38mm BP motors

[Elapid]

i see that casings are readily available and tooling sets are offered at retail sites for construction of 38mm BP motors.

so who is flying all these 38mm BP motors?
any pics?

another thing i noticed is that there don't seem to be any BP EX records listed on the Tripoli website. Is this an indication that it's open territory for exploration?????

thanks!

 

[aksarben10]

What retail sites are offering tooling for BP 38mm motors?

Scott

 

[Ryan S.]

thats because it is against tripoli EX rules to fly BP motors.

 

[rstaff3]

Larger BP motors are difficult to construct reliably. The propellant tends to crack, which increases the burn area, and....

 

[wwattles]

. . . KABLOOIE!!!

Paging Dr. Cato... Paging Dr. Cato...

 

[aksarben10]

The only real source of large BP type engine information that I know of is the new Sleeter book.

I think the biggest motors that he shows in the book are large H's.

Scott

 

[solrules]

BP motors don't have alot of things going for them: very low specific impulse (80 vs 200 for AP), hard to cast (espically to get the outside inhibitor to stick to the propellant), brittle (prone to cracking if you look at it funny), much more dangerous to cast than most other propellants, and not much in the way of changing the FAST burn rate (unlike AP). Not saying that it would not be cool and/or easy, but is far from being an ideal rocket motor propellant.

 

[Elapid]

that's what brought up this topic.

5.0 Black Powder Altitude Competition

The black powder altitude event is for any rocket powered only by black powder motor(s). There is no limit on the number of motors used, or total impulse. All of the motors must be certified and the total impulse of all motor(s) must not exceed 40,960 newton-seconds. Clustering and staging of motors is permitted.

Record Information: The record for this class of rockets will be the Tripoli Black Powder Altitude Record.

that's from the Tripoli website... ( https://www.tripoli.org/records/overview.shtml ) it looks like they DO allow BP motors...doesn't it? though they seem to require Certified motors for the BP altitude class. odd for an experimental group to require certified motors...
make up yer minds, dudeskis!

Sleeter recommends Sodium bicarbonate to slow combustion rates, and from the thrust curves supplied, i have to agree that it seems very effective.

he also mentions the MISCONCEPTION that BP motors are dangerous to build. he has an exercise where you take a small pinch of BP and try to detonate it with a hammer blow. all that happens is you get flattened BP. i'd think handling Mg powder or AP flour might be slightly more dangerous...

oh well, i guess i'm on my own.

 

[solrules]

Originally posted by Elapid
he also mentions the MISCONCEPTION that BP motors are dangerous to build. he has an exercise where you take a small pinch of BP and try to detonate it with a hammer blow. all that happens is you get flattened BP. i'd think handling Mg powder or AP flour might be slightly more dangerous...

oh well, i guess i'm on my own.

Now try this (not really!): Take equal masses of black powder and AP based propellant. Light a match to both. Which one is more dangerous? In my opinion, burning propellant is safer than exploding propellant.

 

[Ray Dunakin]

Tripoli has an altitude record category for BP motors because at one time there were certified, commercially manufactured, high power BP motors. RocketFlite used to make them, in 29mm and 38mm sizes up to I motors.Someday maybe they'll be available again, or some other company could produce large certified BP motors.

BP motors are not allowed under the Tripoli EX rules for home-made motors.

 

[Elapid]

Originally posted by solrules
Now try this (not really!): Take equal masses of black powder and AP based propellant. Light a match to both. Which one is more dangerous? In my opinion, burning propellant is safer than exploding propellant.

that is a very dangerous proposition!
maybe you should suggest igniting it remotely to avoid people getting hurt.

firstly, unless confined, neither will explode as you may know.
you may be confusing slow-burning rocket-propellant with quick-burning GUNPOWDER...??
one should NEVER use gunpowder for making BP motors.

the difference between burning APCP motors and BP???

the AP Composite Propellant cannot be extinguished by normal methods, the BP can be extinguished with plain old everyday water.

secondly, lit matches are rarely found in rocket propellant production or storage areas, so that is not really a concern. if you want to address static electricity, the danger is probably equal for both BP and APCP, but, since BP is so easy to extinguish, my money lies on BP as the 'safer' propellant from a manufacturing standpoint. usling low-mass tooling precludes enough pressure build-up (should ignition occur) during tamping to cause detonation during BP motor assembly.

once made into motors, the AP is most likely safer (at least for the rocket!) since the rubbery compound can take more abuse without cracking internally than the BP equivalent.

so, Tripoli won't let me launch them at EX launches?
NAR won't be any help....

i guess i really am on my own!
i'm ok with that.

 

[Elapid]

i ordered a bunch of 38mm casings, a box of 25 - 12" casings for BP motors, and about 45" of 38mm phenolic for AP motor casings.

i have a friend that sells CNC machinery that mentioned "if i need anything machined..."


i'd say i need tooling...
unfortunately, sleeter has about 100 pieces of tooling to cover the different motor designs/casings.


i heard through the grapevine that jim flis might have experience with bigger BP motors...any comments or advice, Jim?

thanks!
rob

 

[llickteig1]

Originally posted by Elapid
so, Tripoli won't let me launch them at EX launches?
NAR won't be any help....

If you proceed with this idea, please be careful. Perhaps you should attend a propellant making/safety course before you proceed much further.

And you are correct. TRA will not allow BP motors at TRA EX launches. From the TRA EX Safety code:

Chapter 5 Exclusions

5.1 General. Only composite propellant rocket motors and hybrid rocket motors as defined in this code are permitted at Tripoli Research Launches.

5.2 Black Powder Rocket Motors

5.2.1 Black powder-based motors shall not be included as composites, regardless of binder and/or formulation modifications.

5.3 Liquid Rocket Motors

5.3.1 With the exception of nitrous hybrid rocket motors, liquid rocket motors are prohibited at Tripoli Research Launches.

5.4 Additional Prohibited Propellants

5.4.1 The following propellants shall also be excluded from Tripoli Research launches: double- and triplebased propellants, and micro-grain propellants, including zinc/sulfur propellants.

HTH, --Lance.

 

[Elapid]

that the methods outlined in Sleeter's book are not safe?
there is a pretty large segment devoted to safety concerns.

 

[llickteig1]

Originally posted by Elapid
that the methods outlined in Sleeter's book are not safe?

I certainly don't see any reference in my prior post to anything in Sleeter's book ... safe .. unsafe ... or otherwise. Does anyone else?

--Lance.

 

[Elapid]

is it (Sleeter's text) incomplete?

my sincere apologies are in order; i thought i had mentioned that i have read the book thoroughly, and understand the chemistry quite well...i do have formal laboratory safety training and years of experience in the lab...my bad!

is there a BP motor-making course you'd recommend?

most of the courses advertised online are geared toward AP/AN propellants.

 

[n3tjm]

Let me make a few friendly comments. Black Powder IS shock sensitive. Just because it did not burn when you hit it with a hammer, does not mean it won't. There are meany articles in newspapers, even publiched in NAR magazines with tails people getting close calls when their ramming rod decided to become a bullet. Both ESTES and QUEST have had motor blow in the manufacturing process... even with the processes they use to make it safer... it is BP... and BP has its characteristics.

I never read the book you are referenceing, but from all the motor making books I have read... the author comments that in his experince, x does not happen when I do y. He also says that just because nothing bad happened to him, does not mean that it can't happen. You forgot factor Z. Factor Z... what is different beween you and him...

Differences include

Where you are located
Climate
Brand of Material
Properties of Material
Batch of Materal

Aerotech found out the Hard Way that THIS does matter. That is why J350's now have .5" cores... to many of them blew up with the original 3/8" cores... because the property of the finished propellant WAS different because it was made in Texas, NOT NEVADA... Completely different environment.

Another danger of BP.. As it gets older.. it becomes more dangerous. I am not sure how long it will take for BP powder deteriate before it become to dangerous to move... Many people found out the hard way what an exploding can of BP can do to their home...

I don't think Jim has any experience making BP motors (I could be wrong). I know he knows quite a bit about them, and I know he shares my belief that BP motors manufacturing is not something to mess with. I talked to him many times about the subject.

If you decide to experiment with BP... be very carful... Leather Welding Gloves, and Welding Face Sheild is a very GOOD Idea!!!

Good Luck, and be safe.

 

[llickteig1]

Originally posted by Elapid
is it (Sleeter's text) incomplete?

my sincere apologies are in order; i thought i had mentioned that i have read the book thoroughly, and understand the chemistry quite well...i do have formal laboratory safety training and years of experience in the lab...my bad!

I'm glad to hear you're experienced, well trained and well read. Carry on. I won't bother you any more.

Best of luck, --Lance.

 

[n3tjm]

My apologies to if you were offended about what I wrote to . Its all good stuff to know

 

[Elapid]

while the dangers you mention are always a possibility with high-potential substances, proper care and understanding of the principles involved will help avoid mishaps.

the hammer test is suggested in Sleeter's text. it is a demonstration of the relative insensitivity to shock of black powder compositions.

Sleeter addresses the black powder's propensity to ignite easily with the slightest spark or friction. in fact, the propellant-ramming incidents are quite possibly attributed to the friction of the black powder blowing past the ram during compression blows. using small quantities of bp and a low mass ram are important concepts to understand. also not putting your face over the ram while tamping...

black powder is very stable.
i have used 30-year-old estes motors successfully. so have hundreds of other rocketeers. i think you may be confusing the issue with KN Sugar motors, or maybe you're thinking of dynamite, which leaches out nitroglycerine after time...

 

[Zippy]

Pressing with either a hydrolic press or an Arbor press instead of hammering makes it all much safer. Much less dust flying around and allmost zero chance of spark. BP would still be a little sensitive but at least no one would be holding the ram and the hammer. Larger tools like presses also allow you to hide behind them somewhat and only expose the (body) parts you need to work the machine.

 

[Elapid]

except for the inherent hassle, i would think gloveboxes would be more popular for working on these things...have blowout panels on the sides to direct any unexpected forces...and a fume hood would keep dust from building up in the lab area.


i figure that these things aren't used due to the magnitude of the danger...pretty low.

if the ram is low-mass, no detonation can occur. only rapid burning. maybe a 'slight overpressure'...

with all of the copies of Sleeter's text that have been sold, it is quite telling that there have been no flurries of accidents reportedly attributed to its release.

of course, since the BP motors aren't acceptable at organized launches, data is hidden away in private ventures. i don't think that's a great thing since valuable data is lost to future experimenters. Our hobby is founded on the principles of experimentation in a quest for knowledge.


thanks for the replies, it is good to get this stuff out, de-bunk fallacies, and learn to proceed safely.

i look forward to posting my experiences if that's acceptable here.
i guess we'll find out!

 

[MarkABrown]

Originally posted by Elapid
i look forward to posting my experiences if that's acceptable here.
i guess we'll find out!

Experiences are good. Let's just make sure that nothing gets posted that would allow someone to attempt to duplicate your work without understanding as much as you do.

 

[Elapid]

to stay on the right side of that 'line'