mikeee Posted June 19, 2015 Posted June 19, 2015 Webski, http://www.flashnet.dk/rts/ You might have this site already, but this tool works pretty good for spindle profiles based on fuel and motor types.
stix Posted June 20, 2015 Posted June 20, 2015 ... I'm really trying to dial in my dry mix sugar comp.and would really like some info on spindle size and nozzles so get close to right without all the trial and error.I'm making 5/8 and 3/4 rockets. thanks for your help As pointed out by mikeee, the way you make your fuel ie, pre-milling and pressure will vary from person to person. My brother swears by the "dry powder mix method" and from what I've seen, it works very well and burns more consistently than any of my "melted" varieties - This has always been a good source of learning and competition between us. The key points with the dry powder method is to ensure that you pre-mill your KNSU very finely - he ball mills his in 3 kilo batches over 24hrs then presses the motors using a heavy duty screw press in smallish increments (something like 10 increments per 3 inch length). Unfortunately I don't know what pressure, that was never measured but it was enough that fuel became as hard as rock and never became hygroscopic. For the record, these are the specs: Internal/Core burner -Casing ID: 3/4 inchNozzle Diameter: 1/4 inchFuel Core: 1/4 inch (along the entire length)Fuel Length: 3 inchesFuel Density: 1.6 grams per cubic cm. That motor produces as specific impulse of around 100 seconds and has been reproduced reliably. Start smaller and increase the length. It's always good when experimenting to be able to measure the results. A simple set of kitchen scales, video and a bit of math will enable you to determine the performance you are getting. Cheers.
Rocketier Posted June 20, 2015 Posted June 20, 2015 (edited) That motor produces as specific impulse of around 100 seconds and has been reproduced reliably. Stix! Are you heading for the moon? 3/4" = 19.05mmFor the core I would use an opening about 9.5mm and a length about 140mm this to start of with. When cato just shorten the spindle bit by bit but i expect there is no need to do that. Make shure to make the spindle tappert. For ideal design use the rts skether mentioned by Mikee. Sugar has an higher peakpuls then bp but as far as I tested that BP related toolsizes are usefull. 5/8" = 15.875mmFor the core I would use an opening about 8mm and a length about 120mm this to start of with. Make shure to make the spindle tappert..When using the rts skether for whistle I think it shows spindle lenght on the save site. For more power just switch after design it in whistle mode to custom mode. Then adjust the spindle length for the longer gaining more power. Edited June 20, 2015 by Rocketier
stix Posted June 20, 2015 Posted June 20, 2015 (edited) Stix! Are you heading for the moon? Well not yet and highly unlikely with a sugar rocket. 100 seconds in this instance doesn't refer to the burn time. The unit of measure for specific impulse (Isp) is seconds. Which is derived from the total impulse of the motor / the fuel weight. The total impulse being average thrust x burn time. It's an easy way to tell if you're getting the best out of your fuel. With KNSU you can reach an Isp of 130, perhaps more - Black powder is around 80, the space shuttle srb's around 250. The advantage with Isp being in seconds is that it doesn't matter what base unit of mass is used ie. kilo's, pounds, elephant's balls etc. If you're using knsu as the fuel and were using "bee's dicks" as your unit of mass and told me that you measure around 100 seconds, that's all I would need to know. It's universally understood, and I would say "Not too bad Rocketier". If you told me you were getting around 60 with knsu, I would be telling you that you need go back to the drawing board and look at the design of your motor and/or your fuel making method. Simple measuring equipment and basic math can tell you a lot. Cheers. Edited June 20, 2015 by stix
Rocketier Posted June 20, 2015 Posted June 20, 2015 (edited) Fun Stix first I tought you made a typo. But thanks I need some reading up to do. I'am never using calculations on the motors I make. It would be need to do someting like that. Found some need info on the Isp stuf on wiki. Link What i did long time ago is put some motors on an weighingscale and film the readout of the display and motor exhaust. That was fun to do but I don't want to irritate the neighbours. Edited June 20, 2015 by Rocketier
stix Posted June 21, 2015 Posted June 21, 2015 Fun Stix first I tought you made a typo. But thanks I need some reading up to do. I'am never using calculations on the motors I make. It would be need to do someting like that. Found some need info on the Isp stuf on wiki. Link What i did long time ago is put some motors on an weighingscale and film the readout of the display and motor exhaust. That was fun to do but I don't want to irritate the neighbours. I find that wiki link a bit confusing - but please don't ask me to explain it any better. I got my original info from a book many years ago and can't remember the exact reasoning, but have always relied on the specific impulse number as very important when doing static tests. +1 about not wanting to annoy the neighbours - a 3/4" ID (E class) motor can make a hell of a noise . Someone on these forums recently suggested a "silencer" type device for a mortar when shooting shells - made from chicken wire and non-combustable material. I wonder if this sort of thing could be employed for a thrust meter? Cheers.
webski Posted June 22, 2015 Posted June 22, 2015 Some nice info and a great starting resource (rocket sketcher).I just got back from the test range (gravel pit near my cabin) today and I"m thrilled with with the results....NO CATOS !Some really good flights,whistle headers worked great. 3 sized rockets:1/2 x 3" with 5/32 x 1" core5/8 x 4" with 3/16 x 1.5" core3/4 x 4.5 with 1/4 x 1.5 core all used the same fuel dry mixed 65/35 KnSu. (that had been ball milled prior to mixing) and 2% RIO added.all were hand rammed with good consistancy.(Hopefully I can duplicate these results) I realize now that my cores were a bit skimpy as per Rocket Sketcher calculations ( used whistle calculations),but this worked for me and now I can fine tune and try to add some interesting headers Your help and insight was very timely useful thanks, Mikee, Stix and Rocketeer
Rocketier Posted June 22, 2015 Posted June 22, 2015 (edited) A film or it didn't happen! Edited June 22, 2015 by Rocketier
stix Posted June 22, 2015 Posted June 22, 2015 (edited) A film or it didn't happen! Ok, I know this wasn't directed at myself but... A test from about 2 months back. A bit of nozzle erosion but not too bad overall. https://www.youtube.com/watch?v=SNAJ4a01Guo&feature=youtu.be Cheers. [EDIT] The specs don't look very clear on the video, so image attached. Edited June 22, 2015 by stix
webski Posted June 22, 2015 Posted June 22, 2015 That's pretty impressive.how do you get or measure those stats ? comparing fuels.5/8 x 4' rocket, 5/16 x 1.25 " core and nozzle hot BPwhistle mixKnSu mix which would provide the most thrust ?what would the approx numbers be, assuming all were optimal mixes ? this rocket science is pretty cool, even tho I don't understand half of it !getting better
mikeee Posted June 22, 2015 Posted June 22, 2015 Hot Whistle fuel will test the strength of most rocket tubes including the old NEPT tubes.But I have seen the other fuels made properly destroy motor tubes when made with hot mixes. Also depends on how fast you want to get from point A to point B.The acme test stands are good tools if you want to measure the energy output of your fuels.There are a number of rocket motor makers that post test results for different fuels if you want to study the thrust curves.
stix Posted June 23, 2015 Posted June 23, 2015 (edited) That's pretty impressive.how do you get or measure those stats ? comparing fuels.5/8 x 4' rocket, 5/16 x 1.25 " core and nozzle hot BPwhistle mixKnSu mix which would provide the most thrust ?what would the approx numbers be, assuming all were optimal mixes ? this rocket science is pretty cool, even tho I don't understand half of it !getting better The thrust was measured on a thrust meter (load cell) at 100 samples per second with 1 gram resolution. The data was imported into a software program I wrote. The calculations are basic math, ie. Total Impulse = Ave. Thrust x Time, which is often expressed in Newton Seconds. These calculations can be found pretty easily. The motor in the video didn't burn as I would have liked. It should have had increasing thrust, then a quick finish. Like the image attached, which had a max. thrust of around 15.5 kilos (34lbs) It was done almost 5yrs ago - time flies... I don't know much about whistle mix, but KNSU fuel can have a specific impulse as high as 130. Hot black powder 80. In other words, theoretically - for the same amount of fuel, knsu will outperform bp by approx. 50%. In regard to well made rocket motors that is. There's no getting around that fact. Cheers. [EDIT] btw. The fuel I'm using isn't strictly KNSU - I use Dextrose/Glucose powder (KNDX) which is pretty much the same result, but melts lower @ 146C. Edited June 23, 2015 by stix
stix Posted June 24, 2015 Posted June 24, 2015 What is the + CD3 in the formula ? Cheers webski - I've posted the answer here:http://www.amateurpyro.com/forums/topic/10910-more-powerful-sugar-rockets/?p=145595
deer Posted June 24, 2015 Posted June 24, 2015 My brother swears by the "dry powder mix method" and from what I've seen, it works very well and burns more consistently Does he use any binders? OTOH I imagine if it's ground so finely and under those forces the sugar and humidity would make it stick as is.
stix Posted June 25, 2015 Posted June 25, 2015 Does he use any binders? OTOH I imagine if it's ground so finely and under those forces the sugar and humidity would make it stick as is. No he doesn't use any binders. I had that same discussion with him some time back and came we to the same conclusion as yourself - the natural humidity and slight moisture already in the mix is enough to make it stick together and become rock hard under a lot of pressure. Cheers.
kramrocket Posted August 31, 2016 Posted August 31, 2016 No he doesn't use any binders. I had that same discussion with him some time back and came we to the same conclusion as yourself - the natural humidity and slight moisture already in the mix is enough to make it stick together and become rock hard under a lot of pressure. Cheers. Yep, didn't use any binders back then, just a ratio of 65% Pot. Nitrate and 35% sugar, but have been experimenting with swapping 1% of the sugar for paraffin wax lately. I was hoping for a less dusty and easier to compress powder. The results are that the fuel is tougher when pressed. Density is 1.81 grams/cubic cm. A pressed disc of 19.6 mm diam by 5mm thick cannot be snapped in half by hand, I had to use a vice to hold it and two thumbs to snap it !!!
stix Posted August 31, 2016 Posted August 31, 2016 How does it burn with the addition of the parafin wax - any noticeable unburnt material?
Redrocketman Posted August 31, 2016 Posted August 31, 2016 Coping Johnny 61616 is where I 1st started!!! That tutorial is the real deal for a good start point for beginning your sugar rocket experementation. My very 1st one broke the cloud barrier at least 2000ft up in around 2 seconds!! ( no lie, got it on video, geez the old lady shit herself!!! ) had 2% RIO. I don't mean to sound like a gumby, but I think the poor guy is going to get a bit overwhelmed by some info provided, yes, it's all very true & correct, but one thing at a time. To start with, buy a cheap exercise book and record everything you do. Weights, ratios, rocket dimensions. Then you can narrow down what works best by trial and error. If you don't, after time you'll never remember the finer details of what made that one fly better than the other. After your having regular successful flights, move to the Nakka Rocketry site if you want to move to more comprehensive motors, it is the gospel of rocketry. Good luck & be safe & read read read!! (Ps, as I said, I'm not at all disagreeing with any previous posts, just complicated for someone starting out I think )
stix Posted September 1, 2016 Posted September 1, 2016 I think the level of info in this thread is about right (if you minus off the pink undies episode) although even with that, there is some knowledge to be gained - there was no reason for me to buy them afterall If first time rocket enthusiasts are put off by tecnichnical details then Youtube beckons. Those who want more will seek out the likes of Nakka and others. This forum is perhaps in-between. Most of the people who participate regularly in this 'Rocketry' forum have at least sought a better understanding, and there are many that have a great deal of info and experience. Newcomers who are serious, ask questions and get good answers. Unfortunately the lazy ones wander off back to youtube. TRIM_20141214_004043.mp4 So this is the rocket that i made. Can sombody tell me why i did not fly? I'm just happy that I had an excuse to use my book cover again.
kramrocket Posted September 1, 2016 Posted September 1, 2016 (edited) How does it burn with the addition of the parafin wax - any noticeable unburnt material? Burns nice and clean, no noticeable difference at all compared with the no-wax blend... I was hoping for an easier to press/ less dusty powder, but it's not noticeably any different than using no wax. Also, it seems that if ball milled for too long (many hours) that the powder begins to compress/cake here and there, so maybe the mill needs to be more aggressive. However the result is certainly a tougher and denser fuel, I could only get a density of about 1.76 grams /cubic cm without the wax but I got 1.81 with the wax, so that's interesting... Forgot to ask, what is considered to be a normal density with a 65/35 melted KNSU ??? Edited September 1, 2016 by kramrocket
stix Posted September 1, 2016 Posted September 1, 2016 (edited) . . . I could only get a density of about 1.76 grams /cubic cm without the wax but I got 1.81 with the wax, so that's interesting... Forgot to ask, what is considered to be a normal density with a 65/35 melted KNSU ??? Well, your density is better than any melted version I've ever made. My average is around 1.72. So that's good for your "powder pressed" method. It would be good if you knew exactly what pressure you are using. Time to implement a pressure gauge Kram? I'd also be very interested to know what density others get with their sugar fuel (melted or dry). Perhaps a bit too technical for some? Not that hard to work out though. Edited September 1, 2016 by stix
Redrocketman Posted September 1, 2016 Posted September 1, 2016 Dunno about what density I gained, but yesterday I performed a nozzle vs nozzle less test, using two motors of same dimensions, same weight fuel, identical, bar one nozzle less, and the other nozzled. 3/4" X 5.5". 8mm core ( excuse my mixing imperial & metric!! ). 7.8mm nozzle. Both fitted in a 1.5" X 60" kit rocket. The nozzle less motor provided one of the funniest videos I've ever seen. It just had enough thrust to push the rocket off the rail, just out of the top of the screen ( it got maybe 10m up!!! ) turns and plonks nose 1st into the soft ground, and nearly stabbed a chook!!!The nozzled motor is a totally different kettle of fish. It launched so quickly I couldn't keep up with the camera ( & sounded like an F-1 11 on take off!! ) and popped the chute perfectly at around 2000ft. Not bad for a 50c motor. I'll make some 8" jobs today, they should burn a tad longer and get up there. I won't even go into the K class scratch build, that was simply scary...... ( earmuffs! ) Long and short, as I've said, I'm no uni student or genius in any way, but I CAN make sugar motors that work - well. I can see nozzle less motors defy ave their place, especially in pyrotechnics, but for rocketry, I can't see them being of any benefit when trying to lift heavy loads. They just don't have the thrust required ( for my applications anyway ) and burn way to slow even with burn modifiers added. I wish I could re size these vids so I could show u, but my iPad won't.
Redrocketman Posted September 1, 2016 Posted September 1, 2016 Stix, sorry to sound dumb, but how do u determine fuel density? I've still got sooooo much to learn....
NeighborJ Posted September 1, 2016 Posted September 1, 2016 Hi Red, the density can be found by weighing the fuel grain and then calculating the volume. Or you could just build a small box 10x10x1 cm fill it with fuel and divide the weight by 100. It gets more accurate with larger batches. Also the nozzleless motors will need to be much longer to compensate for the slow burn rate. They have the ability to scream off the pad much faster than a nozzled motor but it has a regressive burn.
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