Small Homemade Tubes (Rocket Motor)

If you can’t buy the tubes, you can make them yourself. It takes a little time, but the materials are cheap, and if you make them properly, they’ll be just as good as the commercial tubes. The smaller and shorter tubes are the easiest, and the level of difficulty rises as the length and the diameter increase. Commercial tubes are made on machines that cut the paper, coat it with a water-based glue, and roll it around a mandrel. It seems logical that you could make a homemade tube in the same way. But when making homemade tubes, this method will not work.
A commercial machine makes about 20 tubes per minute. Each tube passes through the machine so quickly that the paper doesn’t absorb the water from the glue until after the tube is rolled. Then the paper swells with moisture, the tube expands, and shrinks again as it dries. When making a homemade tube, anywhere from 1 to 3 minutes can pass from the time you apply the glue to the time that you roll tube, and the paper has plenty of time to absorb the water from the glue. The rolling is therefore done with the paper in a premoistened and swollen condition. A tube made in this way looks fine when you take it off the mandrel. But as it dries, the layers of paper shrink away from one another, and separate, creating wrinkles, voids and air pockets that render the tube useless.
To make a commercial-quality tube by hand, you have to minimize the amount of water in the paper during the rolling process. After struggling with the problem for several weeks. I found that I could coat the paper with glue ahead of time, let it dry. and lightly remoisten it just prior to rolling. This minimized the problem, but if I dampened the paper too much, or waited too long before I rolled the tube, the problem reappeared.
The best glue for making a homemade tube is common white glue. Once it is dry. you can resoften it with water or alcohol, and though water makes the paper swell, alcohol does not. But alcohol alone makes the glue so slippery that rolling the tube is impossible. As the alcohol evaporates, the glue becomes sticky again, but the time window before it dries is so short that you don’t have enough time to work. Through trial and error I learned that, for remoistening the glue, a mixture of alcohol and water works perfectly. Important note. Two parts alcohol to one part water works well for papers up to .010″ thick, and a one-to-one mixture works best for anything thicker. Different size tubes require different thicknesses of paper, and slightly different construction techniques. You can make a 1/2″ or 3/4″ i.d. tube up to 8″ long from a brown paper shopping bag. and here’s how to do it.
 A piece of ribbed, vinyl "hallway runner" makes a nice tube-rolling pad.
Figure 8-3. A piece of ribbed, vinyl “hallway runner” makes a nice tube-rolling pad. You’ll find it at carpet and flooring shops, and big hardware warehouses like Home Depot. The cut edge in this photo is shown actual size with 8 ribs per inch of material width.


A 3/4″ TUBE MADE FROM A SHOPPING BAG MATERIALS LIST

1. A large, heavy duty, brown paper shopping bag 8. A pair of scissors
2. A smooth, round metal bar, 3/4″ dia. x 12″ long 9. A small, short nap paint roller with tray
3. A straight, heavy, steel block at least 8″ long 10. A sponge
4. A carpenter’s framing square 11. White glue (like Elmer’s “Glue-All”)
5. A smooth, flat, washable surface to work on 12. Some old newspapers
6. A 2 ft. square piece of vinyl or rubber sheeting 13. Waxed paper
7. An oven or refrigerator rack 14. Water, and some denatured alcohol

When you buy groceries at a supermarket, most checkers will ask if you want plastic or paper bags, so always say paper. I often shop at one of those big warehouses where you save money by bagging your own groceries. If I double-baa everything. I come home with six. large, heavy duty shopping bags, and that’s enough to make ten of the tubes in this demonstration.” If you ask your friends to save their bags for you. you’ll have more paper than you can use.
The round, metal bar can be made of any metal, but it has to be smooth. You make the tubes bv rolling the paper around the bar. and when you are finished, you have to slide them off. If the bar is rough, you won’t be able to do it. Cold rolled steel, stainless steel, brass, and aluminum work fine, but hot rolled steel, with its typically rough finish, does not work. If the bar you find is gouged or scratched, smooth it with a file and some #120 sandpaper. If you’can’t find exactly what you need, you can make it on a metal lathe. The straight, heavy steel block (square or rectangular in shape) is used as a straight edge, and it has to be heavy, so that once in place, it doesn’t wiggle around.
White glue comes in plastic bottles up to a gallon in size, you can buy it almost anywhere, and the most popular brand is probably Elmer’s “Glue-All”. Stationery stores and places like Walmart sell the small bottles, and the big hardware warehouses like Home Depot and Lowe’s sell it by the gallon.
The flat, washable surface can be a Formica counter top. but most counter tops are not perfectly flat. An uneven surface generates uneven pressure as the tubes are rolled, and uneven pressure causes areas where the paper is poorly bonded. The vinyl/rubber sheeting acts as a resilient rolling pad. and evens out the pressure between the high spots and the low spots. For this demonstration. I bought a 27 inch-wide x 2 foot length of black, ribbed, vinyl “hallway runner” at Home Depot (Figure 8-3) A found it in the department where they keep the rubber floor mats. To use it. I turn it upside down and put the ribbed side on the bottom.
The water-thinned glue is applied to the paper with a small, short nap paint roller.
Figure 8-4. The water-thinned glue is applied to the paper with a small, short nap paint roller.
The paint roller should be the small 4″ to 6-1/2″ type used for trim work, and the nap should be short. The roller puts the glue on the paper., and if the nap is too long, it soaks up more glue than you need.
Before you begin, make up the following two solutions:

GLUE SOLUTION:

1 cup (8 oz.) of water +1 cup (8 oz.) of white glue
and
ALCOHOL SOLUTION: 1/2 cup (4 oz.) of water +1 cup (8 oz.) of denatured alcohol
The GLUE SOLUTION is applied to the paper ahead of time, and the ALCOHOL SOLUTION remoistens the glue during the rolling process. Because the balances of water to glue, and water to alcohol are important, you should keep these solutions in sealed containers so that they are not altered by evaporation. Plastic soft margarine tubs with snap-on lids work fine, and they’ll keep longer if you store them in a refrigerator.
1. Cut the bottom out of a large, heavy duty shopping bag. Cut away the vertical seam in the back, and trim the paper so that the edges are square and straight. Set up an ironing board, and using a steam iron with the steam turned ON. and the heat set for cotton or linen (i.e. hot), iron out the creases as best you can. You’ll end up with a sheet of paper about 16-1/2″ x 36″. and about .006″ thick.
2. Lay the sheet on two layers of newspaper, and using the paint roller and a paint roller tray, coat one side with the GLUE SOLUTION (Figure 8-4 ). The coating needn’t be thick, but it must completely cover the paper (i.e. no bare spots). Lift the glue-coated sheet off the newspapers, discard the newspapers, and set it aside to dry. When it is thoroughly dry. turn it over. Lay it on two fresh sheets of newspaper, coat the opposite side in the same manner, and let it dry again. Then inspect the both sides of the paper carefully. As the glue dries, leaves, insects, dirt, and other debris can become trapped in the glue. If you see anything in the dried glue, scrape it off with a putty knife (Figure 8-5 ). Then cut the paper into two 8- l/4″-wide x 36″-long strips.
Important Note. As the first side dries, the paper will curl. As the second side dries, the paper will straighten out again.
Small bits of debris are scraped away with a putty knife.
Figure 8-5. Small bits of debris are scraped away with a putty knife.
The rolling setup for small tubes. A vinyl pad forms the work surface. A heavy metal block and a carpenter's square are used to align the paper.
Figure 8-6. The rolling setup for small tubes. A vinyl pad forms the work surface. A heavy metal block and a carpenter’s square are used to align the paper.
3. Lay the vinyl pad (the upside down hallway runner) on a flat, washable surface. Lay the steel block on the vinyl, and lay the carpenter’s square against the block (Figure 8-6).
4. Pick up one of the paper strips. Bevel the corners of one end (cut them at a 45° angle with a pair of scissors). Align the paper’s edge with the inside edge of the carpenter’s square, and as shown in Figure 8-7. hold it firmly in place with a heavy weight (i.e. a can of V8 juice). Without wiggling the paper or disturbing it’s position, remove the carpenter’s square.
 A strip of paper is aligned with the carpenter's square, and held in place with a heavy weight: in this case a can of V8 Juice.
Figure 8-7. A strip of paper is aligned with the carpenter’s square, and held in place with a heavy weight: in this case a can of V8 Juice.
The waxed paper-covered bar is aligned with the forward edge of the metal block.
Figure 8-8. The waxed paper-covered bar is aligned with the forward edge of the metal block.
5. Cut a piece of waxed paper 5″ wide x 10″ long. Roll it around the bar as tightly as possible, and align the bar with the forward edge of the steel block (Figure 8-8). The waxed paper keeps the bar from sticking to the tube during the rolling process, and the steel block insures that the bar is square with the edge of the paper.
6. Pressing firmly down on the bar so that it doesn’t wiggle, roll it forward onto the paper (Figure 8-9). Without wiggling the bar. lift up the beveled end of the paper. Roll it over the top of the bar. and tuck it under the bar as tightly as possible (Figure 8-10). You will find that long fingernails and the beveled corners of the paper are helpful when doing this.
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7. Holding the bar firmly in place with one hand, soak the sponge in the ALCOHOL SOLUTION. With your free hand, squeeze the sponge about 3/4 dry. Dampen about 6″ of paper in front of the bar. taking care to squeeze the sponge as far under the bar as possible (Figure 8-11). The amount of moisture needed isn’t much: just enough to make the glue glossy and sticky again. Without delay, roll the bar forward over the dampened paper, pressing down firmly as you go (Figure 8-12).
8. When you reach the end of the dampened area, remove the weight (the juice can). Lift the bar-with-paper off the pad. and take it back to the starting point. Resoak the sponge. Wring it out again. Dampen another 12″ of paper, and roll the bar forward again. Continue dampening and rolling in this manner to within 1/2″ of the paper’s end.
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9. Squeeze the dampened sponge between the end of the paper and the tube, dampening both surfaces in the process (Figure 8-13 ). Without delay, roll the bar forward, and rock it back and forth over the end of the paper until the end is firmly bonded.
At this point the tube is almost finished, but not quite. You will probably find that a 3/4″ i.d. tube with a 1/8″ thick wall takes more than the 36″ of paper that you’ve already used, and you’ll have to keep adding paper until the outside diameter equals one inch. To do so. proceed with step 10.
10. Place the bar with the partially completed tube against the metal block. Cut a piece of preglued paper strip 8-1/4″ wide x 12″ long, and dampen its entire surface. Without delay, slide one end of the paper under the bar until its end touches the partially completed tube (Figure 8-14 ). Roll the bar forward onto the paper, and rock it back and forth until the end is firmly bonded. Continue rolling until the outside diameter equals 1.00″. as measured by an accurate pair of calipers. Then cut off the excess paper, and repeat step 9.
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11. Slide the finished tube off the bar. and inspect the inside of each end. The inside end of the paper should be firmly bonded to the inside of the tube. If it is loose, fill a small, disposable syringe (page 48) with the ALCOHOL SOLUTION, and squirt it under the end of the paper [Figure 8-15 ). Allow the excess to run out the opposite end of the tube and back into the solution container. Without delay, slide the metal bar without the waxed paper back into the tube, and roll it back and forth in rolling pin fashion (Figure 8-16 ) until the end of the paper is firmly glued in place. When doing this, you will find that the inside of the tube is slippery, and you'll have about 30 seconds to work before it gets sticky again. When you are finished, without delay, slide the finished tube off the bar. and let it dry on a rack indoors for 48 to 72 hours (Figure 8-17).
12. When the tube is thoroughly dry. cut it to the length required for the motor you are making (a bandsaw with a 4 tooth-per-inch woodcutting blade works best), and sand off the resultant paper fuzz with a belt sander or #120 sandpaper. Then give the ends of the tube a visual inspection. If you've done everything right, it should look like the one in Figure 8-18: a solid wall of paper and glue with no voids or air pockets.
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