158 MODEL AVIATION
[[email protected]]
Control Line Speed Dave Mark
A short history of Jet engine supplier Earl Bailey
Also included in this column:
• Bill Capinjola’s efforts to
continue producing jet
engines
Engine heads are produced 24 at a time
to reduce setup costs that are generated
during the manufacturing process.
Three pieces that make up the combustion chamber are mounted on an arbor to
maintain the correct alignment during the welding process.
Bill Capinjola (center) presents Larry (L) and Brent Murgatroyd with a Fast Jet in
appreciation of their producing the new pulse-jet engine mounted on the model.
A CASUAL observer who looks at a pulse-jet
engine used in the Open Fast Jet event might
think, “What is so complicated about this
engine? There is only one moving part.”
As is often the case, looks are deceiving.
This stainless-steel tube with a chunk of
machined aluminum on the end is the result of
many Speed fliers’ tremendous dedication
and effort throughout the years.
For years the Dynajet was the most
common engine used for the Speed event. The
stock heads were modified in many ways in
efforts to produce more power.
When new, the stock engines’ tailpipes
were not usually round, but more of an oval
shape because of the manufacturing method
used to shape the pipe halves. It was common
practice to run the engine several times to
soften the material and then draw a hardened
steel plug through the pipe to resize it to a
round shape.
The pipes often varied in length. It was
common for Jet fliers to have quite a
collection of pipes in their shops.
Jet engine tuners felt that after many
modifications the stock head design had been
pushed to its limits. This drove people to
build their own designs. As all this
development was going on, the stream of
Dynajets was drying up.
Along came Earl Bailey of Houston,
Texas. He had been a fan of the Jet event for
many years, and he thought that if someone
06sig5.QXD 4/23/07 9:37 AM Page 158
didn’t produce the engines the Speed category
would die.
Earl ran a machine shop and had an
extensive background in fabricating machined
parts for many industries. He took on the
project of building the engines from scratch.
Doc Charlie Davis supplied Earl with a
one-part head design called a Raven that Mike
Hoytt designed. This head had propelled Doc’s
model to a record.
Earl wanted to provide a pipe that was built
to tighter dimensions than the Dynajet offered,
which proved to be quite a task. The tailpipe
on the Fast Jet consists of five parts, four of
which are made from .015 thick stainless steel.
Welding this stock would have made less
determined people throw in the towel.
Since these engines’ production numbers
were not large enough to warrant building
stamping dies, the metal parts were cut by
hand. Before edges could be welded they had
to be trimmed straight and square; otherwise
the weld would fail. Fixtures were built to
allow the ends of the tapered cones to be
trimmed to length and squared.
Each welded part required a circular and a
longitudinal weld. The circular weld required
that a lathe be modified to rotate the part at a
speed slower than that offered by the gearbox
and a weld head be adapted to the bed.
Copper arbors were built to support the
parts as they were welded. It was discovered
that the two tanks of inert gas needed to be
heated to an exact temperature or gas flow
would be erratic, causing holes to be blown in
the weld bead.
The machine shop was not air-conditioned
and it was found that as the room warmed up
during the day the welds started failing
because of the temperature change. Earl built
an air-conditioned enclosure around the
welders to stabilize the temperature.
After spending tens of thousands of dollars,
enough engines were produced that Earl began
selling them. Orders poured in for the product
from all over the world.
On the next run of pipes the welder could
not be made to produce a hole-free weld. The
factory representatives were called and many
more thousands of dollars were spent trying to
repair the welder, with no success. Earl began
the search for a better welding method.
His quest took him to a machine made by
Weld Logic Pulse Arc, Inc. It uses a pulse
welding system that produces a tight, beautiful
weld. He purchased the welder and rebuilt all
the tooling to work with the new system.
Earl suffered a stroke and died April 30,
2006, while he was in recovery. This ended the
supply of pulse-jet engines.
When dedicated Jet fliers Bill Capinjola of
Ohio and Richard Hart of Texas heard the
news of Earl’s passing, they decided that they
would make an offer to purchase the tooling
from Earl’s estate.
After a deal was struck, Speed flier
Steve Perkins, who was an employee of
Earl’s, loaded the tooling and welders onto
a U-Haul truck and delivered it to Bill’s
auto-repair shop in Akron. Steve unloaded
the equipment, built the air-conditioned
June 2007 159
room, and installed the machines.
A big problem was that no blueprints
could be found for the engine parts. Bill had
to reverse-engineer each component’s sheetmetal
layout.
There were no instructions for the
methods Earl used to weld the pipes. Steve
had a general idea of the techniques used, but
he said that building the engines was a project
Earl had run by himself.
Steve returned to Texas, and Bill
continued his efforts to sort out the welding
process. He spent every spare minute reading
the pulse-welder manuals and attempting
welds.
Bill cleaned each part before welding and
found that if the slightest bit of fuzz from the
cleaning cloth was left on the edge of the
part, a blowhole would be produced in the
seam. A change of just 2° in room
temperature or humidity would cause the
weld to fail. He gradually refined the welding
process to the point where eight out of 10
parts were good.
The next step in the process was to trim
the parts to length. Bill was unable to produce
smooth trimmed ends with Earl’s tooling, so
he designed and made his own tooling to do
the job.
Before Bill took on the tube project he
had been designing his own head for the Fast
Jet event. He wanted to build 25-50 at a time
and was on the hunt for a machine shop that
would take the job.
Every shop Bill talked to looked at his
sample and print and told him they were not
interested. He was getting worried that he
would not be able to find a shop to do the job.
Bill mentioned the problem he was having
to a friend, who suggested that he call a shop
in Canal Fulton, Ohio, called JonMar Gear
and Machine, Inc. When Bill stopped by to
have people with the company look at his
project, they said they would give it a try.
JonMar owners Brent and Larry
Murgatroyd have an extensive background in
supplying precision-machined parts to many
large companies such as Parker Hannifin,
Akron Brass, and the military. Parts they
have produced are in everything from
submarines to spacecraft.
When Bill picked up the first batch of
completed heads, Brent told him they had
come within minutes of calling him to tell
him they could not do the job. Bill says the
Murgatroyds have been a pleasure to work
with from the first time he presented the
project to them. They applied a strong
personal effort to the project and solved many
complex setup problems as they worked their
way through the process of machining the
heads.
Bill recognized the Murgatroyds’ efforts
by presenting them with a completed Blue
Thunder Fast Jet model, complete with the
latest version of the pulse-jet engine they
helped produce. These people’s combined
effort has created an almost turnkey system
that will run in excess of 190 mph with ease.
Sources:
Jet Bill Products
Bill Capinjola
(330) 699-0577
[email protected]
JonMar Gear & Machine, Inc.
13786 Warwick Dr. NW
Canal Fulton OH 44614
(330) 854-6500
[email protected]