One of the things I have been battling is time. The time it takes to mix and pour investment one flask at a time has been a real drag. So to speed things up a bit over this summer I plan on building an investment mixing machine that will mix and pour 50 lbs of investment all in one shot and in less than 10 minutes. (Less clean up time). First thing I was in need of was a killer vacuum pump. I quickly found out how expensive these suckers can be new, so off to the evil bay I went. Took me a few tries and offers to get what was needed but picked this up after a week or so for $150.00 with shipping. Lybold d16a sitting next to my cheap Taiwan pump that will now be permanently coupled to the vacuum wax injector.
This one has been listed on our CL for months. Originally listed $1200. It's an S160. Is it the same size? https://charlestonwv.craigslist.org/tls/d/leybold-heraeus-vacuum-pump-industrial/6878779952.html
Hell no, that one you posted is huge and 7.5 hp!! Probably weights in at 500 lbs. Mine is only 1 hp and weighs in at 70 lbs.
I have an ancient Edwards Speedivac two stage: there was a guy in England selling full rebuild kits for a modest fee that brought it back to new performance spec. There should be something similar available for your pump too.