KAC1.pdf

The only real difference I can see, as far as specs are concerned is that
G-10 has a tensile strength of 40,000 lbs/sq.in., while GP03 has a tensile
strength of 10,000 lbs/sq.in. Everything else seems very close. The
difference in tensile strength might matter as far as a rotor is concerned,
but I'll still probably try it. For a Scott gap, it should be fine.
Comments?

Dan 
<mailto:ntesla-at-ntesla.csd.sc.edu>ntesla-at-ntesla.csd.sc.edu "