Fellow enthusiasts, The following is written with my
sincere belief it may save a life. Comments welcome.
DELRON BUSHING WARNING!
In 1974 while doing about 70 mph on QE2 just north of Lake Ontario, the
right lower fulcrum pin in the A-arm suddenly broke. It was all I could do
to control the car. I am one of few to survive such a break.Two years
earlier I replaced the original rubber/steel sleeve bushings with delron but
reused the original pins after magnafluxing them. I had the broken pin
examined by an expert metallurgist. His professional opinion was the pin
failed with a twisting fracture most likely caused by lack of lubrication and
the pin not rotating in the bushing. Fortunately other than the A-arm and
fulcrum pin, the Tiger was not damaged.
I replaced the right A-arm and replaced both fulcrum pins with 4140 super
strong pins. I used new delron bushings that I lubricated well when I
installed the pins. The A-arm rotated easily around the pin before I put it
on the car. Every spring, as part of my preseason check, I lubricated the
pins
and checked for ease of movement.
Last fall while my son was making a left turn, the right fulcrum pin suddenly
broke again! There was no way to steer the car. He hit an Explorer on his
right, rolled it over and totaled it. He then took down a light pole spinning
around the concrete base while the pole was in the air. He was not injured
because he was wearing a seat belt. My insurance company totaled the car. I
am now in a painfully slow process of acquiring the parts I need.
When I found part of the fulcrum pin at the accident scene, I knew what
happened. I took the broken pin back to the same metallurgist. After
examining it he concluded that the pin was indeed a 4140 pin and that it did
not fail with the twisting fracture he saw 14 years earlier, but failed due
to an excessive load being applied to the pin. He felt that most likely cause
was the delron bushing transmitting excessive loads to the pin under certain
conditions and cracking it. This process would continue (perhaps for years)
until without warning the pin would fail and loss of steering would result.
He felt that the original rubber/steel sleeve bushings provided some give
that helped protect the fulcrum pins. A fulcrum pin would be less likely to
break in this type of bushing than in delron. Though he would not say that
there was no possibility of a pin breaking in original style bushings. He
also felt that lubricating the pins, while addressing the twisting failure,
did nothing to address this type of break. He emphasized greatly that EVERY
PIN WHETHER, STOCK STEEL, 4140 STEEL, TITANIUM, ETC WILL FAIL WHEN USED WITH
DELRON BUSHINGS. He said again EVERY PIN WILL FAIL. He asked me to warn all
owners.
His qualifications include: PHD in metallurgical engineering, over 20 years
doing industrial failure analysis, senior member of the American Society
for Metals, received the 1999 NACE International Award for outstanding
contributions to science, has co-authored two books on failure analysis that
are used as the standard textbook at most engineering schools, and has done
over 3600 failure analysis. He is an expert in the field.
Short of redesigning the entire front suspension he recommends that if you
are using delron bushings you should be very aware of the risk and make plans
to replace the bushings with the original style as soon as practicable.
You can reuse the fulcrum pins but only after having the fulcrum pins
magnafluxed and microscopically checked for cracks, particularly in the
shoulder area. If you are using original style bushings you may not be
at risk now, but NEVER replace them with delron. Personally I have purchased
another set of 4140 pins and will install them using new polyprolene/steel
bushings.
Delron bushing are meant for racing applications. This means that as part of
the preseason checkout, the pins should be removed and magnafluxed. They are
NOT meant to be installed and the pins never checked again. If you insist on
using delron, you must check and magnaflux the pins often no matter what the
pin is made of.
If you think you can ignore this, I recommend you read the metalurgistbs
qualifications and his recommendations and base that against what makes you
think you can ignore him. Remember what happened to me.
Dave Johnson B382002668(under repair) Aurora, IL
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