Convolute tubes are not as common as the spiral kind, but they’re easy to find if you know where to look. To make the motors in this topic, the sizes you will need are 1/2″ i.d. x 3/4″ o.d.. 3/4″ i.d. x 1″ o.d.. 1″ i.d. x 1-1/4″ o.d.. 1-1/8″ i.d. x 1-1/2″ o.d.. and 1-1/2″ i.d. x 2″ o.d.
Convolute tubes are often used in the packaging of paper and fabrics. Check with friends and businesses. If you know someone who uses a lot of computer or fax paper, or works in the garment industry, you might find a free supply. If this doesn’t work, look for the companies that sell tubes to the fireworks industry. You’ll see their ads in the classified sections of magazines like Popular Science. Soldier of Fortune. Guns. Shotgun News, and American Fireworks News (page 175). Check the PERIODICALS section at the library, and look for the ads offering things like chemicals, fuse, and fireworks-making supplies. Some of these companies sell convolute tubes, and even the ones who don’t can often tell you where to buy them. Failing that, you can order the tubes needed to make most of the motors in this topic from the Teleflite Corporation at www.teleflite.com and www.amateur-rocketry.com.
To buy the tubes in large quantities, you can order them directly from a manufacturer. As of the year 2000.1 know of six U.S. companies that make convolute tubes in sizes and wall thicknesses suitable for rocket motors. They are:
Figure 8-1. A spiral cardboard tube. Its basic design makes it unsuitable for building a rocket motor.
Figure 8-2. A convolute cardboard tube. Its solid wall of paper and glue make it ideal for buildinv
| Caraustar (formerly Star Paper Tube) | Newark Paperboard Products |
| 1379 McDow Dr. | 10215 San Sevaine Way |
| Rockhill, SC 29732 | Mira Loma, CA 91752 |
| New England Paper Tube | Pacific Fabric Reels |
| 173 Weeden St. | 3401 Etiwanda Ave., Bldg. 811-C |
| Pawtucket, Rl 02860 | Mira Loma, CA 91752 |
| Sonoco Products Co. | Thames River Tube Co. |
| 1 North Second St. | 64 High St. |
| Hartsville, SC 29550 | Ashaway, Rl 02804 |
I ve spoken with each of them, and they all said that they’ll make tubes for anyone who pays the setup charge and meets their minimum order requirement. Tube manufacturers are geared toward making large quantities of tubes to vour specifications. They ll accept small orders, but their minimum charge usually makes runs of fewer than 500 tubes uneconomical
fU ‘I! me 0t” gr°UP Hke Trfp011 °r the RRS- y0U might consider finding other me”*ers to share the cost of a lar^e order. When you buy tubes in this way. you’ll pay less than you’d pay for the materials needed to make them yourself and you 11 pay just a fraction of what a retail tube dealer would charge.
When placing an order with a manufacturer, tell them to use plenty of glue. One of the difficulties in making convolute tubes is judging how much glue to use. If the machine operator uses too much, the tubes stick together as they dry. To avoid this problem, inexperienced operators sometimes reduce the amount of glue to a point where there isn’t enough. In many of the industries that use convolute tubes, the amount of glue doesn’t matter. In the rocket industry it is very important. It is therefore important that you explain your needs ahead of time, and ask the manufacturer to have one of his more experienced machine operators handle your production run.
The type of glue used is also important. Most manufacturers like dextrin, because it is cheap and easy to clean up. A silicate glue makes a stronger tube, but the post-production cleanup is difficult. Manufacturers often shy away from silicate unless you insist on it. You can expect to pay an extra cleanup fee for silicate, but if the fee is reasonable, the increase in the tube strength is worth the added cost.
Most convolute tubes, including the ones used in fireworks, are made from partially recycled kraft paper. The model rocket industry uses a much stronger tube made from a cream or “manila” colored paper with a very high virgin wood fiber content. These tubes have several times the burst strength and burn-through resistance of a standard fireworks tube. If you use them to build the rocket motors in this topic, you’ll be able to push motor performance substantially higher than the listed figures.
The problem is that, as of this writing. New England Paper Tube is the only company that makes them. They are very expensive, and people on the West Coast must pay the substantial charges involved in having them shipped all the way from Rhode Island. In August of 1995 I spoke with Newark in California. They expressed an interest in making these tubes, but only if they receive enough orders to justify the 10 ton minimum purchase of the special paper required. I encourage anyone who needs large quantities of these tubes to contact Newark. New England Paper Tube also makes the standard kraft paper fireworks tubes, and they’ve assured me that they can make the 1-1/2″ i.d. x 2″ o.d. tubes needed for the 1-65.
