Introduction: Hobby Rocket Motor Paper Tubes ( Parallel )

By
About: Experimentalist, electronics engineer, and dad of two that needs to see the doctor over a serious case of the irritable instructables. Always interested in alternative sources of energy and recycling.
This is a quick instructable on how I make my Kraft paper tubes for my homemade motors. These are only parallel rolled, but you can use a similar method to make spiral tubes as well. Sorry for the poor quality of the images and lighting. I don't have a proper lighting or tripod setup as of yet. The images will be updated at a later date.

Materials:
  • Kraft paper ( local newsagent or craft store )
  • Glue or Glue Mix - 1 part water, 4 parts wood glue or craft glue
  • Wooden dowel - 7cm length
  • Scissors or sharp blade
  • Sandpaper of light strength

Step 1: Take a Look

Here are an example of the tubes in action after filling with bentonite clay nozzle mix and black powder single grain fuel. Below you can see a movie of it in action as well.

Step 2: Start Prep and Cutting

I am missing the first couple of images on how I created the quick wooden 'tools', but you can see in the image here pretty much what I use by the labels. The ramming jig is the small section of the dowel 5mm length, glued onto a piece of scrap wood I had laying about. The finished tubes fit beautifully over this.

Start with your 7cm long bit of dowel and measure and cut a section of Kraft paper about 5mm larger on each end of the dowel motor form. My Kraft paper roll is 32cm in width, so I cut two pieces, both 8cm wide, 32cm long.

Step 3: Roll It Up

I then very carefully and evenly, roll the paper around the form, using a moderate, but not too much pressure to make the paper meet the other side. Kind of like rolling a cigarette paper if you have done so. I check at this stage that the paper is lined up to itself dead on. If you don't, it will cause the paper to roll over to one side too much, though a little is fine. I sometimes get up to 4mm of movement that I clean up later.

When you feel it is aligned correctly, do a full half-roll, and then apply a stripe of glue across the length of the paper. Note: if you don't do the half-turn, the paper will get stuck on the form and you won't be able to get the dowel out later! If you want to be extra sure that the paper won't stick to your form, cut a small strip of paper, roll it, and then tape it. Then glue the long first strip of paper to that.

Spread the glue with your finger to give an even layer and 'dryer' glue amount.

Step 4: More a Rollin'

You should be able to gently twist and pull the form in and out a little as you progress with gluing and rolling until no more paper is left to roll. I put an even finger smudge of glue about every half turn, and keep an even holding pressure while I roll the tube and paper. Keeping a steady hand, even pressure and glue amounts, are all key to the tube holding its shape better and hold when fuel is burnt within it.

After the first layer of Kraft paper has been rolled and glued in place, I roll it under the palm of my hand with even pressure again. There is another design of form I will have to show that I have seen elsewhere, but what happens if you use one like I used here, is the tube will fold around the sides of the form, sometimes creasing the roundness of the tube. It is not too much of a problem as you will see in the next step though.

Repeat the glue and rolling steps for the second, third paper sheets for however thick you need the tube to be.

Step 5: Trim N Tidy

Once you are happy with a tube shape, trim it up with whatever means possible to the length of the dowel or the length desired. If you rolled the tube under your hand, this will tidy up the sides so you can remove the form a little again. I hold the form in one hand and the tube in the other, twisting and giving a slight even pressure to help make a nicely shaped tube. Don't remove the dowel form completely just yet.

After the sides are cut, hold the tube vertical and sand the edges lightly with a gentle sandpaper to even the edge, and to also aid in the paper edges join to one another.  

You should now be able to push the dowel through the tube with your finger gently enough to be able to twist and pull it out completely.

Step 6: Strengthen

Add a bit more strength to the ends of the tubes by applying a small bead of glue around it's edge and smooth with your finger and try to squish some between the paper layers if visible.

Wait for all of the glue to dry, slowly twist in the form again and twist it about to make sure the tube shape is correct and can fit over the form without an issue of getting stuck. It should be a very close, but not tight fit.

Your tube should now be dry and complete, ready for your hobby rocket motors or even rocket shape!

Step 7: Parallel Tube Machine

I will most likely build a simple machine that is either motor or hand cranked, based on the image / idea I drew up in 3d studio max. It provides a constant even pressure on the roll, and a constant even glue layer as well.

Rather simple design, I should start it in the coming weeks.

Cheers for checking out my 'ible!