Monday, August 15, 2011

Tennis Ball Launcher

Ham Radio is not ALL about Electronics and/or QSO's ?

For the last few days I have been searching and collecting the parts to build a Tennis Ball Launcher, the goal is to Launch lines over the trees around my Shop for several Dipoles.

Previously I had collected Pulleys and Lag Bolts with plans to hire a tree climber to install the supports for an antennas.

Rod Ready to Fire
But, during Salmoncon (see previous post), Rod - KE7X showed me how easy it is to put lines over very-very tall trees for supports, using a Tennis Ball Launcher. In fact, the Tennis Ball Launched line can be put higher into a tree than possible with a tree climber.

I got-to-have one of these!

A little web research suggests there are many designs and configurations for a Launcher.

The first problem is finding right size Launch Tube, a Tennis Ball is about 2.65 inches in diameter. Standard 2.5 inch Schedule 40 PVC pipe is about (as you might expect) 2.5 inches inside diameter. A Tennis Ball can be forced into this tube, with a ram of some sort. Many designs found on the web use this commonly available size PVC pipe (with a ram), and apparently they work quite well.

But, Rod (and other web users) suggest it is worth finding a length of lesser-available "2.5 inch SDR-21 PVC Pipe", a Tennis Ball fits fuzz tight in this slightly thinner wall pipe. The fittings for this size are readily available as they are are the same as used for normal Schedule 40 PVC pipe. Although 2.5 inch pipe and 2.5 inch fittings are not available at the standard Box Hardware Stores (Lowes).

With a little Googling, I found a local Whole Sale Plumbing Supply house that stocked 2.5 inch SDR-21 pipe in 20 foot lengths, and the price was not bad, at $22.00 per stick. They also had the fittings. I will add a parts list here (that I will use) later.

The next task was to find a valve, the larger the better, but at a reasonable price. There are several types and vendors available from the Box Hardware Stores. The valves are typically used for under ground sprinklers which are power and controlled by a timer. I wanted at least a 1 inch valve. Most newer Launcher designs seem to use one of this size. Rod's design (and other web users) uses two valves in parallel for more air flow, I may try two valves later. Some of the available values are complex and are overkill for a simple launcher. I found a simple One Inch Orbit Valve (#57101) for $12.00, we will see how well it performs.

The next task is to decide on the fill connection, pressure gauge, and release trigger mechanism. The fill connection and Pressure Gauge were found at an Auto Parts store, the gauge is a little bigger then I want but it will do.

For initial trials, I will use the standard electrical connection to the valve for the release. Rob, and most web users modify the valve to allow for simple pneumatic release and therefore not requiring a battery. The valve I purchased appears to operate correctly with just a 9 Volt battery, and yet it is simple enough that can be modified for pneumatic release if necessary.

Most published designs use a PVC pipe with caps for the air reservoir, I found one design, The Trident, that uses plastic coke bottles, which make the Launcher much lighter. I think my initial design I will try this approach. I am drinking the content of the first bottle as I write.

More details will follow !


1 comment:

  1. There's nothing like the lure of very high antennas! Keep us posted Eldon.