End Burner Problem

[leedrill]

i love it and i love the way with this one i put a light peice of paper on top of the grain and added the few green stars and could hear a lovely snort at the end too . cheers

[PyroCube]

Hi all

 

I tried a 15mm ID enburner with my fastest Paulownia BP and the result was quite surprising

The engine was able to lift 80g payload with ease, maybe even higher loads are possible, but I think

80g is quite good.

If you are interested, I`ll post a video, I think I will use endburners to lift 2" and 3" shells in future, I think

I will even be able to lift a 4" shell with a well manufactured 24mm endburner...

 

 

Greets

[Flaky234]

Nice!

 

Where are you going to post it?

 

Youtube?

[Flaky234]

Hi,

 

The Endburners still have some troubles.

 

Now the tube has a bulge and when it ignites it flys in slowmotion 5cm? and then explodes upwards

 

Is the bp too hot??

[AirCowPeacock]

Well either your tubes to weak, your BP is to hot or your nozzel to tight. Those are the all of the possiblities.

[AirCowPeacock]

Oh, or your grain is not sufficiently consolidated.

[Mumbles]

It is impossible to have too hot of BP. Anyone who thinks this is the case has other deficiencies.

[Flaky234]

Ok,

 

the tube is extremely strong and it flys alittle bit before cato so it must be the end plug.

 

The nozzle is formed with heavy hammer and the bp is rammed with light hammer and the endplug with heavy hammer I think thats the problem!

 

I let you know!

 

And you are right there is no too hot bp because you can use whistle and I use commercial tooling!

[AirCowPeacock]

Describe your CATO.

[nater]

Is there a reason you are using a light hammer to ram the BP? I wonder if you aren't cracking the BP grain when you are switching to a heavier hammer when ramming the plug? That could explain why it flies and then CATOs.

[Flaky234]

Ok,

 

But normally end burners cato silent but from my two test it was really loud

 

I am going to stick to the heavy rammer, because i noticed that the bp grain got smaller when i pressed the end plug with the heavy rammer.....

[dan999ification]

When mine pop they are not quiet at all, not like cored rockets but still.

As Nate said either the grain is cracked, or since you felt it move I'd say it is not dense enough/porous and the pressure is forcing the grain to burn at once.

 

Dan.

 

[leedrill]

I agree with all the statements above but my 2 cents as a beginner as well you say your tube had a bulge this must not happen at all if there is a bulge I suggest very carefully cutting the motor open to inspect the inner of the tube for damage if you are using anything with the hardness of nept tubes the really do crack or tear easily if over pressure and not supported wich is Easier to do than you'd think with no support this way you will save the fuel from that motor and also get a detailed picture of what's going on inside when ramming I have tried to find a specific loading pressure for bentonite nozzles and found nothing so I tend to press it to the same as recommended for the fuel I'm using but have read under pressure it flows like a liquid so you are right in using a big hammer for it but the blows don't really need to be that big just enough of them instead of big ones this is my opinion only I'd listen to the boys that have been doing it for longer if they disagree but if not supported properly you will expand the whole tube slightly rather than making a nozzle that has compacted the inner walls of the tube slightly to hold on to and you will run into what nater suggested of cracking the grains I'm not sure entirely how the react to impact but after pressed to recommended pressures bp grains feel like rock and is actually hard to drill through

 

I hope this helps sorry about the whole no punctuation thing I'm on my phone

If any of you can correct anything I've said I'd greatly appreciate it

Edited April 22, 2013 by leedrill

[nater]

The only thing I disagree with is when you said a bulge must not happen at all. Even using NEPT with a support, you will get a slight bulge where the nozzle is pressed. It is easier to feel than it is to see, but it is there. The theory is that this helps lock the nozzle into the tube and prevent blowouts. I cannot confirm or deny that, but I do know that a slight bulge from the nozzle does not cause problems.

 

I press the nozzle and the fuel to the same loading pressures. Everything for my rockets is pressed at 7500 psi on the comp. Nozzles, BP, Whistle, ect - all get the same loading pressure. There is only one thing I do differently when pressing a nozzle. I load a slightly larger increment than I use for fuel (for 3/4" rocket a heaping teaspoon of clay, and a level teaspoon of fuel). Once the increment is loaded, I press it to about half the pressure, release the jack, give the nozzle forming rammer a twist and raise it up a little. Then I press it to the full loading pressure. I have had to do this to prevent the clay from flowing into the very small gap between the outside of the rammer and the inside of the tube.

[dan999ification]

A bulge is fine even if the whole tube expands slightly.... If the paper de-laminated and is

Forced down with the compressing grain or the paper just splits inside is where the problem is, this applies to most hand rolled and spiral tubes.

The support sleeve won't help if the tube de-laminated while ramming or pressing, it's there to allow the tube to expand on the inside without bulging too much which would cause stronger tubes to split (but not de-laminate)

 

Good strong tightly wound tubes will compress the inner walls slightly, locking the nozzle

And grain in place but they will not bulge outside or de-laminate inside while doing so.

 

I also adjust the first rammer to prevent clay creeping up

 

Dan.

[Flaky234]

Must i see the bulge?

 

I press until i have a 2-3mm bulge...

 

Is this ok?

[dan999ification]

No it depends on your tubes mainly.

if the nozzle is recessed and the tube did not de-laminate, the engine flys... It's ok.

 

In an ideal situation there will be no bulge just a slight compression of the inner wall, a good test is to place a steel ruler along the width of the engine and you'll soon see if it wobbles because of uneven bulges.

A well fitted support sleeve will allow your tube to

Compress inside but not bulge outside but only if the paper will compress and not de-laminate or crack will it fly. if poorly made ( for its purpose) the tube most likely not compress and fail due to the paper cracking or de-laminating.

 

Dan.

 

[leedrill]

 

 

 

Good strong tightly wound tubes will compress the inner walls slightly, locking the nozzle

And grain in place but they will not bulge outside or de-laminate inside while doing so.

 

 

 

This is what I was talking about nater Dan just worded it better I believe you meant the same thing but I could be wrong I have pressed my 1" I'd rockets to 6900psi with a pressure to force gauge with a 1 square inch piston and placing a metal ruler vertically on the motor I have no outer bulge at all I have nept from Jim at hobby horse and they are great but if I have my support sleeve loose like I did my first few attempts ( due to me ending up having to force my rammers in) I ended up with outer bulges now I have t bolt hose clamps and two layered PVC supports before I had commercial tooling I was trying with tooling I had made at a shop of some plans and was using PVC tubes and sugar fuel I kept having nozzle blow out redline seemed to keep changing due to the PVC tubes had a few fly right by scratching several rings into the nozzle bonding area but the PVC is quite thick I was using and I could get it to bulge quite easily which makes me want to ask a question what pressure can be achieved by hand ramming with a hammer to me it seemed quite high not as high as pressing but I've always thought if I where to hand ram again I'd still need a sturdy support am I wrong in thinking this

 

[Mumbles]

Hand ramming does not yield as high of pressures or compaction as pressing. Well, you might be able to achieve similar or higher pressures, but the sustained pressure of using a press aids in maintaining that level of compaction.

 

Even with NEPT tubes I've felt a slight exterior bulge when using a support sleeve. They certainly bulge a little on the inside. Cutting a tube open will confirm that. However, you can usually feel a slight bulge on the outside if you run your fingers across it. It's almost impossible to see, but you can feel it.

[Bobosan]

A thread somewhere here on APC had a cutaway showing the nozzle and bulging tube. I think nater posted it.

[Flaky234]

Hi,

 

The half motor rammed only with heavy hammer and it worked!

 

^^ thanks for your helps!

[leedrill]

cool well done