Bill,

A  titanium rotor would be  58% to 66% the weight of cast iron and more

than

twice as strong as aluminum.  With the casting price  plus machining the
item gets pricey. If they could retail for under $500 each would there

be a

market for them?  Units sales would have to be over 500 pieces a year to
offset the price of the expensive mold. Would have to depend on the auto
racers no doubt.

A large part of the rotor weight still contains the inner gear of which

how

much I would like to know.  Can anyone weigh it for me?  But lets say by
making it out of a titanium/aluminum alloy  we can lower the total

weight to

at least 6 lbs.  What does a lighter rotor do for our aircraft engines?
Allows them to run at higher rpms and hence higher HP.  Disavantageous?

We

need with a 3:1 or higher gearbox to handle the rpms.

Why not make it out of  aluminum and strengthen it with the carbide

flame

spray method?  Titanium would be less expensive because of the high

force

aluminum "Squeeze casting" techniques needed to insure a part without
inclusions. IMHO I believe the flame spray technique would involve more
production steps at different locations, and labor costs as well.

  TITANIUM: (Pulled from some long forgotten website)

" Depending on the predominant phase or phases in their microstructure,
titanium alloys are categorized as alpha, alpha-beta, and beta. This

natural

grouping not only reflects basic titanium production metallurgy, but it

also

indicates general properties peculiar to each type. The alpha phase in

pure

titanium is characterized by a hexagonal close-packed crystalline

structure

that remains stable from room temperature to approximately

1,620$B!<(JF. The beta

phase in pure titanium has a body-centered cubic structure, and is

stable

from approximately 1,620$B!<(JF to the melting point of about

3,040$B!<(JF.

Adding alloying elements to titanium provides a wide range of physical

and

mechanical properties. Certain alloying additions, notably aluminum,

tend to

stabilize the alpha phase; that is, they raise the temperature at which

the

alloy will be transformed completely to the beta phase. This temperature

is

known as the beta-transus temperature.

Alloying additions such as chromium, columbium, copper, iron, manganese,
molybdenum, tantalum, and vanadium stabilize the beta phase by lowering

the

temperature of transformation from alpha to beta. Some elements, notably

tin

and zirconium, behave as neutral solutes in titanium and have little

effect

on the transformation temperature, acting instead as strengtheners of

the

alpha phase.

Alpha alloys: The single-phase and near-single-phase alpha alloys of
titanium have good weldability. The generally high aluminum content of

this

group of alloys ensures good strength characteristics and oxidation
resistance at elevated temperatures (in the range of 600 to

1,100$B!<(JF). Alpha

alloys cannot be heat treated to develop higher mechanical properties
because they are single-phase alloys.

Alpha-beta alloys: The addition of controlled amounts of

beta-stabilizing

alloying elements causes the beta phase to persist below the beta

transus

temperature, down to room temperature, resulting in a two-phase system.
These two-phase titanium alloys can be strengthened significantly by

heat

treatment consisting of a quench from some temperature in the alpha-beta
range, followed by an aging cycle at a somewhat lower temperature.
Beta-phase transformation, which would normally occur on slow cooling,

is

suppressed by the quenching. The aging cycle causes the precipitation of
some fine alpha particles from the metastable beta, imparting a

structure

that is stronger than the annealed alpha-beta structure. Although
heat-treated alpha-beta alloys are stronger than the alpha alloys, their
ductility is proportionally lower.

Beta alloys: The high percentage of beta-stabilizing elements in these
alloys results in a microstructure that is substantially beta. The
metastable beta can be strengthened considerably by heat treatment.

Titanium is used in corrosive environments or in applications that

require

light weight, high strength-to-weight ratio, and nonmagnetic properties.
While commercially available in many alloys, most requirements can be

met by

a grade of commercially pure titanium, titanium-0.2% palladium alloy, or

by

the high-strength Ti-Al-V-Cr (beta type) alloys. These grades, which are
available in most common wrought mill forms, are covered by ASTM-AMS
specifications and, in most cases, by a similar ASME specification.

Beta-21S is a new beta alloy developed as an oxidation-resistant

aerospace

material and as a matrix for metal-matrix composites. Composition is
Ti-15Mo-2.7Nb-3Al-0.2Si, with molybdenum and niobium working

synergistically

to raise corrosion resistance to very high levels. It also offers one of

the

lowest hydrogen uptake efficiency levels of any titanium alloy. The
combination of high strength and high corrosion resistance make it an

ideal

candidate for orthopedic implants, deep sour oil wells, and geothermal

brine

wells.

Like stainless steel, titanium sheet and plate work harden significantly
during forming. Minimum bend-radius rules are nearly the same for both,
although springback is greater for titanium. Commercially pure grades of
heavy plate are cold formed or, for more severe shapes, warm formed at
temperatures to about 800$B!<(JF. Alloy grades can be formed at

temperatures as

high as 1,400$B!<(JF in inert-gas atmospheres. Tube can be cold bent

to radii

three times the tube OD, provided that both inside and outside surfaces

of

the bend are in tension at the point of bending. In some cases, tighter
bends can be made.

Despite their high strength, some alloys of titanium have superplastic
characteristics in the range of 1,500 to 1,700$B!<(JF. The alloy used

for most

superplastically formed parts is the standard Ti-6Al-4V alloy. Several
aircraft manufacturers are producing components formed by this method.

Some

applications involve assembly by diffusion bonding.

Titanium plates or sheets can be sheared, punched, or perforated on

standard

equipment. Titanium and Ti-Pd alloy plates can be sheared subject to
equipment limitations similar to those for stainless steel. The harder
alloys are more difficult to shear, so thickness limitations are

generally

about two-third those for stainless steel.

Titanium and its alloys can be machined and abrasive ground; however,

sharp

tools and continuous feed are required to prevent work hardening.

Tapping is

difficult because the metal galls. Coarse threads should be used where
possible.

Titanium castings can be produced by investment or graphite-mold

methods.

Casting must be done in a vacuum furnace, however, because of the highly
reactive nature of titanium in the presence of oxygen. Typical

applications

for titanium castings are surgical implants and hardware for marine and
chemical equipment such as compressors and valve bodies.

Generally, titanium is welded by gas-tungsten arc (GTA) or plasma-arc
techniques. Metal inert-gas processes can be used under special

conditions.

Thorough cleaning and shielding are essential because molten titanium

reacts

with nitrogen, oxygen, and hydrogen, and will dissolve large quantities

of

these gases, which embrittles the metal. In all other respects, GTA

welding

of titanium is similar to that of stainless steel. Normally, a sound

weld

appears bright silver with no discoloration on the surface or along the
heat-affected zone..."

Doug in Japan

Titanium and its alloys have really low thermal conductivity. which could
limit
it's use for the rotor which has thick sectiond that must be cooled. We
actually
used titanium for thermal isolaters in some rocket applications - it has
lower
conductivity than ceramic alumina - Vance

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