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Re: Strong Rotor Material???

Original poster: "Scott Hanson" <huil888@xxxxxxxxxxxx>

Gary -

Any unreinforced plastic material is a poor choice for a high-speed rotor.

By far the most suitable materials (tensile strength, shear strength,
heat-deflection temperature, cyclic fatigue characteristics, arc-tracking
resistance, dimensional stability, resistance to weakening by exposure to
ultraviolet light, etc) are the epoxy impregnated composite materials using
woven fiberglass cloth reinforcement ("G10", etc).

Next choice would be the epoxy impregnated composites with non-woven
fiberglass reinforcement (glass mat).

Linen reinforced phenolic would be next on the list, but the mechanical
characteristics are not nearly as good as the G10 or G11 materials.

Remember also that Lexan is extremely sensitive to solvent-induced stress
cracking (sensitive to oils, cleaning fluids, common solvents, etc) and also
very sensitive to mechanical stress risers (tiny nicks, burrs, scratches,
etc) can initiate microscopic cracking that can quickly result in a
catastrophic failure of the disk.

(I hope the formatting is preserved on this chart ....)

                                LE Phenolic       G10 Epoxy/glass    G11
Epoxy/glass    Lexan
Tensile strength         13,000 PSI         38,000 PSI             37,000
PSI             9,000 PSI
Shear strength           13,500 PSI         21,500 PSI             22,000
PSI             6,000 PSI
Flexural strength        18,000 PSI         60,000 PSI             75,000
PSI            13,000 PSI
Max operating temp    258F                285F                      355F

Regards, Scott Hanson

----- Original Message -----
From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Friday, January 07, 2005 7:01 AM
Subject: RE: Strong Rotor Material???

> Original poster: "Paul Marshall" <klugmann@xxxxxxxxxxx> > > Gary, > First of all I'd do some simple calculations to determine how much > centerfugial force you will have (How thick the rotor has to be) at max > RPM. The RPMS are high but the radius is fairly small, which is good. My > material of choice would be lexan. The only thing that may cause problems > would be heat. Lexan should have good strength properties until it hits > about 350 - 400 F. I could see where might exceed that in localized > heating, but I don't think your rotor will ever hit 350F. > > > > Paul S. Marshall >

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