Think Spring TuneUp!

We have faced the worst of the winter - short days and long nights. Christmas is over.

Sure there's still some snow left to annoy us, but we can at least see warm, long evenings at the end of the tunnel... SPRING. In spare moments we work on some new flying machine that we are convinced will tear up the sky.

Now is a really good time to think about the most important, and often neglected part of our aircraft. The BATTERIES. Without them our flying machines, no matter how powerful or light simply cannot be controlled.

If you haven't flown since October like me then the transmitter and receiver batteries are pretty much depleted just from sitting. A standard rule of thumb says that Ni-Cads loose 1% of their capacity per day. Sometimes you get a big surprise and find a shorted or open cell, this renders a pack unusable.

A typical receiver pack is 4.8Volts. Fresh off the charger you may read as much as 5.2 Volts but this is only temporary. The best way I know to check battery capacity is with a battery cycler.

A cycler performs it's function by placing a fixed load on the battery pack and notifying you when the pack has reached a threshold, usually on a receiver pack the threshold is 4.4 Volts. There are many of these cyclers on the market, and most do a good job. So lets cycle (exercise) those packs and get them in shape for the upcoming flying season.

A Work of Art By Ray Williams, Utica NY

Two years ago I built the 1/4 scale 4cylinder inline Gypsy DeHavilland engine per Merritt Zimmer’s design. This engine was flown in my scratch built Gypsy Moth and is a blast to fly, especially with a homemade engine.

Each year I visit the Old Rhinebeck Aerodrome for the model meet and in my mind the Camel with the 160 Gnome rotary always stands out.

What a whacking roar when it powers up!!!

So here was my next challenge a scale rotary. While at the meet last year Tom Polapink of Rhinebeck said he had a dismantled engine in the hanger. So I borrowed a set of vernier calipers and started blueprinting. However not all the parts were available so I made contact with Fred Murrin who owns Murrin Antique Aero in Dayton, OH. I met him in Dayton at the biplane meet. He was there with his full scale Fokker Triplane and original Lehrone engine.

What a piece of work!!!

I set up an appointment to continue the blueprinting of his disassembled 160 Gnome. Using CAD, I was able to draw scale plans of the outside, the insides were a different matter. I wanted to maintain the original mechanics and yet be as anti-friction as possible.

When you scale down engines, the bearings and gears that are commercially available become very large. This was one reason for choose 1/3 scale. At that scale the engine is large enough to replicate all the original mechanicals. Most 1/4 scale model engines are never dynoed for power, run only once, and become mantle pieces. To create a strong setup I had to used needle bearings in the design. The crutch rod carrier is the only bronze bearing. Lubrication is castor oil supplied from a piston pump as per original. Fuel is standard two stroke 32:1 gasoline mix providing additional lubrication. However the castor oil does not mix with the gas in maintaining lube.

C&H made the sparkplug wires and ignition and my electronics friend Tim Spoon, designed a circuit to duplicate the magneto interrupter on the 160 engine. This gives all, one half, one quarter, or none of the cylinders firing per revolution. This means the throttle control has three speeds.

The original dyno testing gave a thrust of 58 lb and 75 ft-lb of torque at 3300 RPM with a Zinger 36/22 prop. Having this much torque would scare me when taking off and in right turns. With a “true scale” prop the engine was detuned to dyno at 42 lb thrust and 18 ft/lb torque. This still gave more than enough power for flying. The airplane will fly at half speed (14 lb thrust).. The stroke (2”) and bore (36 mm) is scale at 27 cu.in displacement. To get the low frequency sound, I needed to run the engine at about 2500 RPM. With a scale prop it runs 2600 RPM

It took 6 months to build the engine and it fired right up in the 20 degree January weather for the test flight.

AIRPLANE

Tom Polapink also suggested the AVRO 504K suggesting everybody models the. It turns out that this was a good choice since there are many unknowns in applying a rotary to a model, and the AVRO proved to be forgiving. I bought the WINDSOCK Datafile 28 and used the cover as my color scheme.

I took hundreds of digital pix of engines and planes. Kemitt Weeks’ Fantasy of Flight in Florida has a 504K with the 160 Gnome. As it had been damaged in the hurricane the wings and tail feathers were uncovered. I used some of the same building techniques such as the aluminum wing tips and tail feathers.

I usually scratch build, but Arizona Models had a 1/3 Bob Holman plan listed and was willing to cut a kit. All of my early war birds are built with proven construction design and techniques by John Tanzer.

The airfoil is semi-symetrical modified Clark Y generated using Wingmaster software. The airfoil is slightly thicker to allow for a 1-1/4” wing tube at 2-1/2 deg dihedral. I had Arizona laser cut the ribs. I contacted WORLD WAR I AEROPLANES INC for the Danish Government Archives Plans Set that has all the drawings of every bracket and details the wood construction. I redrew in CAD the details needed by Arizona and then had them water jet cut in stainless steel the frame brackets which were black chromed not painted. I die folded the sheet metal for the control horns and pulley guards to scale.

Making the scale gas tank was a challenge, since I had to learn how to spin the end cones in brass.

The prop is a scale custom made 35x32 from Tennessee Propellers. The 10” Wheels are from Rieds Model Products. Spruce Aircraft Specialties supplied me with some beautiful 6ft long I/4 x I/2” spruce for the spars and 1/8 x 1/4” stringers. Arizona furnished a 15-1/2 ” alum cowl.

I use 0 deg wing and l-l/2 pos stab incidence. This seems to stop the vintage model from power porposing. The engine has 2 deg down and right thrust. The model flew without any trim input and handles well with power surges.

The 12ft wingspan is assembled four thumb nuts on 1/4 x 13 L threaded rods. This makes the wings pull on each other rather than glued wood. All flying wires are pre-strung with 6 passes of 30 lb Kevlar using 23 homemade turnbuckles at 6-40 thd and 20 with 4-40 thd. These per original have phosphor bronze centers and heat treated chrome molly eyes with nickel plated forks. All forks have a 17-4 PH stainless clevis pin, #2 washer and 1/32 cotter pin.

The plane balanced perfectly-guess that 13.5 lb engine helped!!! Total weight is 52 lb and at 5500 sq.in. Wing loading is 22 oz/ft sq. The pilot is 1/3 Vintage by Diane Chevalier.

Custom Graphics! ***Next Meeting***

There has been an alteration to the planned demonstration at the upcoming March meeting. John Hayes has changed from doing a demo on vacumn bagging to a demo on custom made plane graphics.

John will show us how it is done and some of the techniques he uses to put those interesting designs on his always fabulous monokote jobs.

Be there and learn something new.

The Middlessex County R/C Flyers 11th Annual Auction is being held on Saturday, March 30th at the Knickerbocker Club located at 36 Chamberlain Street in Lowell, MA.

• Registration is from 11:30AM-12:30PM.
• The auction will run from 12:30PM-4PM.
• Admission fee is $2. Selling Fee: 10% of selling price. No minimum bid. If bid is lower than seller's desired price, seller may buy back item and club receives 5%.
• Refreshments Available.
• Raffle: Futaba Sky Sport 4 Channel FM Radio.

Directions: from Route 3, take Route 495 to Exit 37 (Woburn Street). Follow Woburn Street to Gaudreau Street and turn right. Follow to Chamberlain Street.

Need Input on the following issues:

• What programs or demos would you like to see at the meetings?
• Need input for the Bullsheet. Articles, jokes, good natured ribbing, pictures of the latest project, hints etc.
• Provide feed back to the Bob Johnson at bobj@rodchuck.com or 673-7368.

A new internet list has appeared run by some folks in District I AMA. I don’t believe it is AMA sanctioned, just folks in the district, but looks like it could be interesting.

Check it out at - http://groups.yahoo.com/group/AMAdistrict1/

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