Fiberglass Motor Cases?

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Actually, his question is just fine. It doesn't include anything about mixing, propellant formulations, etc.
-Kevin

Ya but look at his last post, the 13 years old kids want to know how to make a motor, very not responsible to entertain him.
 
Ya but look at his last post, the 13 years old kids want to know how to make a motor, very not responsible to entertain him.
Thankfully, people entertained me when I was 13 years old and wanted to know how to make motors. Now I have a Ph.D. in solid propellants. Some kids are precocious. Deal with it.
 
A few things.

I am 15.
I am not asking how to make any propellant whatsoever.
I am asking if anyone has ever done it, and if so, is it feasible.
:)

Just saying. Check your facts before you post... Hmmm, sound familiar? :p
Ya but look at his last post, the 13 years old kids want to know how to make a motor, very not responsible to entertain him.
 
Thankfully, people entertained me when I was 13 years old and wanted to know how to make motors. Now I have a Ph.D. in solid propellants. Some kids are precocious. Deal with it.

Completely agree and me as well (minus a Ph.D in solid propellants, but an M.E. nonetheless...). So glad I never ran into the Gerard's of the world.
 
Hey blackbrandt (or is it Matt?); like I said before, don't let this keyboard commando drag you down. Ask whatever you want.

A few things.

I am 15.
I am not asking how to make any propellant whatsoever.
I am asking if anyone has ever done it, and if so, is it feasible.
:)

Just saying. Check your facts before you post... Hmmm, sound familiar? :p
 
A long time ago a debate raged in the HPR community whether metal was legal in commercial HPR motors (not airframes). USRockets, Vulcan, and several others made plenty of composite motors.

--MCS

.
 
Thankfully, people entertained me when I was 13 years old and wanted to know how to make motors. Now I have a Ph.D. in solid propellants. Some kids are precocious. Deal with it.
I entertained David,
By dumping him on Frank as slave labor

I did some single grain FG cased single use. They were grains cast in FG tube about 0.035 thick go into a 38 Kosdon case but I hogged the propellant out of the ends and used an epoxy forward closure and a graphite nozzle epoxied in. No recovery.
500 grams prop in 0.3 seconds with a total burnout weight of 125 grams.
 
I entertained David,
By dumping him on Frank as slave labor

I did some single grain FG cased single use. They were grains cast in FG tube about 0.035 thick go into a 38 Kosdon case but I hogged the propellant out of the ends and used an epoxy forward closure and a graphite nozzle epoxied in. No recovery.
500 grams prop in 0.3 seconds with a total burnout weight of 125 grams.

Now I call that mass fraction!
 
Has anyone ever done a fiberglass motor casing?

Yes, quite a bit, including Professional space-application and military motors, 'professional' consumer motors for the hobby (reusable and SU), and 'amateur". And I'm sure all three have been done before with CF instead of fiberglass.

Like any engineering decision, there are strengths and weaknesses. The strength if obvious; composite cases offer low case mass for a specified design pressure. The weaknesses are many: anisotropic (meaning it's much, much harder to design them to survive a given pressure), lower temperature tolerance, harder to manufacture, harder to inspect and clean after use, more vulnerable to stress concentration problems at snap ring grooves or pin holes, probably more expensive in the long run. Also safety-it's much harder to predict how exactly they will fail, they make shrapnel when they fail, and the shrapnel probably won't show up on an x-ray image.

I imagine people have said all that already, however.

EDIT: Jesus Christ, they tried to cut your head off! Sucks bro. 15, right? I assume you're either in high-school physics or will be next year, right?

It's a bit tough to explain the theory without background, but suffice it to say that when it comes to calculating how strong a piece of metal or plastic is, it simplifies everything enormously to assume that the fundamental material properties (like breaking strength or 'stretchiness') are the same regardless of what direction you measure them in. In general, that assumption isn't possible in composites, where properties of the resin and the fiber are different and the fibers have discrete orientations. That makes making composite cases the 'right' way much harder. That, and the fact that they can't be as easily cleaned, inspected, and reused, is probably why you don't see too many around. I've made some big ones that we never tested; PM me if you want to know more.
 
Yes, quite a bit, including Professional space-application and military motors, 'professional' consumer motors for the hobby (reusable and SU), and 'amateur". And I'm sure all three have been done before with CF instead of fiberglass.

Like any engineering decision, there are strengths and weaknesses. The strength if obvious; composite cases offer low case mass for a specified design pressure. The weaknesses are many: anisotropic (meaning it's much, much harder to design them to survive a given pressure), lower temperature tolerance, harder to manufacture, harder to inspect and clean after use, more vulnerable to stress concentration problems at snap ring grooves or pin holes, probably more expensive in the long run. Also safety-it's much harder to predict how exactly they will fail, they make shrapnel when they fail, and the shrapnel probably won't show up on an x-ray image.

I imagine people have said all that already, however.

EDIT: Jesus Christ, they tried to cut your head off! Sucks bro. 15, right? I assume you're either in high-school physics or will be next year, right?

It's a bit tough to explain the theory without background, but suffice it to say that when it comes to calculating how strong a piece of metal or plastic is, it simplifies everything enormously to assume that the fundamental material properties (like breaking strength or 'stretchiness') are the same regardless of what direction you measure them in. In general, that assumption isn't possible in composites, where properties of the resin and the fiber are different and the fibers have discrete orientations. That makes making composite cases the 'right' way much harder. That, and the fact that they can't be as easily cleaned, inspected, and reused, is probably why you don't see too many around. I've made some big ones that we never tested; PM me if you want to know more.

Thanks for the answers. And FYI, I finished high school physics about a week ago... :) Also Honors Chem (taking the final test in 5 days...)
 
The success or failure of a composite case depends on the insulation between the combustion zone and the casing.

Virtually all prof3essional composite case systems use a case bonded propellant grain design. If you do not keep the casing cool (at a minimum below the Tg temperature) it will fail catastrophically.

Bob
 
Ya but look at his last post, the 13 years old kids want to know how to make a motor, very not responsible to entertain him.

I'm well aware of Matt's age. I'm also well aware of the type of mentoring and encouragement he has both from his parents, and a local club.

Matt concerns me a whole lot less than several adults I know.

Although I've never met him in person, if Matt were in my area I'd have no problem hooking him up with people I know who make their own motors, to let him learn how it's done so that he'd be educated and ready to go when he's old enough to make his own, per Tripoli rules.

I've a feeling that, with his parent's support, there are quite a few people who'd happily let Matt help them make motors. Nothing at all in the rules against that. And if he passes a Tripoli Mentoring exam, he can participate in the flying of those motors, as well.

-Kevin
 
Thanks for the answers. And FYI, I finished high school physics about a week ago... :) Also Honors Chem (taking the final test in 5 days...)

Well, if you're not too busy over the summer, I'd pick up a used copy of this:
https://www.amazon.com/dp/1420062719/?tag=skimlinks_replacement-20
That's the continuum mechanics (strength of materials) book that I used; I know three of the four professors who've worked on it (the latest version at least). It's not super expensive, it is wonderfully clear and concise, and it answers all questions. It'll really open the eyes of college admission people if you can talk about having studied continuum mechanics already also. I'd be more than happy to help you if you decide to work through the book and get stuck anywhere or confused.

Continuum Mechanics is by far the best ratio of coolness/difficulty and usefullness/difficulty of any subject I've studied, other than basic calculus basic physics.
 
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We have made loads of successful composite cases anywhere from 38mm all the way up to 8 Inch diameter with awesome results. I am always willing and excited to help people in their endeavors and pass on my knowledge of what works and what does not.

Curtis-
 
We have made loads of successful composite cases anywhere from 38mm all the way up to 8 Inch diameter with awesome results. I am always willing and excited to help people in their endeavors and pass on my knowledge of what works and what does not.

Curtis-

As it should be. Nice gesture, Curtis.
 
Well, if you're not too busy over the summer, I'd pick up a used copy of this:
https://www.amazon.com/dp/1420062719/?tag=skimlinks_replacement-20
That's the continuum mechanics (strength of materials) book that I used; I know three of the four professors who've worked on it (the latest version at least). It's not super expensive, it is wonderfully clear and concise, and it answers all questions. It'll really open the eyes of college admission people if you can talk about having studied continuum mechanics already also. I'd be more than happy to help you if you decide to work through the book and get stuck anywhere or confused.

Continuum Mechanics is by far the best ratio of coolness/difficulty and usefullness/difficulty of any subject I've studied, other than basic calculus basic physics.

+3

That book is very very excellent.
 
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This is a great topic for a independent study/research paper. My son did one on black-holes and doing this allowed him to not only dig into the topic but allowed him to show that even that he is young does not mean that he has to act his age. In fact I act his age more then he does.

My hat goes off to you Matt for your research and for all of those that have offered you help. Making composite case motors have some very interesting design challenges to work though and can be a great tool to learn the right way to approach them. Since you have access to some great resources do you homework on not only what is used but how it is used. It is the little things that will make the difference....
 
Here is a fiberglass sugar M motor I static tested last year.Worked great.

[video=youtube;Q2YJtmsqKSU]https://www.youtube.com/watch?v=Q2YJtmsqKSU[/video]
 
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