Sugar Rocket Issues

[NeighborJ]

OM is correct, I used Domimo pure cane sugar but when i tried the cheap stuff refined from sugar beats, i needed to adjust the fuel/oxidizer ratio a little to optimize it. Even so it wasnt as powerful.

[jbeuckm]

Different sugar brands have verried fuel values but they all are close enough to at least burn steady. The oxidizer ratio can be adjusted for all types by observing the dross and carbon byproducts. What mix are you using and are you certain all the water is cooked out?

 

I had been using 65% KNO3 + 30% powdered sugar + 5% corn syrup. The batch that worked well was 65% KNO3 + 35% granulated sugar. I'm going to reintroduce the corn syrup in the next batch because it makes casting grains a lot easier with that texture.

 

There is a chance that not every bad batch had all the water cooked out but I tried it enough times with enough waiting that I think at least half of the bad batches would have been dry. The thing that really inspires confidence about the granulated sugar version is the color - ivory - which I think implies fewer impurities. Every powdered sugar batch came out the color of peanut butter.

Edited January 30, 2017 by jbeuckm

[lloyd]

So-called "Powdered sugar" is a blend of sugar and an anti-caking additive (usually corn starch, in the US). It's not even nearly pure sucrose. And different brands of 'powdered sugar' might well vary in the amount of the anti-cake added.

 

If you want to maintain consistency from item-to-item, use pure table sugar, NOT 'powdered sugar' (and even with corn sugar, if you wish). IF you find it necessary to pulverize it yourself, do so in a food processor or blender. Do not rely on the commercial powdered product.

 

My own heavy experience with the material is that, if you 'cook' the blend properly, even granulated sugar will properly dissolve and blend with the KNO3 during the process. But it takes a gentle hand, not a 'brute force, maximum heat" method.

 

There's enough latent absorbed water in the sugar AND the KNO3 to ensure the whole mix will dissolve and blend properly, if you take it slowly, and control the temperature.

 

You might also want to review Jimmy Yawn's "Recrystallized R-Candy" methods. They're enlightening.

 

Lloyd

[jbeuckm]

You might also want to review Jimmy Yawn's "Recrystallized R-Candy" methods. They're enlightening.

 

I had a good ignition yesterday with a granulated sugar grain. Jimmy Yawn's is definitely required reading - thanks!

[stix]

Good to hear you've had success.

 

As Lloyd pointed out, if you're dissolving or melting the sugar then plain white table sugar should suffice.

[Oinikis]

It is a good idea tu use basic table sugar as mentioned, but then ballmill it together with KNO3. That way you ensure that it is mixed properly. Another point that R-candy is a potassium nitrate suspension in molten sugar, thus having it fine is critical. I've had my best results with ballmilled mixuture, cooked dry. Edited February 24, 2017 by Oinikis

[JMan]

You seem to have a very nice rocket, but by cutting your rocket length in half you're actually making the thrust 1/4 because of the surface area that is lost not just the amount of fuel.

 

Yes I know this thred is dead but I wanted to put a simple quick answer for anyone else having this problem.

[dagabu]

There will always be opinions about the method of making R-candy so i let others do all the hard work and exploit it in making my own motors. Nakka, Yawn and others inspired me to dissolve the KNO3 in water and add the sugar then heat it all in an electric skillet.

 

The power it makes this way has been (in all my experience) by far the most consistent and among the highest I have recorded.

[JMan]

I've been making my rcandy by dissolving it all in water and cooking it driving the water off. Unnoticed something today though

 

My rcandy expands

 

Not like a small but I mean a good amount. I'm refilling an Estes tube today and pressing the fuel down and by the time I fill and pack my whole tube (I don't use baits grain I just fill and cast it directly into the tube) and I take the pressure off (just my hand pushing the rid down into the fuel) it expands almost half an inch if I don't keep pushing it back down untill it cools.

 

Is this because I'm compressing it and it's "springs back"? I also thought that when I pack it directly into the tube I get a little air in there and maybe the airpockets are springing back? Has anyone else noticed their rcandy expanding like this? I wouldn't think of this fuel as being compressible. I know bp gets compressed to a solid but does anyone apply and serious pressure to their rcandy during casting and cooling?

[NeighborJ]

Yep, springy fuel is certainly caused by air bubbles, not a good sign. At best the air bubbles will cause surging of thrust but they usually cause CATO.

 

The best way to avoid them is to fill the tube in increments and compress the fuel between each one.

[JMan]

Yah that's what I do NJ. About 1/2 in at a time. Any other way to avoid it. This is also a much smaller tube than normal.

[NeighborJ]

To be honest JMan the small diameter motors are terribly difficult to prevent air bubbles. I avoided making them with R candy, instead I used finely milled, screen mixed, dry ingredients then hand rammed them with a mallet.

 

This was the beginning of what set me off on the path to making fireworks style motors. The hand ramming caused the Estes nozzles to crack so I bought some 1/2" NEPT tubes, a cheap set of endburner tooling, and made my own clay nozzles. Whi!e supporting the nozzle with the tooling,I finally had reliable endburning motors. I proceeded to BP motors so I could more easily add a delay section and ejection charge.

 

I don't have a tested procedure for the small dia R candy motors but I was going to try filling it with a pastry bag to prevent the bubbles but either way it's gonna be messy. It is sooo much easier making the larger motors because the candy can easily be loaded as small blobs in the center then pressed to the casing wall without bubbles.

[JMan]

Well I just lit off 4 today with varying core sizes (longer core made them go higher just proving a point to my self) but no problems with air bubbles during flight they all flew, burnt, delay charge went off, and fell back down (the delay charge was there for a test, they were just motors on sticks)

 

So that made me think maybe it's just magnified with smaller tubes too and that it's really not that big a problem. What ever is causing it they all work fine.

[lloyd]

About ten years before he passed away, John Rahkonen (of Morton Thiokol SRB fame) designed an AmRoc fuel that deliberately foamed-up in the tube, and had to be compressed with a rammer to re-compact it.

 

His point in it was to guarantee that perfect contact (and coating) was made at the tube wall (or inhibitor layer) so that NO gaps could possibly happen along the inhibition surface. It worked a treat, but folks didn't seem to care for that feature.

 

Lloyd

Edited April 12, 2017 by lloyd

[JMan]

I'm sure it worked great because he's a rocket scientist, but to me is sounds like a bunch of micro bubles in the fuel, also something I can't try unless I get a vacuum chamber

 

Humm there's an idea 🤔

Edited April 13, 2017 by JMan

[dagabu]

This is an age old problem with R-Candy motors and yes, the expansion is exacerbated by completely dissolving both the KNO3 and Sugar in water because of the boiling and constant stirring. Being really tired of bubbles and that same expansion, I tried several different solutions and came up with one that works phenomenally well.

 

Make the R-Candy, start it cooling and grate it on dry paper. Cool it fully in a desiccant dried chamber like sealed Tupperware, pour it into your tube just like BP and ram it with your favorite hammer.

 

You get channels for air to escape and consolidate the granules, the bubbles you experience in the hot medium have shrunk when it cools to the point where they become microscopic. Compaction is easier and no spring back is experienced.

 

Give it a try and let me know how it goes.

[JMan]

I don't have anything to make the fuel into a powder form except a blender 😬 Not a smart choice right there. And I bet it wouldn't work to just crumple it up.

 

I was trying some more motors today (1") and they had a little spring to them but I pressed the core and compacted the fuel again and whammo it compressed about 15~20 percent more and stayed down. Just by accident I found this. So maybe I just press/drill my core and pack it down, wash and repeat.

[dagabu]

Cheese grater, $1.00 store.

[JMan]

Never thought of a cheese grater. Will try it and update you. Thanks

[lloyd]

Jman... really? His statement said, "...and grate it...", not "..and grind it...". <grin>

 

I sometimes get chastised for being such a stickler for the correct use of terms and language when talking about fireworks. This is an excellent example of why. Specificity of terminology is important, and becomes more-and-more so the more 'technical' and dangerous the task becomes.

 

Even though (as is the case with most 'labor jobs') my employees were generally poorly educated, they were all taught - and expected to KNOW - the correct technical names for every material and every procedure they used in the fireworks-making process.

 

We ran a very safe and high-quality operation (making stage and indoor fireworks), and I fully believe that was one of the reasons!

 

LLoyd

[dagabu]

I will also challenge anybodies R-Candy in overall thrust to do any better than with C&H Pure Cane Sugar. I live in Minne-snow-ta and we have TONS of Beet sugar in the bag, it just says Sugar, nothing more. I find a reduction in overall thrust of 2-10% when using the cheap sugar from Aldi's or Wall Mart.

 

I also find there is a strange taste when using Beet sugar in Cider or Beer.

 

Powdered sugar is a complete waste of money, throw a pot on the stove and add 1000g of HOT water and 2000g of Cane Sugar, heat it up until all the sugar dissolves into the water. Do the same with KNO3 then combine them both as LIQUIDS (in the proper ratios for your mix) into your electric skillet and proceed as usual in making your R-Candy.

 

I like to add a few teaspoons of pure corn syrup for elasticity (YMMV).

 

Carbohydrate Composition (d.b.):

Dextrose, (%) 20

Maltose, (%) 14

Higher Sacc., (%) 55

Edited April 15, 2017 by dagabu

[JMan]

No it didn't turn out too well. just a bunch of complications. It seemed like the mixture didn't want to consolidate after cooking grateing and hammering. I don't have a high pressure press or I could have compacted it a bit better. I do have a bottle jack and a couple steel cross members I could weld together to wedge a jack rod and motor in to compress it but hammering just didn't stick them together very well. On fireing it just blew chuncks of fuel out and had less power (I'm guessing here but I think since it didn't consolidate completely the fire went through what little air gaps were in there and broke it apart and threw it out causing the less power). Maybe it might be better if someone with BP experience and a good press tries it out instead of me. Sounds like a great idea though. Also maybe grinding it a little finer because I had doubts that the air channels would disappear cus there preset big chuncks Edited April 16, 2017 by JMan

[stix]

I'm not surprised that that particular method doesn't work at first try. There is a "knack" to that method where the grated fuel should be softened first.

 

I've tried it myself without softening first and it resulted in a huge bang!!. A big nice, big bang, but not a rocket motor does it make.

 

Personally, I would steer clear of that method and re-think and go back to basics.

[JMan]

I tried the rectangle core today and boy does that stuff fly.

 

The large core I thought would help poke through any big air pockets and it did quite well.

 

Put into a nozzles motor though that built up so much pressure (4in long 1 in wide) it burnt up all the fuel with in the first 100 feet and contained up another about 500. My core was as thin as possible (maybe 1~2 mm) and spawned the whole diameter maybe the next step is to decrease the diameter to control it a bit more but it sure helped poking any air pockets out

[dagabu]

I'm not surprised that that particular method doesn't work at first try. There is a "knack" to that method where the grated fuel should be softened first...

 

...Personally, I would steer clear of that method and re-think and go back to basics.

 

A few more things to add to this method:

1. Use small increments, you are pressing the motor in increments, not all at once like you would filling it with R-Candy Taffy.

2. Like Stix says, use it warm, 100F is fine, dont lit it get sticky.

3. Use the small grator teeth side of the grator, dont make large cheese noodles.

 

What exactly are the basics? Truth be told, there are none. This is not a traditional propellant, use the method that resonates with you, dont let my opinion or anybodies keep you from finding your way.

Edited April 17, 2017 by dagabu