It seems like, lately, a month or two seldom goes by in which one of the major hobby-related businesses doesn’t close its doors. In the past six or seven months, Fox Manufacturing ceased operation, as did Hobby People with their multiple stores and Macs Products, the country’s largest manufacturer of mufflers,
tuned pipes, header pipes, and related accessories. It was back in the
mid-1960s that the change from .45ci engines to . 60 size for pattern
competition was underway. Due to the larger engines, noise became
a problem at many flying sites, and many clubs began looking into
mufflers as a solution. Wally McAllister foresaw the future and formed
his business, Macs Products. After more than 40 years, Wally decided
to retire and turn the business over to his brother, Dave. This past
September, however, Dave unexpectedly passed away. When no other
family members were interested in continuing the business, Dave’s wife
put it up for sale. My good friend Randy Linsalato, who in conjunction
with his wife, Anching, own and operate MECOA/K&B, purchased Macs
Products. Randy does not intend to continue any production, but he did
receive a large inventory of the products that he will be making available.
So if you are in need of any of the Macs Products’ line of mufflers and
pipes, visit mecoa.com or call 626-359-6972.
Now to the letters.
UI am wondering if you could enlighten me and your readers about the
design of multi-cylinder engines and, in particular, radial engines. Why do
radial engines always have an odd number of cylinders? The only even
number multi-cylinder engines I have seen are always opposed.—Frank
Jordan, Kansas City, KS
Answer: Well, Frank, as most people with any engine experience know,
a four-stroke engine fires every other revolution (i.e., two revolutions for
by ClarenCe lee
Mufflers, Multi-Cylinders, and More
Email your questions to Clarence Lee at MAN@airage.com. q&A
one combustion cycle). In the case of a 5-cylinder radial, the number
one cylinder fires, skips number two, and number three fires, etc. On
the second revolution, number two fires, followed by number four, and
back to number one. Since the engine fires one cylinder and then skips
one, there has to be an odd number to come out even. Radial engines
use a master rod, with the other rods connected to the master rod and
a single throw crankshaft. Opposed engines use a double- (or more)
throw crankshaft depending on the number of cylinders (i.e., a throw for
each pair of cylinders).
Our next letter from
photos, neither of which was suitable for reproduction. Basically, they
showed a piston with a big hole in the center and both rocker arms
broken. Ed’s club members felt the damage was caused by a stuck
valve, but he disagreed and asked for my opinion. Read on.
UI have been reading your columns for more years than I can
remember, and this is the first time I have written to you. The subject
matter is a 15-year-old Saito . 56 engine that quit abruptly in flight.
The engine had previously been very reliable in a number of different
models, including a Telemaster, Unionville Beaver, and Kaos 40. There
has been a lot of discussion in our club regarding the cause, with “stuck
valve” being the most popular view. I have a problem with that since it
does not explain the damage. I think the valve broke off the valve stem,
bounced around the combustion chamber and made a hole in the piston,
jammed the exhaust valve (thereby breaking the rocker), then was
pushed up into the intake port, which pushed the valve spring assembly
out and broke the other rocker. This would account for the damage,
but what would cause the valve to break off the stem, and what would
cause the retaining clip to break and the top of the valve stem to break
off? With your many years of experience, I am hoping you can provide
an explanation of what might have caused this failure. Note: I don’t think
it is worth repairing the engine; I’m just curious about what happened.—
Ed Carew, Carleton Place, ON, Canada
Answer: Ed, in my opinion, I believe your assessment is entirely correct.
The damage had nothing to do with a stuck valve. You did not say how
much fuel had passed through the engine, but having seen use in three
aircraft, it was probably a lot. During that time, it more than likely saw
some lean running, particularly toward the end of a flight, resulting in
detonation. Detonation is a well-known cause in the automotive and
full-size aircraft fields for breaking valves and pistons.
Macs Products’ universal muffler is available for .20- to .60-size engines with
either a strap-on or bolt-on retainer, depending on the engine.