Why doesn't my paper/cardboard tube catch fire?

[BABAR]

It's surprising how much embers comes out of a BP motor. Composites not so much. Don't get to see much of the ejection charge. I'll have to try it sometime in slomo.

Wow, just fly at night and everything is a sparky motor!

Do you really have a built in light on your ignition box?

 

[BEC]

Use a first generation 18mm SU AT D21 and watch your Kraft tubing hibachi. Still burning propellant out the top after ejection.

D10s did this, too. I have one BT-50-based model that had three flights over its 75 on D10s....bubbled paint and in the end a very soft tube above the motor mount. That's why I retired it at that point.

But except for this, I've not had models, even with many, many flights (over 100 in one case) burn significantly inside from ejection charges. Kevlar shock cords, especially tied to motor mounts, are another thing altogether.

 

[OverTheTop]

My father used to tell us of an old bushies trick: fill a paper bag with water and hang it over the campfire to boil the water. Never tried it myself.

TP

I boiled water in a cup folded from regular copy paper, over a bunsen burner, in a chemistry class back in the 70s. You need fuel, oxygen, and have the fuel above its ignition temperature for it to light up.

Somebody mentioned upthread about surface area to volume ratio helping also, although not in so many words.

 

[Daddyisabar]

After many many flights on my Mean Machine it has built up a huge amount of smelly soot in the long tubes. Could this catch on fire like a dirty chimney on a home fireplace? Should I live in fear an E12 CATO setting it all a light?

That night video of the BP motors sparking is frightening. That is a huge sparky danger zone at launch and going all the way up. It can melt through steel blast deflectors like butter? YIKES! If the normies just knew what was really happening in the daylight they would run in fear. Save the children! Run for the bunker Karen! Is there night time footage of a common occurrence E12 CATO? That might put me over the edge. The numerous daytime photos I have seen are scary enough. Best to live in ignorance, safe and sound. What I don't know cant' hurt me.

Golly, are all those sparks and huge burning chunks coming out the back end why the rocket scientists tell me my kiddie-toy BP motors are heavy and inefficient? Is an ejection charge is just like a GUN shot? Say it ain't so!

Is that why there are massive fireworks restrictions where I live, in a big, dry city? Even with the harsh and restrictive laws my neighborhood still looks like that video at night. Follow the safety code people. SAVE THE CAKES!

 

[Ronz Rocketz]

Wow, just fly at night and everything is a sparky motor!

Do you really have a built in light on your ignition box?

The launch controller? I used head/tail LED lights used for RC cars. Red means battery, white means continuity. They're nice and bright, even in the daylight.

After many many flights on my Mean Machine it has built up a huge amount of smelly soot in the long tubes. Could this catch on fire like a dirty chimney on a home fireplace? Should I live in fear an E12 CATO setting it all a light?

That night video of the BP motors sparking is frightening. That is a huge sparky danger zone at launch and going all the way up. It can melt through steel blast deflectors like butter? YIKES! If the normies just knew what was really happening in the daylight they would run in fear. Save the children! Run for the bunker Karen! Is there night time footage of a common occurrence E12 CATO? That might put me over the edge. The numerous daytime photos I have seen are scary enough. Best to live in ignorance, safe and sound. What I don't know cant' hurt me.

Golly, are all those sparks and huge burning chunks coming out the back end why the rocket scientists tell me my kiddie-toy BP motors are heavy and inefficient? Is an ejection charge is just like a GUN shot? Say it ain't so!

Is that why there are massive fireworks restrictions where I live, in a big, dry city? Even with the harsh and restrictive laws my neighborhood still looks like that video at night. Follow the safety code people. SAVE THE CAKES!

As a kid, I used to get bored with my static models so they eventually fell victim to my BB gun. Now I get to make models and put explosives in them. They usually come back.

 

[lr64]

After many many flights on my Mean Machine it has built up a huge amount of smelly soot in the long tubes. Could this catch on fire like a dirty chimney on a home fireplace? Should I live in fear an E12 CATO setting it all a light?

That night video of the BP motors sparking is frightening. That is a huge sparky danger zone at launch and going all the way up. It can melt through steel blast deflectors like butter? YIKES! If the normies just knew what was really happening in the daylight they would run in fear. Save the children! Run for the bunker Karen! Is there night time footage of a common occurrence E12 CATO? That might put me over the edge. The numerous daytime photos I have seen are scary enough. Best to live in ignorance, safe and sound. What I don't know cant' hurt me.

Golly, are all those sparks and huge burning chunks coming out the back end why the rocket scientists tell me my kiddie-toy BP motors are heavy and inefficient? Is an ejection charge is just like a GUN shot? Say it ain't so!

Is that why there are massive fireworks restrictions where I live, in a big, dry city? Even with the harsh and restrictive laws my neighborhood still looks like that video at night. Follow the safety code people. SAVE THE CAKES!

You should scrape out that soot and use it as charcoal to make BP for your ejection charges. Incidentally, does your Mean Machine have any interesting mods? Perhaps an eel's head instead of a nose cone?

From a couple of miles away, I've seen the results of one of those dirty chimneys. On a very icy night when the volunteer firemen couldn't get there in any reasonable amount of time. Save the pine for making rocket fins.

I'm afraid I haven't studied your extensive oevre enough to understand "SAVE THE CAKES!". My apologies.

The launch controller? I used head/tail LED lights used for RC cars. Red means battery, white means continuity. They're nice and bright, even in the daylight.


As a kid, I used to get bored with my static models so they eventually fell victim to my BB gun. Now I get to make models and put explosives in them. They usually come back.

Unless you have them already, it may be just as easy, and cheaper, to get just an LED and a resistor. One that's rated a few thousand mcd ought to be enough for daylight. Take the supply voltage and subtract the nominal voltage of the LED, then divide the remaining voltage by the nominal current to find the correct resistance, in ohms, to use. Both components should be under a buck, and you can get the LEDs in all sorts of pretty colors, and even ones that blink. If you don't feel like an archeological dig at the site that was your local Radio Shack, you can get these at Electronic Goldmine or Aretronics. If they don't have the Goldilocks LED, Digikey probably will, and maybe just as cheap. Those in the Boston area can go to You Do It in Needham or thereabouts. Or Electronics Plus in Littleton.

I have helped a friend dispose of his surplus static models with a .22, but you have to stay a bit more serious when doing that. It's also possible, with the right fuel-air mix, to make a plastic dinosaur breath fire, but I should have been a bit more serious, or at least I should have made sure the tail didn't have a leak. Did not burn down the house, though.

 

[Daddyisabar]

You should scrape out that soot and use it as charcoal to make BP for your ejection charges. Incidentally, does your Mean Machine have any interesting mods? Perhaps an eel's head instead of a nose cone?

From a couple of miles away, I've seen the results of one of those dirty chimneys. On a very icy night when the volunteer firemen couldn't get there in any reasonable amount of time. Save the pine for making rocket fins.

I'm afraid I haven't studied your extensive oevre enough to understand "SAVE THE CAKES!". My apologies.



Unless you have them already, it may be just as easy, and cheaper, to get just an LED and a resistor. One that's rated a few thousand mcd ought to be enough for daylight. Take the supply voltage and subtract the nominal voltage of the LED, then divide the remaining voltage by the nominal current to find the correct resistance, in ohms, to use. Both components should be under a buck, and you can get the LEDs in all sorts of pretty colors, and even ones that blink. If you don't feel like an archeological dig at the site that was your local Radio Shack, you can get these at Electronic Goldmine or Aretronics. If they don't have the Goldilocks LED, Digikey probably will, and maybe just as cheap. Those in the Boston area can go to You Do It in Needham or thereabouts. Or Electronics Plus in Littleton.

I have helped a friend dispose of his surplus static models with a .22, but you have to stay a bit more serious when doing that. It's also possible, with the right fuel-air mix, to make a plastic dinosaur breath fire, but I should have been a bit more serious, or at least I should have made sure the tail didn't have a leak. Did not burn down the house, though.

Save the cakes...fireworks cakes, by making them illegal. My pyro friend keeps me in the BP from his magazine. I put it in my dad's old horn from his muzzle loading days.

All the cool dudes are working on sophisticated electronic deployment and then I pull this out and put a pinch on top of a red lable BP motor because my draggy oddroc abomination likes a zero delay. Gives the rocket scientists a good laugh.

I have always built my mean machines stock, no modifications! Then, after 35 plus flights with a healthy soot build up I had a little mishap.


I cut the way toooo long 12 second, 24mm cheesaroni delay down to 7, resulting in a blow by just after leaving the rod. Lots of black smoke from the smokey motor out the top but dog barf saved the awesome Estes chute and rubber cord I had replaced just a few flights before. Landed in the range smoking but no flame shooting out. Close but not quite enough for an RSO reprimand. So I guess after that the answer is no to soot ignition, but I have even more soot build up in it now. How far can I push the envelope?

Clean the soot out of the tube with a wet towel on a log wooden dowel? No way. What would that do to my hipster coolness image factor if the cool dudes saw me swabbing out my mean machine like a Civil War era cannon? Coupled with the powder horn I could never get a high tech image certification.

 

[Daddyisabar]

The only time I have seen paper tubes on fire were high power CATOS that turned the rockets into Roman Candels. Oh the horror.

 

[shockie]

Can anybody decipher the above chart?

 

[lr64]

First column, W/m-K, is thermal conductivity, units are watts, meters, and degrees Kelvin. (same size as Celsius). I don't have that entirely figured out, but it's per degrees Kelvin. I'm surprised polystyrene foam isn't a far better insulator than Kraft paper. I wonder what type they used? Second is density in kilograms per cubic meter. Water would be 1,000. Divide by 1,000 to get specific gravity. Those foams are something like 2.7 and 3.9 lbs per cubic foot. The blue Styrofoam we're all probably familiar with would be a bit over 2, at least for the slightly heftier flavor. Third appears to be specific heat, i.e. how many joules does it take to warm a kilogram of the stuff by one degree K. Water is something like 4.19, if I can believe the internet. Anyway, all else being equal, the higher the specific heat, the longer it takes to warm something up. I think the last one is thermal diffusivity, which I don't entirely grok just yet. Maybe some thermodynamics wizard can enlighten us. I think it has something to do with how quickly the heat from a transient source gets through a material. I'm wondering where you got that chart.

5.1.1.4 Thermal Diffusivity​

Thermal diffusivity is the thermal conductivity divided by density and specific heat capacity at constant pressure. It measures the ability of a material to conduct thermal energy relative to its ability to store thermal energy. High diffusivity means heat transfers rapidly. It was found that the thermal diffusivity decreased with an increasing temperature [2,8], wet materials had a higher thermal diffusivity, and the thermal diffusivity was a minimum at the α−β transition [2]. For example, the thermal diffusivity for both Barre granite and St. Cloud granite decreased from about 14×103 cm2/s at 10°C to 7×103 cm2/s at 573°C (the α−β transition). From 573 to 700°C the thermal diffusivity slightly increased with increasing temperature.

I found the above snippet at:
https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/thermal-diffusivity
which attributes it to this:
https://www.sciencedirect.com/science/article/abs/pii/B9780128026885000051

 

[Ronz Rocketz]

Unless you have them already, it may be just as easy, and cheaper, to get just an LED and a resistor. One that's rated a few thousand mcd ought to be enough for daylight. Take the supply voltage and subtract the nominal voltage of the LED, then divide the remaining voltage by the nominal current to find the correct resistance, in ohms, to use. Both components should be under a buck, and you can get the LEDs in all sorts of pretty colors, and even ones that blink. If you don't feel like an archeological dig at the site that was your local Radio Shack, you can get these at Electronic Goldmine or Aretronics. If they don't have the Goldilocks LED, Digikey probably will, and maybe just as cheap. Those in the Boston area can go to You Do It in Needham or thereabouts. Or Electronics Plus in Littleton.

I have helped a friend dispose of his surplus static models with a .22, but you have to stay a bit more serious when doing that. It's also possible, with the right fuel-air mix, to make a plastic dinosaur breath fire, but I should have been a bit more serious, or at least I should have made sure the tail didn't have a leak. Did not burn down the house, though.

That's too much work. For $9 Prime, the lights come with the resistor inline.

https://www.amazon.com/gp/product/B0798T9BXG/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

I had a friend who shot his old tablet. The lithium fire was spectacular. The Range Officer wasn't thrilled.

 

[lr64]

That's not bad for 8 of them, though they'd probably weigh more.

Was the RSO more upset about the fire or the gun? I've seen people put a nail through lipos, but never a bullet. A damaged lipo isn't safe to take home until it's discharged somehow.