I was amazed to discover - thanks to my OU tutor - that Barr did indeed develop his chart idea but rather than use the graphical vocabulary of red and black with lines and type of varying size he changed not just his vocabulary but his language and grammar - from coloured lines and boxes to a torpedo! This takes art up to the 1950’s
It appears he sees MoMA’s permanent collection as a torpedo moving stealthily through the waters. .....
The Permanent collection may be thought of graphically as a torpedo moving through the time , the blunt end pushes into the advance field of art by means of the changing exhibitions. The bulk is made of accepted modern art. The tail tapers of into art which has become classical and is ready for the general museum. The torpedo moves forward acquiring, and retails its length of seventy years by giving to other museums 
At the time there was the 1934 MoMA exhibition ' Machine kind ' highlighting the Machine Aesthetic of the time so perhaps we could understand his metaphor of MoMA as a machine exemplified by the torpedo…understand it but not agree with it!
The mind boggles and the metaphors flow. Who was this torpedo aimed at? What waters were the Collection in ? What was the torpedo’s fuel, speed, engine, size ….and what do (could) they stand for? …and art renewing itself every 70 years , giving art to other ‘classical’ museums if not else Barr had a vision!
The drawings seem incomplete yielding none of overt and covert links his Chart revels, the torpedoes simply have a crude time line and artists and schools appropriately positioned along the line typed in the body of the torpedo.
There is some attempt to separate the European from non-European perhaps appealing to his target American audience but this is pretty crude. The torpedo metaphor lacks the didactic elegance of the Chart. There is no idea of the size or importance of the connections yielded by the Chart. So I regret to say the metaphor fails to produce a diagrammatic vocabulary in fact in contrast to the graphical richness of the Chart it became a simple language with one piece of grammar - a noun – the torpedo and that’s it!
 Annie Cohen-Solal quoting him in her article on Barr in Abstract expressionism: the internationally context, Issue 6512 edited Joan M. Marter