Hey Jan,
It seems like great minds think alike

It's funny that you mentioned making a compressor out of a fridge pump, because I converted my old loud crappy Jobmate compressor into a silent compressor just three weeks ago.
It's now quiet and works like a charm.
Furthermore, I also used that same thread that you posted as a wiring diagram.
I found allot of info on Youtube as well.
If anybody is interested in making one of these silent compressors, just let me know, as I have allot of pictures and info on how to build one by converting an existing compressor.
Gio