What went wrong!

[braddsn]

Chunn, 1 thing that will cause performance problems is if your bp is not completely dry. Do you have a dehydrator? 'Most' of the problems I experienced in the beginning of my pyro career was due to things not being 100% dry. Moisture is your enemy! Having your lift charge in a sandwich baggie and taped up tight to the bottom of the shell will help some, and make sure you are pasting 5 or 6 layers on a 3, and using the proper mortar size. FWIW, 3 inch ball shells are the trickiest shells to lift, I have found. For some reason, there is more of a size variance in mortar sizes and hemisphere sizes in the 3 inchers. 4 inch and up tend to fit better.. no idea why. Good luck! You will get there. 1 more thing... a lot of guys will tell you that you should only be using 10% of shell weight to lift your shells. Use that number only as a starting point. Everyone's bp is going to be different.. depending on KNO3 quality, charcoal type, the way the charcoal is cooked, and the ball mill used, etc. There are several factors. You will use anywhere from 10% to 25% of shell weight to lift your shells. If it takes you 18% to lift your shells, so be it. That doesn't mean you have slow bp. Use whatever it takes to get your shell to desired altitude. For 3" shells, I have used anywhere from 12% to 25%, depending on many factors (where my KNO3 is coming from, how I cook my charcoal, where I get my hemispheres from, and the length of the mortar). Don't sweat it if you have to use more than 10% to lift. My guess is that most folks do.

Edited January 28, 2016 by braddsn

[Chunn7704]

Thank you Braddsn, that was very helpful. i will weigh my bp and reweigh it to make sure everything is good and dry next time.

[Mumbles]

One sort of quick test to see if your BP or stars are dry is to put some into a plastic bag, seal it up, and stick it out in the sun for a few hours. This works better in the warmer months. It should still work now, but may just take longer. This isn't a definitive test, but is a simple way to check. Going by mass is most accurate.

[BlueComet24]

Mumbles, are you saying to do that to see if there's any condensation inside the bag? That's a good idea.

[FloridaCracker]

Yep, check for condensation. It is a fairly quick and accurate test and even if there is very little water left it will show a foggy spot on the bag that looks similar to breathing on a piece of glass. Doesn't take all that long when left in a sunny spot.

[lloyd]

"..talking about condensation in the bag?"

-----------

 

He IS! It's an old and honored technique.

L

[Chunn7704]

thank u guys. lots of great info

[Mumbles]

Haha. Forgot the most important detail.

[rogeryermaw]

Don't overlook the clearance between shell and mortar. In my experience, on 3" shells, roughly 1/8" is a good fit. Any more loose and lift gasses will pass around your shell, robbing lift power.

[Chunn7704]

thank u for that comment. ive been wondering whats the max amount of gap u can have.

[deepdixie]

Chunn, 1 thing that will cause performance problems is if your bp is not completely dry. Do you have a dehydrator? 'Most' of the problems I experienced in the beginning of my pyro career was due to things not being 100% dry. Moisture is your enemy! Having your lift charge in a sandwich baggie and taped up tight to the bottom of the shell will help some, and make sure you are pasting 5 or 6 layers on a 3, and using the proper mortar size. FWIW, 3 inch ball shells are the trickiest shells to lift, I have found. For some reason, there is more of a size variance in mortar sizes and hemisphere sizes in the 3 inchers. 4 inch and up tend to fit better.. no idea why. Good luck! You will get there. 1 more thing... a lot of guys will tell you that you should only be using 10% of shell weight to lift your shells. Use that number only as a starting point. Everyone's bp is going to be different.. depending on KNO3 quality, charcoal type, the way the charcoal is cooked, and the ball mill used, etc. There are several factors. You will use anywhere from 10% to 25% of shell weight to lift your shells. If it takes you 18% to lift your shells, so be it. That doesn't mean you have slow bp. Use whatever it takes to get your shell to desired altitude. For 3" shells, I have used anywhere from 12% to 25%, depending on many factors (where my KNO3 is coming from, how I cook my charcoal, where I get my hemispheres from, and the length of the mortar). Don't sweat it if you have to use more than 10% to lift. My guess is that most folks do.

This is a great post, and I appreciate your input. The black powder I make for shell lift would probably be considered "hot" by many as I use Black Willow Charcoal, and make sure all ingredients are finely powdered before a mill run. My ingredients are pure and dry, my mill optimized, yet I still find myself using more than the magic 10% number for lift. I make a lot of 2.5 inch shells, and routinely use up to 20% of shell weight in lift charge for the 2.5 inchers, using the "hot" charcoal. I had originally thought I was doing something wrong along the way, but after many mill runs and many times wet granulating my BP, and having consistent results, I have determined that the 10% number isn't ideal for me and my methods.

[lloyd]

Where does this "magic 10%" come from? Although it does apply to very small shells, it doesn't work over about a pound... too much lift!

 

It's _always_ been for larger shells, over a pound and a half, "an ounce per pound, up to 10lb, then 1/2 ounce per pound beyond". (That's 6.25%)

 

In my 4" plastic ball shell class, I recommend about 1-1/4 ounces (35 grams) of commercial 4FA lift for a shell weighing between 10 oz. and 14 oz. But those are small, light shells. At about 20-25 oz., you MUST decrease that amount, lest you damage the shell by the lift force.

 

Lloyd

[braddsn]

Deepdixie, I went through this exact same thing. I kept trying to chase a problem that didn't exist. 10% was what everyone was telling me, and that rarely was working out. Mill is optomized, ingredients are dry and pure, using ERC charcoal. My lift requirements go down as shell weight goes up (percentage wise), but with the small shells, don't sweat how much lift you are using. USE the amount that gets you to altitude. For me that falls between 12 and 20% of shell weight. It has changed slightly however, because now I am using MCRH to lift 3 and 4" shells.. typically with 3's I am using 18-20g MCRH (7:1 bp:hulls). I am never concerned about over-lifting 3's and 4's, it's almost impossible to damage them if they are pasted properly. 5's and up are a little different.

[Wiley]

10% was what everyone was telling me, and that rarely was working out.

 

No Brad, I was telling you 6.25% Bore obturation (how well the shell fits the mortar) is a huge factor in lift height, as many have already mentioned. Cylinder shells are typically better at using their lift charges effectively, simply because of their increased length and relatively high weight for a given diameter.

 

In my experience, I've noticed that little 1.75" single break cylinders need 10% of their weight in a fairly fine powder granulation to lift properly. 2 breaks and larger really just need 6.25%. But again, that's with my shells, my powder, and my mortars.

[FlaMtnBkr]

Have you ever tried testing your BP batches somehow? That way you know how they compare to each other instead of just relying on doing things correctly and expecting good results. You can launch baseballs or build the FPAG BP tester that is outlined on Skylighter.

 

How long does it take for your BP to dry? If you let it dry slowly so that it stays wet for a long time that can have a pretty big effect on power. What mesh size are you using? And are you making your own willow charcoal or buying it from somewhere? There are quite a few threads from the last year or so that detail problems people were having with their BP and lots of good suggestions on how to fix things.

[deepdixie]

Have you ever tried testing your BP batches somehow? That way you know how they compare to each other instead of just relying on doing things correctly and expecting good results. You can launch baseballs or build the FPAG BP tester that is outlined on Skylighter.

 

How long does it take for your BP to dry? If you let it dry slowly so that it stays wet for a long time that can have a pretty big effect on power. What mesh size are you using? And are you making your own willow charcoal or buying it from somewhere? There are quite a few threads from the last year or so that detail problems people were having with their BP and lots of good suggestions on how to fix things.

I've never done any specific tests, such as the Baseball launching test. I wet granulate my BP using water and a 4 mesh screen. I don't sort it into grades. My mill is rather small so I am not able to produce large quantities where I can sort into 2FA, 4FA, etc.

I dry the BP granules in the sun, so the drying process is done rather quickly. All particle sizes are mixed together and used for lift. I use MCRH w/ slow flash booster for the break charge. I have been buying my Black Willow Charcoal from someone else. Strangely enough, when I used Commercial Airfloat I used about the same amount of BP for lift and the shells were launched to roughly the same altitude. The Willow Charcoal hasn't been worked wonders like I thought it would. I would like to acquire some Cedar Charcoal and give that a go.

[rogeryermaw]

Brad turned me on to that e.r.c. charcoal and man what a difference it made! My pine coal was always sufficient and got the job done but with the cedar, it reduced my powder requirements by at least 10-15%. I guess eastern red isn't a true cedar but classed as a juniper. Wonder if other juniper species produce as well?

[deepdixie]

I see that USA Pyro Supply normally carries Eastern Red Cedar Charcoal, but they are temporarily out. Hopefully they will cook more soon and offer it for sale.

[dynomike1]

I always heard Black willow was good charcoal. I think it makes a difference on what part of the tree you use to make it. I don't cook it, this is just what i have heard other people say.

[lloyd]

It's a good, fast charcoal. It might or might not be as fast as ERC, but it's consistent, and makes great lift powder and burst powder.

 

Where I live (Florida), it's ubiquitous; you find it in every wet roadside ditch for the taking.

 

I choose to cut limbs and stalks less than 1.5" o.d., which keeps most of the wood somewhat 'pithy', rather than hard. Of course it should be dried before cooking, and should be de-barked, as well. The bark contains fairly large amounts of silica inclusions which are not beneficial in pyro charcoal.

 

But de-bark while it's green! The bark just peels away easily then. When it's dried, it's hard to get off cleanly; a drawknife is usually necessary, and a real pain. When green, you can just slit the bark down one side of the limb, wait a day or two, and peel it off like a wrapper.

 

Lloyd

[braddsn]

Chunn, I do have one more suggestion for you. Ned turned me on to this, and I am not looking back!! I use MCRH now to lift everything 5" and under. There are several reasons for this... 1) For me, making a batch of MCRH in my star roller is MUCH easier and WAY less messy than granulating a bunch of bp. 2) It dries MUCH faster than granulated bp. I make the coated hulls in the roller then they go straight to the dehydrator. In a couple hours, they are ready to use! 3) They seem to be a little more powerful than the same amount of granulated bp (this is most likely due to burn rate/flame propagation I would imagine). For example, Ned suggested I use the same amount (in weight) of MCRH as I would normally use in granulated bp as a starting point. I did that, and found that I need to use about 80% of what I would normally use in granulated form. Give it a try, you might like it!

[dynomike1]

Or you could follow a Beaver around , he will strip it for you. I am using ERC now, one reason is Paulinia is to hard to come by. I think it is still at the top of the line. But between it and ERC and Red Alder i am not seeing enough difference to change my timing.

[Chunn7704]

thank you guys. very much appriciated