Author: Joe Wagner
Edition: Model Aviation - 2007/12
Page Numbers: 85,86,88
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Highlighting the SuperTigre G-34

Joe Wagner | [email protected]

Overview

SuperTigre's line of model-airplane engines covers an extremely wide scope. From the smallest—the G-34—to the huge G-2300, all the SuperTigres provide extremely well-built, low-cost glow power. I've owned some of the larger SuperTigres for a while, and I like them a lot. I recently acquired one of the G-34s to see how it compared with them, and I'm quite impressed.

The G-34 is a ringed-piston, double-ball-bearing, Schnuerle-ported two-stroker. It arrived with its carburetor assembly, two-piece muffler, glow plug, and all the associated hardware separately packaged in the box. That packaging is doubtless one reason for the SuperTigres' low price: partial assembly saves considerable time at the factory—and assembly labor is responsible for much of any model engine's manufacturing cost.

Assembly and pre-oiling

When I began trial-fitting the G-34's components, their unusually close fits led me to do something I've never done before while assembling a new-out-of-the-box model engine: I pre-oiled everything before installing it—even the glow plug. That precluded any chance of bare-metal parts scraping particles from each other as I put them together. Everything fit snugly—even the propeller washer and the carburetor retaining bolt.

A 32-page, well-illustrated instruction booklet comes with each SuperTigre. (It's the same booklet for all the engines, from the G-34 to the G-2300, since they all share the same basic design.) Even though I've put together many hundreds of model engines, I carefully read all the way through the instructions before I began assembling the G-34.

Following (and deviating from) the instructions

I admit I didn't follow the booklet in every detail. For instance, the booklet shows the muffler retaining screws being installed from the muffler side. I found it easier to install them the other way around, which makes the nuts far more accessible for tightening.

Another change I make whenever possible on a front-rotary RC engine is to twist the carburetor 10°–15° away from straight-ahead alignment. Doing that moves the needle back, away from the propeller disk, which makes needle adjustment safer. It also causes the throttle arm to work at a slight angle, but that doesn't affect its operation. Repositioning the needle back away from the propeller is easy on the larger SuperTigres, but on the G-34 I had to file off much of the front corner of the bottom fin on the engine's case to provide clearance for the fuel line.

Starting and break-in procedure

The G-34 hand-started easily on my test mount. As do most of the ring-type engines I've run, the G-34 likes to be "wet" for starting—hot or cold. I used 10%-nitro fuel with extra castor oil for the break-in runs. Especially with ringed engines I want ample lubrication for the initial runs. The idea is for the moving parts to burnish one another into proper fits rather than wearing them down during the break-in process.

The SuperTigre instruction booklet calls for leaving the glow lighter connected 15–20 seconds after the engine starts. I've found that to be necessary. Probably because of the extra cooling effect of the tall, closely spaced head fins, it takes a SuperTigre a bit longer to reach its full operating temperature than most glow two-strokers.

I keep my model-engine break-in runs brief. Two or three minutes at a time is plenty to allow all the engine's parts to reach their normal operating temperature. Then I stop the engine (by pinching its fuel line) and let everything cool all the way back to ambient temperature. I repeat this brief run and cool-down cycle four times and then my break-in procedure is complete.

I always break in my engines on a test stand. That way everything is out in the open, for maximum cooling and minimum plumbing problems.

Test mount and tank-holder modification

To test-run most of my engines larger than .20 I prefer the PSP all-metal test mount. However, because model engines vary so enormously in dimensions and needle-valve locations, I found it necessary to modify my PSP unit's fuel-tank holder.

I screwed a 3/4-inch-thick aluminum block (approximately 1 x 2 inches) to one side of the PSP's tank holder. This block has a tapped hole through it to fit a 6-inch length of 1/4-20 all-thread steel rod. I filed down the threads at one end of this rod so it can rotate freely—but snugly—in the existing threaded hole where the PSP's stock tank-holder retaining screw fit. That way I can return it to the stock tank-holder arrangement if I want.

Adding a plastic knob to the top end of my all-thread rod gave me a neat and easily adjustable way to set the tank height. The rod's threaded end locates in the aluminum block's tapped hole, and the tank rests on a rectangular piece of 1/16-inch-thick aluminum secured to the rod with the knob. My mod gives enough adjustment to fit nearly any size engine; the height can even be adjusted while the test engine is running.

I had hoped that the fuel and vent tubing from the tank would provide enough twisting resistance to keep the tank position stable; not so. I had to add a vertical tank-alignment guide, which I made from hardwood, alongside the new assembly. Now everything works fine.

Fox .049 restorations

In the October column I mentioned the disappearance of many American-made 1/2A engine manufacturers of yesteryear. Yet some U.S.-made .049s are still being put together. Doug Martin has acquired a considerable quantity of original 1960-era Fox .049 parts. From those components he has been custom-assembling three Fox 1/2A engines and making them available to fliers in Nostalgia FF and CL events.

Two of those .049s have single bypasses; they were originally intended for ready-to-fly plastic CL airplanes. The third Fox .049 is the twin-bypass "FAI Special." The name comes from Duke Fox's expectation (in 1963 when he decided to produce this engine) that the FAI would make .049 the upper limit for 1/2A competition events. Alas, Duke guessed wrong: the FAI set .061 (1 cc) as the limiting size for 1/2A, which made the Fox FAI Special an orphan—and it's the reason why ample stocks of its parts survive today.

Doug Martin custom-fits each Fox .049 he sells and does something no other American 1/2A engine maker ever did: he test-runs each engine before sending it to its buyer. That way he can be certain he's delivering a fine-performing product.

GloBee IntelliTach tachometer

I waited for months for GloBee's new digital tachometer—the IntelliTach—to become available. I have one now, and it's well worth the delay.

Notable features:

  • Bright red case that is easy to spot during engine-testing sessions.
  • Positionable readout screen with half-inch-tall LCD numerals that are easy to read, even at an angle.
  • Screen snaps into any of five angular positions, from flat to 45°, which helps when taking RPM readings from behind the engine and shields the display from back splatter of raw fuel and oil.
  • Presettable propeller-blade selection for two-, three-, and four-blade props.
  • Three memory functions that can retain RPM readings from one test session or flying event to the next — useful for matching twin engines.

One more handy hint: fuel filters

In-line fuel filters, such as Du-Bro's, can save a power flier considerable troubleshooting time. It's amazing how easily tiny foreign particles in fuel can mess up a needle setting or the ability to idle reliably. I believe the biggest reason for recapping a fuel jug promptly after drawing fuel from it is to block the entry of airborne crud. Especially at the flying field, dust particles and shredded grass blades abound: they're too small to be easily visible—but not too small to give you plenty of trouble if they get into your model's carburetor.

Fuel filters prevent that problem. They also block air bubbles in the fuel line. With a filter installed up close to the needle valve, any fuel foaming in the model's tank becomes inconsequential.

Sources

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