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AT Graphite Nozzles/Casting Mandrels

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DannyB

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Hi! I'm looking for a couple things...

Aerotech Compatible Graphite Nozzles:
I've reached the end of the internet looking for Aerotech compatible graphite nozzles. I'm not interested, well really my wife is not interested, in the mess that is involved with turning graphite. Does anyone know a vendor for these? Or, does anyone make their own nozzles who would be interested in making/selling some to me? I'm interested in various nozzle sizes for cases ranging from 38mm to 98mm, excluding 75mm. I want reusable nozzles so bad that I'm in the process of switching to Loki cases for testing me ex propellant, but I would much prefer to stick with AT and the dozens of cases I already have...

Mandrels:
Again, I reached the end of the internet looking for star or finocyl mandrels for 29mm to 98mm grains. The closest I got was TruCore, but they no longer make them. Does anyone have star or finocyl mandrels that they are looking to sell? Or, does anyone make their own who would be interested in making/selling some to me? Any tips on how to make my own would also be appreciated, so far I'm at the point of making a 3D print and using it to make a foam mold then filled with a plastic/rubber for the mandrel, as I would imagine that the 3D part alone has too much friction to release from the grains.

Thanks in advance for any help or insight!

-Dan
 

cavecentral

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Most of us use snap ring cases for research motors. I know a few people used AT casings. Not sure if I seen graphite nozzles for AT sold, but Mike Fisher of Binder Design would be a good start to enquire on getting some made. Some others here might be able to as well.
 

djs

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Danny- Have you checked RCS for nozzles? However, i think all that they sell are phenolic. Does AT even use graphite nozzles?

Dan Patell can make you custom graphite nozzles.. I'm not sure he's made any to AT size, so you might need to give him some dimensions.
 

blackjack2564

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Steve Eves & Chris Pearson up in Ohio have graphite nozzles for AT 54 cases. someone just sold some a week or so here in yard sale. Getting ahold of theses guys,,,,don't know what to tell ya. I was flying with them last couple years, not going to Ohio this year.

Could try club website....http://www.skybusters.org/Home.asp ........contact list.

Don't know if they will make more, worth a try.
 

Rocketjunkie

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A direct clone of an Aerotech nozzle will fail. Graphite must be used in compression. An aluminum carrier in the shape of the Aerotech nozzle works with a graphite insert for the throat.
 

pondman

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Steve Eves & Chris Pearson up in Ohio have graphite nozzles for AT 54 cases. someone just sold some a week or so here in yard sale. Getting ahold of theses guys,,,,don't know what to tell ya. I was flying with them last couple years, not going to Ohio this year.

Could try club website....http://www.skybusters.org/Home.asp ........contact list.

Don't know if they will make more, worth a try.
I designed a couple of AT graphite nozzles and had Ed Romani machine them for me. I tucked all the graphite inside the case to avoid destroying the nozzle when the rocket landed. This is a common problem with e direct clone. You will loose some propellant length if that matters to you. Mike fisher would be a good place to start.
 

claytonbirchenough

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Might be a ridiculous question, but no problems with the graphite nozzle and heat-soaking the case?


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DannyB

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Thank you all for the very helpful responses. I actually bought that yard sale nozzle a couple weeks back and that's what turned me on to graphite. Clayton, definitely not a ridiculous question. I fired a Loki graphite nozzle for the first time today and the heat soak was so bad at the nozzle it melted the case. There was some other form of failure that led to the CATO as well, as the nozzle was fractured. But I have never in thousands of firings felt a motor so hot! Brings up the question of whether it's worth it. Kevin makes a good point that I've been noticing, which is that most ex is done with snap ring closures. Any idea why? It seems AT threaded cases are so much more convenient, is it a cost factor or performance/safety? Thanks again for all the very helpful feedback, this community is awesome!
 

dhbarr

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Snapring machining is easier / faster / cheaper.
 

tbonerocketeer

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Thank you all for the very helpful responses. I actually bought that yard sale nozzle a couple weeks back and that's what turned me on to graphite. Clayton, definitely not a ridiculous question. I fired a Loki graphite nozzle for the first time today and the heat soak was so bad at the nozzle it melted the case. There was some other form of failure that led to the CATO as well, as the nozzle was fractured. But I have never in thousands of firings felt a motor so hot! Brings up the question of whether it's worth it. Kevin makes a good point that I've been noticing, which is that most ex is done with snap ring closures. Any idea why? It seems AT threaded cases are so much more convenient, is it a cost factor or performance/safety? Thanks again for all the very helpful feedback, this community is awesome!
What did you fire in it?
 

DannyB

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Hey Chris, good to see my favorite vendor chime in. The case was the one that I bought from you the day before...needless to say I did not get too many uses out of it. I used an ex propellant that is pretty tame (0.94mm/s at atmospheric) and has been successfully used in an aerotech case. It was a 38mm 6 grain BATES that was cut to the exact specs of the Loki J712. Here's the formula I used. I don't have a/n numbers for if yet. Do you see any issues in it? I guess I'll be on your site getting my replacement later today. Thanks for the help!

(Formula deleted, sry, didn't realize I left the ex threads)
 
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dhbarr

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This is not the place to post or discuss formulas. Please delete this information.
 

tbonerocketeer

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Hey Chris, good to see my favorite vendor chime in. The case was the one that I bought from you the day before...needless to say I did not get too many uses out of it. I used an ex propellant that is pretty tame (0.94mm/s at atmospheric) and has been successfully used in an aerotech case. It was a 38mm 6 grain BATES that was cut to the exact specs of the Loki J712. Here's the formula I used. I don't have a/n numbers for if yet. Do you see any issues in it? I guess I'll be on your site getting my replacement later today. Thanks for the help!
Generic Burn sim numbers with the theoretical density and isp show this formula and grain setup to be running at almost 2000 psi, with a mass flux near 3.5....
 

DavidMcCann

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This is not the place to post or discuss formulas. Please delete this information.
Thank god we have people like you protecting this super secret information from falling into nazi hands
 

dhbarr

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Thank god we have people like you protecting this super secret information from falling into nazi hands
I don't make the rules, I just try to help people follow the rules as they are. *shrug*
 

DavidMcCann

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It's playful ;). But I really don't get why everyone acts like you're mailing the NOC list to the russians every time anyone says "motor"
 

dhbarr

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It's playful ;). But I really don't get why everyone acts like you're mailing the NOC list to the russians every time anyone says "motor"
Bartlett's Annotated ITAR makes for excellent reading, if a bit dry.
 

ksaves2

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I don't make the rules, I just try to help people follow the rules as they are. *shrug*
Nothing wrong with you pointing out the faux pas and yes, there are plenty of other online sources the disparate harbingers of "evil"
can consult with. Keeping this forum out of that group I believe protects us from "over-regulation". Kurt
 
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