The swing arm( Clamp toggle) is rated 180 Lbs .And was the hardest thing to locate (see note).
the compression plate at the top of the swing arm  is fixed  onto a welded backplate with 2 small S.S.  bolts .

Notice the "half moon" cut at the end of the launch arm compression plate. 
Necessary To wrap around the bottle neck. 
All the components of the launch head in this picture are sealed or glued. 
only the launch tube is free to slide over the copper sleeve. 

Note: you can find 2 models of Clamp toggle rated 150 or 180 lbs.

ref No:  
 Clamp toggle s/hn s/h bar ss107 -50/L80BS
the Price at the time was: $45.56 AUD plus tax .to a total of $56.80 AUD

got it from a place near  Sydney 
J.BLACKWOOD & SON LTD
Suppliers of engineering, industrial,electrical products & metals
1-7 ADA Ave
Brookvale   NSW 2100 
AUSTRALIA
Tel: (02)  9938 4144
Fax: )02) 9938 4211