Shelf life of whistle motors

[NeighborJ]

I've finally got a little free time on my hands so I'd like to explore the possibility of premaking some whistle motors for the upcoming new year's celebration. My go to comp is the 76-23-1-2.5minreal oil, cuoxy, sali whistle mix. I've tested this comp extensively and have matched spindles to shell weights so the reliability is not in question, BUT that reliability drops off considerably after a week of storage and especially if it is humid or exposed to extreme temperature swings. My goal here is to extend the shelf life to a minimum of 2months. One of the ideas rattling around in my head is to omit the mineral oil and bind the comp, in the tube with Phenolic. I've done a test and found it to be promising. But it still has not been tested over any length of storage time.

[OldMarine]

Ned Gorski says that with waxed tubes,a clay end plug and the nozzle covered with foil tape, the rockets will store much longer.

That would be awesome if the phenolic works!

Edited November 4, 2016 by OldMarine

[NeighborJ]

The Phenolic works but I believe my test was a little fuel rich, it whistled at a much higher pitch, had a slightly slower ignition and I'll need to shorten my spindles because it did Cato once it got up to 50'. And that was with the shortest spindle 2.5" in a 1lb. Edited November 4, 2016 by NeighborJ

[OldMarine]

There's someone else working on the phenolic whistles on one of the forums. I'm going to hook ya'll up when I find him so ya'll can get that ball rolling and ready to play when I step up to whistles! I'm thinking I was reading on rec.pyro so I'll go back and search my history.

[Mumbles]

I hadn't read about the foil tape before, but I like it. Storing with a desiccant is usually the route taken. Swapping out sodium for potassium salts also tends to reduce the tendancy to pick up water. Unfortunately that is harder using Sali since potassium salicylate is not readily available commercially.

 

One idea I've had bouncing around in my head is using a silicone based oil or grease instead of hydrocarbon based. Polysiloxanes are quite hydrophobic. It's the principle behind things like Rain-X and some car waxes. I don't know how well it'd work, but seemed relevant to the topic at hand.

[OldMarine]

I've got tubes of Dow 111 (polysiloxane) on my work truck. It's not cheap but I don't buy it!

Ned says he fuses his whistles from the side at the bottom of the grain and doesn't even need to remove the tape before launch.

[NeighborJ]

Mumbles I like where this is going. I'll try anything once, silicon grease, lithium grease, maybe some form of dielectric grease? I'll need to put together a shopping list.

Unfortunately it's not just humidity which affects the normal whistle, the wide temperature swings in the pyroshed seem to be the biggest uncontrollable variable. I'd store them inside the house at a steady 72degrees but that's out of the question. The Phenolic test was my attempt to combat suspected thermoshock stress fractures even though I've never found them.

[Col]

I`d knock up a a small climate controlled storage box for the shed. I`ve stored Na benz whistle motors for around 6 weeks vacuum packed seperately in mylar foil bags. The bags were closed with a 15mm wide crimp seal using a handheld constant heat sealer, much like a pair of giant hair straightening tongs.

[Maserface]

I stored some sodium sali whistles in open air, with fluctuating temperatures and humidity, for 4-6 months and had 0% failure rate on them. I've been unusually lucky.

[OldMarine]

I haven't tinkered with whistle yet but I do store my BP motors in Ziploc bags with desiccant.

[NeighborJ]

Maserface, maybe I should send the motors to you for storage. If I remember correctly you press your motors at a much higher pressure than I do, also you use wax instead of mineral oil. Somewhere in there is the key to storage unless it is related to purity of chems (Ph)?

I've brought some scrap material home from work to redesign my press and increase its capacity from 4t to 12t. I'm certain that it will have less variations of density with a higher pressure.

OM, we really need to get you into whistle.

Edited November 5, 2016 by NeighborJ

[OldMarine]

I'm working on it! I've got the chems, tooling, etc.. Just need more education. I'm not messing with whistle or flash until I'm comfortable with my level of knowledge. I'll probably use whistle to boost my BP motors before using it as the main fuel.

[dynomike1]

I,m not into rockets just serpents rite now. Anyway i stored some whistle in a stainless thermos since last year. i pressed a couple of serpents yesterday, and the first one had a low whistle. I thought i had pressed to much at a time, so i pressed another one with just a pinch on each increment and still a low whistle instead of a loud scream. I guess i will wait till next year to make serpents and use what i have for some little rockets. I never could understand how whistle whistles.

Edited November 16, 2016 by dynomike1

[NeighborJ]

Mike, my first thought was that the mix had oxidized the stainless container but if you didn't notice any corrosion then I'd look at your building teqniques. Does the serpent have a resonance cavity? It needs at least 1-1/2 times the tube dia in order for those stressed gasses to build up their vibrations. If neither of these are the problem then I'd think there is a possibility of an acidic reaction in the chems, causing a loss of reactivity or worse. I would try to reconsider storing any potentialy explosive composition inside a sealed metal container, it's a good recipe for an accident. I've noticed that my whistle seems to degrade after a few months of storage but the rockets are certainly not suffering for lack of power, just a little quieter. One of these days is like to buy a ph meter so I can check the chems, it would be nice to get to the bottom of it.

[dynomike1]

I've noticed that my whistle seems to degrade after a few months of storage but the rockets are certainly not suffering for lack of power, just a little quieter. That is what mine are doing. I am putting 1" of whistle in a 3 X 9/16" tube.

Edited November 16, 2016 by dynomike1

[NeighborJ]

Most of my whistle is sali, and mixed for a very fast burn but the Benny also seems to degrade. I lean towards the perc being the culprit. I have some perc which is very pure and it makes whistle extremely hot, it has not given me any problems with storage. I save it for certain occasions. The less expensive perc appears to be the culprit even thou it is very pure.

[OldMarine]

I've got 5 lbs of Swedish Perc I'm saving for whistle since it's overkill for most other purposes. It's part of the original chem collection a customer of mine bequeathed me before he and his wife moved to a retirement community and he had to give up pyro. He got me hooked on this hobby and sometimes I don't know whether to thank him or beat the tar out of him!

[NeighborJ]

I'd love to buy only Swedish perc for everything but it's expensive, at $10 per pound plus shipping. The cheap stuff is closer to $4 and for most applications it works great. This year I've used close to 60lb of perc and I foresee even more next year, so until I find a deal, the cheapo stuff will need to do. The cheap stuff has its merit as well, it isn't quite as hot so it can be used on longer spindles, this allows for more fuel and a longer burn which equates to more thrust and heavier payloads.

[OldMarine]

Where are you finding the Swedish Perc? I only find the US or chinese on my supply faves.

I'm wondering if Phil's would be comparable????

http://www.ihaveadotcom.com/cart/index.php?main_page=product_info&cPath=72_119&products_id=539&zenid=mmqsgek5pv6hae2dh1q8dqasm1

Edited November 17, 2016 by OldMarine

[NeighborJ]

Phil sells it.

[dynomike1]

OM this customer didn't live in Kentucky did he.

[OldMarine]

OM this customer didn't live in Kentucky did he.

No, he lived in Nashville. He tinkered around at it building 3" shells for backyard stuff until golf caught his eye. I got a pretty good stash of stuff I still haven't used any of yet such as TPA and zinc and whistle ingredients. He warned me it could be an all consuming hobby!

[NeighborJ]

OM, I was wrong, Phil doesn't have the sveedich perc but he does have some awesome perc, and it's a little better price than what I get. I'd also like to source some real Swedish perc for comparisons.

[OldMarine]

I have several pounds of perc from Skylighter and it works just fine in all comps I've tried. I have some fine milled stuff I can't remember where I got it from. I've taken to labeling things better now.

Edited November 17, 2016 by OldMarine

[NeighborJ]

That skylighter perc can stand with anything else I've tried. It is so hot with sali that it reports like flash powder when lit as a loose pile. I take advantage of the 3# free perc deal every time Harry offers it. And as far as storage goes, it stores well as long as it isn't a tuned up spindle. I still haven't figured out how to store those yet.