Rotary vacuum mixer – part II

So all parts came in to construct the manual vacuum rotary feedthrough. I will use this as a proof of concept and possible will stir some propellant with it before upgrading to the motorised unit. It took me a good 2 hours to machine the temporary shaft and base part. The shaft was machined slightly conical to ease sliding on the bearing over the entire length. While inserting the rotary seal with a vise and using the shaft as a plunger, I managed to damage the outside of the seal in the boring likely due to a too small leading chamfer. On top of the seal the bearing was pressed into position without any trouble. The bearing has a larger OD than the seal so when under vacuum the bearing presses on a step / ridge and not on the seal.

Rotary vacuum was screwed into scrape piece of aluminium with a G1/2″ BSP thread. Vacuum connection is M10x1mm metric fine thread – similar to what we use for head end motor ignition.

Tested the plate on a 6 litre pressure cooker, hooked it up to the vacuum pump and it turned out OK . With the vacuum pump running it managed to pull -0,87 bar similar to previous vacuum casting sessions.

Since the vacuum pump was running I’m unsure whether there is a leak or not over the feedthrough shaft. I’m unsure the seal is actually working or the same effect could be achieved with a 2RS bearing (double rubble seal bearing) as commonly used in a vacuum chuck for wood lathes. But the shaft ran freely, there was hardly any pull on the shaft “into” to pan. At -0,85 bar you could still easily pull out the shaft from the base part.

Next steps: Design a paddle / mixer blade and get a 12mm thick polycarbonate plate somewhere cheap to start melting.

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