S&S Cycle Dynamic Balancing - Manual (Page 2)

BALANCE TECHNIQUES
In mid-August 2000, S&S ® began spin-balancing most production
flywheel assemblies with an American Hoffman ® dynamic
balancer. With this technique, flywheels, crankpin, rods, and
shafts are assembled, the weight of the piston assemblies and
other components entered into a computer, and the completed
flywheel assembly spun to a preset rpm on the computer-
operated dynamic balancer. The computer determines how much
weight must then be removed from the outside of each flywheel
rim to achieve the 60% balance factor normally used by S&S. No
additional disassembly/assembly of the flywheels is required.
With our previous method of balancing, the 60% factor was
obtained by weighing the rods, crankpin, and piston assemblies,
and then removing the required amount of material from the
inside surface of each flywheel. Afterwards, the flywheels and
components were assembled according to normal procedure. No
additional disassembly/assembly of the flywheels was required.
WHY CHANGE?
Our primary reason for changing balance techniques was to meet
increased production demands while maintaining the quality
that S&S customers rightfully expect. As a point of interest,
flywheels balanced using our previous static-balance method
were assembled and then checked on the dynamic balancer. The
difference between the two methods was less than two grams, or
approximately 0.1% (one-tenth of a percent).
While production flywheel assemblies (complete assemblies
assembled by S&S only) will normally be spin-balanced, S&S will
offer static balancing as a no-cost option when shop time
permits. Spin balancing is available only with complete flywheel
assemblies assembled by S&S. Unassembled flywheels will
continue to be static balanced unless ordered unbalanced.
It is possible to determine whether flywheels balanced by S&S
were statically or dynamically balanced by removing the timing
inspection hole in the crankcase, slowly rotating the engine, and
observing for balance holes. Balance holes are .4375 inch in
diameter and will be visible on the outside rim of flywheels that
were dynamically balanced. Balance holes are on the inside rims
of flywheels statically balanced by S&S, and not visible through
the timing inspection hole.
WARRANTY ISSUES
In the past, S&S has discouraged dynamic balancing. Our
objection was that sources who balance flywheels dynamically
typically assemble the flywheels, mainshafts, and crankpin
without the connecting rods, spin the assembly to determine
how much material must be removed from the flywheels, and
then disassemble the flywheels for balancing. The connecting
rods are then installed and the flywheels reassembled.
It has been S&S’s observation that, if not correctly performed, the
additional disassembly and reassembly procedure required for
this method can alter the tapers in the flywheels, mainshafts, and
crankpin. This can change critical tolerances, make subsequent
assembly and truing procedures difficult if not impossible, and
lead to premature engine failure by preventing the precise
mating of parts that is required for maximum strength and
durability.
S&S no longer voids its warranty on flywheels that have been
dynamically balanced by other sources. However, when
evaluating warranty claims, S&S reserves the right to determine
if flywheel, crankpin, mainshaft, or connecting rod damage was
caused by improper assembly or balancing techniques. The S&S
warranty will be rendered void if it is determined that
procedures undertaken by a third party weakened or damaged
any of the parts in question.
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