An important item to build black powder rocket motors is strong parallel rolled paper tubes. Paper tubes have an number of advantages for rocket motors. They are inexpensive especially if you make them yourself. They are biodegradable and if the motor should burst it does not throw dangerous shrapnel around. I use Elmer’s white glue for the adhesive. Epoxy or polyester resin could be used but the tubes would not be biodegradable.
You can buy some sizes of suitable paper tubes but I thought it would be a fun project to build a machine to make the tubes. David Sleeter in his book “Amateur Rocket Motor Construction” describes a rather complicated and tedious method of hand rolling tubes. I found only a couple of items on the internet about making a machine to roll tubes. None of which I liked. So I took ideas from them and added some of my own ideas to come up with the design. With some of the machines you had to cut the paper to length and then feed it into the machine. I wanted my machine to hold a roll of paper. One design you brush the adhesive on the paper as you rolled it up. Other than being tedious applying the adhesive makes the paper soggy and difficult to roll. In my machine the adhesive is placed as a bead just before the paper is rolled up. The pressure of the rollers squeezes the adhesive in a thin film onto the paper. After the picture below was taken I shortened the springs a bit to increase the pressure on the rollers. This makes the glue film a bit thinner which improves the tube roundness.
For the frame of the machine I made the sides out of 3/4″ MDF and the bottom from 1/2″ plywood. These materials are easy to work with and I had plenty of scraps laying around. There are 3 rollers in the machine. One roller a 3/4″ steel rod supports the roll of paper. A rubber roller applies pressure to the paper as it is wound on the steel roller that determines the inside diameter of the tube. Springs press the rubber roller against the tube roller. The tube roller fits into slots in the sides so that it can be easily taken out to remove the completed paper tube. I found that it is necessary to keep the paper tight as it is rolled up so a rod is held against the paper roll to act as a brake. The ends of the mandrel are machined to fit 12mm bearings. There is a 11mm hex on one end to work with the crank which has an 11mm socket welded to it. This makes it easy to remove the crank when taking off the completed paper tube.
In the image above are two tools I made to go with the tube roller. The metal strip helps get the paper started wrapping around the mandrel. Below that is a gage to determine when the tube is the desired size.
The tube on the left is a purchased tube and the one on the was made by my machine.
I posted a short video on YouTube https://www.youtube.com/watch?v=q8Fan9tJDFE showing the tube machine in operation.