dinsdag 7 juni 2016

Simple do-it-yourself automatic (black)powder mixer

This simple, cheap home-made powder mixer can be used to mix relatively large quantities of powder, such as blackpowder, automatically.

Since a picture says more than a 1000 words, let's start with 160 pictures in rapid succession:

Above: The powder mixer in action. This video says more than 160 x 1000 words.

Note that the final model looks slightly different; in the end we moved one of the rolls to the opposite side of the box so that the mixing container is spinning between the powered and the non-powered roll. This reduces the friction on the container so that it spins around more easily.

Shopping list

  • 1 hand-held drill (battery powered or otherwise is fine) to provide rotation
  • 1 plastic box (cheap at IKEA or simular) to support the axles
  • 2 cardboard cylinders
  • 2 axles (we used metal bars but wood should also work)
  • glue to attach the cylinders to the axles

Mixing container

The mixing happens inside a container. We used a metal container with a plastic lid, which is not ideal for pyrotechnic powders - see the "Safety Improvements" section below.

To ensure proper mixing, we glued a wooden stick to the inside of the mixing container. That way, the powder gets scooped up and dropped down continuously, similar to a concrete mixer.

We also threw in a few plastic cubes, again to have better mixing by creating some "chaos" or randomness in the mixing process.

On the picture below, the wooden stick is barely visible because of the blackness of the powder:

The powder mix container filled with black powder.

The results

This blackpowder is of the best quality that we have made with any dry mixing process so far.

The only superior quality that we obtained in the past was with a liquid mixing processes, such as the process that involves boiling water, a blender and isopropyl alcohol, but that is more cumbersome and the quality we have here will suffice for our igniters.

We will be able to use this powder for our igniter tests, as documented in the article "Electrical model rocket black powder igniter with steelwool".

Safety improvements

In hindsight, mixing black powder in a metal container with a plastic lid is not ideal for safety. Should the black powder ignite for whatever reason, and should the plastic lid fail to release, then  the pressure would build up inside the container and it could potentially blow up. 

In general, it is recommended never to place pyrotechnical substances inside metal or glass containers because they could shatter when the substance ignites. Also, make sure that the container has a lid that easily comes off to ensure no pressure can build up inside. 

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