It turns out that you can't ignite clay

At the last MDRA launch, I put an F15-4 in my Cheetah. After the stock igniter failed to light it, I tried a Q2G2. No go. I decided that maybe there was some clay over the nozzle. I scraped it lightly and tried another Q2G2. Still no joy. More scraping and a home grown igniter. STILL it sat on the pad. I decided to go at the nozzle with a drill bit (slowly!). After it was way in there and I was still getting clay, I figured out that something was really wrong. I ended up putting it on a static test stand and burning it from the top end. As expected, the nozzle remained plugged. Back home, I inspected the motor in question and performed some measurements. Using a caliper, I found the plug, which is clearly visible from the top, is about 3.4 inches down. I measured another spent motor and its nozzle is about 3.9 inches down. This implies the 'bonus plug' is about a half inch deep.

I inspected the other motor from the pack and all my other 29mm E/F motors and found you can see the propellant in the nozzle. That's a good thing. I filled out a MESS form and emailed Estes. I contacted them via the web form on Sunday evening, got a response back on Tuesday, got a shipping notice that Friday. A new pack arrived today. 9 business days - that's a pretty darned good turn around in my book. :clap::clap::clap:

What a weird error. Were there any other like that in the pack?

Nope...nor in the many other packs that I have and have flown.

Looks like the machine screwed up and gave you a double scoop of poopy clay with a delay charge on top!

You’re lucky you didn’t manage to get that clay to burn.
Then you would be in trouble for flying an experimental propellant.

I had that happen once with an F15-6...but I only had to go down maybe a millimeter or so with a drill bit (carefully spun by hand!) to hit black powder.

You know, these nozzle issues could be the reason that these Estes F15 BP motors take up to 0.5 seconds to hit peak thrust (I found the thrust curve on thrustcurve.org). I crashed my Estes majestic once because of that...fortunately it lawn-darted into soft dirt and survived to fly again.

Maybe they (Estes) could bore out the nozzle a little bit bigger and get faster peak thrust and fewer plugged nozzles?

boomtube said:

You’re lucky you didn’t manage to get that clay to burn.
Then you would be in trouble for flying an experimental propellant.

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That would not be a problem at MDRA There are club members who claim their started will ignite concrete. They probably have more total impulse than my motor. :lol:

rstaff3 said:

That would not be a problem at MDRA There are club members who claim their started will ignite concrete. They probably have more total impulse than my motor. :lol:

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There are guys at MDRA who make starters that classify as at LEAST a G80.

This was a really weird manufacturing error. I'm trying to picture the process that could produce that without anyone noticing.


Sent from my iPhone using Rocketry Forum

rstaff3 said:

At the last MDRA launch, I put an F15-4 in my Cheetah. After the stock igniter failed to light it, I tried a Q2G2. No go. I decided that maybe there was some clay over the nozzle. I scraped it lightly and tried another Q2G2. Still no joy. More scraping and a home grown igniter. STILL it sat on the pad. I decided to go at the nozzle with a drill bit (slowly!). After it was way in there and I was still getting clay, I figured out that something was really wrong. I ended up putting it on a static test stand and burning it from the top end. As expected, the nozzle remained plugged. Back home, I inspected the motor in question and performed some measurements. Using a caliper, I found the plug, which is clearly visible from the top, is about 3.4 inches down. I measured another spent motor and its nozzle is about 3.9 inches down. This implies the 'bonus plug' is about a half inch deep.

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I had the exact same scenario with a Estes C 6-3. Plugged nozzle, Estes and Quest igniters failed to start it ,drilled it out by hand and used it in my Mars lander today without a problem. Strange and unusual things.........:confused2:

mrichhcirm said:

(I found the thrust curve on thrustcurve.org).

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You do know that the NAR provides that information too, right? It's right here. Wait until Monday and check out the entire NAR website. It's changing!

mrichhcirm said:

Maybe they (Estes) could bore out the nozzle a little bit bigger and get faster peak thrust and fewer plugged nozzles?

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That would lower the thrust.


Christopher Short
Chris' Rocket Supplies
www.csrocketry.com
850-554-6531

billspad said:

You do know that the NAR provides that information too, right? It's right here. Wait until Monday and check out the entire NAR website. It's changing!

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Ooh NAR looks pretty now!

Test, test again.