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Final steps in making BP motors - seeking advice


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#81 SharkWhisperer

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Posted 29 March 2020 - 12:57 PM

 

Welllll.....I got a mixed bag on that.  :)

 

So, the altimeter wasn't working on that flight.  #&^@!  I loaded another motor and shot it the next day.  I received a parachute release device (Jolly Logic, also, like the altimeter) later the day of flight 1 and used it in flight 2.  Between the heavier ejection load with the parachute release and maybe my stiff paper towel homemade wadding (paper and baking soda and water...King of Random (and others) have info on YoutTube), the parachute didn't eject.  I have a video of that but only of it going up.  I used that wadding on flight 1 but...variables and more mass to eject...no poofy.  I'll post that sometime, too.

 

The rocket took off more slowly than the first day.  That may be because I added that parachute release device and it weighs an appreciable amount or it may be it was just as fast but didn't seem like it to me, or who knows?  Maybe my motors are not consistent.  They should be, I use a hydraulic press with pressure gauge and it was the exact same batch/tub of powder.  But, I did get data on that flight.  I got a replacement screen for the AltimeterTwo yesterday and put it on and have that data now.  :)

 

Max altitude: 739 feet

Max speed: 137 mph

Thrust duration: 3.34 sec

Peak accel: 15.2g

Avg accel: 1.9g

Coast to appog: 4.3s

 

This is the kicker.....

 

Descent speed: 62mph

 

Duration: 15.9 sec

 

The AltimiterTwo does not report the G force at the end.  :)

 

The fall didn't kill it but that sudden stop at the end did a helluva number on it.  Broke the LCD on the AltimeterTwo, smashed the nose cone (NC), ruined the body tube, ripped the motor/motor mount tube from the motor mounts and put it hard on top of the altimeter and the parachute device (and the parachute).  I had thought, when I first walked up on it, that the EC (ejection charge) had forced the motor mount tube and motor out the back instead of ejecting the parachute.  Nope, it was all intact until a significant decel G load strategically re-located the motor mount tube/motor into the nose cone.  That sure solves my CG/CP balance.  Put the NC fully into soft-ish dirt. 

 

The EC did ignite, the front clay plug/cap was blown out as it should be.  I had 1/4 tsp (which measures out, as I recall, not being in front of my notes, to 1 gram) of 20-30 mesh BP, like the first one for the EC.  I suspect, as stated earlier, the stiff wadding (I used good paper towel to make my home made wadding...it's thick and fluffy) and the added restriction of the parachute release device kept the stuff from kicking out like it was supposed to.

 

Sucks, but I bought three of those same models for a reason...this is the reason.  Failure was expected in the process.  Of course, I thought after the first flight I had avoided it.  I was wrong.  :)

 

This isn't hurting my feelings one bit.  I got it to fly right once, the failure in this flight was not my motor.  I'm building another of the kits with my son now.   And we'll paint this one, too.  We'll get it sorted.

 

Video of the crash is non-existent: I had a knock-off GoPro sitting at the launch pad, looking up.  I got the rocket going up, smoke trail, then nothing.  I couldn't see the rocket on the way down.  I didn't even carry the camera to where the thing hit, so I have no images/footage there.  I'll post it.  I had FITS with my home made igniters and wound up using a piece of visco.  It's okay, relax, it's NAR-certified rocket-launch visco.  ;)

 

Video is uploading now.  I didn't grab the URL for the video when it popped on screen in the upload process so I'll have to update this later.  It's on the same page/channel whatever as the one posted earlier in this thread.   I may re-do the video in terms of adding some pictures of the damaged rocket but I don't know what good that will do; it's damaged, not much value in seeing it.

 

--HC

Hey man, that is a learning experience, definitely not a "failure". Your motor burn time and max altitude significantly exceed any Estes C motor expectations with that specific rocket, even with all the added weight. Sounds like a success to me.

 

"NAR-certified rocket-lauch visco", bwaaaah hahh ha ha ha!!!!! Love it. Gonna give the NAR/Tripoli purists some sleepless nights. For sure don't mention homemade igniters with....my gawd....hot pyrogen. That'll get 'em calling in sick for a week.

 

Never trusted or needed those "chute releases" and they're kinda expensive, too...



#82 Mumbles

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Posted 30 March 2020 - 10:16 AM

If you're looking for consistency or at least would like some real-life data, you may want to look into making or getting a rocket test stand.  It sounds like you have some machining and engineering skills, so it's probably within your capabilities to build one.  At their core, they're basically just a slightly modified load cell.  I'm sure they exist within the model rocketry world quite a bit, and probably much fancier than what I'm about to say.  There is a pyro customized one on the market called the ACME Rocket Test Stand.  It was developed by Pete Hand a number of years ago, and has gone through a few iterations of manufacturers.  I haven't heard from Pete in a while, but he's a former Western Pyrotechnics Association board member, and a member here as well.  Currently, it's offered pre-built from Woody's Pyro Shop.  There are also a few home built ones around as well.  I included some relevant links below.

 

The simplest ones I've seen are just a weight scale (usually analog or mechanical scale) with a coupling to hold the rocket motor and a video camera.  This will get you peak thrust, thrust duration, and sometimes a sustained thrust.  The next step up is probably a load cell.  This makes things a little more advanced, as you can get better real time data and automate some things such as total thrust and average thrust, and other calculations.  Past there, there are things like the ACME thrust stand where there's internal memory, e-match automation, and some more advanced analysis.  

 

Original Thread about the ACME: www.amateurpyro.com/forums/topic/7184-rocket-test-rig/ 

 

ACME stand from Woody's: https://www.woodysro...t_Stand_.html#/

 

ACME Manual: http://www.pyrobin.c...sers Manual.pdf

 

Some work on software by another member: https://www.amateurpyro.com/forums/topic/11545-thrust-metertest-rig-prototype-ver10/page-1 

 

https://www.amateurp...t-of-my-rocket/


Just so you guys quit asking, here is the link to the old forum. http://www.xsorbit2....forum/index.cgi

The sky is my canvas, and I have 2,113 pounds of powdered paint in the workshop.

#83 hcb

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Posted 02 April 2020 - 09:52 AM

Hey man, that is a learning experience, definitely not a "failure". Your motor burn time and max altitude significantly exceed any Estes C motor expectations with that specific rocket, even with all the added weight. Sounds like a success to me.

 

"NAR-certified rocket-lauch visco", bwaaaah hahh ha ha ha!!!!! Love it. Gonna give the NAR/Tripoli purists some sleepless nights. For sure don't mention homemade igniters with....my gawd....hot pyrogen. That'll get 'em calling in sick for a week.

 

Never trusted or needed those "chute releases" and they're kinda expensive, too...

I try to own my stuff...even the failures.  But, yeah, I spanked the Estes C class motors.  :)  And that failure to eject wasn't the motor not doing its part, it was 1) stiff wadding and 2) more stuff to eject.  Revising....I'll have another launch in the next few days...when the replacement rocket is ready.  :) 

 

Ya like that?  I couldn't resist.  I was using straight NC lacquer on the igniters but it's just not enough (I believe you may have made mention of such a fact).  Plus, hitting the straight NC lacquer with 12v was no bueno, it didn't really burn, based on the examination of the failed igniters.  The Estes factory igniter just blew up but didn't burn.  I've made up a new batch with some BP and Al added to it.  These light fast on 12v and burn for about a second which is forever in an igniter.  Easy to make, slim to fit into the EB 1/8" throats, fire fast, burn long.  I need to do a video on making those, too.  They're labor intensive, but with a few cheap tools, easy to make.  Lot cheaper than the $0.50 each for ... I just looked it up on Amazon...try over $1 per each for Estes igniters.  Yeah....nope.    I've posted the video of the second motor test with the "new" way of prepping the BP (wet, fluffy screen granulate, dry, press) in an end-burner.  If you watch closely during the Crappy Slow-Mo segment of that launch, you can see the igniter is hanging down well below the motor yet is still burning/sparking.  Got that igniter problem stitched up.  :) Thank God I'd gotten that certified visco in time for that test launch with the Patriot.  I'd have been SOL with regular visco. 

 

https://youtu.be/1HZxnm3rxcg 

 

Well, my property isn't conveniently laid out for the prevailing wind direction of N-S (or reverse), so I have a big place but a narrow footprint across the wind.  And a major-league A-hole for one neighbor (and I've had to recover one from his place).  I thought it would be handy to have it get closer to the ground before popping yet not do the step of making the decent faster by cutting a hole in the chute (or using a smaller one).  Both of those solutions are viable, I just chose to try the chute release.  And, yes, damned expensive.  $130.  Maybe on my 4CB, 4CB, 4EB, 2EB, 1EB, 3/4" tubes all around, Saturn XXV I might build someday.  If it comes back from black space.  ;)  Where's that FAA waiver form.....

 

--HC



#84 hcb

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Posted 02 April 2020 - 01:00 PM

If you're looking for consistency or at least would like some real-life data, you may want to look into making or getting a rocket test stand.  It sounds like you have some machining and engineering skills, so it's probably within your capabilities to build one.  At their core, they're basically just a slightly modified load cell.  I'm sure they exist within the model rocketry world quite a bit, and probably much fancier than what I'm about to say.  There is a pyro customized one on the market called the ACME Rocket Test Stand.  It was developed by Pete Hand a number of years ago, and has gone through a few iterations of manufacturers.  I haven't heard from Pete in a while, but he's a former Western Pyrotechnics Association board member, and a member here as well.  Currently, it's offered pre-built from Woody's Pyro Shop.  There are also a few home built ones around as well.  I included some relevant links below.

 

The simplest ones I've seen are just a weight scale (usually analog or mechanical scale) with a coupling to hold the rocket motor and a video camera.  This will get you peak thrust, thrust duration, and sometimes a sustained thrust.  The next step up is probably a load cell.  This makes things a little more advanced, as you can get better real time data and automate some things such as total thrust and average thrust, and other calculations.  Past there, there are things like the ACME thrust stand where there's internal memory, e-match automation, and some more advanced analysis.  

 

Original Thread about the ACME: www.amateurpyro.com/forums/topic/7184-rocket-test-rig/ 

 

ACME stand from Woody's: https://www.woodysro...t_Stand_.html#/

 

ACME Manual: http://www.pyrobin.c...sers Manual.pdf

 

Some work on software by another member: https://www.amateurpyro.com/forums/topic/11545-thrust-metertest-rig-prototype-ver10/page-1 

 

https://www.amateurp...t-of-my-rocket/

Yes, I would like to be able to measure the thrust curve of the motors.  Sharkwhisperer had, elsewhere, suggested videoing a motor burn on a scale, which I did.  It didn't work out too well as it seems the initial burst of power caused the digital scale to jump up and bounce around.  By the time it settled down the burn was about halfway finished.  So, yes, I would like a way to record what's going on.  I can do a lot of things but electronics is not my strong suit.  I have lots of components and tools (soldering iron, hot air rework station, oscilloscope, and blah blah blah).  But I suck.  I have never done the programmable ICs (PIC, arduino, and such) and forget the Raspberry Pi.  Some of the load testing stuff I found required integration with a Raspberry Pi or similar.  I may re-visit that in the future but I've got a long-standing trend of not being good at electronics.  I can build from a schematic and that's about it.

 

Wow, that's, um, expensive.  $575.  Yeah, I'll be trying to build one or doing without.

 

The problem I had with the recording of the digital scale was that it had flex/bounce in the scale, I guess, and maybe some latency in reporting what was registered.  The load cell idea with a recorder sounds like a better idea.

 

I read the manual (in part, anyway) for that Acme rig.  Wow, that's a slick setup.  Having done a few things, and spent time as a computer programmer, too, I can appreciate the effort that went into that.  That's awesome. 

 

I'm reading through those last two links.  Thank you for the information.  If I come up with a solution to measure this stuff, I will come back and report that.

 

--HC



#85 hcb

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Posted 02 April 2020 - 02:33 PM

Hey man, that is a learning experience, definitely not a "failure". Your motor burn time and max altitude significantly exceed any Estes C motor expectations with that specific rocket, even with all the added weight. Sounds like a success to me.

 

"NAR-certified rocket-lauch visco", bwaaaah hahh ha ha ha!!!!! Love it. Gonna give the NAR/Tripoli purists some sleepless nights. For sure don't mention homemade igniters with....my gawd....hot pyrogen. That'll get 'em calling in sick for a week.

 

Never trusted or needed those "chute releases" and they're kinda expensive, too...

Follow up: I'm not quitting.  I was working on the second Patriot kit and my son and I watched some videos of rockets and that lead to...wouldn't it be neat to do 2 stage?  And that lead to this.  The red tail is from the first one (with the upper body tube standing in the background.  I put a new motor mount tube in that section as the first one rode with the motor into the nose cone in the crash.  I've never done 2 stage before (factory or otherwise).  What the hell, why not?  If my EB motors will get the mass off the ground with any pep at all, I think I can hit 1,500 feet easily.  Maybe.  Or make another tulip hole in the pasture.  :)  Damn the torpedoes.

 

--HC

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