Safety Code for Relay Launchers

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Well-Known Member
Jun 2, 2011
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Is it just me or do you feel the safety code is severley lacking information about relay ignition systems?

The current info seems to cover the handcontroller circuit but I can't see anything (both NAR and UKRA) about safety on the ignitor circuit, or specific to relay systems. With the popularity of kits such as the Deuce, more and more are building cluster-capable relay systems and there's little info on safety requirements.

My £0.02
Once your confortable with standard control systems, moving on to cluster relay and/or very long lead HPR relay systems isn't difficult or confusing at all. the very same safety concerns must be addressed the a relay system as with a simple launch circiuit.

What is your main concern?
Originally posted by Mike
Any thoughts?

The primary concern I have is a welded relay, and the easy solution is a piezo buzzer that sounds when the relay is closed. A related problem is that people may underestimate the electrical requirements of multi-igniter ignitions and use undersized parts, which become maintenance issues over time.

IMO there are many more issues with multi-pad launchers than relay launchers. The big one is mis-selected pad, especially if the club uses a misfire alley approach to launching. A related issue is accidental drag races. Another problem occurs if the pads are close together and people use the wrong set of clips. There are various solutions to these, such as pad-armed lights at the pad, a single-pad-only rotary switch or other lock, and good range practices.

My $.02,

Relay launchers with remote power sources will sometimes have the contacts on the relay weld in if the proper relay is not used.
This creates a very dangerous condition. I ALWAYS touch the igniter clips together and look for a spark before hooking them on to the ingniter. It doesnt happen often but there is always the possibilty the leads could be hot. I seen a video from LDRS 22 where the motor did ignite as the guy was hooking it up I don't think anyone was hurt but it looked pretty scary I'm not sure a welded contact was the cause but watching the video really drove it home for me.

I keep a dual filiment automotive light bulb at the pad with the filiments wired in parallel to test for welded contacts. I test the bulb before I launch for the day, and the second filiment ensures that if one is burned out, I have a fail safe.

The thing that concerns me is the "Continuity test" button at the relay box that a lot of folks use. At NSL-2004, I connected my bird and the launch pad director pushed the continuity test button when I was still standing next to my rocket... wired...ready for launch. It was only a G-35, but...

I usually use my own gear, and my system is wired such that it beeps whenever the key is in, regardless if a pad is selected or not (it hase five ckts). The key goes with me to the pad to ensure that there is no possibility of firing or voltage at the pad when I'm there. I walk back to the controller and then check for continuity... from minimum safe distance. It's like "Lock-out, Tag-out" protection.

That's how the safety code is written, but many seem to have missed the point. A real problem on "Club" systems, and an accident waiting to happen, IMO.
Joel, I don't know what you're talking about? Copperheads work 100% of the time. I've never had one fail. I did learn that they are not enough "poof" to light an Ellis Mtn G-35, but that time the igniter still burned.

I forgot it was a launch weekend. My "other" hobby has me pretty busy lately. (ball joints, Brakes on THREE axles, CV boots, etc.)

As for the flyer, I wonder who it was?

As for my Key. I use a 1/4 inch phono plug and the key is a shorted plug. I do not rely on the switch inside of it, and I inspect it regularly. You may have missed in my last post that I have a buzzer that beeps whenever the system is armed. whether or not a pad is selected. If the key were shorted, stuck, whatever, my buzzer is making noise. I did this for this reason. Of course, The LCO always mistakes if for continuity :rolleyes: I also can disconnect my battery at the pad If I so desire.

I also wear my key around my neck, so If I don't pull it, I cannot go and recover my bird without dragging the controller and pad along with me...but the pad DOES have wheels on it...