Clustering motors

[pr_rocket04]

This is a beginner question I know, but I have never clustered motors before, and I was wondering if someone could tell me how to wire the ignitors? 14.4v is ok too, right?

I didn't know if it made a difference if you wired them in series, or if they needed to be wired parallel. Thanks.

 

[cydermaster]

Firstly, welcome to the forum - you've come to the right place for your answers!

You want to wire them in parallel. If you were to wire them in series, as soon as the first ignitor ignites, the circuit is broken; the other ignitors have no chance of being set off then!

As for the power source, its the AMPS that count not the volts. Normal everyday batteries just don't have the 'umph' in them. I use a car jump-starter, most succesfully, but other people use car batteries or R/C aircraft gel-cells with no problem.

Any earlier thread, on a similar subject can be found here.

Hope this Helps!

 

[Micromeister]

re-rocket welcome to the forum

Cydermaster is correct you need Amps not volts, depending on how many motors your clustering. General rule of thumb I've always stuck with is 2amps per igniter. Those little 12v 7 amp/hr gel-cells are great for 2 & 3 motor clusters but are pushing it on 4, tho in a pinch I have launched 4 motor clusters from one on a fresh charge.
Igniters are the other main worry in cluster ignition. Test TEST TEST!!!!! before inserting, and after inserting in the motor. Do not assume a new igniter out of the package is good, Can't tell you how many perfect looking igniters I;ve tossed after continuity checking them right out of the pack.. We'er talking about Estes standard solar igniters here. For clusters I also cherry pick the ones with the most pyrogen for clusters, especially for D12's
Here's a graphic you may find useful, Its helped me go through 30 some years of clustering with a single hand of unlit motors. Note, you will always be using an even number of igniter clips with this system no matter the number of motors in the cluster ie. 3 motors 4 clips, alternationg + & - clips around the cluster.. A little more involved than just sticking on clips or bus wiring but ya can't argue with success

The other major factor is the use of a Relay Ignition system.
A Relay in conjunction with as High an Amp/hr rating battery as you can muster and properly installed igniters are all part of the "ART of Clustering". Use as heavy a wire gage and shortest length practical between the battery to relay and relay to clips. I try to limit the clip whips to under 18" long and not smaller than 16gage stranded copper wire.

If you'd like, in the library section of www.narhams.org is a Tech-Tip on BP clustering you may find helpful. Tech-Tip-006 Clustering Black Powder motors.

Hope this helps

 

[pr_rocket04]

Thanks a lot for that info guys. About the amps, if it came down to it, I always have a deep-cycle car battery sitting in my room, or would this be overkill?

 

[Micromeister]

Originally posted by pr_rocket04
Thanks a lot for that info guys. About the amps, if it came down to it, I always have a deep-cycle car battery sitting in my room, or would this be overkill?

Nope! Not at all, You'd be ensuring plenty of power to vaporize those igniters nearly the instant the relay closes

 

[powderburner]

The phrase "nuke 'em 'till they glow" seems somehow appropriate here.

These other guys have told you correctly, use lotsa amps. One might even go so far as to skip the Estes igniters entirely, and go with your own nichrome wire creations tipped with commercial pyrogens.

The other part of clusters is to design your rocket so that two or three motors are included in the deployment sequence. That way, if one motor somehow misses on ignition, you have one or two others that will still pop out the 'chute.

 

[jflis]

ALERT! Way Off Topic...

Originally posted by powderburner
The phrase "nuke 'em 'till they glow" seems somehow appropriate here.

As I heard that phrase...

"Nuke'em 'till they glow...

...then fire at the light."