Borrowing a point from one of the other questions: Most hardware stores sell paint mixers which are basically a blender blade on the end of a rod, intended to be used with an electric drill. If you really want to homebrew a fountain-style motor-on-top machine, that might not be a bad piece to start with; all you'd need to add is the motor, fittings to couple motor to blade, appropriate switches/interlocks, and appropriate chassis/case materials.I still think just buying a blender makes more sense.
i actually figured something out but thankyou
No BUT you can do a seriously god job with a standard kitchen blender.
+1.If you really insist on making the soda-fountain-style machine, it's really just a blender upside down: Motor, long shaft, blender blade at the tip, interlock to ensure it can't be turned on unless the cup is firmly clamped in place to protect the user from the spinning blade. Another approach to safety would be to put a shroud around the blade to keep the user away from it. That's what some of the "bar blenders" do. I don't know whether any of those have enough power to handle milkshakes; probably not unless you're using the Boston definition of "milk shaken with syrup." (If you want a thick shake in Boston, order a frappe.)
Note that you can, of course, _buy_ the soda-fountain-style machines. But they really don't have much if any advantage over a standard blender.
+1 I make all my milkshakes with an ordinary blender.