24mm Sorbitol motors:
Drysophila Project: Case Construction

The casing is made of paper and clay nozzle similar to commercial low power single use motors. A 19mm dowel is used to roll Kraft paper to an outer case diameter of 24mm. White glue and flour glues had burn through problems so I switched to Sodium Silicate solution diluted 4 parts to 1 part water

Caution: Caustic; Wear rubber gloves and eye protection. Rinse with lots of water if contacted. Also for skin, weak vinegar can help.

The tubes are allowed to dry thoroughly.

For the clay I grind the kitty litter brand below.
I use a primitive rock mortar and pestle to grind it to a fine powder.
Combining old technology with new makes it more fun 4 me.

To pressure flake: Press the antler tip to an abraded platform on the obsidian biface

,,,,,,,,,,OOPs.....sorry.....wrong hobby....

I didn't have the tools or patience to lathe a solid nozzle spindle so I turned a copper dowel in a hand drill to an angled point. This short pointy dowel then went into a metal washer with a 24mm diameter. Over this I placed a rubber plumbing washer to give shape to the exit nozzle.

Several wraps of narrow masking tape will help with nozzle retention. A dowel is placed up the casing leaving 3cm depth into which clay is poured.

The spindle is placed into the clay and carefully turned over onto concrete floor.

A section of PVC pipe is placed snuggly over the nozzle end to prevent too much distortion on ramming.

I used a large C clamp to press the nozzles but have found it easier to use a hammer to ram the dowel into the clay. Removing the spindle the washer may remain and need to be pulled out revealing the pre-nozzle.

I then use a 3mm drill bit spun back and forth between my fingers to drill a minimum diameter throat.

The 3mm throat is then gently drilled to 5mm or whatever diameter is desired. The clay is a bit crumbly since I don't use wax in the clay. Why use a binder that melts? Instead I strengthen the clay nozzle by dipping the rammed nozzle in a 50% Na-silicate solution and allow to dry in warm oven. Then dip in a strong solution of Calcium Chloride, again dry. Then another dip in 50 - 70% Na-silicate and again air dryed in warm oven. A third silicate treatment can be done. This makes for a strong nozzle that doesn't erode unless the KN is over about 150.

Now on to propellant grain design click here.

To return to the D16 main page click here

Caution: Na-Silicate solution is Caustic; Wear rubber gloves and eye protection. Rinse with lots of water if contacted. Also for skin, weak vinegar can help.

6/2007 A recent SugPro post mentioned the use of talc to harden silicate solutions.

For this 24mm system a light solution (low talc) might make a smooth strengthening finishing surface "paint" Might be able to eliminate the Calcium chloride step for getting the silicate to crosslink better. Will post here if I get around to trying it.

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