Rocket fuel burn mechanics?

[NeighborJ]

Hahaaaaa I got it to work, just shortened it a little and cut the swab from a q-tip, coated it in CA glue and shoved it into the bottle neck. I didn't even wait for it to dry. That thing took off like all hell spit the q-tip out and accelerated into oblivion.😄

[DavidF]

Nothing like being told "you can't" to motivate a guy to succeed! But, now we want video of the next one Congrats!

[NeighborJ]

It'll need to wait till tomorrow. My neighbors probably think I'm selling drugs or something because I'm up and down the road about ten times a day, running to the test site.

[Maserface]

I love the 4oz "pusher" on that site, they make a hellofa rocket! here is a video a friend of mine shot of a handful of them.

 

I agree with dave, this is definitley NOT the wrong crowd, in fact this is probably the writest crowd you are gonna find Keep up the good work and keep us posted.

[NeighborJ]

OK you asked for it, I did the hybrid whistle test on video but it catoed. I know why though. The first time I tested it I had trouble keeping the cotton swab away from the core wall and as a result, some of the 1st stage core was glued. On this test I managed to insert the plug without touching the wall, so more of the core was exposed. This tells me that my first stage core is too long. I did the math and it has around 20% more initial surface area than the standard pusher core. I could just spread extra glue but I will turn the first stage down just a little bit more, to ensure repeatability.

I've enlisted the help of my son and his mad editing skills😉 to put together this clip of the test and the 4oz + 1lb pushers. I attached single large sticks this time and they looked ridiculous but it worked.

Edited August 9, 2016 by NeighborJ

[DavidF]

Good stuff! I'm surprised how slowly the 1lber took off, compared to the other one. The CATO was fun too! How much whistle was pressed above the spindles? Also, a request: if you have a pleated paper condiment cup, could you fill it 1/2 to 2/3 full and video it burning? I'm just curious how your mix burns compared to mine for no real reason. Thanks for posting those.

[NeighborJ]

David the 1lb takes off quicker with two sticks but I only used one. If you look at the slow mo, it wobbles as the motor torque flexes the stick.

🤔 is that a joke about the condiment cup? Oh well, I know what will happen.

Oh yeah the 4 oz only had 7/16 comp above the spindle and the 1lb had about an inch. They both needed a lot more to reach apogee but in not in the habit of wasting extra comp on a test.😉

Edited August 9, 2016 by NeighborJ

[DavidF]

No joke, and thanks NeighborJ! I always like to 'test' my powders in condiment cups to get an idea of the strength. I have to say, I have not ever had whistle propellant explode like that in a cup. Yours must be some kinda hot! I use the pleated paper cups though. My hot whistle makes a loud chirp and turns the cup into a flat disc of paper. You must be using good perc too, yes?

 

I can judge the general power of my BP with the cups too. I look at how belled out the cup is, and if it is scorched or has any burn holes. The 'cup test' tells me right away if I made a booboo in my compounding. Again, thanks for humoring me.

[NeighborJ]

It's the cheap perchlorate given away by skylighter for ordering enough crap. It's all in how well it's mixed mine has zero chunks of unmixed ingredients. 76-23-1+3 and when I mix it I use the Dan Thames method in a baggie only after mixing by hand I split it up into 3 large baggies and roll it out with a rolling pin, only rolling out a tiny amount of the dough at a time. It is so thin I can see thru the bag and I'll spend extra time rolling out any clumps I find. It's as close to perfect as I can make it, without better ingredients. I test my bp the same way. The staghorn sumac charcoal is by far the hottest stuff I've ever seen, even the milldust will self confine in a ketchup cup. It's why I make separate spindles for my nozzleless bp motors. Edited August 9, 2016 by NeighborJ

[NeighborJ]

OK I've gotten the two stage whistle to work perfectly😏. The last little spindle shave did the trick. I layed a piece of aluminum foil inside the lower core so I wouldn't get any glue on the walls and used it like a shoe horn for my core plug. I'm attaching video in which you can hear the bulkhead spit out and the second stage take over. 😁

I can say that this spindle being so long is very difficult to remove. It may get easier when I make the 1lb version but I doubt it.

[NeighborJ]

I have some potassium benzoate whistle I could re-test those three spindles if you'd like. I had intended on this anyway but I haven't gotten around to it yet.

I suspect it will show the same end result, but we can see!

I think if you want to extend the burn time, you will need to go with bates grains or two or three stage rockets. I've also considered adding something to whistle to reduce the burn coefficient, maybe ammonium perchlorate or potassium nitrate.

I gave the three stage rocket a try with my two stage spindle and an endburner on top. All motors were stacked on top of each other in the same case. The motor outgrew my tube support so I tried pressing above it for the better half of the endburner phase. I had two successful flights so I tried filming the third but the second stage catoed because of a crack. If I make the longer tube support I think this will be a reliable motor.

I've also been trolling Dan Criegans site and I found more whistle info which he describes using titanium dioxide as a negative catalyst. In fact it was that same info which I found over a year ago which inspired me to use it in my bp delay formula at a ratio of 1-1. To this day I haven't found anything which burns at such a predictable rate of 8 seconds per inch.

[Maserface]

Just noticed that I linked the same impulse twice- I fixed it and added the step core impulse.

[MrB]

It's the cheap perchlorate given away by skylighter for ordering enough crap. It's all in how well it's mixed mine has zero chunks of unmixed ingredients.

 

I have no opinion on the purity of the product, i haven't used their stuff, wrong continent. But, chunky or not has no meaning for pyro purposes. If it's pure, it's pure. The chunks has to be broken up, for sure, but that is something we deal with on a daily basis...

 

B!

[NeighborJ]

MrB you might be right. All I know is that the first couple batches I used perchlorate from supplier "a" and they were slow and inconsistent. But I started ball milling it before mixing and it became fast fast fast. Now I'm using up this new stuff from supplier "b" simply labeled "general purpose potassium perchlorate" and I cannot tell a difference. I have been using the same sali on all batches. I'm out of it for now so I will find out when I order new chems.

I think there is a point where impurities make a difference. But if I do everything the same and to the best of my ability every time it should stay fairly consistent baring certain kinds of contaminants.