About this Plan
Voltswagon. RTP model for electric power, using Mabuchi FT-36D slot-car motor.
Note this plan also appeared in the book 'Electric RTP Flying' of 1972.
Update 20/11/2012: Replaced this plan with a higher resolution clearer copy, thanks to aeromeddler.
Update 04/02/2021: Replaced this plan with a clearer copy, also added article, thanks to theshadow. This is the plan as published in AAM Aug 1968. See supplement 'previous' file for the plan as it appeared in the book 'Electric RTP Flying' of 1972.
Quote: "Voltswagon, by Pat March. Electric indoor tether flying with slot motors and light balsa planes is ideal club-oriented activity. Elevator and motor control are used.
FLYING powered models becomes more difficult with vanishing flying sites and complaints about noise. Voltswagon solves these problems as well as offering complete throttle and elevator control, ability to fly indoors or out, and no starting problem. The modern slot racing motor makes this possible.
I have built electric-powered pylon models with wing spans from 4 to 25 in, with areas up to 150 sq in. Larger wing areas make for remarkable maneuverability. Speedsters using hefty motors and small, high-pitched props have logged speeds of over 40 mph. These models are flown on a tether from a pylon, with power brought out from the pylon head through slip-rings. A single light cord concentric with the slip-rings serves to operate the elevators. Up-elevator only is used, since down-elevator turned out to be a disaster.
Voltswagon is an ideal introduction to the field of electric flying. It is docile at the controls, yet has good maneuverability and speed. It lends itself well to experiments with Payload, Speed, Carrier, and other such events as may be dreamed up. It is also useful as a primary trainer for U-Control.
You must first obtain a suitable power-pack. Fourteen volts at 2-1/2 amperes was needed to match the full capabilities of the motor used. It is suggested that you go first class on power-packs because you will wish to make other, more demanding electro-planes after experimenting with Voltswagon. Perhaps your club could be persuaded to purchase a suitable industrial power supply that will give plenty of capacity for future needs. A slot-racing throttle regulates power to the motor. The 'brake' feature on these units is undesirable and should be left disconnected.
A 12-volt automobile battery also is suitable. There is plenty of amperage and long life between charges. When discharged you can have it recharged at a gas station. A second-hand or reconditioned battery is fine. The voltage will be adequate but, if your motors demand more voltage, a 6-volt battery can be used in series with the 12-volt one for a total of 18 volts.
The motor used is the Mabuchi FT-36D, marketed by Revell, Cox, and others under various trade names. Use the photos and drawings as a guide for choosing the correct motor. Other motors have flown in different models, ranging from the tiny-size Mabuchi to the big Tradeship and MPC Dyne-Chargers.
Since the Voltswagon was built many much more advanced types of high-torque motors have become available. With some of the newest slot-car racing motors an armature rpm of over 70,000 is not uncommon. Torque is tremendous and current consumption high. Again, use of low-pitched small-diameter props will let the motor turn up efficiently. Or you might try some simple gearing arrangement, so that the propeller turns at only 15,000 rpm while the motor is turning at 30,000 rpm. Be sure to have adequate cooling available since more power means more heat. With gearing, more pitch and/or diameter can be used.
Having secured your motor, power-pack, and materials, start construction of the pylon. A first-class approach will pay dividends. (This might also be an excellent club project.) The most exacting portions of the pylon are the head and brush holder; study the drawings and photographs carefully. The head consists of inner and outer slip-rings made from 1/8 and 1/4 in brass tubes. Cut the outer ring 1/2 in long and solder into a hole in a sheet-metal bracket. Cut the inner ring one in. long and solder a small wire lug around the lower end. Insulate the inner ring with a paper or fiber disk just above the lug. Wrap it with Scotch Tape until it is a snug fit in the until the brushes make good contact with slip-rings.
Fit a small long-shanked eyelet to the inside diameter of the inner slip-ring. Pinch the shank slightly out of round to make it a tight fit within the slip-ring. The eyelet serves to hold the brush-holder down and provides a smooth, rounded surface for the elevator control line to pass over. If you cannot obtain the eyelet, solder a small washer to the upper end of the inner ring and smooth off the edges as much as possible to minimize chafing the elevator control line.
To make the pylon structure, fasten a sturdy 2 ft long wooden post to a piece of plywood at least 15 in square. This joint takes a heating so use strong glue and at least two husky screws. You may wish to equip it with guy wires if doubtful about the integrity of the joint. Mount the head on the upper end of the post with screws. Finish off by connecting about ten feet of lamp cord or other two-conductor insulated wire to the pylon head. Solder or crimp one lead to the lug on the inner slip-ring. Connect the other to one of the pylon head mounting screws. Tape or tie the wire close to the post.
Install a small screw-eye in the base very close to the bottom of the post directly below the pylon head. Use light nylon, dacron or linen cord for the elevator control line, feeding it through the pylon head and the screw-eye with a swivel installed in between. At the pilot's end of the string, pass it through a small hole in the end of a piece of hard cardboard or sheet plastic about 3 x 6 in. An eyelet in this hole will reduce friction. This is used to keep the line close to the floor, and prevents accidental 'carrier landings.' Then tie a ring or bar to the end for a hand-grip. A small wire hook tied to the upper end of the string serves as an attachment to the airplane.
Obtain a length of light double-conductor stranded wire. Number 24 speaker cable is suitable. Cut to the length needed for the airplane leads. Five feet is suggested. Three feet can be used and as much as 12 feet is possible. Split and strip the ends and attach small wire lugs. Make sure the lugs grip the insulations as well as the conductors or the wires will soon fatigue and break. Hook up one end of the wire to the screws that hold the brushes.
Construction of the airplane is straight-forward with only a few points worthy of special mention. The propeller mounting is one. The recommended method is to use a brass No. 10 machine screw drilled through the center as an adapter. Solder it to the motor shaft. This drilling is easily accomplished with a metal lathe, but is nearly impossible otherwise. Any small machine shop should be able to drill out a screw at little or no cost. A good prop to use is a 5-1/4 diameter by 4 pitch Topflite, drilled to fit, and clipped to 4-5/8 inch diameter to avoid a motor overload.
The spinner can be made from a balsa block, using your motor as a lathe for finish sanding. Force the adapter screw into a hole in the rough-carved spinner and sand with very light pressure. Blow sanding dust out of the motor frequently to prevent overheating. Cut a cavity to fit the prop hub and notches for the blades. To mount the spinner dead true, cut an accurate disk from fiber or light cardboard with a hole in the center fitting the No.10 screw. Fit this behind the propeller and cement the spinner to it.
Make the 'engine room' by tracing off and cutting out a pair of doublers, a firewall and a shelf from 1/4 in hard balsa. Don't skimp on the holes in the shelf and firewall. These motors release a lot of heat, and need every bit of cooling air they can get. Assemble these parts as shown on the drawing. Add cross blocks to the shelf, notching them to fit the front and back ends of your motor. Fit wire hooks fore and aft for a rubber-band motor holddown.
Make the fuselage sides from medium 1/16 sheet balsa and cement to the motor mount assembly. Add formers, then sheet in the underside from the tail to the wing trailing-edge position. Make sure the two side planks do not come quite together at the rear. A 1/4 in gap is about right..."
Supplementary file notes
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