Newbe rocket test/fail

[jallafish]

Tested my first rocket engine, and here it is: https://m.youtube.com/watch?v=aZ8oMWyNvxo

 

I dont know why it happen, so any tip?

 

60/40 pvc 40 shedule and kitty litter nozzle.

 

My only guess: too small hole in the nozzle

[Rocketier]

It could be a bad consistency of the fuel. Is it well mixed? I think the fuel is also not solid enough. There might be some gaps in the load.
KNO3 Sugar has a high puls. A standard BP rocket has a nozzle opening of 1/2 the tube width. Start of with that in mind. Also try to make the fuel more solid. How is your fuel prepared?

Edited April 30, 2015 by Rocketier

[GMetcalf]

It does very much look like the fuel isn't burning consistently. What exactly is the fuel and how did you put it into the motor? Is it rammed, cast, pressed, etc?

Without knowing what the fuel was I would say that looked a lot like a mix containing Aluminium passing through too small a nozzle and causing it to periodically become blocked with slag. I've had the very same problems with fountains when I was starting out...

[deer]

I'd try 65:35. Too much sugar can cause extra dross that can block nozzle.

As others pointed out, consistency / binding can cause this too. Loose pieces of fuel separating and getting stuck in core / nozzle until they burn down.

 

Also, how long after preparation this was? If not sealed, they go bad quite fast. Humid rcandy can smoulder very slowly or burn erratically during the wetter parts of it.

[FlaMtnBkr]

You haven't given us much info at all. How about some actual details.

 

And you are lucky it didn't fail in a different way or you and your friend would probably be at the hospital having pieces of PVC picked out of you. Being that close testing something new to you and made of PVC, you could easily be blind right now if that clogged nozzle, or many other possibilities, caused the motor to blow.

 

If you aren't going to use cardboard tubes then put up a blast shield or get a lot further away. You should be using cardboard and be further away.

[Arthur]

If you give us a full set of dimensions, and the grain structure, then we may be able to help you better.

 

If you want to fire things close to buildings and property be very sure they are tested perfect devices. Damaging property usually brings this hobby into disrepute, and your wallet to additional stress!

[jallafish]

Sorry for not answering.... been verry busy. The fuel i used was mixed in to boiling water, so all of the powdered mix dissolved. Then i boiled out the water. I did not caramelise the mix.

 

As Rocketier sad, I think it may be some gaps in the load.

 

The di. in the nozzle hole was 8 mm (0.32 inches) and the outer diameter of the tube was 20 cm (7,87 inches). The nozzle hole is probably too small to.

 

Ty for answers.

 

And Arthur, don't worry, I will only test it at sea

[Arthur]

That seems like a very large rocket case, and a very small nozzle.

[jallafish]

Woops... 2.5 cm (0.98 inches) outer diameter.

 

Too tired last night

Edited May 2, 2015 by jallafish

[Rocketier]

Hey Jf, I watched your movie again. The tube you use is Hostalite I think. This tube does not splinter and is a nice tube for engines. The inner diameter I expect it to be 22mm. That tube is impactproof but if it is real PVC do not use it anymore please, I attached an example from a tool you can make, I designed for you with the rockettoolsketcher.

Also noticed that there was no core in the fuel.

 

Try to make the tooling and be sure to make a good sleeve to support the tubes while ram or better pressing.

Best thing to do is make the kittylitter nozzle about 25mm, then on top of that fill the tube with fuel at a max of 7cm long. On top of that a kittylitter clay plug about 25mm. Make sure that all the stuf is compact without gaps. After removing the spindle gently drill a hole (core) in the fuel about 6cm into the fuel. You can use a 8mm drill to do so. Please use the slow speed to no speed on the drill. No friction! Then test again. Also use some more distance, a longer fuse and stick the motor upsidedown in the ground. It definitely will fly away when you do not fix it firmly.

 

As an example Some tooling I made for rockets.

 

Good luck an show us the next test.

rts tool.pdf

Edited May 3, 2015 by Rocketier

[jallafish]

Thanks Roketier! Realy helps me out . Just one question: why not use real pvc? Is it becouse the toxic gass? Or is it other things? (Don't take me wrong, I don't like inhaling toxic gass..)

 

And upgrading my tools is a good idea the tool I made for this one was just a realy simple thing made fast out of a nylon cylinder with my lathe. Have to make som real shit with steel...

 

Will probably make and test a new engine tomorrow, and maby send one to the skyes

Edited May 2, 2015 by jallafish

[Rocketier]

Just wack it with a hammer and you'll know. PVC will shatter to peaces when it comes to a cato. The peaces will hurt you or worse somebody else. Some people say that you have to use cartboard tubes because of environmental issues but I think thats hypocrite when you also do burn of heavy metals like barium or lead. I always try to recover my devices so...... Invest some time or spend some money on tools it will increase your results for the better. Looking forward to the next movie.

Edited May 3, 2015 by Rocketier

[deer]

PVC explodes with sharp shrapnel, paper just breaks down in small flakes, bursts open.

 

BTW Just had my first 20mm PVC fly (3rd rocket so far, first two failed to generate enough thrust). First impression - add means of locating it (siren, bright colour tail, rf beacon). Although it seems small it flew high and far, couldn't even see when the motor went out.. actually so far that I'm thinking I need bigger test site. Where do you usually test yours?

 

Also, my test:

https://www.youtube.com/watch?v=6S_qhtKiIe0

 

EDIT: corrected youtube embedding, typo's.

Edited May 3, 2015 by deer

[mikeee]

A longer fuse will allow more time to safely exit the launch site. When a pvc tube ruptures you don't want to be anywhere close to the motor when it catos. The pvc may work for R-candy fuel but when you start using higher energy fuels the motors tend to cato more often when you start testing new fuels until you get the process dialed in. You can always place the rocket behind a solid barrier or stand behind a solid barrier after you light the fuse. Safety glasses are a worth while investment when working around high energy materials, you run the risk of loosing your eye site from a catos if you are too close when it goes off. Most motors will cato on the initial ignition and within several feet of lifting off. Hearing protection is another valid consideration when launching rockets, I have had (2) occasions when motors have cato'ed and had ear drums ruptured from the shock wave. One of these was a larger BP motor the other was a whistle motor.

[jallafish]

Ahh. no CATOs yet, but I better be prepared! No test today, boat trip with family. I will probably make one tomorrow, but I don't think I have time to test it, busy all the day....

[MrB]

Some people say that you have to use cartboard tubes because of environmental issues but I think thats hypocrite when you also do burn of heavy metals like barium or lead.

Ah, so, since we cant be 100% environmentally friendly, we should just light uranium on fire, to heat our houses? Personally i try to keep pollution to a bare minimum of what has to be done, to achieve an expected goal. So i use wood for fire, and uranium in reactors. It means the radioactive particles that would be going up my chimney, and end up in the environment remains in a relatively easy to handle package. I do the same thing when i fill my car up, i use unleaded gasoline, or, low sulfur / no sulfur diesel. And again, the same applies with fireworks. I use biodegradable paper over PVC tubing as casings. Some people swear by the yellow endcap, i, make paper tubes, and cap them with bentonite. I don't despise them, but i admit, i do wish they would use a biodegradable alternative.

B!

[Rocketier]

Hey dude, I said: "I always try to recover my devices so......" That's my contribute that my stuff will not pollute the earth for ages.

Good for you that you do your part but stay from the uranium stuf. It's bad to inhale they say.

Edited May 5, 2015 by Rocketier

[deer]

I'd love to use paper, but it's pain to get / make. I get 3 meters of PVC for something like 2.50 EUR 5 minute ride away, while similar paper tube goes for 27+ EUR and must be shipped. I'm considering rolling my own tubes though.. if I find cheap paper source.

 

Also, I wanted to ask. What point is there in using the syrup, when my rcandy obviously caramelizes anyway. And it does so, even before boiling (so the temp can't get any lower). Should I try different syrup or that fructose+dextrose recipe instead, or something else might be wrong?

[GMetcalf]

It's a pain for everyone to roll their own tubes, but it's just another important part of pyrotechnics.

In terms of paper, I found the cheapest (and easiest) source for rolling tubes is wallpaper lining paper. It's nice and thick and pretty strong, so you need less turns than you would Virgin craft to make the same thickness tubes. I don't know where you live deer, but here in the UK all major hardware/DIY shops sell the stuff! Couple that with some nice thick wallpaper paste mixed with PVA glue and you've got rock solid tubes in no time at all!

 

Are you starting off with your ingredients in powder form? Dissolving it first in water then boiling down the water might help make fuel that isn't caramelised, at least that's how I make my R-Candy fuel and it doesn't caramelise.

[dagabu]

I'd love to use paper, but it's pain to get / make. I get 3 meters of PVC for something like 2.50 EUR 5 minute ride away, while similar paper tube goes for 27+ EUR and must be shipped. I'm considering rolling my own tubes though.. if I find cheap paper source.

 

Also, I wanted to ask. What point is there in using the syrup, when my rcandy obviously caramelizes anyway. And it does so, even before boiling (so the temp can't get any lower). Should I try different syrup or that fructose+dextrose recipe instead, or something else might be wrong?

 

 

OK, lets address the PVC pipe issue once and for all then lets move on to making some working rockets?

 

PVC pipe is somewhat frangible in that it *does not distort greatly before it breaks and does so along the lines of the greatest stress. This causes sharp edges and long slender pieces of PVC missile to be ejected with some force when a CATO causes a gross over pressure. When this happens, persons that are too close can get hurt or killed.

 

PVC is also a "plastic" and distorts greatly when heated to relatively low temperatures of *less than 100°C. End burners and R-candy motors with nozzles fall victim to heat often in PVC and blow out the nozzle but since it is so cheap, n00bs use it often and much of the time with less than stellar results.

 

Ultimately the question becomes one of "why?" use it? My personal view is two fold:

1. Price & availability

2. Ignorance

 

Here is the deal, the first one of price and availability is a myth. White glue and soda/beer cardboard containers make excellent tubes, the cardboard is made from a high percentage of virgin pulp and is tempered a bit for strength. Each tube you make at home will be a fraction of the cost of the PVC tube. The second part is easily solvable as well but as even shown repeatedly here in this thread, stubbornness trumps knowledge every time. Just read this quote, "I'd love to use paper, but it's pain to get / make."

 

Nonsense! There is no place on the planet that does not have some sort of paper, virgin kraft is among the best but even copy paper is suitable if glued properly.

 

 

*PVC pipe becomes plastic at 92°C

-PVC.ORG

 

*PVC Threaded Pipe Tolerances of 120°F MAX, THE MAXIMUM SERVICE TEMPERATURE FOR PVC IS 140°F.

-Georg Fischer Harvel

 

 

Now that that is done, JALLAFISH, could you draw us a sketch of your tooling?

[deer]

Ahh.. so you just glue whatever cardboard you can get your hands on? Good thing I’ve been collecting some already . Any specific setup or just glue them around something cylindrical and compress with hose fasteners or something? What is "white glue", some sort of brand? I was thinking of using PVA, but which one? Cheapest, D2, D3? Can you dilute it to use brush and economy it?

Because several guides online used store purchased craft paper in rolls (1.5mx50m costs ~5eur here, very thin), that were fed in diy rolling / glueing machines, I assumed using random / thick papers is bad.

 

As for the dissolving, that's what I basically do:

https://www.youtube.com/watch?v=if6VbQ0rmgQ

(In this case I used 142g of water)

Anyway, I plan on switching to BP as soon as I finish my mill and press

 

P.S. I must apologize to the author for kinda stealing his topic, but I think these questions are newbie rocket related and will be of good use to the OP too.

[fosva]

hello guys i'm not able to create a new topic, so could you please give me some suggestions about this?

 

 

i am using PVC 1" x 5" for the engine, this video shows the engine just like that, we lost sight of the engine for at least 5 seconds, sorry for not a longer video but i was really excited https://www.youtube.com/watch?v=008FjBOyCNw

 

i made a cone of cardboard also the fins (the entire body is the engine). It is a r-candy rocket but i am not cooking anything, so any suggestions for stability issues? https://www.youtube.com/watch?v=Wg3k9bFMTDA

 

 

 

 

also i tried doing a bigger rocket (the engine is still the same) but is not launching as it should be any material suggestions for bodytube (also for a proper ejection charge) cause we are using PVC 1 1/2 the cone is made of plaster, and the total weight is 400 grs (with an aluminiun washer which keeps the engine in place, a parachute of standard cloth) - https://www.youtube.com/watch?v=-yLJaU23Do8

 

 

Btw. Is it really necesary to do a hole trough the entire engine reaching till the top of the fuel and so the engine can deploy? or Is just necessary untill it reaches the bottom of the fuel?

 

PS. Sorry for my bad english is not my native language

Edited May 6, 2015 by fosva

[Rocketier]

Look at this video where a few simple rocket balancing is explaned. It pinpoints a few basic principles.

 

Edited May 6, 2015 by Rocketier

[GMetcalf]

deer:

You want to use paper which will sort of hold its shape when wet so it won't fall apart when rolling it. Virgin Kraft is good for this and so is most paper (except something like newspaper). Personally I like to use rather thick wallpaper lining paper (used to line walls to make the surface smooth before sticking up your fancy wallpapers). This is purely to save on rolling time... The thicker the paper, the less turns you have to do to get a tube of the same thickness. There is of course a limit to this though!

White glue and PVA are the same thing. When it comes to glue for tubes though, you need something which will dry harder than PVA. If you've ever seen PVA glue dry solid, it becomes a rubbery mass which is very flexible. This is great for sticking two bits of paper together but isn't very stiff. So you need to add something to the PVA to increase the amount of solid content in the glue so when it dries, it dries stiffer and gives you harder tubes. The best way I've found to do this is to use wallpaper paste, dissolved in far less water than suggested on the box so it forms a thick, jelly-like mixture, then add some PVA to that so you get the best of both worlds. Stiffness from the wallpaper paste and stickiness from the PVA.

 

fosva:

Where is the balance point of your rocket? From the smaller rocket test, it looks like the balance point is above the nozzle hence it's flipping and not flying straight.

Talking about the 'hole through the engine' I'm assuming you mean the core through the fuel? It is not necessary to have the core through the entirety of the fuel grain, but the longer the core, the more surface area is exposed to burn and hence the more thrust will be produced by the engine.

[jallafish]

Hay again. Finaly the rain has stopped ☺. Soo bad wather the last week. Still too much wind to test my rockets, so I tested an engin instead. Successful this time 😃! Ty for the advice.

 

Video: https://m.youtube.com/watch?v=AnsfrUPmqa4