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 nm 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 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 dol1ars, 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 Halt 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 V-Haul truck and delivered it to Bill's auto-repair shop in Akron. Steve unloaded the equipment, built the air-conditioned 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 sheet-metal 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 Hannifm, 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.