This month’s profile is not about a person but about a useful device for launching electric models.

PVC Pedal Launcher

My little electric “Hawk” had suffered multiple, serious, damage when given, er, let’s just say, “very poor” hand launches by two particular people, straight into the ground – they know who they are! This was going to be a short-lived, costly and frustrating model, unless ….

Hand launching on a bungee might have been possible, but wouldn’t take care of the main requirement on such a small model – a wings level launch.

So, based on an idea from a link Rob Bailey passed me, but which I think I improved on a little, I constructed a “Pedal Launcher” for my Hawk model. I am sure it should work equally well for other models lacking an undercarriage – (a common way to save size and weight on electric powered models). After seeing it work, Robin and Paul both want to use it, and of course the CFI has it in mind to launch a Ready 2 from it, inverted! (He flew and landed a Ready 2 with just his toes remember, so anything’s possible with him!)

As you can see from the photos, the whole contraption is about 5 feet long, and features:

• Take-off rails (width-adjustable for larger wingspan models)
• Ground-spike anchor points at each end
• A permanently fixed coach bolt as the bungee restraint (threaded portion must be sawn off)
• A ‘hinged’ Iroko (hardwood as in garden furniture) “pedal”, drilled to fit over coach bolt pin
• A flat metal plate about 1” x 6”, in which three suitable holes are drilled
1. At the front, for the bungee to be tied to
2. At centre, to allow this retaining plate to sit down on retaining pin
3. At rear, to tie on nylon tow rope

In fact it took some research to find suitable parts. Normal ‘waste’ or ‘water’ pipe would have been OK, but it is impossible to find the 2 ‘X’ cross pieces needed to anchor each end, in the same size as the pipe available! Even major Plumbers Merchants could not help, and could only offer diabolical methods of achieving this. Eventually I found a specialist “Plastics” company in Brimsdown. They stock a ¾” range of very high pressure piping, in which the needed “X” pieces are available.

So the full components to make the Launcher comprise:

Plastics

2 ¾” cross-pieces (for front and rear of launcher) 3 ¾” T pieces (for each “foot” of launcher frame, plus hinge arrangement) 4 1” T pieces (to allow launching rails to slide for differing wingspans) 4 1” to ¾” Reducing Bushes 6 90 degree elbows 5 Plain end caps 1 ½ litre tin of Jet UPVC solvent cement 2 6 metre lengths of ¾” high pressure UPVC pipe (which I had to cut at supplier to get home in car!)

Other components

1 screw on tow hook 1 length of bungee rubber (about “14-paces” seems to be a good amount so far) 1 Dog-lead screw-in tie down to anchor bungee 2 ABS Tent Spikes (to hammer into ground to restrain each end of the Launcher) 2 ¾” pipe “U” clamps and nuts 2 Lengths of pipe insulation foam tubing (to fit on rails to avoid wing hitting elbows) 1 About 6’ x 3” length of “Iroko” hardwood 1 flat metal plate about 1” x 6” 2 1” key-rings (one to fix bungee to metal plate, one at string end to pull tow hook) 1 Length of nylon string to use as tow rope 1 Steel Coach Bolt (portion including threaded end sawn off and discarded) 2 Steel washers to sit on coach bolt either side of tube 1 Spring-steel “C” circlip to retain bolt in launcher frame

We’ve done about 10 launches, all successfully now after we’d got the length of bungee about right (dog-lead ground spike about “21 paces” in front of the Launcher).

There is no need to power up the electric motor until clear of the launcher (in fact, to do so would loosen the strain on the string and probably ruin the launch). In fact, but for the trees in front of our take off run, there is probably enough momentum from the bungee alone to manage a complete small circuit back to the launcher without switching on the motor).

Larry Tuwie

Launcher with Hawk.

Launcher with Hawk, side view.