DRIVESHAFT SAFETY SOLUTIONS

 

DRIVESHAFT DONUT HISTORY, FAILURES AND SOLUTIONS

HISTORY.  Back in the 1960s, Alfa Romeo's race shop, Autodelta, came out with a donut shield for the race cars of the day, which made up to about 170 HP.   Today's vintage Alfa race engines are making up to 200 HP and have exceeded the safety limits of the original Autodelta shields.    At 7000 engine RPM, your driveshaft is doing about 8700 RPM in fifth gear.  If you are geared for 8000 in 5th, your drive shaft is spinning in the 10,000 RPM range.   The energy stored in a spinning drive shaft and the risk of failure increase exponentially with higher RPM....and the failures always occurs on the top end - generally at high speed in 4th or 5th gears.  In the early days, drive shaft donut failure started with a buzz of vibration, giving a bit of warning. The high RPM failures of today are just a huge bang with horrendous consequences for both car and driver.  

FAILURES 101/105/115 SERIES CARS.  The advent of the high RPM 200 HP engine far exceeded the capacity of the 1950s rubber flex joint.  Unlike earlier cars, these drive shafts are retained inside the tunnel by a body cross member and stronger support bearing. This prevents the shaft from exiting the car and the forward end of the short shaft thrashes about.   Last year a 2.0 GTV had a large piece of floor chewed away and the driver was seriously injured.   Subsequent forum discussions have been a great benefit to the awareness of this problem and need for prevention of future failures.

PREVENTION. Ben Franklin that stated: "an ounce of prevention is worth a pound of cure"? In over fifty+ years of being a shop owner, dealer and racer, I have seen both street and rac e donuts have catastrophic failures.

 

SOLUTION "A"  

DRIVESHAFT DONUT SAFETY KIT  (OEMS-KIT)

Protect your Alfa from catastrophic donut failure.  OEM donut failure is not a matter of "if", but when.

Tri Plates secure tag ends of driveshaft bolts, preventing the buzz saw affect when donut explodes.

Kit Contains

  • OEM Stock Donut PN 605-15851
  • Two Tri-Plates
  • Six Nyloc Nuts

UPGRADE TO HD DONUT #605-15851-HD, ONLY $10.75 EXTRA.

  

         

SOLUTION "B".  Our $148 street conversion kits ( part # 515851eck) should be good for street performance and autocross cars.  At this price, it should become a standard replacement for the Alfa donut.  The German flex disc that replaces the Alfa donut is the same as the race kit.  This street kit features tri-hole spacer end plates mounted at the tag end of the drive fork bolts.  This arrangement should be sufficient to preserve the concentricity of the rubber flex disc during a low RPM failure.  With the run out controlled, the driveshaft should not jump around and reach the critical orbit that causes tunnel damage.  We give credit to a customer in Holland that suggested the tri-hole plate solution some time ago.  He sent this photo.

  

 

SOLUTION C These are CNC machined from a solid billet of 4340 annealed steel,  heat treated to a Rockwell hardness of 38-42 and shot peined.   Theyt provide 360 degree containment that further enhances the ability of a failed disc to preserve concentricity and not reach critical orbit.  Rated at 390 HP, this disc features a fabric core that prevents unrestrained chunking. The difference in street failure and race failure is exponential.  Imagine the difference in energy stored and then released in a race drive shaft running at speeds from 8000 to 10,000 RPM as opposed to 5000 RPM on a street machine.



 

This is Paul's installation on his own race car.  Driveshaft and gearbox axis should be on the same centerline and have very little angle in acceleration/deceleration.   The gap between the shields is an essential tool for adjusting the driveshaft angle.   When properly aligned, the gap should be the same for 360 degrees. 

 

 

 

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