I keep hearing about this relay setup stuff, but I'm not sure what it is. The Handbook of Model Rocketry makes reference to it, but doesn't expand on it. What exactly is it, how does it work, and where can you buy one or how do you build one? I'm curious and would like to know more.
Also, how do you test the igniters without actually igniting them?
I'm not in NAR yet, but I intend to join. I think there are some clubs in my state, but none too close to me. I've thought of joining Indiana Rocketry in Lafayette, and I think there's also a group in Indy I might look into. Someone suggested to me that I start a club, but I need more experience, need to hang out with a club a few times to see how it works, feel I should join NAR first, and need to find at least one other person interested in doing this on a regular basis.
Thanks! I was so looking forward to trying a cluster - the egg was just the icing on the cake.
[Edit] And thanks for the link. I'll check it out.
Hopefully the link will answer many of the questions you ask.
Relay ignition systems move the battery (power supply) from the controller side of the circuity 15 to 50 feet away to under the Pad, increase the size of the connecting wires between Battery and Relay, the limit the length of wire to each igniter making the distance and more importantly the current carring capacity to each igniter as large as possible. Simply put we want to vaporize all the igniters in the cluster as instantaniously as possible. We're talking about 100ths or 1000ths of a second difference but these Slight delay can and do cause some motors in the cluster NOT to ignite. With a relay system the "controller" Launch button is actually connected to the 12v electromagnetic coil the closes the contacts of the relay. Lots more info in TECH-TIP -006 Clustering BP Motors. I wrote this tip some time ago but it's been updated a couple time to keep the info as useful as possible. It covers in depth igniter preperation and testing(including making your own igniters).
Your controller continuity test is NOT sufficent for cluster use. YOU MUST TEST each and every igniter in the cluster
individually before inserting in the motor, After they are installed in the motors and AGAIN one last time as the microclips are being attached AT THE PAD before flight. This procedure is Critical with 3 or more motor clusters.
The Tech-tip also covers the added length of clip wires need to allow and account for the models "first motion" giving slower to ignite motors a chance to get going before the clip and igniter are ripped from the nozzle as the model raises.
You will learn that a "Clip Whip" is not the ansewer to anything with regard to reliable cluster ignition. Please remember this if nothing else from this post: "A clip whip, no matter how well made is ONLY an EXTENSION of the current carring system it is attached to".
Further in the Tech-tip there are at least two different schematics for building a heavy duty 12V 40amp pre contact DPDT relay system and a smaller 10amp DPDT "Range-Box Relay" unit I invented almost 30 years ago. I use both on a regular basic to this day. Note that I always used Double Pole Double Throw (DPDT) relays breaking both Positive and Negative power terminals (It's a safety feature).
In the tip and attached is the schmetic for a simple AA or AAA 1.5volt igniter tester that i've been using on all igniters (Q2g2's included) for many years. I'll attached a couple pics of these units below.
Cluster ignition is as much an ART as Science. There are many more things going on within the circuit, wires, igniter and motors then meet the eye.
As I mentioned earlier I'd much rather cluster a bunch of BP Motors then fly a single APCP motor anytime. I've been flying 2 to 12 motor BP Clusters since the very early 70's and in all that time, logging over 2000 seperate clustered flights I've still only had 13 unlit motors in all those clusters. One was an intentional test to see what would happen if one of the outboard C6-0 motors in my Estes SR-71 3 motor cluster conversion did not ignite so no igniter was installed, but the flight is still logged as a cluster flight, 11 of these unlit motors occured before I switched over to using a Relay ignition system in 1974. So you can see since converting to Relay ignition for my clustered flights (over 1800+) I've only logged one unlit motor. It's pretty hard to deny that kind of reliability flying all class motors from 1/8A MMX to BP E & F's.
I'll also post below the 2 to 7 motor wiring scheme i've been using all these years and a couple pics of my relay systems. Trust me when I tell you They WORK.
I Love clustering almost as much as I Love Micro Maxx models.
Hope you find this material and information helpful in your modeling journey.
Don't hesitate to ask any question you need when it comes to Clustering. I'm more they happy to help in any way I can.
View attachment RangeBox Relay-a2c_Rev Drawing & Wiring_01-31-96 Rev.06-23-10.pdf
View attachment Cluster Wiring Diagrams-2c_Dwg(Revised)_09-17-12.pdf
