29mm RMS Ejection Charge Problem

[yankee42]

I recently started flying my 29mm reload case which i have had for a while. On its 2nd flight today, on a G71-7, the ejection charge did not fire. My LOC Weasel is now in pieces :(. When i cleaned the motor, i discovered that the delay had fired, but it had not ignited the ejection charge. Is this a common problem, or was it a mistake i made when i build the motor?

[brianc]

Sorry to hear about your Weasel...

Did you pour a small amount of BP initially and ensure it entered
the hole to touch the delay grain?

Did you add dog barf or wadding to fill any extra space in the well
after using the appropriate measure of BP? If not, was the motor/rocket
tipped nose down during handling?

Those are two common issues...

[Jerry Irvine]

There can be a variety of causes for this and "sit down for this", it is not a defect in the system.

One cause is grease on the delay face where the BP touches, which acts as an inhibitor.

One cause is delay blow-through time being sufficiently short the BP simply does not ignite. On numerous occassions I have seen CHARRED BP!!

One cause could be low air pressure which does not apply to your flight.

Solutions:

After assembling the motor and before installing the BP, run a drill bit through the transfer hole and slightly rough up the delay face. When you install the charge, shake it side to side a bit. Be sure you use REAL BP either 3F or 4F. Put a bit of tissue or flameproof wadding to fill the space above the charge before you apply the plastic cap or masking tape over it. Do not rely on a paper disc for retention. It does not reliably adhere.

Safety note: Delay "rough up" will result in a slightly shorter delay so make sure "rough up" involves about 1/64" or less (1/2 second coast) of material.

Someone should market a tool with these instructions attached and buy me drinks every time we see each other.

If you drill delays, most of the drilling should occur at the combustion chamber face, but 1/32" should occur at the ejection face to increase the flame action time.

In case you have not noticed, rocketry is an art MORE than it is a science.

This industry needs a global FAQ.

Jerry "told you so" :D

[yankee42]

Thanks for the solutions. I'll keep them in mind next chance I get to fly.