So all parts came in to construct the manual\u00a0vacuum rotary feedthrough. I will use this as a proof of concept and possible\u00a0will 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\u00a0using the\u00a0shaft as a plunger, I managed to damage the outside of the seal in the boring likely due to a too small leading\u00a0chamfer. 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\u00a0not on the seal.<\/p>\nngg_shortcode_0_placeholder\n
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.<\/p>\nngg_shortcode_1_placeholder\n
Tested the plate on a 6 litre pressure cooker, hooked it up to the vacuum pump\u00a0and it turned out OK . With the vacuum pump running it managed to pull\u00a0-0,87 bar similar to previous vacuum casting sessions.<\/p>\nngg_shortcode_2_placeholder\n
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\u00a0rubble seal bearing) as commonly\u00a0used in a vacuum chuck for wood lathes.\u00a0But the shaft ran freely, there was hardly any\u00a0pull on the shaft “into” to pan. At -0,85 bar you could still easily pull out the shaft from the base part.<\/p>\n
Next steps: Design a paddle \/ mixer blade and get a 12mm thick polycarbonate plate somewhere cheap to start melting.<\/p>\n","protected":false},"excerpt":{"rendered":"
So all parts came in to construct the manual\u00a0vacuum rotary feedthrough. I will use this as a proof of concept and possible\u00a0will 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<\/p>\n