5 replies to this topic

[spanner]

I became curious as to what was meant by the different sizes of rockets when described by weight.

Everybody knows that a 4 ounce rocket is 1/2" ID, a one pounder is 3/4" ID, etc. While the idea has been broached that this is the weight of a lead or iron ball of the same diameter, this does not check out. Maybe a cylinder of the same diameter, of some set length?

A call to both Skylighter and Firefox got no definitive answer. Wolter's on holiday, and Google got me no conclusive answer, either.

So, does anybody know what these designations represent?

[Frozentech]

I became curious as to what was meant by the different sizes of rockets when described by weight.

Everybody knows that a 4 ounce rocket is 1/2" ID, a one pounder is 3/4" ID, etc. While the idea has been broached that this is the weight of a lead or iron ball of the same diameter, this does not check out. Maybe a cylinder of the same diameter, of some set length?

A call to both Skylighter and Firefox got no definitive answer. Wolter's on holiday, and Google got me no conclusive answer, either.

So, does anybody know what these designations represent?

Well, by 1634 at least, in John Bate's Second Book the ounce/lb scale had been set.

In "Proposition XII." of his 1696 book, The Making of Rockets, Robert Anderson states "Rockets are estimated either by Measure or by Weight; if by Measure, then they are estimated by Common Standard by Inches or by Feet; if by Weight, then they are estimated by Cast Iron, that is, by the Gunner's Rule, viz. An Inch Rocket weigheth two Ounces and a quarter: and Inch and half Rocket weigheth half a Pound: a two Inch Rocket weigheth a little above a Pound: a three Inch Rocket weigheth almost four Pounds: a four Inch Rocket weigheth nine Pounds: an eight Inch Rocket weigheth seventy two Pounds, which may be called a Rocket Royal."

Even though the exact weights are incorrect, it is obvious that they attempted to follow the 'Gunner's Rule' of the day, where the size of the cannon bore was described by the weight of the ball it shot, i.e. a "5 Pound Gun", etc. Since that time, due probably to the fact that pyrotechnic Art was passed down by Master to Apprentice for the most part, it became imbedded in the art. 10 years of Internet hasn't wiped out 500 years of tradition, yet.

Edited by Frozentech, 27 December 2006 - 02:04 AM.

[spanner]

Thanks for that information. I'll relax now, knowing that there's no real rhyme or reason behind the designations.

Maybe I'm way too anal in regards to such things (gms. for "g", amm. perc for ammonium perchlorate or NH4ClO4, etc., etc., etc. makes me CRAZY).

I'm somewhat dismayed that in a field so fraught with the potential danger of mishandling or misusing chemicals and compounds, that the proper nomenclature isn't insisted upon by the powers that be.

Old hands know their way around. Not so with new comers. I wonder if anyone has mistook a bastardized abbreviation for "grain" as "gram" and found themselves in a heap of hurt?

Alas, as I said, WAY too anal...

Edited by spanner, 11 January 2007 - 04:42 PM.

[Richard H]

Spanner, I applaud your pedantism!

[Andrew]

Nice!

IMHO I think that being a little more scientific could not be bad at all. I think that all rockets/drivers/SRMs should be classified by the total impulse and Specific impulse they provide. Not by the weight of the propellant or some other historical legacy. I must admit I never knew what a 1lb rocket meant!

[Mumbles]

I've heard this in several reputable sources and books.

It's not the mass of one lead ball, as has already been discussed here. It is the mass of lead ballS (note the plural) of the same ID as the tube that will fill the tube, so 10 lead balls. 1lb whistle is a misnomer, it would technically be an 8oz whistle if you went by the same sizing method as they are half as long. The sizing is done for BP tubing only of standard size, the sizing of other types of fuels and longer tubes and such piggybacks off the original method.

I've actually done this out for a 4oz rocket, and it is very close, within a 5grams or so.