Old Timers-2011/12

Old Timers - 2011/12

Bob Angel | [email protected]

Four Glider events

Gliders were around before powered flight and are still used as a learning tool in designing powered aircraft. The Society of Antique Modelers (SAM) organization has competition classes for four glider categories. Yes, I know modern glider pilots prefer that they be called sailplanes, but let's relax about nomenclature—especially when the term glider came first.

Three of the glider events are free flight (FF) and are held at the annual SAM Champs. They are Hand-Launched Glider, Towline, and Catapult-Launched Glider. The RC event is Old-Timer (OT) Glider.

• Hand-Launched Glider
• Should be self-explanatory. There is an unsettled rules discussion about whether wingtip (tip) launches will be permanently permitted. Tip launches test a flier's agility to a higher degree and elevate the competition level over more conventional launch techniques.

• Catapult-Launched Glider
• The catapult is a simple 6-inch-long dowel with a 9-inch (unstretched) loop of flat rubber band attached. One hand holds the dowel and the other holds and releases the glider. This event obviously favors the flier with the longest arms, but proxy launches by pet orangutans are specifically prohibited. For many in SAM's average age group the catapult event is more docile.

• Towline (FF)
• Allows either a 200-foot handheld towline or a 25-foot hi-start with 150 feet of line attached. Modern circle-tow devices aren't allowed, but auto rudder is okay.

• Old-Timer (OT) Glider (RC)
• The RC event allows launch by either hi-start or winch. In practice pilots usually observe an unwritten agreement to stick to hi-starts. Modern "hot" winches—which would elevate the competition level—require more support equipment and beefier aircraft structures; that would probably result in the eventual demise of the event.

Glider designs for the FF events must predate 1943. The RC OT Glider rules allow designs through 1946. As with any competition, get the rules straight before setting out to build a model. Do you suppose I chose this glider subject just as an excuse to show that fine-looking Cleveland Albatross photo? The model was kitted in 1944, so it's only eligible for the RC event that allows designs up through 1946.

Ray Arden and the glow plug

Ray Arden is generally credited with inventing the glow plug. As with many inventions, there were other contributors—some competitors, some collaborators. Ray collaborated with Ben Shereshaw (designer of the Bantam engines) and Ed Chamberlin. These men likely took clues from full-scale engine experimenters who used various "hot plugs" for ignition.

In the early 1900s model engines provided low power and were heavy—their weight was measured in pounds, not ounces. Ray Arden was obsessed with designing smaller, lighter engines and support equipment. As a teenager he built his first engine in his home shop. His ignition system was a vibrating-coil type that provided a continuous series of sparks. These untimed random sparks didn't provide optimum power. At one point he added an early glow plug, used along with the continuous spark, to achieve smoother running.

I once had an accidental acquaintance with vibrating continuous spark while breaking in an Ohlsson & Rice .23 on a test stand. The alligator clip on the coil's point lead popped loose with the engine running. The clip came to rest, lightly touching the timer case. It vibrated against the grounded case, producing a steady stream of sparks. To my surprise the engine continued to run, slowing very little, until I switched off the battery power.

Before modelers had ever heard of glow plugs, I remember a new hot fuel that was marketed as "Liquid Dynamite." Through experimentation—and maybe some accidental luck—Ed, Ben, and Ray found that with this hot fuel you could get an engine running strongly, then disconnect the spark ignition system and have the engine continue running. The spark plug's side electrode became hot enough to act as a glow plug.

Today, hot plugs occasionally cause problems for OT fliers when using FAI fuel in spark-ignition engines. The engines don't always quit running when the ignition is shut off. Colder spark plugs usually cure this.

Ray Arden succeeded in designing and marketing small, lightweight engines, starting with the Atom .09 and later the Arden .09 and Arden .19. He developed lightweight coils and finally a small free-flight chassis that integrated the complete ignition system in a slender plastic package. But those experiments with Liquid Dynamite had sparked the idea of eliminating the heavy coil, condenser, batteries, and wiring.

Ray and Ben Shereshaw contributed to developing the final coiled-wire glow plug. Then a plating of platinum/iridium was added to the wire to provide more heat through catalytic action. I recall a vivid demonstration of this catalytic action in the form of a novel cigarette lighter that resembled a lipstick tube. The tube was lined with methanol-saturated cotton and a platinum-plated wire was stretched across the top of the main body. When the cap was removed, the reaction between methanol, platinum, and air would make the wire glow red and ignite the methanol. Replacing the cap extinguished it. You didn't want to lose the cap in your pocket.

According to Arden's biography on the AMA website, the Arden glow plug first appeared at a contest in 1947, when Ray showed up selling them out of his car trunk. Those Arden glow plugs still work well today. Replaceable wire elements were available for Arden plugs, but I don't recall ever having to replace either a burned-out element or any of the other early glow plugs.

Arden glow plugs are easily identified at swap meets by their distinctive ball-shaped brass dome on top. You'll find a lot more interesting information about Ray Arden's life and inventions—he's said to have held more than 200 patents—on the AMA website.

As modelers replaced spark plugs and ignition systems with the new glow plugs, an unfortunate thing happened for today's engine collectors and OT fliers: those ignition systems, and especially the engines' breaker-point assemblies, hit the trash cans by the thousands. Reproduction timer assemblies are available today for most common engines, but at higher prices than the original cost of the entire engine. Clear plastic fuel tanks were often a built-in part of early engines; many of those became victims of the new hot fuels which promptly melted them.

Why Arden engines performed well

At our local field we have a monthly engine-running session along with our Saturday OT flying sessions. We recently ran one of the last model spark-ignition Arden .19s, which gave us a chance to study why Arden engines perform so well.

Key design features:

• Minimal distortion
• Ardens are noted as one of the "snappiest" engines you'll encounter when you're flipping the propeller without running it. Their basic design keeps the piston/cylinder combination almost perfectly round during heating and cooling cycles, which yields excellent compression and low friction whether running hot or cold.

• Threaded head and cylinder
• Rather than being bolted down, the threaded head screws on, much like later Cox engines. The threaded cylinder screws into the crankcase for the same reason. Bolted assemblies can cause small stresses and distortions, especially in light engines with comparatively thin cylinders.

• Symmetrical exhaust porting
• The four exhaust openings are evenly distributed around the circumference of the cylinder, as opposed to the asymmetrical porting on almost all other two-stroke engines.

• Ball-and-socket connecting rod/piston assembly
• Similar to Cox engines, this design helps the piston remain perfectly round. A normal wristpin could create a tiny warp in a piston when heated.

• Roller cam follower
• This feature minimizes friction and eliminates any perceptible cam "bump" when you turn the propeller over slowly. It's a feature I haven't seen on any other production engine.

Our test engine turned in excess of 12,000 rpm on an 8-inch propeller, which is about the prop size I'd choose for a small model.

Arden engines were described in SAM Speaks issue #105 (May/June 1992) in a series of engine analysis articles by Charlie Bruce. Charlie also published a book of those 101 articles he prepared on various engines for SAM Speaks. He describes in detail each engine's construction, followed by takedown and reassembly sequences. He runs the engines and gives test results.

Sources

• AMA History Program
• www.modelaircraft.org/museum/whatshere/history.aspx

• SAM Speaks back issues
• Two-CD set: $30 (postpaid in USA)
• Order to:
• Karl Gies
• 131 13th Avenue South
• Lewiston MT 59457
• (405) 538-8503
• [email protected]

• Old Engine Analysis (Charlie Bruce)
• 200-plus page book: $45 (includes US postage)
• CD: $28 (includes US postage)
• Order to:
• Charlie Bruce
• 384 Rhum Rd.
• Kerrville TX 78028
• (830) 367-7740
• [email protected]

Transcribed from original scans by AI. Minor OCR errors may remain.