248 replies to this topic

[Pretty green flames]

Almost there portfire Only thing i'd suggest would be adding 15% charcoal instead of 20%, 5% made a big difference with my rockets, 5% = CATO, 10% = An excelent flight.

Cheers

[dr thrust]

just tried another "brock" 13,7,2 very good! this guy knows what he was talking about had a longer stick this time about 55inch i thought it would be to heavy, boy i was wrong! it shot off no prob! just tried out the 65,25,10 ball milled for one hour and viseline riced though a kitchen seive!(its all ive got ) and i have to say its the best yet!there was no dust whilst ramming,it pours down my funnel a treat,not getting clogged up like bp in fact there was no mess! the rocket was a 1lb,er with a 30g flash 3"shell and boy it went high! good stuff thanks jerronimo hmm i wonder what would happen if you added more vaseline? say 5%, 2% seemed a bit dry?

Edited by chris m, 01 October 2007 - 10:11 PM.

[Jerronimo]

Hey, nice to hear that vaseline propellant worked very well for you, I agree it's realy nice to work with.
When ricing normal rocket comp with just water you still get dust everywhere when ramming.
Why do you think your comp is to dry ? who cares as long as it works.

I heard you can add up to 5 or 6 % of vaseline before the rocket starts chuffing, ofcourse adding more will slow down the fuel.
There's no point in adding more unless you're getting cato's, or your rockets are going to high .

[dr thrust]

hi just thought that 5% would help the grain in binding together better when ramming?

[portfire]

Hi folks.Well my first 15mm w/header is ready to go I did get a little over enthusiastic with the header

Here's some build pics




And the finished rocket



I'v left my notes in the "workshop" on weights for things like burst,stars etc.The stars are 6mm(ish) chrys#6 and the burst is just 10-20 mesh fast willow B.P.There's no booster due to the fact that i haven't experimented with whistle yet, and not going near 70/30 flash at this stage.I have made nitrate flash but doubt that will be upto the job.

Pasting was alot harder that i expected,i did start with wheat paste,did one layer and gave up (i was getting everywhere ) and ended up using 10mm strips of gummed tape.4 layers in total BTW

The rocket is my standard 15mm w/10mm delay (nothing special,just the fuel) on top of the core.Above that there's a 10mm void which i filled with granulated B.P which the shell-fuse sit's into,to ensure ignition(it being shogun fuse BTW,thanks again paul for dropping that off )

I hope to be firing it tonight but,as always,the winds getting up so we'll see.

regards
dean

Edited by portfire, 09 October 2007 - 03:00 PM.

[marble]

Hope this one works for you

[aquarius]

Looks good Dean.
Some of my projects include much the same, both 12 and 15 mm coreburners(?) and various ballshell headers.

I came to think of a few things, mostly the construction of the rochet and header.
Do your motor have a top plug or did you "just" ram fuel as the delay?

In my experience 10 mm of rammed fuel will not stand up to the internal pressure.
I built motors from "slow go's" to perfect CATO's, and many of my CATOs were due to the top plug.
Some fast powders even blew through the centrelocated passfirehole (now, I dont use that config any more..)
As a simple delay I use 60:30:10 with 10 % linseed oil. Burns slow, sets hard and easy to funnel and ram.

You wrote that you included 10 mm of BP on top of the delay. Then the ballshell probably will pop or shoot. Hopefulle the rocket at this point is at apogee or below. Or you will have a fast falling ballheader with a burning fuse...
But all that aside, it is not not meant as critizism.

Your pictures are very good and to my own satisfaction, it seems to me that I do things much the same way as you.
Good luck with your testing, and if you please could post some details on weight etc?

[marble]

Thats the size of the nozzle of the rocket made with my tooling (coreburner), that looks way to small to me for a rocket of that size.

Just tested one with 65:25:10 fuel and it cato'd, also tried one with a 5mm hand rolled tube and had the same result (went a few meters first)

http://pyrobin.com/files/cato.avi

Edited by marble, 10 October 2007 - 01:36 PM.

[portfire]

Thanks for your comments aquarius.Much appreciated (although i think i could have done a better job lol),and hey,any criticism is good criticism,if you ask me

Anyway. No end-plug on this one just 10mm of fuel.All of my tests with these rockets have had one though and never had one fail (and they've been rammed as hard as the fuel).I tell a lie,a month ago i had a CATO but,i'v had to adjust milling times since i'v updated the ballmill and is now running alot faster.Even then it was the tube that failed,went with a right crack but,having not been able to find anything,(only the stick with charred masking tape still in the tube) i'm only guessing on that one.

Yes,there's granulated B.P on top if the delay and with fast shogun fuse in the shell,i'm hoping it will break at apogee.The reason i'v not gone down the passfire-hole route is that this is my first header and wanted to give it the best possible chance of working.I still have fears about a 2" ball shell landing in a field and not been able to find it. and to be honest,if it were to fail i'd rather it CATO and the shell break on the ground (I'll be far enough away BTW)

I did go up to the test-site last night but decided it was to windy.If everything does go to plan,i don't want the lovely tail on those chrys#6 stars to be blown away The weather's looking good so far so,hopefully be testing tonight

dean

[portfire]

Well what can i say...WOW!!.

http://video.google....357679030515304

As the saying go's,you learn more from failure,and that i did.

aquarius,you may have been right but,i'm thinking the delay was to blame at the moment.Using the fuel for the delay is obviously NOT a good idea.A greenmix with a small % added C and maybe abit thicker (15-20mm) would have been more suitable?..

That said.I was quite happy with the break,although i was expecting more of a disorganized "round-burst",it didn't look that bad at all IMO.I hope i can get them looking like that often

dean

[icarus]

ive had afew end plugs blow out if you smear a sticky glue in the case end then dip it in dry sharp sand when you press the bentonite nozzle the sand is forced into the case sides ad its much harder to blow the plug out you dont have to wait for glue to dry its only to hold sand or grit in place

[icarus]

looks like end plug blew out smear sticky glue ie evo stick around bottom inside of casing dip in sharp sand or grit no need to wait for glue to dry when you press bentonite core grit is forced into case walls forming a more pressure resistant nozzle that wont blow out

[portfire]

looks like end plug blew out smear sticky glue ie evo stick around bottom inside of casing dip in sharp sand or grit no need to wait for glue to dry when you press bentonite core grit is forced into case walls forming a more pressure resistant nozzle that wont blow out

There was no end-plug on this rocket,which is one reason (probably was the reason) it failed.

Watching the video in slow-mo and frame-by-frame,looks like the delay couldn't stand up to the presure aquarius and you can see the shell "pop off",if you look

I have enough fuel left for two more rockets (but need to roll some 15mm tubes first) so,will do a couple of tests with the passfire-hole method,using granulated B.P on top as i have done,and use small B.P salutes for headers this time.

dean

[aquarius]

Looking at the video, your delay/endplug was not long enough to withstand the internal pressure, as you pointed out. When you have rolled some more tubes, try again.
But this time with a endplug.
Make the endplug at least 10 to 15 mm, and try with at least one centrelocated and one offcentre, near the wall of the tube.

The problem with centrelocated passfires is that the rammed fuel is at it's thinnest and weakest between the end of the spindle and the beginning of the passfire hole.
And if your delay is not long enough, the internal pressure will break throuh and ignite your header.

If you on the other hand make the passfire hole near the wall, the pressure will not be so high near the hole and you might get away with a shorter delay.
It takes longer time to burn to the far end than to the centre of the delay due to the burning charistics of a coreburner.

A tip: Weigh your ballheader and make a dummy with a plastic bag filled with sand and a small charge in the middle, fuse the same way as with a header.
Launch the rocket in daylight, and you will clearly see when the sandbag blows and how your timing for that weight is (not taking in account for different air drag but that's a different ballgame).

Now, WHEN your rocket flies, try with different lengths of delay to zero in the right time for the header to blow.

Good luck, you are closer than you might think!

[marble]

Greg Boyd is a top guy, let me buy the 1lb tooling off him for only $40 due to my misadventure.