CORVETTE PARTS REAR AXLES

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Manufacturing CORVETTE REAR AXLES
Corvette Parts Online looked into producing forged Corvette 1963-1982 rear axles in  1992 because of the ever
increasing cost of GM stock axles and the reputation of low strength.  Material strength was the major factor, stock
axles were not the best for high output engines, especially when used for track.

There were two driveline specialists turning out “super stock” rear kits where axles were turned from 4340 material from
solid stock. Corvette Parts was one and Tom’s Differentials was the other.  This type of manufacture for axles, (lathe
cut from solid stock), was very costly and since it cut through the material grain lines it was not as strong as a forging
where grain lines follow form.

Corvette Parts contacted Moser Engineering, perhaps now better known as Moser Axle. They had in their plans a
Corvette axle for future production.  This was to be a 4340 forging.  They already had a production print but didn’t have
a production date.  As Corvette Parts was already in the Corvette parts business, Moser decided to send their
production print to us and we would assume production.  Spencer Forge in Ohio was the choice for the forge work
mainly because they produced forgings for Dana-Spicer and had a track record for forged driveline parts.   Attached is
a copy of the final axle print and an inspection sheet.  

Spencer Forge agreed to do the forging and produce the necessary tooling of (4) Four pass dies and headers and
tread racks, as well as maintaining the tooling.    Agreement attached.       The material used in this flanged axle
production was 4340 HR ASQ/SBQ material.  The process was Upset Forge, Through harden, Machine complete,
Induction harden and Centerless grind. Threading was form rolled - not die cut.  This is the strongest type of thread.  
The axle used a ¾” with 20 thread which is not common and an automotive use only that goes back to the 1950’s, as
was its 17 spline.
Initially, because of the material used, all axles went through X-Ray to insure against  possible internal flaws. This
eventually dropped to one of every ten axles X-ray checked.  Attached photo of axles (spindles) coming out of
production.

The machining operation required various steady rests for machining and supports for induction hardening.  Induction
hardening (heat treat) is by electric arch.  Axles require support while in this form of heat treat.   The longer the axle
length the more likely it will emerge less straight – hence the use of supports.  With our short axle, this problem was
minimal.  

Rich Ackerman of LNS America handled all the set up for machine work and machine fixtures; he also produced the
CNC lathe program (CNC is Computer Numeric Control) for all machine work.  The resulting axle production began to
flow in October 1992 and was absolutely the strongest Corvette Axle ever produced with thousands in use today.

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DEVELOPMENT OF CUSTOMER BASE

Corvette Parts OnLine's first large commercial account was Qualified Automotive Remanufacturing in Pompano Beach,
Florida, who was the caliper and master cylinder rebuilder for Wagner Automotive products.  Qualified also had their
own brand label which was Florida Caliper.  
We were later confused with Florida Caliper but the name was registered by Qualified and used in their own product
line which included brake calipers for Corvettes.

Qualified, owned and operated by a Canadian group, had a 50,000 sq. foot facility where tens of thousands of calipers
and cylinders passed through every year.  We were sent all the Corvette calipers halves for assemble, which arrived to
us by tractor trailer in pallet crates.  Wagner, at that time did not use any form of sleeve for caliper recovery.  A great
majority of these castings arrived as new, and were assembled only as halves (the 2 halves were not bolted together).  

Later, Rayloc was the first national supplier to handle sleeved Corvette calipers, through their NAPA stores and we
supplied them for a decade for stores east of the Mississippi River.
As volume grew we bought our first of three CNC (Computer Numerical Control) turning center with barfeed for
hydraulic piston and stainless sleeve production (picture attached of 2 of these machines).  By the time the third CNC
arrived we also bought a Cinturn Centerless Grinder and our hydraulic parts product line came to 109 separate
hydraulic piston part numbers for both foreign and domestic cars. These parts went to part suppliers for private label.

This broad hydraulic piston product line was later sold along with its corporation, Florida Precision, and trade names
and we continued with the main corporate structure with its equipment to focus on our core business of manufacturing
Corvette related products for ourselves and for private label, particularly in the area of drive line, suspension and
differentials.  Some of the items we produced  included  Corvette axles (spindles) dropped forged and induction
hardened (picture of 2 pallets of axles just out of final machining), rear trailing arm backing plates, stainless 65-82
emergency brake parts, differential gear conversion kits to expand differential ratio selection.
Everything made only in the U.S.A.

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6 PISTON MOTORCYCLE CALIPER DEVELOPMENT

During the eighties we were approached by Eric Buell for a solution to a brake binding problem encountered by his
modified Harley Davidson race bikes, and street versions, marketed under the name “Buell”. At the time ‘Buell’ bikes all
used UK Lockheed 4 piston calipers on their front wheels.  Street use was quite acceptable, but track use presented
some problems – the brakes would begin to bind during hard use.  

The cause, as I found out, was that the caliper housing would begin to expand as it heated up during a race. The
caliper would bow when pressure was applied – as the housing bowed the pistons would still remain square to the rotor
but went into shear, (the piston centerline was no longer on caliper bore centerline, resulting in the pistons locking in
the caliper bore.  Improving the heat sink (rotor) by Buell, using stainless clad aluminum, worked excellently but the
structure integrity of the caliper was not adequate.   

Beginning from scratch, we developed a 4 piston caliper that used 4 bolts rather than 2 to retain the caliper halves and
were tested to fluid pressures up to 1500 psi, far greater than a motorcycle master cylinder can generate.  Track
testing showed good results without any binding.  The caliper was than further improved by increasing the size of the
rear pair pistons by 25%.  To over simplify, the idea was that as the rotor would pass through the pads the heat would
build and the rear pistons would require more pressure to effectively equal the front pistons braking force.
This caliper went into production with the “Buell” name cast into the outer face of each caliper.

Continuing with caliper development, we than designed and prototyped a 6 piston caliper that would mount directly to a
stock motorcycle front fork, (not using a separate bracket), photos attached.
This motorcycle brake line was manufactured by us using solid blocks (often referred to as ‘billet’) of aluminum
machined on horizontal CNC (computer numerical control) machining centers.
This caliper was tested and passed the German TUV for autobahn use and was the first motorcycle aftermarket caliper
to do so.  Sold under the “Harrison” marketing name, the Harley interesting enough, was the biggest market for this
caliper line.

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O-RING CALIPER DEVELOPMENT
COVETTE PARTSONLINE   started in the Corvette brake caliper business in 1975 with a brake caliper casting recovery
process via boring the caliper and installing a 303 stainless steel sleeve - much the same process as engine machine
shops use to salvage damaged automotive engine blocks.  Corvette calipers 1965-1982 use a lip seal mounted on the
piston which allowed the induction of moisture, creating corrosion.

The real problem was the factory lip style seal used, (carried by the piston) - it would seal only in one direction and any
motion of the piston would allow air to be pumped around the lip seal along with any dirt and moisture.  The piston
design would allow the piston to "rock" in the caliper bore with only a spring to "hold" the piston against the brake pad
when brakes were not employed, (residual pressure would not do it), and brake pads are subject to motion not the least
cause of which is rotor run-out.

In 1986 we looked at other earlier caliper systems that used a similar system where the piston carried the seal.
There were a number of designs going back into the 50's that were quite successful without the corvette system
corrosion problems, and all of these systems used an O-Ring.

We redesigned the Corvette caliper piston so that it would accept an "O-Ring" style seal and the lower piston land was
enlarged to prevent piston "rock" and eliminated the piston spring. We have always manufactured our own caliper
pistons and sleeves via computer numerical controlled machinery. This system we also applied to a number of other
calipers types such as Bendix and General Motors multi-piston rigid mount calipers.

All our brake modifications were subjected to outside engineering reviews and tests, I.E. Link-Chase data etc.

(Note: none of what we did was patentable because it is prior art. We began using this new system in 1988 for corvette
calipers we supplied to Cardone Industries and Rayloc (NAPA).
When this new system went on the market there was much 'talk down 'of the system by competitors but today all others
in the Corvette brake caliper business are using our Corvette retro-fit O-Ring Design.

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VALVE / SEAT DEVELOPMENT AND RESULTING PATENT

Circa 1991 Corvette Parts was approached by Consulier Engineering for a GM project to develop a modification to a
production engine that would allow it to be performance competitive for the next 2 years of production until the new
design engine came on line, the modification however had to be a "running change"; which means it would need to be
changes made on the engine manufacturing machining line only.

We brought in Craig Walters whose air flow talents lead anyone to believe that he actually could see air move. Given a
mountain of prints and other material from GM, we identified (where we believed) the best possibility of creating a
change that would actually produce something. This particular engine had a "Heart Shaped" combustion chamber that
lent itself to excellent burn characteristics.

At our shop, we produced a continuous line (several hundred) of prototype intake/exhaust valve and seat
arrangements for testing and where we (quite literally) walked into a combination that produced a venture effect at the
valve seat area with a slight mixture swirl.

To make a long story compressed:  the seats and the mating valves were radius formed that, in the final design,  
produced an excellent mixture acceleration that continued even after the piston reached BDC, (Bottom Dead Center),
creating a mild supercharger effect (slight positive displacement).

This radius type valve arrangement that included stem changes could be easily affected on the production line by close
numerous multiple valve and seat angles, and other machine operations that were easily adapted,  that would create
the near same flow effects.

This project was a success and we were paid for it.  (If you like, I could send you a factory production print, these are
quite interesting if you have never seen one, and perhaps a couple of valves).

We continued with this radius development and learned that it was not a universal fit.  Each engine took a slightly
different radius/stem/seat approach unique to its own flow characteristics.  However, the actual changes between
normal valve/seat types and our radius system was a common denominator – hence a patent was applied for and
awarded:  #5081965.  The declaration page of the patent documents is really what the patent applies to.

This is a synopsis of how ours reads:  A valve for an internal combustion engine has a stem and head with differing
diameters for the stem and the upper section of the head.  A radially irregular blend region placed between the stem
and upper head is aligned to have a slight runout creating a non-coaxial region with the axes of the stem and head.  
This blend region is positioned on the valve to be below the valve guide when the valve is closed and in the mixture flow
path when the valve is open.  The radially irregular blend region creates additional turbulence which focuses the flow
path of the fuel mixture into the opening between the open valve head and cylinder head increasing the velocity of the
fuel mixture through the opening.

Moving forward we produced a valve and seat kit for Harley Evolution engines that produced 10-12 horsepower with no
other changes.  We advertised the package as a 10 HP immediate improvement without so much as a spark plug
change.  We have numerous chassis dynamiter tests run by shops and dealerships showing the 10-12 HP gain with
some few going to 15 HP.

Attached is a photo of a batch of Harley intake valves and a family shop of all the Harley products we produced.  The
valve and seat kit of course, forged roller rocker arms, floating rotors and 6 piston direct bolt on brake calipers. All
these products were sold under our “Harrison” marketing name.

We were the first after market brake producer to qualify in the German TUV test for autobahn use.  That story will be
another write-up.

One last thing, we took an offer for the patent and we did sell it with the provision we could continue with our own   
production.   
TECHINFORMATION


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