Low Power Launch Pads

The Thrifty Rocketeer blog continues...

A couple of months ago, I posted a picture of a power cord that had been modified with alligator clips to be part of a launch cord lead.

It was my attempt to start assembling my own set of launch gear, in the event that it would ever be needed.

Little did we know at the time that a choronavirus pandemic was coming, and that many rocketeers would be self-isolating, and building up their fleets.   Or that all NAR club meetings, assemblies and launches would be cancelled.

But here we are.

Now, most low power guys (whether they started as boys, or joined the hobby as men) have acquired at least one Estes launch pad and controller, sort of as a rite of passage.  The small controller box, with a key, indicator light and launch button, holds something like 3 or four AA batteries to get up to 6 volts an at least 15 feet of twisted pair wires that run out to small alligator clips.

I can't tell you how many of these I have run into, having found them at second hand stores, in yard sales, or donated by other rocketeers who are cleaning out their garage.  So, I admit that I have somewhere between 3 and 5 right now...having given one or two sets away to other budding young men or their family.

But I think if you stay in the hobby for more than a summer, or get into medium power or affiliate with a club, you start to see how the big boys do it.  And there's a natural tendency to try to emulate or assemble the gear so that you can do it on your own.

(Now, there are some good reasons why you shouldn't try to go solo, but I won't get into that debate here.)

Let me just say that while I have been looking at a number of launch pads, from home brew to commercial units, and the creativity has been impressive.  Some have modified work bench clamps. Some have built tripods or saw horses or out of PVC pipe glued together.  Others have repaired various rails or big clamp systems.  No matter what you build or use, the bigger motors always seem to burn or scorch the blast shield badly by the end of the season. (as they should!)

Now, my first home brew launch system was a one inch by one foot square piece of pine wood, with an 24" yard sale sign metal stake used as the launch rod.  A 12 foot roll of twisted pair Bell hook-up wire and two mis-matched alligator clips were my leads.  And my controller? That was a camping lantern battery with spring contacts for momentary contact of the wires to launch. 

But in my ignorance, my blast shield was an aluminum lid from a cat food can.  ...Now, I know what you're thinking, and you're right.  "How dumb can he be?"   Well, for 1/2A3-4 and A8-3 motors, that can lid held up for about two launches, but melted through pretty darn fast.  As a result, it was replaced and then abandoned in favor of a steel soup can lid.  But even that didn't last long.

Recently, I have heard a suggestion to take a large steel vegetable can (like canned tomatoes, or pineapple juice can)  and to cut both ends out when empty. Cut the length of the can with tin snips to flatten the can down to one sheet. [Another version says flatten only until the can compresses to look like a lower case letter "m"]  Drill a 1/8" hole in the center of the flattened sheet, and round off those wicked sharp corners.  You have a cheap blast shield that can easily be replaced.    I assume the thicker cans used for tomatoes or acidic juices stand up to the blast heat better.

I have looked at the Mantis Z-shaped blast shield, as well as some other shields and still have not settled upon a good home-brew shield yet.  But my sights are currently set on an electrical junction box cover plate.  I'll have to drill a hole through the center to fit the launch rod, but it's the best and cheapest solution that has presented itself to complete my own launch pad.

Do you have any other suggestions?  Is there something that I am overlooking that could work well.

Let me know in the comments, and until then, keep your glue capped, and save your scrap balsa.

UPDATE:  After posting on a social media site, I got a short response from a fellow rocketeer:  A Terra cota pot plate.    It was brilliantly simple.   These are commonly available. And I picked up two of them at Lowe's the next day.  First one was about 5 inches across, and the next one up in size was about 7.  Both accepted an 1/8" drill bit to insert a launch rod without difficulty.  I also picked up a simple electrical box cover plate and drilled that as well.  So I have lots of options now.  I also went up a size for the larger plate, in case I wanted to use a 3/16" rod and the bigger Terra cota plate.   

My wife looked over my shoulder as I was finishing drilling, dismayed that I had ruined a water holding plant plate. "Why did you do that" she asked accusingly?   "To make myself a blast shield," I said uncommittedly.  The lines were drawn.  I knew that she wouldn't hesitate to abscond with my plates and plug the holes with gorilla glue at the first opportunity.

I moved the plates into my hobby area and hid them in the carry basket that acts as my jump kit when I go to launch.   I knew she wouldn't hunt for them, but if I did leave them out...who knows where she'd put them.

So, I'm ready to go now.  Next stop, the launch field, once this NAR ban is lifted.