WARNING AND DISCLAIMER:  If you are underage, then consult with your parents or guardians before attempting any of this.  You are on your own - I'm not responsible for your actions or harm you may bring to others because of your actions.  Making the items described below  can result in injury or death to you or people in your vicinity. Some things mentioned here may be illegal to make in your city, county, state, or country so check the laws that apply to you before you attempt anything described here. These notes are not complete on purpose. If you are reading them and new to pyrotechnics, then you are making a mistake. Stop now - this page is not for you. Get a beginning book on fireworks (see Skylighter or American Fireworks News (very quick shipping)  for a start) and read up. You can't make any of this work without more information so read up or join a club or ask someone to help you.

Tables

 

Rocket Engine Sizes

  
'Poundage' I.D. Normal Length
     
2 oz 3/8" 2.75"
4 oz 1/2" 5"
8 oz 5/8" 6-1/4"
1 lb 3/4" 7-1/2"
2 lb 7/8" 8"
3 lb 1" 10"
3.5 lb (estimated) 1 1/8"  11" (estimated )
4 lb 1-1/4" 12"
6 lb 1-1/2" 16"

 

Granulations of Potassium Nitrate Black Powders

as posted on rec.pyrotechnics

Source:

AMCP 706-175
Engineering Design Handbook
Explosive Series
Solid Propellants Part One
September 1964

Mil Grade of Powder Retained Sieve Max % Through Sieve Max %
A1 4 3 8 5
A2 4 3 12 5
Cannon 6 3 12 5
A3 12 3 16 5
A3a 12 3 20 5
Musket 14 3 25 5
FFG 16 3 30 5
A4 16 3 40 5
Shell 16 3 50 5
FFFG 20 3 50 5
A-5, Fuse 40 3 100 5
FFFFG 45 3 140 5
A-6 100 5 140 15
A-7 100 3 140 50
Meal 100 5 200 50

 

Commercial Grades/Sporting Retained Sieve Max % Through Sieve Max %
Whaling 32/64 3 4 12
Life Saving Service 6 3 12 12
Cannon 6 3 12 12
Saluting 10 3 20 12
Fg 12 3 16 12
FFg 16 3 30 12
FFFg 20 3 50 12
FFFFg 40 3 100 12


"A" Blasting Retained Sieve Max % Through Sieve Max %
FA 20/64 3 5 12
2FA 4 3 12 12
3FA 10 3 16 12
4FA 12 3 20 12
5FA 20 3 50 12
6FA 30 3 50 12
7FA 40 3 100 12
Mead D 40 3
Meal F 100 3
Meal XF 140 3
 

from: Illustrated Dictionary of Pyrotechnics (shortened) and rec.pyrotechnics

The "Retained Sieve" and "Through Sieve" categories are confusing. However, the way AMCP 706-175 describes them is that the 'retained' sieve is accompanied by the percent that would be retained. The 'through' sieve is accompanied by the percent that would pass through (whew!). So for the first line:

Powder         Retained Sieve         percent         Through Sieve         percent
A1                         4                             3                         8                              5

For A1 powder and a sieve of 4, 3% would be held. For A1 powder and a sieve of 8, 5% would pass. That actually makes sense if you take a couple of cups of coffee and stand on your head. ;-}

Note that these would only be useful to the hobbyist if one were attempting to duplicate the commercial grades.  Some would say that such an undertaking would not be practical since it would be easier to purchase the graded powder. However, I've done sillier things and it is good to see the specifications in print.

Dan Williams (http://www.wecreate4u.net/dwilliams/top.html - website now down) created a more practical range of sizes by not overlapping the grains. His sizes (not official!) are

2Fg 4 to 10 Mesh
3Fg 10 to 20 Mesh
4Fg 20 to 40 Mesh

Why would one want to make artificial sizes like this? Probably the best reason is to categorize homemade BP. It is unlikely it would be meaningful to others but it would help make loads more consistent.  I like a 4Fg that includes more than just 40 mesh stuff. I run it out to about 100 just like the commercial version. The reason is that the grain is still good and hot. Anything past 100 is considered dust (thus slower) and is used for coatings or recycled and repressed.

Calculating Altitudes of Test Shells

The following are approximations but are close enough for most purposes if an accurate timing mechanism is available. I use a digital camera. Note that these do NOT take into account wind resistance. Wind resistance can be a huge factor in some cases so you are really just estimating with this method.

If you time the flight of a shell, half the flight time is when the shell was at apogee. This helps determine the timing fuse length and lift powder adjustments. The formula for total height is:

H=1/2 x A x T2

H=Height of the shell
A=Acceleration (32.2 ft per sec2)
T=Time to maximum shell height

For example, if the total flight time is 6 seconds, the shell reaches apogee at 3 seconds and the maximum height is 1/2 * 32.2 * (3*3)  or about 145 feet. Seven seconds total flight time (3.5 seconds to apogee) would be about 197 feet and eight seconds total flight time (4 seconds to apogee) would be about 257 feet.

Minimum Display Site Radius
outdoor displays
  < 3 in.   140 ft.
  3 in.   210 ft.
  4 in.   280 ft.
  5 in.   350 ft.
  6 in.   420 ft.
  7 in.   490 ft.
  8 in.   640 ft.
  10 in.   700 ft.
  12 in.   840 ft.
  > 12 in.   AHJ approval

The display site radius represents the total area from which the public is not allowed to enter during setup and display of an outdoor show. 

Source: NFPA 1123-1990 (through Passfire.com)

 

Minimum Mortar Length
(inches)
 
 
  Mortar ID (in.)   Single Break   Double Break   Up to 4-Break
  3   15   18   21
  4   20   23   27
  5   24   28   32
  6   28   32   37
  8   34   40   46
  10   40   46   54
  12   46   52   62

The mortar length is measured from above the bottom plug. A rule of thumb is 5 times the mortar diameter for shells under 8 inches, and 4 times the mortar diameter for shells 8 inches and up.

Source: Illustrated Dictionary of Pyrotechnics
 

Shell Burst Height
 
  Shell   Size      Burst   Height
  (in)   (mm)      (ft)   (m)
  3   76      400   120
  4   102      500   150
  5   127      600   180
  6   152      700   210
  8   203      900   270
  10   254      1050   320
  12   305      1150   350

The height above the ground for which a shell should typically break. Rule of thumb: 100ft plus 100ft for each inch of shell diameter.

Source: Illustrated Dictionary of Pyrotechnics
 

2Fg Lift Charges For Common Mortar Sizes

There is a table of lift charges posted in Pyrotechnica IX that uses 2Fa powder. Generally, it recommends 1 oz of 2Fa powder for each pound up to 10 pounds and 1/2 ounce per pound thereafter.  This table is often posted on the different Pyro sites as a guide to lift powder charges. Unfortunately, most of us amateurs can only easily get 2Fg which is much more powerful than 2Fa. Using the Pyrotechnica tables and 2Fg powder might result in serious overloading of the mortars. 

For mines, use a 1:5 ratio of lift to weight of stars if using 2Fa. I f using 2Fg use a 1:6 or even a 1:7 ratio.

As a rough estimate, use 2Fg for lift up to about 5" shells (there are experiences posted for larger shells but over 5" is pushing it). After 5", most think cannon powder (1fg) or the Fa powders should be used.  Always send up a test shell to determine the proper load. 

Since it is much easier to make Benzolift than hot BP (especially if one can't get/make the reactive charcoals), I've included Benzolift in the following table. These are small diameter rules of thumb for lift quantities that I go by (your mileage and cardboard shrapnel may vary):

 My 2Fg Lift Powder Loads (your shrapnel may vary)

Tube 2Fg Benzolift Notes
1.5" 3.5 grams 2 grams  
1.75" 3.5 grams 2 grams  
2 " 5 grams 2.5 to 3 grams  
3" 10 grams 5 grams  
4" 18-20  0 Don't use Benzolift for over 3" shells. Use BP - even poor BP will lift a 4" shell and Benzolift would probably destroy it
5" 35-40 0  
over 5" 0 0 Use 2Fa powder or cannon grade or something less hot than 2Fg

Well, just to prove there are a lot of opinions out there about this - here are some more inputs on lift powder quantities for 2Fg. The information was taken from Passfire, Best of American Fireworks News, United Nuclear, and David Bleser. Use this to get a feel for the starting size of your load.

Common 2Fg Lift Powder Loads (in grams)

Tube Bleser

Round Stars and Shells (p. 62)

 John H (Passfire) Jason Murri (Passfire) Chinese Festival (by autopsy - 2Fg equiv. assumed) Best of AFN II page 140 Shimizu (approximately 2Fg/3Fg - roughly converted to grams) United Nuclear (2Fg assumed)
1.5"
1.75"       3.5    
2" 8           
3" 17  15 round, 18 cyl (18" mortar) 20      
4" 25  19 (24" mortar) 40 35
5" 45  60 36 - 45 
6" 80  90-100 75 - 85  60
7" 110 - 130
8" 200-250 100
8.5" 170 - 190
10" 240 - 280
12" 450 - 500
24" 4100 - 4850

Many variables will affect the lift charge amounts. Shell type (cyl or round), weight, size (diameter), length if canister, powder grain, powder quality, tube length, loading space (distance between shell and powder charge), shell clearance, etc. (summarized from BAFN II page 138)

 

 

Common Sieve Designations

(not complete)
Sieve Designation Nominal Sieve Opening
Standard Mesh inches mm Microns
5.66mm No.3 1/2 0.223 5.66 5660
4.76 mm No. 4 0.187 4.76 4760
4.00 mm No. 5 0.157 4.00 4000
3.36 mm No. 6 0.132 3.36 3360
2.83 mm No. 7 0.111 2.83 2830
2.38 mm No. 8 0.0937 2.38 2380
2.00 mm No. 10 0.0787 2.00 2000
1.68 mm No. 12 0.0661 1.68 1680
1.41 mm No. 14 0.0555 1.41 1410
1.19 mm No. 16 0.0469 1.19 1190
1.00 mm No. 18 0.0394 1.00 1000
841 mm No. 20 0.0331 0.841 841
707 mm No. 25 0.0278 0.707 707
595 mm No. 30 0.0234 0.595 595
500 mm No. 35 0.0197 0.500 500
420 mm No. 40 0.0165 0.420 420
354 mm No. 45 0.0139 0.354 354
297 mm No. 50 0.0117 0.297 297
250 mm No. 60 0.0098 0.250 250
210 mm No. 70 0.0083 0.210 210
177 mm No. 80 0.0070 0.177 177
149 mm No. 100 0.0059 0.149 149
125 mm No. 120 0.0049 0.125 125
105 mm No. 140 0.0041 0.105 105
88 mm No. 170 0.0035 0.088 88
74 mm No. 200 0.0029 0.074 74
63 mm No. 230 0.0025 0.063 63
53 mm No. 270 0.0021 0.053 53
44 mm No. 325 0.0017 0.044 44
37 mm No. 400 0.0015 0.037 37

A good reference for screen sizes: http://www.wovenwire.com/reference/mesh-locator.htm


Charcoal Tests Tables

The charcoal tests have assumed a life of their own so they now have a whole page all to themselves. See it at: charcoal_tests.html.

 

Cannula Diameters
 (from Pyrotechnica IX and Experimentation)

Make from lightweight aluminum sheet. Roll on an appropriately sized dowel or former and tape with thin strong tape. Stranded tape was used in the 1/2" version above. You can also use cardboard tubing or a couple of turns of heavy paper to make a cannula.

Shell Size Diameter
2" 1/2"
3" 3/4" to 1"
4" 1" to 1-1/4"
5" 1 1/2" to 1 3/4"
6" 1 3/4" to 2"
8" 2 1/4" to 3" 

 

Pressures that Burst Common Rocket Tubes

(as done by Ned Gorski and posted with permission)
 Type Tube Burst Pressure
1/8" wall from PGI vending 3200
1/4" wall from PGI vending 4500
1/4" wall from Skylighter 3600
1/4" wall from Skylighter with Minwax 4300
1/4" wall Precocious Pyrotechnics Tube 3400
1/4" wall Precocious Pyrotechnics Tube with Minwax 3900
1/8" wall New England Paper Tube 5700
1/4" wall New England Paper Tube 10000

Spolette Lengths


The following is a post from Mike Swisher on Passfire. It is reprinted here with permission.


The customary sizes are:


1-1/2" long X 5/16" ID X 1/2" OD
2" long X 5/16" ID X 1/2" OD
2-1/2" long X 5/16" ID X 1/2" OD
3" long X 5/16" ID X 1.2" OD


The above are for timed-report and hammer shell inserts and for 3" shells. The 1-1/2" length is for between breaks in 3" multi-break shells and for the tops of 3" 1-breaks. The 2" length is for the tops of 3" multi-breaks and for shorter timings in inserts. The 2-1/2" and 3" lengths are for longer timings in inserts.

2-1/2" long X 5/16" ID X 5/8" OD
3" long X 5/16" ID X 5/8" OD
4" long X 5/16" ID X 5/8" OD


The above suit shells 4" and up. The 2-1/2" length is for the tops of 4" shells and between breaks in 4", 5", and 6", unless an extremely long timing be needed. The 3" length is for the tops of 5" and 6" shells, for bottom shots in those sizes, and may be made to work between breaks in 8" and occasionally larger shells. The 4" size is for the tops of 8" shells and may be made to work for 10" shells; it also suits between breaks in 10" and 12" shells. I mostly use metal spolettes on the tops of 10" and larger shells. They can be cut to whatever length needed.


If you are ordering un-cut tubes, then, only two sizes are needed: 5/16" ID X 1/2" OD and 5/16" ID X 5/8" OD. It is better to have the OD run on the large size than on the small, so it fits tightly in the hole of a disc. I have some old red-rope tubes that are about 21/32" OD and they work nicely if one has discs that are slightly loose on 5/8" OD spolettes.