Motors for a cluster rocket

[golmschenk]

I have a few E9-8 motors and I was thinking about sticking three of them in parallel into a rocket. However, the motors all have ejection charges. I'm wondering how exact the time from ignition to the ejection charge is. What's the uncertainty in those? Because if they all fire at approximately the same instant it should work fine, but if not there could be a problem. Thanks.

 

[Gillard]

when i've clustered estes motors the ejection charges tend to go off either at the same time or within a fraction of a second of each other - but i have had two occasions where there has been a largish gap (1 and 2 seconds).
hope this helps.

 

[JRThro]

I have a few E9-8 motors and I was thinking about sticking three of them in parallel into a rocket. However, the motors all have ejection charges. I'm wondering how exact the time from ignition to the ejection charge is. What's the uncertainty in those? Because if they all fire at approximately the same instant it should work fine, but if not there could be a problem. Thanks.

I've flown several cluster rockets with 2, 3, or 4 motors, for maybe 10 or 15 flights in all, and even though the ejection charges don't fire simultaneously, there's never been a problem. The first ejection charge ejects the parachute, and the ones that follow don't do anything except go off and make popping sounds.

 

[Pantherjon]

It is very rare for multiple motors in a cluster to fire their ejection charges at exactly the same time, even if all motors have the 'same' delays..It is pretty cool to have a 4x clustered rocket that doesn't fly too high, and you can hear(and count) the 4 charges going off, pop,pop,pop,pop..

 

[golmschenk]

Awesome, thanks for the info everyone.