Can't get lift!

[Xzanth]

Yeah I'll dry out the sycamore and mesquite first. Let it sit in the hot az sun hahaha. Takes but a few days after I chop it lol

[FlaMtnBkr]

You do not want dextrin in your powder for hand ramming rockets. It's too hard and will not reliably compress. At least it's not reliable enough for me and you really don't want a motor that isn't completely reliable in a model rocket you spent a bunch of time and money making that is meant to be reusable.

 

Also, 3% water is not feasible unless you are compressing your BP with a press to a certain density and breaking apart which is called corning and different than granulating which is BP wet to a dough like consistency and pushed thru a screen. Probably a more accurate comparison is modeling clay and I usually have to add 20-25% water to achieve that. I've found I can add 18% water to any BP and then slowly add more with a spray bottle and work it in. It takes little water to go from the perfect consistency to a wet, soupy mess. If you weigh your dry BP and the correct consistency wet BP, you can figure out how much water you need to add next time for those chemicals and that batch of charcoal. Different charcoal will require a different amount of water as some charcoal is a lot more 'thirsty' than others. Still a good idea to add one percent less water than you measured and add a couple spritzes of water to sneak up on the correct amount.

 

I then screen my BP onto plastic trays about a 1/4" deep and put in the hot sun. Once the top layer is dry enough to touch and not fall apart in about 45-60 min, I gently stir it up to get the wet stuff on bottom to the top. I do that 1 or 2 more times which gets it dry in 2-3 hours. It will be hard and crunchy dry and pretty easy to tell it's good and dry. A good trick to verify something is dry is to throw some in a clear plastic bag and leave in the sun for a good 30-45 minutes and any retained moisture will quickly show it's self as condensation in the bag.

 

If your BP is taking 24 hours to dry, or more (!), it will be measurably and noticeably slower. If I'm going to all the work to make hot BP using good charcoal and sufficient mill time, then I want to dry it as quickly as possible and not undo that work.

 

If you granulate your powder it will be noticeably faster in a loose pile uncompressed. The grains let the flame front flash thru instead of having to progress thru a solid pile of powder. But even once it's compressed into a solid grain in a rocket motor, it seems a little more powerful than had it not been wet and granulated. However, that is my seat of the pants feel for things and I don't have a way to measure if that is in fact the case.

 

Also, I have heard mesquite isn't a very fast wood. But it's good to test and verify for yourself. It wouldn't hurt to test anything you can get your hands on locally. Even bigger, woody weeds can make decent charcoal. Another member has also reported that newspaper makes a suitable charcoal for making BP though I haven't tried it yet.

 

Edit: not sure why the post is showing up twice?

 

Edit 2: it went away but added a "removed double post" at very bottom that I didn't write?! I assume a moderator is lurking in the shadows

 

Edited April 10, 2016 by FlaMtnBkr
removed a double post

[Xzanth]

Pete and repeat Sat on a fence. Pete fell off. Whose left?

[Xzanth]

Oops. Miss Edited April 10, 2016 by Xzanth

[Xzanth]

Oh, you fixed it

[FlaMtnBkr]

Yeah, I'm not sure what's going on and how the text got put in twice as I only typed it once. I think. Maybe when I did a quick edit it somehow put a glitch in the matrix?

[Mumbles]

It was me. We must have been editing at the same time or something. When I edit a post, I can leave a little message like that if I choose and by default it shows my username. I do this a lot, and most of the time it goes unnoticed.

 

The double post looking thing shows up when you submit multiple posts in a certain time period (60 seconds or so). Usually this happens because of some server or browser hangup sending the data twice. It seems to be a lot more common among people using cell phones or mobile versions of the site for some reason.

[Xzanth]

Well I made a new rocket. Only weighs about 9oz. And is abouta foot tall or less

[stix]

. . . If your BP is taking 24 hours to dry, or more (!), it will be measurably and noticeably slower. . .

 

Interesting FlaMtnBkr, that's not what I have experienced. I'm not saying you are wrong, but there must be a reason for what I have experienced which I reckon is worth exploring.

 

I'm thinking that adding 3% dextrin perhaps slows down the drying time? I'm not an expert at making bp and haven't made a lot of it - my last small batch was made around a year ago. The bp I did make was of high quality - ie. fast burning with very little residue.

 

My 20 mesh granules took 3-4 days to dry within a regulated 25C (77F) environment. So perhaps with the addition of the dextrin the small granules create a crust, sort of like "driven-in" and take a while to dry - worth thinking about. Maybe my home made dextrin was the problem?

 

Xzanth, I would still suggest in the interest of research to leave some aside and test a week later. I'll be happy for you to say "Stix, it made NO difference at all" . Then perhaps it's the charcoal?

 

Xzanth said: "Well I made a new rocket. Only weighs about 9oz. And is abouta foot tall or less"

 

Looking forward to seeing the results.

 

Cheers.

[Xzanth]

Here she is.. Hahahahahahahahahahah makeshift tester. Weighs a total of 13 ounces. We'll see Edited April 11, 2016 by Xzanth

[OldMarine]

At least you didn't use a purple egg.

[Xzanth]

Well. I'm happy about the lift off.. But I guess this is what I get for taking 10 minutes to make it. Hahahahahahahahahahah. But at least I have z power now

https://youtu.be/v642hQKOaL8

[Xzanth]

Now if someone direct me to some tubes of all sorts to make a decent one and all the tools I'll need to build a good one. I would appreciate it

[lloyd]

Xzanth,

That looked like it had plenty of 'go power'. You might consider putting your motors on sticks, instead of 'finning' them, until you get everything dialed in.

 

That looked more like a center-of-thrust vs. center-of-balance problem than anything wrong with the motor itself.

 

LLoyd

[Xzanth]

Flying just on a stick might be illegal in Arizona. But on a stick this thing is gonna fly. And I only pounded the motor half full with no delay

[FlaMtnBkr]

I think most of us make firework rockets that are attached to a stick and that carry a payload to explode and create various effects. So you might not get a lot of input on model making here.

 

Have you consider making your own tubes? They don't need to be terribly strong or thick and not very hard to make. You can use cheap recycled kraft paper, or even grocery bags, and some elmers glue. Then use a former to make the size you want PVC is available in lots of sizes and would be a suitable tool that's cheap and reusable. There are some threads on it here or I'm sure we can give you the basics.

 

Stix, it's not surprising to me that it takes that long to dry at that low temp. I stick mine in the hot Florida sun as I described above which really dries the black powder quickly. I'm not saying you can't make great powder if it takes that long. Just that you can tell it's slower when compared side by side with the quickly dried stuff. If it takes long enough though it can go from great to good or from good to mediocre. At least that's been my experience and if I'm trying to make the hottest powder for use in an end burner, a nozzle-less core burner, or breaking small shells, etc, then drying quickly is another step in the process. Plus, after having an accident that didn't hurt anything but was quite eye opening, I want to dry my powder quickly away from anything that can be damaged and then get it packaged and stored safely as quickly as possible which drying in the sun like I described allows me to do. Hope that is a little more clear?

[Xzanth]

Just got some eastern red cedar!!!!! Gonna do that. And buy an Estes rocket from the store. Use that over and over while I work on a nice one ^-^

[stix]

. . . You might consider putting your motors on sticks, instead of 'finning' them, until you get everything dialed in.

 

That looked more like a center-of-thrust vs. center-of-balance problem than anything wrong with the motor itself.

 

LLoyd

 

+1 to what Lloyd said. The motor itself looks like its producing enough thrust - now it's a matter of stability.

 

. . . Stix, it's not surprising to me that it takes that long to dry at that low temp. I stick mine in the hot Florida sun as I described above which really dries the black powder quickly. I'm not saying you can't make great powder if it takes that long. Just that you can tell it's slower when compared side by side with the quickly dried stuff. If it takes long enough though it can go from great to good or from good to mediocre. At least that's been my experience and if I'm trying to make the hottest powder for use in an end burner, a nozzle-less core burner, or breaking small shells, etc, then drying quickly is another step in the process. Plus, after having an accident that didn't hurt anything but was quite eye opening, I want to dry my powder quickly away from anything that can be damaged and then get it packaged and stored safely as quickly as possible which drying in the sun like I described allows me to do. Hope that is a little more clear?

 

Yeah, thanks FMB, that's a lot clearer . I have actually read (probably on this forum) about "needing" to dry quickly after granulating, but there seemed to be differing views so I didn't worry about it. Is the reason to do with the KNO3 crystallizing if left too long?

[FlaMtnBkr]

I believe that is likely the reason. I think the longer the water takes to evaporate, the bigger the crystals grow. If you look at growing crystals at home such as sugar crystals for a children's activity, the slower they evaporate, the bigger the crystals and when heated to accelerate they are much smaller. At least from what I remember. I think minimizing crystal growth is the major objective and I have noticed a pronounced difference when BP takes a day or more to dry.

 

KNO3 solubility is also greatly affected by temperature. One day when I feel like experimenting and making comparisons I'm going to try using ice water to wet BP and try to keep it cold as long as possible while processing it and then dry it quickly. This should minimize the amount of nitrate that dissolves in the first place and then also minimize crystal growth. Much cheaper than using alcohol and other solvents to stop any nitrate from dissolving. That's likely why red gum and alcohol BP is often said to make the hottest BP.

[Arthur]

When pressing a rocked, milled powder is perfectly adequate, as long as it is good and well milled. For pressing or ramming there is no need for granules. If you use granulated powder it's easier to handle cleanly but you break the granules as you pound the rocket.

 

Small rockets need fast powder but bigger rockets (in terms of bore diameter) need to use progressively slower powder or they cato.

 

It's futile trying to work with poor charcoal -it's a small ingredient but has a major influence on the powder quality.

[Xzanth]

Wow...... Just realized I was reading g my scale wrong........ Not 3 pounds... 3.2 ounces and around there.. I just made one that's 5 oz. My fuel just sucked and didn't have very good tooling. Now that I used the tlud and have red cedar.. Let's see what this can do sooo.

[lloyd]

Um.... That's a pretty big error. What's the gross capacity of your balance? And why are you using ounces and pounds? Also, what is "reading g my scale"?

 

I'm a US-based, American-born businessman. That said, I have no use for lb/oz measures in technical endeavors. Since ALL of the scientific community has 'gone metric', it behooves amateurs to do so, also.

 

If your balance has the ability, I'd recommend that you switch to g/Kg, and just get used to it.

 

LLoyd

[schroedinger]

I'm a US-based, American-born businessman. That said, I have no use for lb/oz measures in technical endeavors. Since ALL of the scientific community has 'gone metric', it behooves amateurs to do so, also.

 

If your balance has the ability, I'd recommend that you switch to g/Kg, and just get used to it.

 

LLoyd

+1

[Xzanth]

Cool. Good story

[stix]

Xzanth, it's absolutely crucial that you get your measuring system correct and consistent. Everything else follows from that. I'm sure that you'll sort it out.

 

. . . Small rockets need fast powder but bigger rockets (in terms of bore diameter) need to use progressively slower powder or they cato . . .

 

Are you sure about that Arthur? The way I look at it is that if you are "truly" scaling up dimensions of a smaller motor, then one would have to scale "up" the burn rate of the fuel as well in order to achieve comparative and expected performance. So my view is completely contrary, ie. you need to "speed up" the fuel burn rate when making larger motors.

 

I have tested this on a thrust meter and the results have been conclusive. Perhaps your experiences have lead you to the wrong conclusion. An important aspect to remember is maintaining the "density" of the fuel. With black powder (or most powdered pressed fuel) it's harder to maintain density when you make bigger ones because it's going to be a lot harder to press - to that same density.

 

If bp is not compressed enough, then it's going to burn quicker, and hence cato.

 

I'm pretty sure what I've said is correct, otherwise I'm going to banish myself from this forum. But before doing so, I'd like to hear alternate views that make sense.

 

 

Um.... That's a pretty big error. What's the gross capacity of your balance? And why are you using ounces and pounds? Also, what is "reading g my scale"?

 

I'm a US-based, American-born businessman. That said, I have no use for lb/oz measures in technical endeavors. Since ALL of the scientific community has 'gone metric', it behooves amateurs to do so, also.

 

If your balance has the ability, I'd recommend that you switch to g/Kg, and just get used to it.

 

LLoyd

 

Yep, agreed Lloyd. It's good to see that some Americans have come to terms with the simplicity and benefits of the metric system although confusion can still arise sometimes.

 

I have to say that I'm a bit conflicted between the two systems. I was about 6yrs old when the metric system was introduced here in Aus and was just starting to make sense of the "imperial" (English) system. Therefore I use both interchangeably depending on the circumstances.

 

A case in point:

 

Police Officer: Mr. Stix, there have been complaints regarding unusual and loud "whooshing" sounds coming from your property - can you explain this?

 

Stix: Yes, I heard it too, I was frightened. I saw someone fleeing in "that" direction.

 

Police Officer: Are you able to give a description of the offender - ie. height?

 

Stix: He/She was about "5 foot ten".

 

Police Officer: Ok thanks. Also according to other reports, some sort of object was launched into the air. Did you witness it, and if so, how high in your estimation did it go?

 

Stix: Yes I saw it, it went up about "200 meters". There was also big flames coming out the back. Sometimes I hear booms and laughing. It's certainly an "ounce" of luck that no-one has come within an "inch" of their life.

 

Police Officer: Mr. Stix, I put it to you that you are using subterfuge by using alternate measurement systems to misdirect and confuse this investigation?

 

Stix: Nothing could be further from the truth your lordship.

 

--

 

[DISCLAIMER] None of the events described in the above text actually took place, they are merely fictitious scenarios conjured up by the author.