BP Cluster

[geof]

Is there any substantial difference in success probability for igniting 6 versus 7 Estes motors using a good 12V relay system with standard Estes ignitors and sufficient clip whips to handle each motor separately (or maybe a couple in pairs). And, is the probability significantly better for 5, or even 4 motors if I scale back a bit? I think the battery is a motorcycle battery, but that's all I know about it.

One of my next projects is a cluster, and I'm wondering just how high I can go. I've got designs ranging from 2E+3C up to 4E+3C or 5E+2C. (Yes, I know these are beyond the low-power thrust range.)

 

[kandsrockets]

I have a big daddy with 6 -18mm and launch it using my 12v relay system and the battery is a 12v ryobi drill battery and it has fired all 6 motors everytime and this has been flown 19 times on this system. The biggest thing I find is test your ignitors with a ohm meter to make sure they are good.

 

[Micromeister]

geof:
I've had no trouble over the years with 2 -12 motor clusters with a standard DPDT 40amp HD power relay and 27amp/Hr gelcel. The standard clustering rule of thumb is 2 amps per igniter. Your motorcycle battery should have planty of reserve cold crank amps for what your attempting.

As with just about everything as you increase the complexity the chance of malfunction increases. I've found if you pre-test all igniters before and after they are installed in the motors and again on the pad you will have greatly increased your likelyhood of a successful flight with all motor burning.

Heres a hook up scheme I use to this day. Note that your always using equal pos and neg clips even on Odd numbers of motors.
hope it helps a little.

 

[boris katan]

I have done a number of cluster launches with up to 8 BP engines and ignited all engines so far. To avoid the potential failure points added by using clip whips, I have always used Magnelite igniters by Rocketflite. They are insulated and the shortest are 12" long, so the igniter leads can be twisted together and the wrapped around one set of ignition clips.

Can see igniters here, click on the picure to enlarge, sparks in lower left image are the igniters just before the engines kick in:
https://www.cmass.org/index.php?opt...&Itemid=28&place=displayimage&album=45&pos=26

More fun here too:
https://bkatan.home.comcast.net/~bkatan/

Had good luck with these and AP clusters too.