Try this very basic device.

A piece of 7/8 pipe 6' long, stick your oxy/act tip in on end (middlish if possible) leave this end still open to the air, turn on oxygen (really you should use nitrogen to be safe) but it is the tip that is important. (motive force)
What you should see is that air is pulled into the pipe at one end (suction) and quite alot flow coming out of the other end. ( alot more flow that just the oxygen flowing from the tip)