Shell Lift

[mickyp]

If you were to take three identical shells and use the same tube, how much difference to the lift would be made by the bonding of the cup charge, I am just thinking that if a certain pressure is reached prior to the breakaway point would the initial

"push" be more and is the sealing of charge to shell a variant that should be accounted for? i hope this question makes sense.

Micky

[AirCowPeacock]

I have heard it will increase a significant amount, but I personally have not noticed any significant increases, except wirh very light and small shells.

[pyrojig]

There will be very little diff. The main reason for gluing the cup to the shell is to make the shell easy to load and shoot like commercial shells. Confinement will make very little diff, unless the tube was excessively short. All the powder will be consumed before the shell leaves the tube, so it will achieve the full push the bp has to offer .,

[CrossOut]

the purpose of the lift bag / cup is really only for safety and transportation purposes.. traditionally Japanese would simply dump BP into the bottom of their mortar and drop a red hot ember in to set it off. that said there will be little to no difference as all the BP should burn up before the shell leaves the gun.

[mickyp]

Thanks for that, I was trying to think of an analogy for it like revving an engine before dropping the clutch for a quick getaway, / initial push

[Mumbles]

There is some basis behind confining the lift. Particularly with ball shells, I seem to get a better lift with at least mildly confined BP. I typically tape the lift onto the bottom of myshells with a layer of aluminum tape, or paste a few patches of paper over the lift bag. If I leave the lift just loose in the bottom of the mortar or in a poorly confined bag, I tend to need more lift or the shell will under lift. To me it's not the confiment, but just the BP being located in a confined bundle so the fire spreads quicker and it gets to the critical confinement or pressure inside the mortar before the shell starts moving significantly

 

There are of course also the Maltese examples where a lift maroon is used, and can drastically cut the amount of BP required for heavy shells.

 

I've heard of that japanese method before, but there really is really only the description in F.A.S.T. and a short description from Mike Swisher on rec.pyro as sources.. I think the hot ember or star they used is called a sindoro, which can help in finding stuff. There is a video showing this method in action. http://pyrotechnics.no-ip.org/files/004.mpg

 

Honestly, I'd rather fire shells as Shimizu describes with the hot coil instead of the sindoro. Most certainly if there was any consideration for reloading.

[californiapyro]

The hot coil seems really practical, except I'm not sure how long it would stay hot enough to ignite the BP. Also, it seems that method may afford a little more time to clear one's hand from the mortar.

[Mumbles]

Shimizu says about ten 6" shells per coil. It seems like relatively few, but I'm also not about to prove him wrong.

[californiapyro]

Guess you've got to drop them fast, then. A system where the lift gasses heated the coil enough to set off the next shell would be ideal, i think.

[Seymour]

There will be very little diff. The main reason for gluing the cup to the shell is to make the shell easy to load and shoot like commercial shells. Confinement will make very little diff, unless the tube was excessively short.

 

 

the purpose of the lift bag / cup is really only for safety and transportation purposes..

 

With decent Black powder of a relatively fine granulation I pretty much agree. However I think the exceptions are far from uncommon and should be mentioned.

 

With lower speed black powder the difference between confining the lift charge and having in a flimsy container or loose in the mortar with just the shells weight to confine it can be enormous. Two layers of recycled kraft can convert a 50g BP charge from something that lobs a 4" shell a few meters out of the mortar, allowing it to explode on the ground, to something that throws a 4" shell to pretty much the same height as if it was commercial powder. I've found the same can apply with very coarse commercial lift.

 

While I fully subscribe to the camp that worships the ritual of milling black powder for a full length of time, producing powder where confinement is largely for fireproofing and so on, I understand that there are people in situations where for various reasons, eliminating or reducing the amount of live ball milling is a priority. Having premium BP is good on all levels, and for making really awesome BP end burners it's a great benefit, but for lift, it's certainly not necessary.

 

As Mumbles mentioned, the Maltese have a system for lifting their marvelous multibreaks with well confined lift charges utilising much less BP than would be typical according to the various lift guidelines. I believe that at least some of them use under milled BP compared to how we traditionally do it, like 1-2 hours and get away with both less and weaker lift. I guess when your confinement consists of a spiked canister of BP that crushes a layer of newspaper in to a tight fitting wad below a shell resembling a small tree trunk, it does not need to be that fast.

 

I used 1.5 hour milled BP for quite a few years that was pretty lousy with traditional lifting techniques, using twice what would be needed with commercial grain to get things in the air, and even then being unreliable. However with those two layers of Kraft it could be used 1.1 with commercial lift, reliably and with similar results. My current 8 hour milled Paulownia BP, granulated through a kitchen sieve with 2% Gum Arabic added is another beast altogether. Substituting that, and other home made premium grains, with commercial lift 1.1 I've killed a few mortars.

 

Guess you've got to drop them fast, then. A system where the lift gasses heated the coil enough to set off the next shell would be ideal, i think.

 

You'd have to drop them really fast, perhaps too fast to be humanly possible, and if it is, it would be pretty scary. Though you're hot firing, so it's not like you've volunteered for a relaxing experience. I'm sure that an electric glowing coil would work, for those determined in the pursuit of longer hot firing experiences. Considering they came up with the system of hot firing to get shells in the air at the highest rate possible, I think they would have tried to put shells in fast enough to stop the iron cooling, but they are saying it only lasts so long. However you just keep your second coil in the embers of a fire nearby

 

The hot coil seems really practical, except I'm not sure how long it would stay hot enough to ignite the BP. Also, it seems that method may afford a little more time to clear one's hand from the mortar.

 

I've hot fired a single four, and agree that the time you have to withdraw your hand is a positive step. It was exciting and dangerous enough as it is. As with all quick methods of hand firing, you have a lot of trust in that thin paper shell full of explosives.

[Peret]

Have you seen videos of Japanese using the hot coil method? It's insanely dangerous. Not only do you have just milliseconds to get your hand out of the way, but you're crouching down inches away from the mortar, usually with a number of live shells on the ground in front of you for the reload. A muzzle break would seriously hurt you, and a flash salute exploding in the mortar would probably kill you.

[psyco_1322]

Have you seen videos of Japanese using the hot coil method? It's insanely dangerous. Not only do you have just milliseconds to get your hand out of the way, but you're crouching down inches away from the mortar, usually with a number of live shells on the ground in front of you for the reload. A muzzle break would seriously hurt you, and a flash salute exploding in the mortar would probably kill you.

 

That video Mumbles posted was scary looking too, that guy put his fingers nearly into the gun, a half a second slower, he would have lost a few.

[marks265]

 

There are of course also the Maltese examples where a lift maroon is used, and can drastically cut the amount of BP required for heavy shells.

 

 

The maroon is only part of the lift "system" or sabot to make that happen. The maroon alone would be far less effective.

[Pretty green flame]

The maroon is only part of the lift "system" or sabot to make that happen. The maroon alone would be far less effective.

 

What do you mean by lift system?

 

From the pictures i've seen of Maltese shells, the BP maroon (bottom shot if you will) consists of a paper case that has been heavily spiked with string. Ofcourse this thing packs one hell of a punch, so the maltese use a shock absorber between the maroon and the shell itself. I've heard that using compressed cotton, wool or even towels (cotton, I know) is fairly common. The shock absorber would also likely act as a sabot as you mentioned, when compressed it exapnds in diameter creating a tight fit in the tube.

 

Come to think of it, we're probably talking about the same thing.

[marks265]

PFG,

 

Yes, you answered your own question Your last line is the most important aspect.

[mickyp]

With decent Black powder of a relatively fine granulation I pretty much agree. However I think the exceptions are far from uncommon and should be mentioned.

 

With lower speed black powder the difference between confining the lift charge and having in a flimsy container or loose in the mortar with just the shells weight to confine it can be enormous. Two layers of recycled kraft can convert a 50g BP charge from something that lobs a 4" shell a few meters out of the mortar, allowing it to explode on the ground, to something that throws a 4" shell to pretty much the same height as if it was commercial powder. I've found the same can apply with very coarse commercial lift.

 

While I fully subscribe to the camp that worships the ritual of milling black powder for a full length of time, producing powder where confinement is largely for fireproofing and so on, I understand that there are people in situations where for various reasons, eliminating or reducing the amount of live ball milling is a priority. Having premium BP is good on all levels, and for making really awesome BP end burners it's a great benefit, but for lift, it's certainly not necessary.

 

As Mumbles mentioned, the Maltese have a system for lifting their marvelous multibreaks with well confined lift charges utilising much less BP than would be typical according to the various lift guidelines. I believe that at least some of them use under milled BP compared to how we traditionally do it, like 1-2 hours and get away with both less and weaker lift. I guess when your confinement consists of a spiked canister of BP that crushes a layer of newspaper in to a tight fitting wad below a shell resembling a small tree trunk, it does not need to be that fast.

 

I used 1.5 hour milled BP for quite a few years that was pretty lousy with traditional lifting techniques, using twice what would be needed with commercial grain to get things in the air, and even then being unreliable. However with those two layers of Kraft it could be used 1.1 with commercial lift, reliably and with similar results. My current 8 hour milled Paulownia BP, granulated through a kitchen sieve with 2% Gum Arabic added is another beast altogether. Substituting that, and other home made premium grains, with commercial lift 1.1 I've killed a few mortars.

 

 

 

You'd have to drop them really fast, perhaps too fast to be humanly possible, and if it is, it would be pretty scary. Though you're hot firing, so it's not like you've volunteered for a relaxing experience. I'm sure that an electric glowing coil would work, for those determined in the pursuit of longer hot firing experiences. Considering they came up with the system of hot firing to get shells in the air at the highest rate possible, I think they would have tried to put shells in fast enough to stop the iron cooling, but they are saying it only lasts so long. However you just keep your second coil in the embers of a fire nearby

 

 

 

I've hot fired a single four, and agree that the time you have to withdraw your hand is a positive step. It was exciting and dangerous enough as it is. As with all quick methods of hand firing, you have a lot of trust in that thin paper shell full of explosives.

 

Very informative post thanks, I think confinement is the way to go for lift charge

[TritonPyro]

I had a problem gluing the lift cup on a plastic canister shell. Even at 10% of the shell weight the punch would rip out the base of the shell and Cato. I found the remains of one and part of the lift cup had ripped out the shell bottom. No more glue, I use 1 inch masking tape to seal and no more problem.

[coalman]

Good plan, the shell should be as intact as possible which is why it's sometimes better to use a slightly slower lift. Does anyone know roughly how much power (%) is transmitted to the shell velocity from a fast burning BP lift charge?