32 replies to this topic

[Rip Rap]

The end bottom end plug blows out. I ram a 1ID plug out of clay (bottom and top), i have also reinforced the clay with some coarser mesh so it has better grip.

For the casing i am am hisong homemade tubes which have a wall thickness of 3.5mm.

Well, i think firstly i'm going to try reducing the milling time and see if it helps.

Your comp is too hot. When talking about cored & choked rockets, 75/15/10 is only needed for small bottle rockets. Generally speaking, the larger the ID of the rocket (& consequently the core) the slower the comp needs to be. Also, you don't need to mill your rocket comp. Green mix, dampened & run over a sieve (to cut down dust) is fine.
What ID are your rockets? Working on an ID of 10mm, use green mix + 5% extra C. If a larger ID, eg 20mm, try + 10% C.
Let us know how you do.

[Pretty green flames]

My rockets are 14mm ID. So just green mix with a reactive charcoal should be fine?

[Rip Rap]

My rockets are 14mm ID. So just green mix with a reactive charcoal should be fine?

Yes, fine. If you are using willow C, try green mix with 6% extra charcoal. If they still CATO, push it up to +8%, then +10% etc.
Obviously, if you start at +6% & they fly but look a little weak/slow, cut it back to +5% etc. Good luck.

[Silverturk]

When I am making endburners, I'm making the hottest BP I can make - out of barbQ charcoal (even though I can make willow C, but thats a messy s**t), and re-chrystalizing the KNO3 using CIA. 75-15-10 ratio.

The wall-thickness of my rocket casing is about 4-4.5 mm. 12mm ID. Nozzle 3mm (works with 3.5mm, but has no thrust, and 2.5mm will just CATO.) I'm hand ramming my rockets. Remember not to ram all BP at the same time, fill it with 5ml meal powder and ram several times instead.

What i think you are doing wrong is that you are not ramming your end plugs hard enough. I ram my plugs 50 times really hard. Try that. And if your casing cracks, just make it thicker. Or use some sort of glue when you are rolling.

Or try this:
Use something like that BP I make (just use a slower charcoal) and fill your rockets with it. Make a couple of rockets. Then use 4mm nozzle, 4.5 mm, 5 mm etc. If your rocket becomes something like a fountain just after a nozzle size that CATO:ed, your rockets will never fly. Then your casing is too weak.
Ex: 5mm = CATO 5.5mm = Fountain

Edited by Silverturk, 01 September 2006 - 04:24 PM.

[Rip Rap]

When I am making endburners, I'm making the hottest BP I can make - out of barbQ charcoal (even though I can make willow C, but thats a messy s**t), and re-chrystalizing the KNO3 using CIA. 75-15-10 ratio.

The wall-thickness of my rocket casing is about 4-4.5 mm. 12mm ID. Nozzle 3mm (works with 3.5mm, but has no thrust, and 2.5mm will just CATO.) I'm hand ramming my rockets. Remember not to ram all BP at the same time, fill it with 5ml meal powder and ram several times instead.

What i think you are doing wrong is that you are not ramming your end plugs hard enough. I ram my plugs 50 times really hard. Try that. And if your casing cracks, just make it thicker. Or use some sort of glue when you are rolling.

Or try this:
Use something like that BP I make (just use a slower charcoal) and fill your rockets with it. Make a couple of rockets. Then use 4mm nozzle, 4.5 mm, 5 mm etc. If your rocket becomes something like a fountain just after a nozzle size that CATO:ed, your rockets will never fly. Then your casing is too weak.
Ex: 5mm = CATO 5.5mm = Fountain

I dont think we are talking about end burners anymore (even though that is the title of the thread) because pretty green flames said -

The end bottom end plug blows out. I ram a 1ID plug out of clay (bottom and top)

- this I took to mean he is ramming a clay choke, which obviously cannot be an end burner.

[StarScream]

I dont think we are talking about end burners anymore (even though that is the title of the thread) because pretty green flames said - - this I took to mean he is ramming a clay choke, which obviously cannot be an end burner.

Rip Rap: We are talking about end burners here. Pretty Green Flames started the thread, asking for help with end burners. Not sure what you mean by "he is ramming a clay choke, which obviously cannot be an end burner". Huh? All rockets need a choke to produce thrust, be it an end burner or core burner.

Pretty Green Flames: If your clay plugs are still blowing out then I suspect they are not anchored into the tube well enough. Grog would likely help, as it helps to lock the clay particles into place much better. I've also heard, as you mentioned, that grog and also titanium can be very hard on your tooling.

[Rip Rap]

Rip Rap: We are talking about end burners here. Pretty Green Flames started the thread, asking for help with end burners. Not sure what you mean by "he is ramming a clay choke, which obviously cannot be an end burner". Huh? All rockets need a choke to produce thrust, be it an end burner or core burner.

Sorry - my mistake. This is probably a misnomer that I & my local pyro friends use - to us "endburners" are unchoked rockets.

[Pretty green flames]

Excelent, my end burners are flying, although a bit lazy the important part is that there are no more CATO's.
For the propellant i used 15minute ball mill BP, i will increase milling time to give a stronger propellant and hopefully they will fly better than this time.

Just as an additional piece of information, i have settled on the 30% ID nozzle as lancaster reccomends.

[Pyromaster2003]

Been making end burners tonight for testing thrust. Tubes were 3/4 inch ID, 5 inch long with 4 mm heavy convolute walls. Made loads like this before and they havnt burnt through as the wall are very thick. they are end burners and i rammed cat litter into the tube (possibly harder than usual -- is this the problem??) and then the bp charge and another clay end then drilled a choke in first clay end. Would love to know why this is happening all of a sudden when it hasnt done before? 3 out of 4 rockets did the same as the one in the vid bellow..

Anyone know why/how this happened to a commercial parallel wound tube -

[pudi.dk]

Been making end burners tonight for testing thrust. Tubes were 3/4 inch ID, 5 inch long with 4 mm heavy convolute walls. Made loads like this before and they havnt burnt through as the wall are very thick. they are end burners and i rammed cat litter into the tube (possibly harder than usual -- is this the problem??) and then the bp charge and another clay end then drilled a choke in first clay end. Would love to know why this is happening all of a sudden when it hasnt done before? 3 out of 4 rockets did the same as the one in the vid bellow..

Anyone know why/how this happened to a commercial parallel wound tube -

You might wanna consider a rocket spindle. Without the V shape over the nozzle, the thrust is not directed through the nozzle, and that is the result.

[Pyromaster2003]

How do you mean? Can you describe what exactly i am doing wrong by drilling the nozzle? Why would making it on a spindle change this?? Cheers

[James P]

When you just drill a nozzle out, the clay you have used for your endplug has a flat surface (on both the inside and outside face). This means that the gasses released from the comp will be pressing directly against the nozzle.
However rocket tooling allows you to ram the nozzle so that it has a sloped inside (and outside in fact) face. Therefore the gasses are channelled out of the nozzle with much less force actually acting on it.
Overall this means that less pressure will be built up inside the rocket and therefore the rocket tooling rockets will have less thrust. However this change is minimal compared to the change in thrust achieved by actually adding a nozzle to the rocket.
Hope this helps,
James

[pudi.dk]

Bad drawing, it was just a quicky.

Edited by pudi.dk, 03 July 2007 - 05:57 PM.

[Pyromaster2003]

Spot on advice lads cheers! Was a stressful night last night when all 4 rockets failed with the type of tubes i was using lol..couldnt get my head around my other ones working could have been using a different rammer thinking of it.

I will sand the bottom of the rammer around the edges to make a dome/convex shape to try sort this out thanks very much for your help.

[cooperman435]

at the risk of being flamed I have a different opinion

whilst certainly a conical back to the clay plug will aid gas flow it will increase heat in direct contact with the paper tube next to the plug.

in your drawing you have failed to allow for the fact that gas is being forced down the tube equally so where the gas is shown to rotate and go towards the sides of the tube in the left hand diagram it would actually swirl creating a slightly lower temperature "air dam" around the top of the plug as the gases would have chance to burn out and wouldn't actively be burning next to the paper tube.

I wouldn't like to speculate about if this will effect thrust but the flat top plug will increase pressure in the chamber so could effectively give more thrust.