Introduction and Statement of Intent.

[ThomasGTipton]

Hello, I wanted to address the board and express the nature of my interest in this hobby. To begin, let me say that I would be called a "Born Again" rocketeer. I played with Century and Estes model rockets as kid and learned a lot of what to do and what not to do in the smaller engine classes. It's been years since I've flown a rocket and so I couldn't help but notice the multitudes of heavy duty paper cores that my firm disposes of on a daily basis. Since day one in the plant I saw those and said to my self. "Self, those would make some fantastic model rocket engines." These tubes are about 1/4 inches thick with a 3 inch ID. Length is 27,5 inches. So I've set myself the goal of joining my local Tripoli club and working towards my certifications and eventually building, launching and recovering a rocket based on engines made with this housing. Much of my tinkering has to do with seeing something useful about an object and following the path of learning and experimentation required to get me to that goal. Looking forward to reading up on the knowledge to be gleaned from these pages and maybe even getting to know some of you at launches in the years ahead.
Regards

Thomas

 

[ThreeJsDad]

Welcome Thomas and the path you have chosen is an ambitious one. Ex motors are a vague interest to me. For the most part I focus my efforts on Composite air frames. I do some odd rocks but most of my builds grow out of me rolling a fiberglass or carbon tube and then deciding what to do with it. I has my L2 once upon a time but still did not pursue molding my own motors. My home club does not have Ex launches and this may be the main reason I did not go down that road.

I am sure I will be going for my L1 before the summer is over but not sure I have my L2 in the near future.

If you are going to go straight to scratch building I suggest you start with basic designs like 3FNC or 4FNC. You could even play with some saucers, they are easy to make and a lot of fun.

I think you will find a wealth of knowledge in this forum and others. These are some great folks who are eager to help.

 

[jimzcatz]

I sincerely doubt those tubes will handle the pressure of APCP motors. Maybe as a liner in an aluminum case.

 

[ThreeJsDad]

I sincerely doubt those tubes will handle the pressure of APCP motors. Maybe as a liner in an aluminum case.

I presumed his intent was to use them as a mold or liner. You are not that far from me, what club do you fly with?

 

[kuririn]

 

[jqavins]

I'd suggest doing one or two LPR kits just to dust off the skills you developed all those years ago. Making one's own motors is a big deal, as ThreeJsDad said. I recently heard it described as a whole hobby all by itself. If you're going to pursue it, you might want to join this site's restricted research subforum. You need to be L1 certified to gain entrance, so get the L1, join that subforum, read a whole lot, then start.

And, welcome to TRF.

 

[BABAR]

Welcome!

I think your plan to join a local club is the perfect first step in your path.

Straight trails!

 

[Zeus-cat]

As ThreeJsDad said your goal is ambitious. One of the problems with repurposing a non-rocketry item into rocketry is all the mods you need to do to the item to make it conform to the actual rocketry stuff.

I know a guy who makes his own motors and he says if your doing it to save money you don't understand the fundamentals of making your own motors. I'm sure he saves money, but he is making and flying a lot of APCP. Keep in mind that this isn't as easy as watching a YouTube video. The chemicals involved are highly energetic since that is what you need for rocket motors. Mistakes can be very dangerous.

 

[ThreeJsDad]

As ThreeJsDad said your goal is ambitious. One of the problems with repurposing a non-rocketry item into rocketry is all the mods you need to do to the item to make it conform to the actual rocketry stuff.

I know a guy who makes his own motors and he says if your doing it to save money you don't understand the fundamentals of making your own motors. I'm sure he saves money, but he is making and flying a lot of APCP. Keep in mind that this isn't as easy as watching a YouTube video. The chemicals involved are highly energetic since that is what you need for rocket motors. Mistakes can be very dangerous.

I think this is why I focus on air frames. I am set up to do composite work, curing oven, mandrels, cloth sources, resin supplier and a lot of experience. I save a bunch of $$ over buying kits. This allows me to afford the motors... If I had to buy kits similar to the rockets I build I could never afford this hobby right now. I can see learning to make motors for the knowledge but from an economic perspective it isn't worth it to me.

G's are very reasonable for the performance they offer and even small-ish HPR motors are not super high. I bet most folks who buy lunch spend for lunches in a week than a J reload would be.

 

[ThomasGTipton]

Welcome Thomas and the path you have chosen is an ambitious one. Ex motors are a vague interest to me. For the most part I focus my efforts on Composite air frames. I do some odd rocks but most of my builds grow out of me rolling a fiberglass or carbon tube and then deciding what to do with it. I has my L2 once upon a time but still did not pursue molding my own motors. My home club does not have Ex launches and this may be the main reason I did not go down that road.

I am sure I will be going for my L1 before the summer is over but not sure I have my L2 in the near future.

If you are going to go straight to scratch building I suggest you start with basic designs like 3FNC or 4FNC. You could even play with some saucers, they are easy to make and a lot of fun.

I think you will find a wealth of knowledge in this forum and others. These are some great folks who are eager to help.

Thank you ThreeJsDad. Seems much like the Ham Radio community. A lot of super smart people eager to share in their expertise.

 

[ThomasGTipton]

As ThreeJsDad said your goal is ambitious. One of the problems with repurposing a non-rocketry item into rocketry is all the mods you need to do to the item to make it conform to the actual rocketry stuff.

I know a guy who makes his own motors and he says if your doing it to save money you don't understand the fundamentals of making your own motors. I'm sure he saves money, but he is making and flying a lot of APCP. Keep in mind that this isn't as easy as watching a YouTube video. The chemicals involved are highly energetic since that is what you need for rocket motors. Mistakes can be very dangerous.

Zeus-Cat, I'll only be attempting lower power sugar candy motors for this enterprise. KNDX or something on that order. And no, it's not about saving money. It's just about getting a bug up my butt about whether or not I can pull something off. I have a lot of respect for the high power motors and in no way do I expect to get that kind of performance from these. But I expect it will be an adventure all the same.

 

[ThreeJsDad]

Thank you ThreeJsDad. Seems much like the Ham Radio community. A lot of super smart people eager to share in their expertise.

I help when and where I can, if you need something drop me a note.

 

[Zeus-cat]

Just to make it clear, sugar motors are not allowed at NAR or Tripoli launches.

 

[tim cubbedge]

Just to make it clear, sugar motors are not allowed at NAR or Tripoli launches.

You sure about Tripoli launches?

 

[rharshberger]

Just to make it clear, sugar motors are not allowed at NAR or Tripoli launches.

Sugar motors covers a "range" of formulations of which sucrose (table sugar) motors are not allowed at either organization. Formulation containing dextrose and sugar alcohols erythritol and sorbitol are allowed at TRA launches with a L2 certification. The cardboard tubes of the size you have would make HPR sized motors not LPR size. A "sugar" motor the size of a Estes motor will produce more thrust and duration than a Estes Black Powder motor iirc. NAR does not allow any EX motors at their launches. I would recommend finding another use for the tubes you have and purchase or make some aluminum reloadable casings and nozzles of proper material if you have the tools to do so. Joining a club and learning from other EXPERIENCED motor makers will go a long way towards keeping all your fingers and other various parts undamaged and attached.

 

[jimzcatz]

Sugar motors are most certainly allowed at Tripoli launches. That being said, it must be a research launch, which most Tripoli launches are.

 

[ThomasGTipton]

Sugar motors are most certainly allowed at Tripoli launches. That being said, it must be a research launch, which most Tripoli launches are.

Yes, I was aware of that. Tripoli also has some provisions for certification of an experimental engine, though I am not interested in manufacturing, only in earning permission to use them to launch with.

 

[cbrarick]

Go for it! Just find another use for those tubes. They are NOT good enough to make even sugar motors..unless your ultimate goal is a Roman Candle....

 

[ThomasGTipton]

Go for it! Just find another use for those tubes. They are NOT good enough to make even sugar motors..unless your ultimate goal is a Roman Candle....

cbrarick, Dimensionally, these tubes are pretty much on par with the construction of an Estes rocket motor. many, many, overlapping laminations. What exactly makes you so certain they would not be suitable for even a single use, cast-in-tube, KNDX motor? I'll see if I can figure out how to post a picture so we'll be on the same page.

 

[BABAR]

Better yet, bring some of these tubes to a local club launch, preferably along with one or two low or mid power rockets that you build and the appropriate low or midpower engines to launch them.

I think face to face contact with some experienced rocketry people, as well as getting reacquainted with fly model rockets, will provide you much more satisfying assistance in your endeavors than you are likely to get on this forum.

 

[cbrarick]

cbrarick, Dimensionally, these tubes are pretty much on par with the construction of an Estes rocket motor. many, many, overlapping laminations. What exactly makes you so certain they would not be suitable for even a single use, cast-in-tube, KNDX motor? I'll see if I can figure out how to post a picture so we'll be on the same page.

let's see here.....in no specific order
1. burn time. D-12 is 1.7 seconds. 3 seconds aren't unheard of in sugar motors
2. rocket candy burns between 1400 and 2000 C. Black powder 300-464 C. so wound paper might work for a D motor, but it's burning on a factor of 4 lower then rocket candy
3. Black powder is a micrograin motor..sugar is a poured liquid
4. Pressure. I fly hard and am not afraid of 1000 psi. go ahead and put that on your paper & tell me how that works.
5. (maybe most important) bring it to a launch where I'm the RSO, you will be bringing it home. Willing to bet you will hear that from many people who RSO EX Motors.. Unless you're going to static test it at the way-away cell. If it holds together then just maybe. You are so, so far away from what's done it's hard put into words. No one, to the best of my knowledge, is working on PAPER motor tubes. We have aluminum, phenolic and I even know of a case-bond carbon fiber one.

please take advice. It will limit your disappointment in the hobby.

I like a good EX and support it (Tru-core) but you need to work in the parameters. Perhaps someone could develop something that could be done with paper motor tubes, but that someone would be a person with great experience in EX motor making with a strong hold of the theory, not a NOOB. After all, you're talking about at least a L motor, if not a M, or perhaps a little more.

 

[Kelly]

cbrarick, Dimensionally, these tubes are pretty much on par with the construction of an Estes rocket motor.

No, they aren't. First, Estes motor tubes are made from high quality virgin kraft paper, convolute-wound. I'm guessing yours are spiral-wound (though you didn't say), and from crappy paper (because no one's going to make cores out of expensiver virgin kraft). So, the construction of your tubes is likely not even close to meeting the material strength properties used by Estes. Second, let's talk about wall thickness. Assuming pressure is constant, then wall thickness needs to scale with diameter. In other words, if you're going to build a motor that's twice the diameter, then you need twice the wall thickness to contain the same pressure. Your tubes are 6X the ID of an Estes 18mm motor; are they 6X the wall thickness?

Experimental rocketry and building your own motors is fun and doable. Stick around, build and fly some rockets, learn as you go, and you'll eventually acquire the knowledge you need to build your own. Have fun along the way, and ask lots of questions!

 

[ThomasGTipton]

 

[jqavins]

cbarick, your cautions (and others') to Mr. Tipton are on target and valuable. I must, however, make one correction. Comparisons of temperature in multiples must always be done in absolute scales, Kelvin or Rankine.

2. rocket candy burns between 1400 and 2000 C. Black powder 300-464 C. so wound paper might work for a D motor, but it's burning on a factor of 4 lower then rocket candy

From these celcius temperatures, BP is burning at 573 to 737 K and R-candy at 1673 to 2273. So it's "only" a factor of 3.

 

[ThomasGTipton]

Here is a picture of the tube in question. The thickness of the tube is 5/16".
3" ID. 21" length. Weights 1.78 lbs. To the best of my ability I am counting about 50 laminations.

 

[Antares JS]

The thing you have to realize is that not only does a motor case have to withstand temperature, it has to withstand internal pressure. That is a spiral wound tube and it is not likely to withstand pressure very well.

As a barebones test, I would suggest sealing the ends of one of those tubes with plywood discs except for a small inlet for a pump, and pressurize the inside of one of these tubes to see if it can withstand several hundred psi. (Someone else might be able to get you a more exact number.) Making sure your case can withstand the forces involved in the first place will save you a lot of wasted propellant.

 

[Steve Shannon]

Yes, I was aware of that. Tripoli also has some provisions for certification of an experimental engine, though I am not interested in manufacturing, only in earning permission to use them to launch with.

No, only commercial motors can be certified. But research motors don’t need certification to be flown at Tripoli Research Launches; they just need to comply with the Tripoli Research Safety Code.

https://www.tripoli.org/Portals/1/Documents/Safety Code/ResearchSafetyCode - 2017.pdf

 

[ThomasGTipton]

I agree, testing with air pressure would be a logical next step. Now, getting access to that kind of pressurized air is the next question. I know someone who works on tractor trailers and rigs. He might be able to help me out with that. I'll see about rigging a tube up for such a test and share the results. I'll cap the ends the same way I was planning on doing for an engine load and provide an air hose inlet in one of the caps. If anything, the lessons learned here may help someone in the future who entertains the idea of going down this path. Using these tubes was the inspiration for bringing me here, so if they turn out to be a no-go it will be a disappointment, but I'd like to be able to prove the naysayers correct before abandoning the idea. Now the only question is where do I find an air compressor with that kind of capacity?

 

[Steve Shannon]

I agree, testing with air pressure would be a logical next step. Now, getting access to that kind of pressurized air is the next question. I know someone who works on tractor trailers and rigs. He might be able to help me out with that. I'll see about rigging a tube up for such a test and share the results. I'll cap the ends the same way I was planning on doing for an engine load and provide an air hose inlet in one of the caps. If anything, the lessons learned here may help someone in the future who entertains the idea of going down this path. Using these tubes was the inspiration for bringing me here, so if they turn out to be a no-go it will be a disappointment, but I'd like to be able to prove the naysayers correct before abandoning the idea. Now the only question is where do I find an air compressor with that kind of capacity?

You don’t. You cap it, add a pressure gauge, and pressurize it with a cheap grease gun.
You DON’T want to fill it with hi pressure compressible anything.

 

[ThomasGTipton]

Well, in light of the difficulty I'm going to have rigging up a pressure test, I decided to indulge my curiosity and take a tube outside and indulge in a little destructive testing. I placed a tube on a concrete slab, placed a brick under each end, and took a couple swings with a ten pound sledge hammer. The first strike merely dented it, but the second strike was far more devastating.

Results:

The tube split along the spiral winding.

The fracture revealed not nearly as many laminations as seemed to be visible from the end profile.

The quality of the paper seemed evidently highly inferior to the Estes type. (having unrolled those as a kid, I remember).

Conclusion.

Gentlemen. I concede the point. These tubes will not be used for model rocket motors.