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Excellent analysis Lynn. Very strange design for a pulley to
have the load so far from the bolts. Tremendous moment on that thin sheet metal.
Easy to over tighten the belt and then you are screwed.
More fasteners, fine. But I'd sure focus on measuring belt
tension.
-al wick
----- Original Message -----
Sent: Thursday, August 04, 2011 7:35
AM
Subject: [FlyRotary] Re: Water pump
pulley departed in-flight
Notice the offset of the pulley vice the flange centerline. The bolts are
in shear for driving forces (very light) and in bending for belt tension
(slightly higher load) so the little guys are working hard, and more bolts is
a better answer. Racers run the single belt with the stock alternator
location, and just about 30% of the water pump pulley engaged with no problems
at all, so loads are light. I use bolts in all 8 holes with Locktite. If your
pumps have only 4 holes, add 4 more and tap. And actually measure belt
tension. There are stock two sheave water pump pulleys, where you run the
alternator and, or, air conditioning with a two sheave crank pulley. And there
is a belt length that you can run the water pump from the Mazda Competition
pulley (smaller diameter) with no idler at all and perfect belt tension.
No pulley failures since that first one in 1980, (with 4 bolts).
Lynn E. Hanover
In a message dated 8/4/2011 7:59:53 A.M. Paraguay Standard Time,
jwhaley@datacast.com writes:
There
are only four small bolts holding that thing in place … noticed in Haynes
pictures this morning that some have four studs and four bolts … guess the
studs are for adding a second pulley?
– but they would also add extra drive surface area. I
think I put those bolts on with standard loctite but am not 100%
certain. Anyway now I’m wondering if my restrictor plate, loading the
pump, may have contributed to more vibration or is this just coincidence
…
Jeff
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