27 replies to this topic

[digger]

The jar is 1.3L and i use half full of ceramic 1" media, the jar rotates at around 75 rpm....

As for the video, I have used the last of my BP so I will post a vid when the batch (currently milling) is done!

Thanks

mmm, I have nothing against the correct ceramic media, I have used them for years without problem. I would imagine that the inside diameter of your jar is about 3.5" for that volume or maybe 4". So I would say that the media are too large for the jar. At a guess you will only have 20 ball in the jar. If this is the case it is far to few.

The problem is that if you go down to 1/2 ceramic they simply won't have the umph in a jar that small. So you may be better switching to 1/2 lead media.

How many grams of bp are you trying to mill in this jar.

D

[dr thrust]

hmm if it doesn't blow up first !, ceramic ahhhhhgg

[portfire]

I also use a 1.3lt jar but use 20mm ceramic, jar is half full. And as Digger said how big is you batch?

[darkfang77]

The jar is 1.3L and i use half full of ceramic 1" media, the jar rotates at around 75 rpm....

As for the video, I have used the last of my BP so I will post a vid when the batch (currently milling) is done!

Thanks

Sorry to interupt, but wasn't there another thread on the forum saying that certain types of ceramic media spark? Or was the verdict inconclusive?

[digger]

Sorry to interupt, but wasn't there another thread on the forum saying that certain types of ceramic media spark? Or was the verdict inconclusive?

A bit off topic. But some types do spark and others don't. So check before you use. It is easy just go into a very dark room, rub and strike them together if they spark don't use them.

[dr thrust]

sorry to be off topic but whats in the media that make some spark and others not?

[RFD]

When burnt loosely does it leave any residue,if burnt on a sheet of white paper it should just leave a slightly sooty mark without incinerating the paper,try pressing into pucks and then breaking up and sieving into BP grades,one of the hardest things to get right is BP in my opinion,if possible try and compare with a bit of commercial,in the early days i thought i had got it spot on until i tested some against commercial,all i can say was the homebrew was poor until i got everything just right,try a percentage of red gum,3% to 5% per 100g will liven it up a bit,dextrin will slow it down but if granulating i dont think there is a alternative,this is why i prefer pressing as it holds together fine without a binder,

[starseeker]

I wonder if dumper has hit the nail on the head with his idea of the morter being damp,when your next batch is ready and fully dry,rather than just tipping it down the morter,make a little baggie from the corner of a plastic bag,put your b.p in this and tie it off, drop this in and try then.

[Vic]

I have not been putting lift cups on them I have just been poring the BP in the mortar and There is a 1/8" hole in the bottom of the mortar

Pouring your BP into the mortar is not going to work very well,you are barely covering the bottom of the mortar, with 3.5g the flame propagation will be slow, try either making a dimple in the bottom of your mortar to hold the BP or use a corner of a sandwich bag to to contain your BP. Bottom fusing like this is a pain but if you use a long piece of fuse you can thread this from the fuse hole and up to the top, you can then tie the bag on and then pull the fuse back down the mortar then cut of the excess fuse, Try it and see.

Edited by fflach, 21 September 2010 - 07:59 PM.

[cooperman435]

Its very good stuff but the willow definitely has the edge over it :-)

Id agree totally with PyroPDC, your chems are unlikely to be the cause (but not necessarily absolutely blame free), bottom fusing wont help but again unlikely to be the cause, try bagging your lift to prevent dampness when in the tube, and also top fusing with QM is a solution to the hole in the bottom of the mortar as u can then fill it and bag the whole shell to prevent dampness.

Are you charging your mill as per the normal volumes? the media is a bit big yep and without trying to PooPoo ceramic (so I dont get flamed by you fans out there) for small mills I think its justified to say lead is better due to its weight

your BP may seem fast but do you have anything to compare it against? fast to one person may be slow to another? Video of tests (open, charged into a tube, narrow lines of it burning etc) and a dummy shell firing would help us to help you a lot too

Phill

[Peret]

I'm with fflach here - that small amount of powder loose in a 2 inch mortar won't burn fast enough to do the job. The grains won't even be touching each other. I had the same problem when I started making shells and tried loose lift, but the same amount of powder tightly confined in the corner of a baggie goes off with an impressive 6 foot tongue of flame and shoots a 35g shell over 400 feet.

[cooperman435]

I beg to differ, as long as there is sufficient lift, loose or bagged it will still do the same job as long as its dry and good to go.

In fact if its confined (tightly packed) it will slow it down slightly.


This really must be down to a basic BP issue me thinks