A friend just told me these used to exist and I was wondering if anyone had some hardware put away they wouldn’t mind parting ways with.
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Found Green Monkey Aerospace 13mm hardware
- Thread starter DrewW
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heada
Well-Known Member
I have a complete set. What are you will to pay for them?
I’ve no idea what makes a complete set, what all is there for 13mm hardware?
heada
Well-Known Member
- 3 cases with casting tubes and liners (2 grain, 3 grain and 4 grain)
- 2 forward closures, 1 plugged and 1 delay
- Styrene stock (I forget it's purpose, narrower than the ID of the casting tubes)
- 3 graphite nozzles, need to be drilled out to desired opening (.090 and .093 were recommended)
- O-rings for both nozzles and closures
- 5 internal snaprings(2 installed in the mid case and 3 loose)I have some knipex snapring pliers too I can include if wanted
- nozzle washer (unknown metal)
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That's cool! I missed those, when were they made?
heada
Well-Known Member
Must have been about 12 to 15 years ago I think. Purely EX and limited demand since 13mm is REALLY hard to work with.
Ahh, I was on hiatus. Neat! it would be fun to doodle with.
As I recall, One needs to be careful not to use "too hot" of a propellant with the smaller motors. I had a 24mm long necked Research motor (about 11 inch) motor that popped up into the air and the motor overpressurized and blew out the side of the rocket. The electronics blew the chutes and recovered everything but the rocket and motor mount was toast.
It was a custom 24mm that our Prefect turned on his lathe and used snap rings, aluminum forward closure and a graphite nozzle. Mind you, the casing was much longer than what Aerotech uses and was Burnsim calculated to be in the baby "H" range for what it's worth.
Ummmm, I had the prefect cut the remains of the damaged case shorter and had one successful flight. Was probably in the high "G" range in a similar twin of the first rocket. I think I used less aggressive propellant. Flew quite high and had a nominal recovery. (The tracker helped.)
Problem is the motor case was hot as hell when I popped it out (always try to do that if I can) and decided to give up on long necked 24mm motors.
If doing 18mm motors in reusable cases, I'd say use as less an aggressive APCP propellant that is out there, simulate like crazy and use a slightly wider nozzle throat as suggested by Burnsim for 2 or 3 ground tests.
ie. dig hole in ground, put motor in nozzle up and fire it from a far distance away. When I designed a wireless firing system, that made it a whole lot easier as I could stand "way" far away for safety's sake.
Oh make sure one uses the erosive phenolic nozzles available. Trust me, graphite is much more "unforgiving".
I had to open an AT J350 nozzle up to accommodate an H/I Research motor in 29 mm. Even with the sim, which at the time didn't allow for nozzle erosion, it was a best guess and worked out fine. Flew rockets with it nominally.
Bad thing is each mix is different and have to do some testing as the consistency between chems is not "exactly" the same. Don't test each batch of Research propellant and one risks an anomaly on launch. Kurt
It was a custom 24mm that our Prefect turned on his lathe and used snap rings, aluminum forward closure and a graphite nozzle. Mind you, the casing was much longer than what Aerotech uses and was Burnsim calculated to be in the baby "H" range for what it's worth.
Ummmm, I had the prefect cut the remains of the damaged case shorter and had one successful flight. Was probably in the high "G" range in a similar twin of the first rocket. I think I used less aggressive propellant. Flew quite high and had a nominal recovery. (The tracker helped.)
Problem is the motor case was hot as hell when I popped it out (always try to do that if I can) and decided to give up on long necked 24mm motors.
If doing 18mm motors in reusable cases, I'd say use as less an aggressive APCP propellant that is out there, simulate like crazy and use a slightly wider nozzle throat as suggested by Burnsim for 2 or 3 ground tests.
ie. dig hole in ground, put motor in nozzle up and fire it from a far distance away. When I designed a wireless firing system, that made it a whole lot easier as I could stand "way" far away for safety's sake.
Oh make sure one uses the erosive phenolic nozzles available. Trust me, graphite is much more "unforgiving".
I had to open an AT J350 nozzle up to accommodate an H/I Research motor in 29 mm. Even with the sim, which at the time didn't allow for nozzle erosion, it was a best guess and worked out fine. Flew rockets with it nominally.
Bad thing is each mix is different and have to do some testing as the consistency between chems is not "exactly" the same. Don't test each batch of Research propellant and one risks an anomaly on launch. Kurt
Here's my set of four 18 mm casings; I think it's the last set Neil sold. Lengths: 2.75", 3.75" 5.75", 7.75". Estimated impulse levels: full C, full D, full E, and mid- or full F. Two plugged forward closures, one closure with ejection well. One graphite nozzle (tiny throat, drill to desired size), three Aerotech phenolic nozzles.
The fellow that made the 13 mm casing on the upper left may recognize it
. Threaded closures and phenolic nozzles. My understanding is that these were CNC machined in quantity(?).
The fellow that made the 13 mm casing on the upper left may recognize it
. Threaded closures and phenolic nozzles. My understanding is that these were CNC machined in quantity(?).
DabCat
Well-Known Member
It looks like the OP found a set. I'm also interested in a set if anyone has another one they would like to part with. 18mm or 13mm, I have uses for either.
heada
Well-Known Member
Really curious when he started offering that extra long case. Wasn't an option when I got mine.
I tried several times to make grains and the 13mm was just too small. Porable ended up everywhere and packable ended up too tedious.
I tried several times to make grains and the 13mm was just too small. Porable ended up everywhere and packable ended up too tedious.
Rocketjunkie
Addicted to APCP
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Made these in late '90s 1/2" with 4" propellant, max delay is 13 sec Came out as a full D40. (Ran several on the test stand.) Still have a couple left. Need more tubes, have plenty of closures and nozzles.
I have 11-1/4" long liners and casting tubes I found for the Green Monkey 13mm motor.
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Anybody else have a 13mm set they're willing to sell? I have casting tubes, now.
heada
Well-Known Member
Yes, but only for the longest one (baby F or full E). I don't know if the machined step version was earlier or later.
