StarScream

Very good program. It’s sad to think that most kids these days don’t care about science, or much else for that matter… other than maybe their Xbox’s and Miley Cyrus.

For those of you that either missed the show or don’t live in the UK, you can download it via BitTorrent. It's a 700MB avi file.

He dissected a E9-6 (24mm), said it had ~0.5g ejection charge. He goes on to use 2.0g of homemade ejection charge in his knock-off.

Thanks Guys

I could have sworn that I read somewhere the 24mm motors use between 0.7-0.85 grams. I always read those Skylighter newsletters... must have forgot about that issue. 2g of polverone seems like a huge amount for an ejection charge, although it's probably ok for a large airframe.

Hey Guys

Does anyone know how much BP is used in the ejection charges of the 3 common sizes of Estes motors (13mm, 18mm & 24mm)? If memory serves me, I think the 24mm motors have 0.7g, but I'm not sure about the smaller ones.

Some good info there StarScream. Made me rethink my method of grinding down charcoal.

Though you may want to check if the metal was present before the milling/crushing process, get a plastic hammer and smash a couple pieces of charcoal and then run a magnet through it. The metal may have gotten into the charcoal during the manufacture process and not during the milling operation.

Metal in commercially produced charcoal is a definite possibility. The wood they use has been known to contain staples, nails, bullets, wire and more.

I’m 99% sure my metal contamination came from my coffee grinder and meat grinder, because I ground a batch of homemade willow with the meat grinder the day before I ground the commercial lump with it, and both charcoals had traces of metal in them. The amount of metal is small, but it’s there nonetheless. Any amount of ferrous (sparking) metal in a batch of ballmilling BP makes me cringe. Even pounding fountains and rockets by hand with traces of a sparking metal in the charcoal makes me a bit nervous.

This is why I always damp or wet mill.

Yuck. Doesn't that just create a big clumpy mess inside the milling jar?

Sodium benzoate! I have never worked with potassium benzoate, but I imagine it's probably very similar. They're both waxy substances that just love to stick to the milling media. Trying to run benzoate through a fairly fine screen is also a lot of fun. One thing that helps the milling of benzoate is to heat it up in the oven for at least an hour or more, then mill it right afterwards.