According to EAA Chapter 23  August Newsletter in Salt Lake city
Andy Venable's plugs up 13B engine seized. Fortunately while on the ground.

This is a very rare occurrence in a Mazda unlike two cycle engines where it is
common. The Mazda oil system seems to be very reliable when the engine
is run upright.

This could be caused by a lack of oil pressure. The oil pump
in a 13B is located below the e-shaft and is driven by a chain. The chain
is normally very close to the oil level in the sump and may get its primary
lubrication from dipping into the sump oil. These chains have been known
to wear and Tracy Crook thought his needed replacing after 800 hours in the
air and 80,000 miles in previous car service as I recall.
Andy had more than 400 hours on the engine built by Dave Atkins.

When the engine is rotated counter clockwise looking at the front
of the engine with the plugs in the up position the chain is well removed
from the sump oil level. Be that as it may I have no idea what caused Andy's 
failure. I have sent an email to him yesterday asking for a report.

Andy has never mentioned, to my knowledge, any trouble with the Ross
gear box. Early Ross gear boxes had no helical gear thrust bearings 
and relied on the Mazda needle thrust bearings at the front of the engine
to take the helical gear end thrust by way of the e-shaft.

A catastrophic failure of this thrust bearing could have destroyed
the oil pump or the oil pump drive but that would be an unlikely 
scenario as there is a rather fine screen protecting the oil pump
from metal particles in the stock Mazda upright engine. If the particles
were small enough to get through the screen the oil pump and oil
pressure would deteriorate much more gradually. If the screen was 
not installed due to the fact the oil pickup tube must be modified 
in a plugs up engine then yes a large chunk of metal in the oil pump could
very well do it in.

The condition of the thrust bearing in the engine can be judged
by the end play in the early Ross gear boxe prop shafts. This in 
fact is what alerted Tracy Crook to Ross gear box problems prompting him
to disassemble the engine and check the Mazda thrust bearings.
Sure enough, they were badly worn.

A third scenario is failure of the oil O-ring between the front cover and 
front end housing. This has been known to fail graduallY soon after 
rebuild if not installed properly.

A massive oil leak of course would be noticed by oil all over the
bottom of the airplane and cowl.

Paul Lamar
 
The AirCraft Rotary Engine NewsLetter.              Powered by Linux.

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