reducing friction

[chronie]

Is there I substance I can coat the inside of my tubes with, to make my mortors leave the tube faster? Or will it even make a difference?

[yeagerb]

Moved to Racks and Launchers as it seemed more appropriate.....

[razorback]

You really don't want to reduce friction, a good snug fit allows gas pressure from the lift charge to build under the shell giving you more hight.

[shrapnel]

Setbacks....

1. Most friction reducing substances are flammable.

2. Whether flammable or not, would cause a lot more residue build up in tubes.

3. PITA!


Marty, did ya get my p.m.?

[Marty]

Is there I substance I can coat the inside of my tubes with, to make my mortors leave the tube faster? Or will it even make a difference?

Not to be picky but, in this context, mortars and tubes are the same thing.

Proper fit of the shell into the mortar will give the best performance, no coatings required.

[Bruce in SC]

There is such a thing called Ballistics, even with fireworks, and what little friction there is in the tube is is reduced when the hot gases completely encapsulate the shell to lift it into the air. We tend to think that the shell is pushed through the tube, but in reality the expanding gases below the tube help to move it along with the gases that are passing by it. There is expanding air that moves upward in a column even before the shell comes out.

Picture a baseball moving through a water pipe with water before it and after it.

[FWX006]

Good analogy Bruce. If you could see a mortar in slow motion as the shell travels up it, you would witness a moving bulge, even in a steel gun. Resistance is necessary for good performance. The thing that really makes the diference is the length of the mortar.

[DennyMo]

Good analogy Bruce. If you could see a mortar in slow motion as the shell travels up it, you would witness a moving bulge, even in a steel gun. Resistance is necessary for good performance. The thing that really makes the diference is the length of the mortar.
Wow, I'd love to see some high-speed video of that!

[FWX006]

So would I!!

Know the theory, but never seen the pix.

[pyroholic]

Yeah; Got it! Like the wind that comes just before the subway gets to the platform. "PH"

[Pyroman6000]

Guys, I actually saw a video in slo mo of a shell being lit in a clear mortar. It looks kind of like the gasses escaping around the shell suck the shell upward. The shell moves slowly up the tube until it hits the top, and then explodes upward into the sky. Looked really cool.

Anybody else notice that when you light a shell, the smoke coming out of the tube is whitish gray while the fuse burns, but just before lift it changes to a THICK brownish gray? Reminds me of the way the smoke conditions change at a structure fire just before it flashes over or backdrafts...

That was a good analogy, Bruce!

[RPS]

There are some high speed shell launch videos here:

http://www.starflightinc.com/HighSpeedVids.html

[SEAHAWK]

those high speed videos are cool! I like the black cat shell, it seems to have to most embers that hang for a while.