28 replies to this topic

[Kembang Api]

Hi Guys,
Could anyone share a BP formula for lift charges, I had try to launch a star using Stailess steel tube that I drill a 2 mm hole at the bottom for the fuse. Each time I fire the star, it does not lift high enough, even I add more BP to more that 2 grams.
I had also try to fire it from the top by dropping the fuse to the tube.

My BP composition is 75/15/10 and are seive passing 100 mesh. Could anyone help me!!! Thank you

[Rhodri]

I had try to launch a star using Stailess steel tube that I drill a 2 mm hole at the bottom for the fuse

Hey, please don't use metal tubes at all. It's a very bad idea.

[Kembang Api]

Hi Rhodri,

Thank you for the advice. Actually I took the idea from Skylighter.com for the purpose of star testing tubes. I used it for the same purpose.
The tube is very thick and If you think it might break, that would be very hardly happen. I had used them for many time even making a big bang.
Please advice! I might left something behind. "Safety First"

[alany]

I've used a friend's steel stargun, it works just fine and is quite safe, even with enough lift to make it ring like a bell. Just never try to shoot crossettes or insert shells with it!

All my guns and mortars are paper, which also works just fine but the fuse hole ablates slowly gving them a life of 50 or so shots.

You shouldn't need any more than 2g of lift. How long is the mortar, and how fast is you lift? If it is just 100 mesh screened greenmix then I am not suprised. Lift should really be milled and pressed, then corned. Try at least granulating it pulverone style.

[Kembang Api]

My BP is make by first mill the KNO3 with charcoal at the ratio of 20:1 (Mix A) and than the rest of the charcoal and sulfur are mill (Mix . Than I mix A and B by passing 100 mesh twice. Finally mix it again using plastic spoon manually.

Yes the BP has never been press, or corned, Is this the reason the star did not lift? So the lift charge should be in the in the granulated form!!

The star testing tube is about 10 to 12 inch length. thanks

[chim-chim]

All my guns and mortars are paper, which also works just fine but the fuse hole ablates slowly gving them a life of 50 or so shots.

Have you tried water glassing the fuse hole?

[alany]

chim-chim: Yes, but i usually don't bother, 50 stargun shots is a lot. I guess you could do the calcium silicate treatment thing to the entire tube if you wanted to, but it is trivial to just roll another tube when the current one stars falling apart.

Kembang Api; Yep, i highly recommend you granulate your lift in one way or another. Moistening your A+B mix and pressing it in a die then corning should give you reasonable speed, perhaps slightly better than just adding dextrin and ricing. However, despite what the BP making bible says, I always mill my BP combined for at least 1 hour. (I generally mill it combined from scratch, for 3-5 hours).

Screening the mix through 100 mesh must be messy!

[Kembang Api]

Thank you so much Alany. I did not realize that. I will try to press them and corning them tomorrow.

I had made a vibrating table and lock the seiving tray with 100 mesh on top of it and left them for few minutes. no dust and not messy.

[Stuart]

Kembang Api, could you please detail how you made a vibrating table? I have been wanting to make something like that but it has always been too violent

Stuart

[chim-chim]

chim-chim: Yes, but i usually don't bother, 50 stargun shots is a lot.  I guess you could do the calcium silicate treatment thing to the entire tube if you wanted to, but it is trivial to just roll another tube when the current one stars falling apart.

Me neither, just thought I'd mention it.

What kind of force do you need to press the BP for corning to get an improvement over ricing? I rice with dextrin now, and have no press, but I could put it between two boards and park a car on it , but seriously, is there a force you have to reach to get any improvement at all, or will any pressure sufficient to 'cake' it be an improvement over unpressed ricing. Does it need moisture, inherent or added, to cake or will pressure alone serve if sufficient?

A 10-15% average relative humidity in the dry season here means I have to moisten bentonite somtimes, and except shellac mixes, nothing I've done takes two days to dry. I've lifted tiny shells (9/16 I.D.) with powder riced three to four hours earlier.

[alany]

The optimal density is ment to be around 1.7 g/cc, however there is research that says that is too high. It is probably a function of the kind of charcoal you use. I just press it until the press groans and leave it under the load for a few minutes.

You have to moisten it or it will come out crumbly, and it has to be water or at least largely so, neat alcohol or acetone don't work.

To tell the truth I hate pressing and corning, most days now I just make benzolift or pulverone and use a bit more.

[Phoenix]

I used to press my BP with about 1.5% water (out of the mill) in a small die (about 20mm) with my 1.5 ton press. The result was _very_ hard grains that were like chunks of porcelain. The burn rate was pretty slow. On the plus side, the resulting grains were practically indestructable. I believe that in this case the sulphur is fused together by the pressure.

Later I changed to a larger die, 37mm ID (40mm waste pipe). The reason for this was that I hate pressing and corning too, so I thought if I could press 50g at a time rather than 10 my life would be a little bit nicer. If I pressed this with 1.5% water the pressed block had no intergrity whatsoever, and crumbled straight back to meal. However, using 10% water meant I could get a hard enough cake to corn, although still a bit soft. Once the grains had fully dried, they became hard enough to handle normally. I think that the pressing in this case just consolidated the powder into lumps, and the extra strenth was provided by dissolved KNO3 binding the particles as it crystallised.

When I came to test some, the low density powder burned much faster than the densely pressed grains. It isn't quite as durable, but that has not really been a problem so far.

[Kembang Api]

Hi Stuart,

Let me draw it down this weekend for the vibrating table and the picture as well.

Basically is a small DC motor driving an unbalance weight (which is moveable to control the vibration) This unit sit on a steel plate. The seiving boxes are mounted on this plate (depending on the vibration adjustment), normally I had 3 sizes of seiving box, during the operation.

The whole plate and the seiving boxes are mounted on 6 spring, the base plate is made of steel box fill with lead (making the base plate heavy).

I hope this will give you some idea.

[Stuart]

Thanks Kembang Api, I think I know what you mean, might have a go tomorow.