I've been working on my MMX cluster technique while my club has been flying off a smaller field. For the record, I'm flying two motor clusters. I'm using a Quest pistol-grip controller with a drop battery cable. My battery is 12 volt with enough mAh to light 4+ motors. I am not using a relay box (yet).
Best success was with the Quest Q2 igniters. I use slivers of balsa wood for plugs and a small strip of masking tape to secure the business end. The leads were twisted together. I lick my fingertips and get the twisted leads as moist as possible before attaching the micro clips. This seems to up the success factor. I did some static tests a while back and tried a dab of vaseline on the leads (used for positive connection on the electric chair BTW). This worked but I have not tried this in an actual flight attempt.
My last launch I used raw Nichrome wire. I found there was enough delay (even with a fully charged battery) to not light both motors simultaneously. I liked using the Nichome however. It is a bit easier to prep the motors. If I pursued this end to light clusters I would build a relay box and/or look into dipping my igniters.
One fellow who flies with my club has experience with dipping his igniters. He shared his recipe once. It involved dissolving Ping Pong balls in Acetone and adding some BP. I should add he used this to get composite motors going but I liked the Ping Pong ball angle.
I recently got some advice from another experienced flyer regarding MMX ignition. It involved the use of a tiny drill bit to clear away any clay in the nozzle that may prevent positive contact between the grain and igniter. I found a small bit in my Dremel box that seemed perfect for this but have NOT tried this technique out yet.
I have to agree 100% that one motor lighting earlier than the other can kill a successful cluster ignition. No matter how careful you prep.
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