Fine Tuning whistle mix

[gelamex]

Folks, a quick question.

When using whistle made from potassium benzoate, Iron oxide and vaseline for a 3Lb rocket what is the best way to 'detune' if the mix is a little hot and results in more CATo's than flights. I have been researching but have ended up more confused than when I begun. Your input is appreciated.

[AirCowPeacock]

Less catallyst or inhibitor.

[dagabu]

Folks, a quick question.

When using whistle made from potassium benzoate, Iron oxide and vaseline for a 3Lb rocket what is the best way to 'detune' if the mix is a little hot and results in more CATo's than flights. I have been researching but have ended up more confused than when I begun. Your input is appreciated.

 

Add more Perc to make more power and remove Perc to make less power. With only 1% of a catalyst in the first place, you don't have much wiggle room and adding more phlegmatizer makes a real mess as the grease squeezes out around the ram.

 

If the mix is already done and riced, simply take your total weight and add 5% Benzoate to the mix, add enough white gas to make a dough out of it, press it through a 60 mesh screen a few times and rice it out to dry.

 

It is rare to see a benzoate whistle rockets CATO with good tubes and made with high pressure, you may want to look at your process and materials before you "detune" your fuel.

 

BTW- What tooling are you using? I know it is 3# but what is the set?

 

-dag

Edited November 1, 2012 by dagabu

[gelamex]

Many thanks for your prompt replies. The tooling is made by pyrostuff in the Netherlands. The spindle is 135mm long. The first couple cato'ing were due to insufficient pressure consolidating the mass. The last one may have been due to a slight bulge in the tube; it let go at about 30m above ground. I will press another couple at the previous pressure to confirm or disprove my assumption. If they still let go I will detune as per your advice dag.

[dagabu]

You likely have the Long Winded Screamer tooling, the spindle length is almost a perfect match. I already see one part of your process that is causing CATOs. If you have a bulge, you have a damaged tube and will likely fail. You need a stout tube support to hold the tube as rigidly as possible or the tube will expand causing tube failure and grain cracking.

 

Schedule 40 PVC pipe with hose clamps all along its length work well but solid metal supports work ever better. You are looking for 9000LPI on the fuel, any less and you are risking lack of consolidation and you should add increments of no greater than 1/2 the ID of the tube (12MM) with each pressing.

 

Also remember to fuse the rocket by just touching the fuse against the bottom of the fuel grain, not inside the spindle hole at all.

 

Good luck and let us know how it goes.

 

-dag

[Col]

You`ll need around 3.1 metric tonnes on the solid rammer, somewhat less on the hollow ones.

[gelamex]

Many thanks folks, I believe the bulge was caused by an incorrectly tightened hose clamp. When it cato'ed a section of fuel pellet about 18mm long was blown to the side and landed unburnt which would point towards a failure of the tube. I will put one together this evening and see how it goes. The info on pressure is spot on Dag, many thanks once again.

[gelamex]

Well, todays test was interesting. The motor was assembled yesterday evening with a pressure of 9000 (with some dwell time at each increment) as advised. On removal from the support, the tube was checked for bulges with a metal rule. None were found. On ignition the motor flew approximately 80 -100m upwards before catoing. The resulting burst threw three burning fuel fragments which indicated that the tube had let go. On recovery, the tube was pretty much in one piece having split longways the full length. The only burn marks that were evident were at the nozzle end. Tonight I will reduce the strength of the whistle mix as advised above and see how I get on.

 

One thought does occur though. Is it possible that each increment of fuel may not be consolidating with the previous thereby allowing the grain to crack?

 

Edit to add: The tubes being used are good and have no problem with BP.

Edited November 2, 2012 by gelamex

[dagabu]

Well, todays test was interesting. The motor was assembled yesterday evening with a pressure of 9000 (with some dwell time at each increment) as advised. On removal from the support, the tube was checked for bulges with a metal rule. None were found. On ignition the motor flew approximately 80 -100m upwards before catoing. The resulting burst threw three burning fuel fragments which indicated that the tube had let go. On recovery, the tube was pretty much in one piece having split longways the full length. The only burn marks that were evident were at the nozzle end. Tonight I will reduce the strength of the whistle mix as advised above and see how I get on.

 

One thought does occur though. Is it possible that each increment of fuel may not be consolidating with the previous thereby allowing the grain to crack?

 

Edit to add: The tubes being used are good and have no problem with BP.

 

I don't have any dwell on mine due to "relaxation" problems with the rocket motor. I found I cut CATOs down significantly when I just pressed until the needle got to the right pressure and got off it right away.

 

Your mileage may vary...

 

-dag

[gelamex]

Again very interesting dag. I will try without dwell time. It may be that the grain cracks as the pressure is let off after consolidation.

[nater]

A few more thoughts, how big is each increment and what kind of tubes are you using?

[Col]

It would be worth checking the spent tube wall for internal cracks/splits, It looks like the tubes have a 5mm wall, if there`s any kind of give in the paper, its possible the tube integrity was compromised during the pressing operation. It may be worth testing a section of unsupported tube in the press to see how much pressure it can take before it splits. Edited November 2, 2012 by Col

[dagabu]

A few more thoughts, how big is each increment and what kind of tubes are you using?

 

Great questions Nate, I didn't even think about that.

 

Also, there are glassy surfaces that will not bond well from increment to increment, for this reason, I scuff the face of my whistle rammers so that they leave an irregular face to each increment. It does not look great but I would rather not have form over function.

 

-dag

[gelamex]

A few more thoughts, how big is each increment and what kind of tubes are you using?

Tubes start off as 25.5mm long and 5mm thick. Cut down to size on the chopsaw with a timber insert. All are parallel wound. Increment size is approx 35mm before compression. The surface of the compressed increment is very glassy so I will roughen up each surface before the next increment.

I have also made up a small batch of 'detuned' mix just to see how that performs.

All good input, much appreciated folks.

[nater]

I am assuming you meant the ID of the tubes is 25.5 mm. With 5 mm thick walls, that is pretty close to the wall thickess of the NEPT I use for 3lb rockets.

 

The height of the increment size before compression does not mean much. Each person's fuel might compress more or less than the next persons, so it is hard to tell if could be using too much fuel in each increment. Like Dag said a few posts up, what is important, is that each increment is no more than 1/2 ID of the motor tall after it is pressed. I have been lucky enough to be mentored by some of the best rocket masters and they have stressed keeping the increments small and consistent to have success. Especially with spicier fuels.

 

Dag's theory about the increments being too glassy and not forming one grain has some merits too. I have not experienced that problem first hand, but I can see where he is coming from.

 

I am also curious how your slower whistle performs. Please don't change more than one thing at a time during your experiments, or you'll never know what the problem was.

[gelamex]

Nater, all the adjustments are being made one at a time otherwise as you say you learn nothing. I have a gut feeling that the increments might not be binding properly too each other hence the reason for the grain breaking into quite distinct but substantial bits. To that end I will have a detailed look at my increments after compression and also how the 'downtuned' mix performs. At the end of the day, every test is both fun and educational and thats what this is all about.

[fiberman]

I made a 700 gram batch of whistle that burned slow (for whistle) and made only a very weak whistle sound near the end of the rocket burn. The new batch was with fresh Potassium Perchlorate from Skylighters, and fresh Sodium Benzoate from Pyrocreation’s chemical site. I made another 100 gram batch to see if I might have measured incorrectly on the first try with the same poor result.

 

 

Potassium Perchlorate 76

 

Sodium Benzoate 23

 

Red Iron Oxide 1

 

Mineral Oil +3

 

Mixed with Acetone about + 7%

 

 

Previous batches of the same mix made from old chemicals that I had had for many years screeched and whistled very well. Small pieces of the old chemicals batch would pop when ignited.

 

 

I made a 100 gram batch with Sodium Silicate (also from Pyrocreations) using the new Potassium Perchlorate and it burned and whistled well, so I don’t think it is the Perchlorate.

 

 

Do I have a bad batch of Sodium Benzoate? Could I add something to the 700 gram batch to get it to whistle? That is a large volume of chemicals for me to waste.

Thanks in advance

Fiberman

 

Watch for my picture on a Wheaties box soon.

[AirCowPeacock]

Perhaps the sodium benzoate is not dry, or fine enough.

[psyco_1322]

I made a 100 gram batch with Sodium Silicate (also from Pyrocreations) using the new Potassium Perchlorate and it burned and whistled well, so I don’t think it is the Perchlorate.

 

 

I think you are meaning Salycilate. The benzoate should be milled, anything coarser, like gritty feeling between fingers, will make a significant difference. Good mixing of the composition helps also.

[fiberman]

Sorry about the spelling error I did mean salicylate.

I will try drying the sodium benzoate and milling it finer for another test batch.

Mixing should have been sufficient. It was mixed at least as well as the batches that worked.

The amount of acetone that I listed was incorrect. It should have been 7 x the amount of oil or about +21%.

I guess at this point I have 700 grams of benzolift?

Thanks for the ideas.

Fiberman

Edited February 20, 2013 by fiberman

[nater]

I guess at this point I have 700 grams of benzolift?

 

No, not even close. Benzolift is basically sali whistle and BP mixed and prepared in a certain way.

[psyco_1322]

No, not even close. Benzolift is basically sali whistle and BP mixed and prepared in a certain way.

 

No, thats salilift, benzolift is made with benzo whistle

 

If you had a longer spindle, like one for bp, you could still make decent rockets with the bad fuel. Otherwise it would be good for boosting shells or making some salutes. I would not try lifting any shells with it, it's not going to turn out good at all.

[nater]

The only formulas I have seen for benzolift call for sodium salicylate and I have heard warnings that it is too hot for lift. I figured the name was a misnomer. Still, the bad whistle is not benzolift.

 

At PGI SLD warned me that you will never get the hottest whistle you can with Chinese perc or mineral oil. I also made a bad batch of sali whistle when I accidently added too much oil. It was too slow for what I wanted and ended up in a salute.

[WonderBoy]

Fiber,

 

How did you mix the composition? Can you see any white specks? Is your benz airmilled? How did you "dry" it?

 

I think it sounds like the benz is not fine enough, it isn't mixed enough, or there is moisture in the mixture. If you put some in a ziplock bag and set it out in the sun for a little while, does any condensation form on the inside of the bag?

 

 

WB

[pyrojig]

Some have reported that the whistle mix's tend to get better with age. Im not sure why, but I have seen a batch that was so-so in quality sit for a few months, and another burn test proved it to be really hot stuff. It appears there is some reaction that takes place, for a more intimate mix. As stated above the particle size is very critical. It should be screened together well to integrate the mixture.