Circumference vs diameter

[NWPA]

Was pondering this and thought I would come to the experts. When did size designation change? On display shells used to be 9" - 12" etc. Now it's diameter. Also when did 1.1G class start. So many classes, was B or C.

[PGH_Pyro]

i am not a BATFE / HAZMAT / DOT expert but I believe the 1.1G thing started after 9-11 . And it applies to shells over 6" and/or salutes ?
i need to go read through the "orange book" .

[jknepp1954]

I am thinking the 1.1 designation was maybe like 5 or 6 years ago???
remember 9-11-01, then all the BATF changes in May, 2003, then it was maybe around 2008 0r 09 the 1.1 thing....
awe shucks - i will just let the 1.3 experts answer that

[displayfireworks1]

I was working a Zambelli fireworks display once somewhere around 2004 I believe, as I was loading shells I noticed a distinctly American made Italian type shell, It caught my attention. It was made at the Zambelli plant. It was stamped with the year 1989, and marked 12 inch shell. In reality it was a four inch shell. when we look back at our pyro history in United States I would love to know if anyone other than Zambelli used this measurement system.
From what I know about this, it is a marketing strategy. When a city is having a fireworks display and receive proposals from more than one company, they start counting numbers. How many shells and what size, how many shots in the air etc. It is most likely a natural way to try to compare the proposals if you know nothing about fireworks. If you are in the display fireworks business you can use this strategy to your advantage. Example: x company is only giving you 4 inch shells! I am giving you 12 inch shells. They reality is the shells are the same. I know Zambelli Fireworks did this for years. It is all a marketing strategy is the word I received on this.
I am not a math expert but I believe the circumference of a pipe or mortar may not always be a multiple of 3 exactly when measuring the inner diameter , it may depend on the thickness of the pipe. It may follow the outer diameter x 3. problem is fireworks use the inner diameter.
http://dandumitrache.com/wp-content/uploads/2013/07/circumference-circle.png
http://industrialsupplyproducts.com/wp-content/uploads/2010/10/bags-diameter.jpg

[wizard7611]

You also showed Youtube this by posting a video in 2010 about the last american fireworks display showing how they used to measure these shells back then.

[Wholesale Fireworks]

Dave
this is very informative and will be very useful in the future. Thank you. I will definitely store this one away for future reference.

[displayfireworks1]

From 2010
You are correct, you can see some of the old measurements in this video. Slide to 4:40 minutes.

http://www.youtube.com/watch?v=qqMKNTb9Ngs

http://www.youtube.com/watch?v=a5wNsE2suhc

http://www.youtube.com/watch?v=wztMad6yBVo

[NWPA]

Now after seeing those shells with the old designation [circumference] I am remembering the ones I saw were all can style shells, not spherical. Matter of fact when I dissected a 9" [3"] one it was made with a paper "medicine can",with fiber discs on either end, wrapped a number of times [end over end] with twine.