At 03:36 29 October 2006, Eric Greenwell wrote:
The belts that broke at the Parowan camp were the propeller
drive belts,
not the fan belt (the water pump is driven directly
by the engine - no
belt). The drive belts on the 26 E fleet did not break
for many years
(for example, mine is 12 years old and has 114 hours
on it), but a few
of newest gliders have had this happen. We've been
told that Gates, the
belt manufacturer, changed the construction of the
belts about three
years ago, and the consequences of that change are
now surfacing.

Eric Greenwell - Washington State, USA
Change 'netto' to 'net' to email me directly

'Transponders in Sailplanes' on the Soaring Safety
Foundation website
www.soaringsafety.org/prevention/articles.html

'A Guide to Self-launching Sailplane Operation' at
www.motorglider.org


The Gates Poly Chain belts are the best you can buy
and in properly designed drives will last a long long
time as demonstrated by their use for driving camshafts
in automobiles for 100,000 miles. In spite of their
strength they have been broken in both DG and ASH drive
systems but possibly for different reasons. What the
belts do not like are shock loads and the internal
cords can easily be damaged by something as simple
as improper storage.
The belt failures on DG’s are thought to be caused
by shock loads imposed during starting/low rpm where
the power pulses are most uneven. On the DG's the best
prevention is to minimize the shock loads by getting
past the low rpm phase as quickly as possible and optimizing
cold start fuel delivery.

The ASH failures may be due to another problem that
being storage. The gates preventive maintenance manual
clearly states that the stored belts should not be
subjected to bending beyond that which is defined as
the minimum pulley diameter as it may damage internal
cording resulting in premature failure.
The belts are obviously designed to be used in a straight
line without twisting which may be the reason why twisting
is not specifically identified as something to be avoided
in the Gates manual.
The ASH drive system puts a 90-degree bend into the
belts when the engine is stowed into a relatively hot
environment. If you explained these failures to a Gates
engineer and showed them the drive design they may
point out that twisting in heated storage could be
a contributing factor.

See we do have some things in common.