I thought I had posted an update on this, but I now can't find it. Here is
my understanding of current status on the AEC cushions.

- AEC designed the cushions to the upper end of the range of the permissible
Durometer hardness (per their PMA), to assure long life.

- There have been no problems with installations on the fixed gear planes,
nor with the Sierra nose gears. These are all the smaller diameter cushions
having the single centered bonded metal disk. There have been several posts
on the installation process, and there are some photos on BAC (including an
Igloo cooler "heater" and a pre-compression rig). If the
pre-heating/pre-compression process is followed (as outlined in the Service
Manual), the job goes problem-free.

- There have been several installations on the Sierra main gear. Two owners
experienced problems with achieving adequate pre-compression. It is
believed that the non-machined upper inside surface of the main gear housing
casting can vary in thickness as much as a quarter of an inch. With the
upper-end hardness of the new rubber, and the two-sided metal bonded discs
on the larger-diameter cushions, it is apparently possible to have a
stack-up of circumstances that makes it impossible to get enough installed
compression on the Sierra main gear.

- AEC has addressed this by ordering more of the large cushions having a
Durometer reading on the lower end of the permissible range (in the PMA).
They will resume sales of the Sierra main gear sets by configuring marked
sets. These will have several of the softer cushions at the top of the
stack, and the harder ones beneath. The softer rubber will be up inside the
upper gear housing, where it will be more protected from the elements (sun,
ozone, solvents, etc.). The AEC original-design hardness cushions will be
placed in the lower exposed positions, and will be better able to withstand
the environmentals as intended. The combined cushion stack will enable
proper pre-compression, even if a thicker casting is encountered. It will
also function as a sort of variable-rate spring, to provide a good ride even
while the cushions are new and stiff.

I'll ask Kamran for an update on resumption of sales of the retract main
gear sets. Sales of the smaller-diameter fixed gear (and Sierra nose gear)
sets have continued, though at a very slow pace. Several of those success
stories have been posted on BAC and MML.

Just as a reminder to those who are contemplating a cushion change: The
large roll pins that secure the stack tube to the compressor plate are
supposed to be checked for straightness during the cushion work (as
described in the shop manual). Many are found deflected due to previous
hard landings. The original MilSpec pins are obsolete for design and
manufacture, and are generally unobtainable. There is a superseding MilSpec
for a stainless-steel version of the pins (per the US Qualified Procurement
List). These are standard hardware parts, and the superseding part is
perfectly legal to use. I actually found a company to make me some of
these, so we would have a source. Of course, I had to have a minimum
quantity made, and I am frankly still well in the hole on the deal (though I
have sold maybe a dozen sets). If you are planning a gear donut project,
please consider purchasing a set of pins to have on hand. I have them
listed in the BAC Classifieds along with my other items, and they are very


From: musketeermail@yahoogroups.com [mailto:musketeermail@yahoogroups.com]
On Behalf Of bpalamara1
Sent: Tuesday, January 24, 2006 11:13 AM
To: musketeermail@yahoogroups.com
Subject: [musketeermail] Alternator

Has anyone used the new AEC Doughnuts? It's about time as they are 34
years old.
How long should it take a good mechanic to do a retract?

Bob Palamara
'72 Sierra


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