248 replies to this topic

[portfire]

Hi folks.

I'v made some 1lb (not quite but close) tooling today.I rolled the tube first and after reading this again,i'd gotton mixed up,so the rocket is an 8oz in length with a 1lb ID ,so went with it and used lancaster's formula for core length/choke dimensions.The choke comes out at 9.5mm,is this about right for a rocket of this size???

Here are some pics






I'll be testing it tommorow (i'v put my wheel on hold,but will be making the frame this weekend).I haven't pressed the grain yet but the mix will be 63:25:12 (is this your own mix BrightStar??) milled for 30min + 20% fine(ish) charcoal.

I'v found making this tooling alot easier than the smaller stuff i'v made,only took around 1hr so if it works i'll be well pleased.

dean

[dr thrust]

hi dean, nice tooling i hope you dont mind me butting in,and good luck with the rocket(will it have a heading)but i think your core is a bit on the big side,thats if its a 3/4 id?really it sould be one third of the id so about 6mm thats what ive been useing anyway,youve got half the id which is fine for whistle! ps the charcoal gives a fantastic orange sparky tail but youve got to see it for yourself! chems

Edited by chris m, 10 February 2008 - 05:01 PM.

[portfire]

Yeah i did think it was on the big side,but on checking,i think it's ok.I'll quote from lancaster's book 'Fireworks Principles and Practice'.

"The choked rocket case is placed over a tapering hard steel spindle, which normally extends into the case three-fourths of its length excluding the choke.The diameter of the base of the spindle is about 1/12 of its length, and this should be the dimension of the rocket choke"

Here are the dimensions of my rocket.
Tube length-160mm
ID-19mm
Base of tube to start of nozzle-10mm
Nozzle thickness-10mm

This leaves 140mm left of the tube,so with what lancaster says, the spindle should extend 105mm into the tube from the top of the nozzle and the base of the spindle comes out at 8.75mm.This all on paper though and the way i make my spindles (electric drill,angle grinder) it comes out at..

Spindle length-101.50mm
Top of spindle-4.31mm
Base at top of nozzle-9.18mm
Base at bottom of nozzle-9.38mm

I'v also found this pic in my "pyro folder",which i think ProfHawking posted some time ago ?? so i'm not that far out.


P.S This rocket won't have a header (need to see if it flys first ),but my 15mm coreburners are quite consistent now and think there ready for a header

dean

[marble]

Looks nice, big core but if its too slow just make the mix faster

/ive got to get some tooling

[portfire]

Well here she is (no stick yet).The tube squashed while pressing (you can't see it,i rolled a layer of kraft around to tidy things up) and lost 20mm on the length. I did use a support slieve,so it was probably that the tube wasn't strong/thick? enough (it only been 4.5mm).Looks like i'll testing it tomorrow now,too wet and windy for my liking.





dean

Edited by portfire, 18 August 2007 - 05:08 PM.

[dr thrust]

Looks nice, big core but if its too slow just make the mix faster

/ive got to get some tooling

hi ,marble i think we are going to fall out i think its better to get as much fuel in there as you can ! so i use a 6mm brass tapered rod that goes to about 3mm at the top, faster mixes invite catos! and i know about that!

Edited by chris m, 18 August 2007 - 11:55 PM.

[Pretty green flames]

Portfire, have you gotten round to testing the rocket yet?

[BrightStar]

I haven't pressed the grain yet but the mix will be 63:25:12 (is this your own mix BrightStar??) milled for 30min + 20% fine(ish) charcoal.

Hi portfire - just spotted this as I have been away on hols... My own mix is 63:25:12 made with coarse hardwood garden charcoal chips, all milled together for about 90 mins. There is visibly some 20-40 mesh stuff left in there when done. This is just a lazy way getting a good mix of charcoal particle sizes for the tail, so I don't add any extra coarse stuff. I fear +20% on top of the 63:25:12 might make your mix a bit slow...

Karlfoxman posted a very similar method but with willow charcoal and its great stuff but very hot and very powerful - too much so for my everyday use.

[portfire]

Hi folks.

Portfire, have you gotten round to testing the rocket yet?

Believe it or not i haven't tested it yet (naughty i know,but it's been kept in a safe place).Having finally moved out two week ago and starting a new job,i'v been really! busy and when i'v had the chance it's always been too bloody windy,plus i'v had to find a new test site which i'v done (better than the old one) so hoping to test it this weekend.

Hi portfire - just spotted this as I have been away on hols... My own mix is 63:25:12 made with coarse hardwood garden charcoal chips, all milled together for about 90 mins. There is visibly some 20-40 mesh stuff left in there when done. This is just a lazy way getting a good mix of charcoal particle sizes for the tail, so I don't add any extra coarse stuff. I fear +20% on top of the 63:25:12 might make your mix a bit slow...

Karlfoxman posted a very similar method but with willow charcoal and its great stuff but very hot and very powerful - too much so for my everyday use.

I fear mine might be too quick.I milled the mix for 15mins then did a small powder test and its about as fast as the fuel for my 15mm coreburners,thats why i added 20% C mainly to slow it down,(I'll add though that i updated my mill before making this rocket and it's now running at around 90RPM,so have to alter milling times) but,as is the case in rocketry,its trial and error,so we'll see when i test it.

dean

[portfire]

Well!! What a anticlimax.

I finally tested the rocket (after the wind dropped) sunday night and it didn't go quite as planned but,as we know,we learn more from failure than we do getting something right the first time.

Here's the vid
http://video.google....=...55&hl=en-GB

And some after pics off the endplug




At first it did look like it lifted but,only slightly before the endplug blew.After watching the vid a few times it looks like the endplug blew almost instantly.

Rather than just fusing with visco (which i think i should've done) i inserted a small peace of QM into the nozzle and my guess is that in using QM,it instantly ignited the core causing an initial spike in pressure causing the endplug to blow or, (i say this because you can hear the grain burn away after it blew) could it have just been that the fuel too quick?


One more thing to add.Due to the case squashing while pressing, there was no delay part to the grain so,it was basically just the core w/endplug,could this have been the problem??


dean

[BrightStar]

Well!! What a anticlimax.

Yup, sorry... Expect at least 3 or 4 more tries before it works. That's just the way it is with rockets I'm afraid

Rather than just fusing with visco (which i think i should've done) i inserted a small peace of QM into the nozzle and my guess is that in using QM,it instantly ignited the core causing an initial spike in pressure causing the endplug to blow or, (i say this because you can hear the grain burn away after it blew) could it have just been that the fuel too quick?
One more thing to add.Due to the case squashing while pressing, there was no delay part to the grain so,it was basically just the core w/endplug,could this have been the problem??
dean

I tried fusing with 3.5mm thick 10cm/s 'visquick' in the past and it always CATOd, so your fusing might be a problem. Try taking a length of 1/16" hot visco (the ukvisco stuff is good) and bending it over 5mm from the end. Push this up about 1" into the fuel grain - it should stay in place quite firmly. No CATOs yet with this method...

If you were using a slow burning charcoal, its unlikely that your fuel was too quick. I can't comment on the pressing - so far I just ram with a big mallet in many small increments.

Good luck for the next attempt

[sasman]

I think the secret of making rockets is using a Press?.Portfire do you use a support sleeve? ..I have just started making a few rockets using a press and a support sleeve & have found its very hard to get a CATO!..You dont need an end plug either if you press it hard enough.

The way i make test rockets is very simple... I simply press in a clay plug about 4 cm thick(the nozzle) then add my fuel in small increments...press the fuel then i always tap the excess powder out of the tube.. then i add fuel then press.... until i have the desired grain length.. then if you wish you can add an clay end plug ..I then simply drill the core out with a sharp drill bit.. Drill the core manually with your fingers!! dont use an electric drill or you may get to much friction and ignition?....

I find the cores drill very easy but i do use a drill press while i turn the chuck by hand...The core diameter i use is roughly 1/3 the diameter of the tube..i then drill about halfway through the length of the fuel grain...Every rocket i have made this way has flown...always to a good height..I can post a few videos of some of my test rockets if you are intrested..

This gives you a very rough ballpark figure but i have not yet had a CATO..You can then experiment using larger diameter drill bit or deeper core...Using 60:30:10 screened (not ball milled).. i could not get it to CATO...I did get a CATO when using straight BP and the core was drilled very deep nearly 3/4 the length of the core...But if i used fuel that fast they fly way to fast and go way to high..

The only reason why i dont get a CATO must because i press my rockets? hard?....Making rockets fly using a press + suport sleeve is very easy...using the above method...Once you have got the core depth & diameter .. i then use my lathe to make up the proper tooling.. so that you dont need to risk drilling the core...

You can knock up a few rockets drill the cores about half way(while in your workshop) .. then take a few of them to your test site fire one and then if its to slow or dont go high enough drill out the core by hand..You dont have to go back home just make the adjustments on site...easy..DONT!! add a header until you make them consitsntly fly good...

Hope that helps..

[Jerronimo]

Yes of course you can use a press, but you don't need it for making good rockets.
What you do need is some good rocket tooling and thick walled parallel wound tubes.
Greg from www.pyrotooling.com (new site under construction) makes some very nice tooling for a fair price.

Never change more than one variable at a time.
Begin with a standard rocket formula like 60:30:10 kno3/C/S mill it for half a hour and rice it trough a window screen, don't ram to much powder at a time use a max of the I.D. rammed,so if you're making a one pound rocket don't ram more then 3/4 inch after compression.
Use betonite clay or even better some ground up cheap cat litter for nozzle material.
make a few rockets and test them, if they CATO simply tone down the formula with charcoal, and proceed until they don't CATO.

[portfire]

Thanx for the replies guys,much appreciated.

I guess i was expecting to much BrightStar. I did have my doubts as one would but, going on the success i'v had with my 15mm coreburners and all of them working pretty well,(not one CATO,just a "chuffing" problem which is sorted now) i would have given it a 80% chance of working. Oh! how i was wrong.

With regards to using QM,i don't know what i was thinking because all i did was to add another variable,so was i right in thinking that it caused a spike in pressure??? I used lumpwood charcoal in the mix it's self and added after.I'v always used lumpwood for all my "charcoal needs" with good results but,i'v finally got some willow so i will try karlfoxman's fuel on the next one.

sasman.I do use a press and did use a support sleeve,(if you have any tips&tricks with regards to support sleeves it would be much appreciated) the only problem i can think of is my tube wasn't thick enough.

The first coreburner i made i did drill the core (i'v only drilled 2 cores) and to be honest i didn't like it at all so,made the tooling (at the top of this page there's pics of the tooling for the rocket in question) for 10&15mm rockets then,just adjust the fuel to suit and i'v had good results up until now.

I can post a few videos of some of my test rockets if you are intrested..

Yeah,it would be much appreciated if you dont mind.

I'll add though...i wouldn't put headers on my rockets until i'v got them consistent which my 15mm coreburners are and, are ready for headers.


P.S. Happy birthday Creepin_pyro

Edited by portfire, 05 September 2007 - 09:23 PM.

[portfire]

Now,having just moved i have to build a new workshop (a dedicated workshop not half pyro half bloody garage)so pyro's going to be slow for a month or two but,on the upside,my old "workshop" is still available ( pyromaniac303 knows the situation)but can't get in there that often.This weekend i can and so,going to make up some test rockets.(i'm going to save the wheel for the first project in my new workshop)

Anyway,i'm going to make another 19mm using Karlfoxman's fuel (90min milling seems to much for me but will try it).I'm also going to fuse the rocket with visco as BrightStar say's.I will roll the tube today which i will dry on the radiator overnight (rad will be on low as not to dry it too fast) and leave it in the workshop until sunday (i'll be charging/firing then[weather permitting])

In the mean time i have some tubes for my 15mm coreburners so going to make 1-2 test rockets.Since my mill is running as it should,these rockets will be to get an idea of mill time,thinking 30mins.

Once thats sorted there ready for headers.Now what effect should i go for??I'm thinking simple to start,where the stars just "pop out".I don't want to go for color yet,so a charcoal star,TT or willow will look quite nice i think

dean