Dialing in whistle rockets

[willowchar]

I gather that is more desirable to create a hot as possible whistle fuel for obvious reasons. For a 1 lb. motor design, I am finding that I cant go much longer than a 1-1/4" long spindle without starting to cato the motors. As a matter of fact, Im finding that if I go with a 1/4" longer spindle I get catos for sure. I am realizing that if I want to create a longer spindle for a longer and more powerfull1 lb motor, I will have to dial back the fuel(slow it down). I see a lot of what seem to be 5 and 6" 1lb. whistle motors in videos, some using "extreme whistle spindles". They must be dialing the propellant to fit the spindle?. I aim to keep my fuel as hot and consistent as possible, and use it as a standard, the adjust down as required.

 

What is the best course of action to slow it down?

 

more / less cat?

more / less lamp oil?

more/ less fuel?

 

Thanks in advance

.

[justvisiting]

I've pressed hot sali whistle on BP tooling, with a waxed tube. What's your pressing force? Increment size?

[willowchar]

Thanks, pressing 1 tea spoon increment @ 12, 800 lbs pressing force

[justvisiting]

You mean 12800psi on the .441 square inch area, which would be 5645 lbs of force on a P to F gauge? Just asking, no point to make. I'm an advocate of waxing tubes and I have found it to be particularly effective with whistle rockets, which are much more prone to CATO. It's easy to try and if it fixes your issue, great. I honestly don't believe that whistle is too 'hot' for an application, per se. I think the physical properties of the propellant grains are the source of the problems. Not much has been studied on it, and not much insight has been gained. The standard instruction is to 'back off', which works, but does nothing to fix the root cause. Same with waxing

[willowchar]

Thanks, just to confirm my conversions are correct with you. I press at 800 psi on the hydraulic gauge , Cylinder is 3 inch drift is 3/4"

using the formula,

 

Loading pressure= pressure (gauge) x area (piston) /area (rammer)

Loading pressure= 800 psi x 7.07 sq. in. / .442 sq.in.

Loading pressure= 12,796 lbs.

 

I realize whistles are pressed at 7500 lbs. can the extra force I am applying cause any performance issues?

Regards,

[Mumbles]

I can't speak from personal experience, but I have heard people postulate that too much force can sometimes be an issue too. The increments may get glassy at the top of each increment, effectively creating a weak spot at every interface. Think of it like a dozen or so stacked donut shaped propellant grains on top of each other instead of one single grain. It might be worthwhile to shine a light up the core and see if you notice anything unusual. If something looks odd, you may also want to cut one open and see how easily the propellant grains break off from one another or what the tube looks like. I believe I've seen some pictures where you can basically pop every increment apart from one another.

 

Less pressure may be something to try out.

[justvisiting]

I have seen what Mumbles is talking about. I have also cut 3lb whistle motors apart to see what's what. I'm probably the one that posted pictures. But yes, the top of an increment becomes glazed, and the next one doesn't stick to it. With extreme pressing forces, the tube might pull down, only to re-expand later, causing a separation (or just a really weak area) between increments, which would then cause a CATO. I'm convinced that the phlegmatizers are the root cause of whistle rocket CATOs. I view the phlegmatizers as anti-binders. Also, if your pressing force is too high, you are probably creating small tears on the inner layers of the paper tube. These small tears can act as firepaths, which results in CATO.

[willowchar]

Great advise guys. Thanks.

 

What you have suggested about the increments "glassing " over is probably the root cause of not being able to press with longer cores.

I will reduce the force to 7500 lbs. and see what happens.

 

Feeling very fortunate to be able to discuss such questions amongst people who share the same interest and passion of this hobby!

 

Cheers!

 

 

[NeighborJ]

I agree with JV about the phlegmatizers being an issue. That issue becomes compounded the longer the motor sits. A tube compresses during construction but because of the support it is only the ID which stretches. Once removed from the tooling and support the grain is now under compressive spring tension. Phlegmatizers allow the fuel to become moldable and flow to fill voids during pressing. The same is true after the tooling is removed, the fuel moves or "creeps" inward from the compressive force exerted by the tube. This creates tiny hairline stress cracks in the grain, most frequently at the interface of the core and delay where there is no room for the fuel to creep in. The glassy faces of increments IMO is a symptom of too high pressing force, pressing force which puts the tube under even greater spring pressure and therefor accelerating the crack causing creep of the fuel grain.

 

Commercial firework companys don't have cato issues and they can store their whistles without any issue. What is the difference? Phlegmatizers, they dont use them, they also don't press the snot out of their motors.

 

Catalysts or burn rate modifiers are another thing which causes issues. Firework manufacturers don't use such agressive burn rate modifiers. Fine mesh Ti, perlite or red gum are the only ones I am aware of them using. They use just enough to ensure a good smooth burn rate.

 

Until a few years ago I struggled with random CATOs from motors stored more than a day. I removed the Phlegmatizer, granulated with water (and dried) only used RG or fine mesh Ti as the burn rate modifier and lowered my pressing force to 4500 psi, all the issues disappeared. I went as far as to store motors In the trunk of an old beater car for a week and others stored for an entire year before testing. The random CATO issue for me is solved and it all started with looking at the examples exhibited from successful fireworking companies. People will grudgingly stand by their phlegmatizers hailing them as what made whistle safe for the masses but if you ask me having unreliable motors is the greater safety issue.

[mabuse00]

 

I view the phlegmatizers as anti-binders

But apart from the glassing phenomenon the binder seems to increase the density at a given loading pressure.

(I assume that in most cases a higher density equals a higher strength...)

 

 

The random CATO issue for me is solved and it all started with looking at the examples exhibited from successful fireworking companies.

Can you elaborate what types of motors you looked at?

 

I never saw anything but endburners.

And it seems to me that

 

-at least some motors where pressed in one single increment (The motors where rather short).

 

-The tubes used seemed to be paper tubes on the outside, but upon close inspection they contain a plastic pipe inside. Some contain an aluminium tube.

Both will allow the fuel to slide down much more easily than a paper tube. Also they are not compressible, thus making it harder for the fuel to get a grip on them and pull them down with the increment.

 

MinamotoKobayashi uses a similar concept.

Edited December 30, 2020 by mabuse00

[justvisiting]

Mabuse00 said:

 

"But apart from the glassing phenomenon the binder seems to increase the density at a given loading pressure.

(I assume that in most cases a higher density equals a higher strength...)"

 

I wonder what makes you think that? I'm of the opposite opinion. My opinion comes from my experiences with black powder rockets. For a long time I pressed nozzleless coreburners with 2% wax dispersed throughout the propellant. I thought this would increase the density by allowing better packing, put it didn't. The wax simply filled the spaces between the particles. It certainly solved any tendency toward CATO, and made motors that I've flown after 5 years of storage. Adding water at the same percentage has a completely different effect. The water lubricates, but it also dissolves the surfaces of the potassium nitrate particles and allows them to slide, giving better compaction, and increasing the density significantly. The water also cements the propellant together into a single monolithic grain. Wax gives no strength to the grain. I would assume mineral oil would be a lesser choice, because it can migrate more easily than wax, especially at elevated temperatures. One time I decided to track down the original user of wax in nozzleless rockets. I learned it from a fellow named Gary Smith. He told me he learned it from Donald Josar, aka DJ, the originator of nozzleless BP rockets. DJ said he switched from mineral oil to wax because a bunch of motors stored in the hot trunk of his car CATOed, presumably because the oil soaked out of the propellant and into the tube. Wax requires a much higher temperature to flow, so the problem was solved.

 

I'm no scientist, so bear with me if I don't explain myself well. It seems to me that liquids are incompressible, and that the wax flows, so it might be considered fluid. The phlegmatizers that are most used for whistle are petroleum jelly (Vaseline or equivalent), mineral oil, paraffin oil, and less commonly, wax. I don't see those things as binders. They seem more like 'fillers' to me. Liquids can migrate. A drop of oil on a piece of paper spreads to make a large stain. I wonder what happens in a whistle motor with a paper tube?

 

American-made Estes end burner motors that I've taken apart show clear increments, but the increments are well bonded to each other. I've concluded by the density and careful examination that they use water when they press the C and D motors available in the hobby shops.

 

Shimizu writes in F.A.S.T. that some tube items are pressed with an inner sleeve, which slides on the outer tube and prevents compression of it. He also mentions aluminum.

 

NeighborJ seems to be one of the very few of us that has looked to what commercial manufacturers do as a guide for what we amateurs might do. It seems to me that the way many of us make rockets is in spite of the way professionals do it. I don't know why that is.

[a_bab]

I'm also using paraffin oil in my BP nozzleless motors, 1%. I never granulate the composition.
This way, the fuel is not dusty and it compacts well. It DOES get very strong and shiny. Not as strong as you'd use water (like, for making BP pucks) but still strong.
I also wax my tubes. These rockets can be reliably flown after many years, without any care in storage (but not in the rain etc).

 

Commercially they may use a water and alcohol mix. It will evaporate faster and what they really get is a very strong grain that one can corn up for a lousy BP, depending on the fuel.

 

I won't say anything about whistle though but in my opinion the waxy nature of the benny / sally fuels may address the phlegmatizer issue so in reality none is needed.

[mabuse00]

 

I wonder what makes you think that?

That's what intuition will tell you, higher density stuff is usually stronger/more rigid.

If that really is the case would be hard to measure

 

I did some tests with 3,5 and 1,8% mineral oil in potassium benzoate whistlemix with various pressures in 9mm iD waxed spoletta tubes (sleeved).

3,5% always beat 1,8% from 2000 to 10000psi in density.

 

At 4000psi I got 2,29g/cm³ for 3,5% vs. 2,26g/cm³ for 1,8%

 

At 10.000psi I got 2,79g/cm³ for 3,5% vs. 2,73g/cm³ for 1,8%

 

That the oil fills the voids and the density of the sole fuel might be the same seems like a reasonable explanation for this...

Whether it's mechanical strength was better I cannot judge - in this case likely not...

 

I should repeat the test without binder sometime, that would be much more interesting.

What I can say is that the oil affected the burn rate of the mix and power in a motor vastly, so 3,5% oil like it is often quoted is a no go for me anyway...

 

I can also say that swapping the 1,8% mineral oil for 2% wax gave a sharp rise in burn rate, apparent flight performance of the motor, and not unimportant for many applications, in agressiveness of sound.

 

 

 

I removed the Phlegmatizer, granulated with water (and dried) only used RG or fine mesh Ti as the burn rate modifier

So - you riced the fuel like one would BP...?

 

I would have expected RG as a binder and granulate with alcohol...

How much RG did you use?

 

And - sometimes not unimportant - would the RG smoothen the burn in a way that it kills the whistle?

 

 

 

 

People will grudgingly stand by their phlegmatizers hailing them as what made whistle safe for the masses but if you ask me having unreliable motors is the greater safety issue.

I wonder how much the phlegmatiser really helps in lowering the friction sensitivity...

 

With the second point I have to disagree. An unreliable motor does not pose a safety issue, why?

Even if they are very reliable, you have be outside the star/debris throwing radius by the time they ignite. If that was OK, than I can also say that I don't need a blast shield for pressing, since pressing seldom leads to explosions

 

edit:

I found one of the motors from a European company lying on a railroad track, has been there for some time and I could not physically reach it without climbing over the fence, but you can clearly see the inner aluminum tube.

Edited January 2, 2021 by mabuse00

[justvisiting]

mabuse00, that's interesting info. It seems to show that in the case of whistle propellant, you can increase the density by adding oil, and you can increase the density more still by adding twice as much oil. It's like a sponge that is a little wet or a lot wet. Interesting observation on the power and sound when comparing wax to mineral oil. It seems to me that your increase in density was very slight, and proportionate to the amount of oil your grain soaked in. The higher density wasn't useful in practice though, as you report. I think wax would give more strength than oil, but still- they are both lubricants. Maybe a better way to say it is that I think wax would prevent strength less than oil would prevent strength My guess is that sugar water would be a better choice IF the strength of the grain was at issue.

 

I've made the military whistle formula that uses red gum. The texture is completely different than 'normal' whistle. The red gum makes the propellant very grippy, much like the rosin weight lifters put on their hands does. I could see red gum being a good binder if the mix was damped with alcohol, but evaporation might really mess with production and consistency.

 

I've been meaning to try 1% PVB dissolved in alcohol (just to see), and also granulating the whistle with guar gum. I read an article about using guar gum to granulate gerbe comp. Apparently, even though the comp is used dry, the guar gum has binding ability under pressure. It might behave the same as the red gum though I have pressed whistle with just water. It worked, but was a bit weak. I was too impatient to wait for it to 'dry'. I never got back to testing it.

 

The whistle propellant is way different than black powder propellant, so you are talking oranges and I am talking apples maybe. In the case of black powder, the wax did not increase the density over that of dry-pressed powder. The water did increase the density, by a significant amount. The density was increased, and the grain became very hard. Not so with wax.

[mabuse00]

 

It seems to me that your increase in density was very slight, and proportionate to the amount of oil your grain soaked in

I agree.

 

 

I've made the military whistle formula that uses red gum

Could you give some details about the formula?

How did it perform?

 

I use 2% red gum to granulate my BP, the same stuff goes into my BP rockets.

I also tried PVB for BP, but heavily affects the burn rate. This will likely also apply to whistle.

(Both where used only for granulation, for rockets I could have just riced it with water and no binder)

 

 

One thing one should not forget is that powders aren't very convenient to work with.

I hate powders.

Granules on the other hand are perfect in that respect.

 

When working with binders, I found that I need +3% to get that.

With 2% wax the mix does not granulate properly, it's still a little dusty...

I tried 3,5% wax but then it's getting slower again.

 

I have some motor types I love to use that are based on rather short tubes, so I can't always have long spindles.

Also, I'm inclined to say that when CATOS happen, the reasons mostly do not originate from a to hot setup.

As you wrote yourself

 

I've pressed hot sali whistle on BP tooling, with a waxed tube.

and I read such statements often nowadays.

 

So - of course I want the hottest fuel possible. I already have the raw materials for copper cromite ready

Edited January 3, 2021 by mabuse00

[NeighborJ]

Mabuse the whistle with RG does burn slower than other catalized whistles do. The difference is very slight. RG burns quite well with perchlorate but not that great with nitrates, you must expect RG in BP certainly burns much slower.

When I tested on the acme with 1.5-2% RG(to avoid the sticky fuel JV mentioned earlier) the burn duration of a 1lb whistle 2.25"spindle was .5 seconds. With cu chromite, ferrocene,RIO,venadium pentoxide, manganese oxide, or cu oxy the burn durration could be as short as .3 seconds. This quicker burn did not yield a higher apogee so I opted to continue working with only the RG as my burn rate modifier.

 

Sali fuel can take the short burn ans high pressure, benny and KHP has proven to not like that high of a pressure spike so I run them fuel rich with the weakest catalyst possible.

Edited January 4, 2021 by NeighborJ

[mabuse00]

@NeighborJ:

 

When I tested on the acme with 1.5-2% RG(to avoid the sticky fuel JV mentioned earlier) the burn duration of a 1lb whistle 2.25"spindle was .5 seconds. With cu chromite, ferrocene,RIO,venadium pentoxide, manganese oxide, or cu oxy the burn durration could be as short as .3 seconds. This quicker burn did not yield a higher apogee so I opted to continue working with only the RG as my burn rate modifier.

 

How exactly did you come to the conclusion that the quicker burn did not yield a higher apogee?

By actually shooting a rocket?

And if yes: was it heavy enough not to accelerate too much (thus working mainly against gravity and not air drag)?

 

Or judging the measure impulse on your acme test stand?

 

 

 

Sali fuel can take the short burn ans high pressure, benny and KHP has proven to not like that high of a pressure spike so I run them fuel rich with the weakest catalyst possible.

Coulkd you elaborate what you mean by "not like"?

Beeing prone to runaway, loss of effeciency...?

Edited January 4, 2021 by mabuse00

[NeighborJ]

By saying that KHP and benny "doesn't like high pressure spikes" I mean that they can't take the combination of hot catalyst and long spindles that sali can (CATO), even thou the sali burns faster.

 

When lifting an appropriate sized shell the quicker burn did not lift the shell any higher than the slightly slower fuel. The findings were confirmed from the acme test stand. The results can also be skewed if you don't use a header.

Edited January 4, 2021 by NeighborJ

[ronmoper76]

I am new to this forum and about a year into rocketry and i have not had similar results.I started with a 1lb extreme black powder spindle from woodys,its very long and I made many BP rockets even adding sali before BP,till i got bored and wanted bigger and better but didnt have any other tooling. soooo... I crammed it to a inch above the spindle with sali,lit it and it went cato louder than a quarter stick. still the loudest cato i have witnessed to date. i then got LWS setup to work well though,just never more than 4 inc of sali before i switch over. but the second fuel a LWS has is crappy at lifting anything of any size i quickly noticed. I started waxing tubes also at some point in the middle of all of this. Next i saw a mention of 76/23/3 benz/vas for a strobe spindle,i still have this freakish long bp spindle mind you but i crammed it to a inch above the spindle and Holy Shit! it was my new favorite rocket,actually they remind me of missles,lol these things lift whatever i put on one and take off like streak. I also tried a LWS setup again but using sali and then 76/23/3 instead of the normal "h 64-32-1-5 or 70-30-1-5 Benzoatebased whistle fuel" Bomb on a stick again. Seems i can run benz fuel as hot as i want on the longest spindle i want but if i use sali fuel I gotta keep either I the core shorter or the top half must be something tamer. If anyone one knows of a sali fuel formulation that allows use on a full BP spindle i would would love to hear your results. On magnalium rockets i can only use 2 increments of sali before it pops. But i must say, the 76/23/3 benz ROCKS! and doesnt need any improvements i can find. I have no use for much better really ...im just looking for a way to make sali work like my benz does on a really long spindle. I made a sali spindle a bit less than 2 inches long from a stainless bolt and it works great for a 4 inch tube but i dont like it like i do using the big long spindle....anyhow thats my two sense and its nice to meet you all!!