Knowledge Base Request: Paint, Corrosion-Resistant Metals

I'm planning to lead a few rocketry workshops in the summer in the hopes of getting some local kids interested in model rocketry. The last time I did this, though, two big things interfered with the fun. First of all, the paint (cheap Tempura stuff) didn't stick to the polished plastic surfaces of the nose cone and fins; and secondly, the

60+ launches were absolutely brutal on the cheap launch controller (and its AA batteries) that I used to send the rockets on their way.

Does anyone know what kind of inexpensive paint can be used that will stick to polished plastic?

I'm building a more heavy-duty launch controller to take care of the second problem; does anyone have advice on what kind of metal resists corroding at high temperatures? Should I buy alligator clips for the igniter that are copper-coated, brass-coated, plain aluminum, or what? And how do people keep them shiny?

Thanks in advance for any advice or help you can lend.

Krylon now makes a paint that is specifically for plastic.

Stainless steel is your best bet for dealing with corrosion. Better launch pads have stainless steel blast plates. A better launch control option would be to pick up either a Aerotech controller that you can hook to a car battery, or Hobby Lobby on occasion has the high end Estes controller that works with the larger rechargable batteries or you can simply rewire it to hook up to a car battery. Regular alligator clips are fine, just keep some sand paper on hand to sand off build up to ensure a good connection.

-Booms

Attach the controller's wires to banana plugs, such as Rado Shack part #

274-730. Slide 'gator clips, such as Radio Shack part # 270-346, over the plugs. This make clip replacement easy.

Replace the clips.

Stainless steel micro clips last a long time.

Before those, most people used #34C solid copper micro clips. Copper plated are

*BAD* as the thin copper plating is corroded away in no time and the plain steel metal underneath then turns to rust.

The Quest controller uses a 9 volt alkaline battery and it has thicker lead wires. This allows it to deliver more power to the igniters. you will still want to have fresh replacement batteries on hand since they suggest that the average alkaline 9 volt will last for 25 launches.

Those of us who launch a LOT use an alkaline lantern battery or we convert from

6 volts to 12 volts and use a car battery. You can also use 7.2 volt nicad packs from R/C cars. The Estes Command Controller uses one or two of those. Too bad it is out of production. they show up on eBay every 2 weeks or so.

-Fred Shecter NAR 20117

Replaceable clips are handy. You may need to adjust the banana plug to get a snug fit. With a small screwdriver you can *gently* expand the plug slightly to get a snug fit. Sometimes the clips will fly off the plug when you're flying mid and high power. Keep a couple of spare sets with your launch controller.

I like to use pre-moistened towelletes to clean motor cas> addams013 wrote:

For the Quest controller, I recommend either the GE/Sanyo or GP rechargable NICAD batteries. Freshly charged, they outperform the normal alkalines. I still haven't got around to testing the NiMh rechargables in this controller. While I don't recommend ANY of the mass market launch systems, this is one is the best of the bunch.

wash the plastic with dish soap and water. dry thoroughly.

or

wipe down with acetone or other solvent.

or both.

depends on how fussy you want to get.

haven't tried stainless steel clips yet, glad to hear someone comment on them that they work. when our clips get corroded I just replace them.

a high power 12V launch system is great. if you have any electronic expertise, build your own.

we started by getting a SureFire launch system from Pratt hobbies, ripping it apart after we killed the battery, and building our own with improvements. I would suggest their GO Box or the surefire system.

[looks like this didn't get posted the first time...]

Here's what needs improvement on the cheap launch controllers:

#1) BATTERY! This is the most critical part of the system. Use something like a 12v 5-12AH gell cell, an RC car or cordless tool rechargable battery pack (9.6-14v several AH), or a car / tractor battery. Make sure it's freshly charged each time you go to launch.

#2) Upgrade the wires to at least lamp cord. The cheapest source for wire in most stores are those orange extension cords. They can be had for much less than buying bulk wire. You can either cut the connectors off and use the wire, or design your system to use a standard extension cord for the cable.

#3) Clips. I recommend using the Mueller #34C solid copper clips. The steel plated clips will start rusting the first time you use them. The crap that Radio Shaft sells will start rusting as soon as you tear open the plastic bag. Expect to pay about 50-75 cents a piece for the good ones. An internet search should find sources. Digikey probably has the good ones.

The clever trick I've used for 3 decades now to clean them is a little wire brush in a rotary tool. For on the field cleaning, an emery board or ignition points file will do. The only part you really need to worry about cleaning are the two little flat jaws that grab the ignitor. Crud elsewhere really doesn't matter.

#4) Light bulb: I replace these with 12v piezo buzzers. It's easier to hear than it is to see a light bulb in strong sun.

Look around on the net and you will find many plans for controllers and pads that are better and cheaper than the stuff sold in the stores. I've been using a relay launcher for almost 2 decades. Crude plans for it can be found at

If you want to buy instead of build, look at the controllers from Pratt Hobbies. Everyone seems to like them, and Doug is a super person to deal with.