Peter Tutty said:
They are a variation of the 'Cyclo' dropout for use with the Super Champion Osgear, the forward vertical position is used in order to get the cluster closer to the derailling forks. The horizontal droput was for use as fixed/single speed, but also in this case a rear derailleur boss has been added, use of a 'conventional' derailleur would be with the horizontal dropout as better shifting performance would be found there vs the vertical dropout.
Neil Foddering said:
Peter Tutty has pretty well described the dropouts.
I would just add that they were sold by Super Champion, the makers of what is commonly called the Osgear, which is what the English distributor, Constrictor, called the Super Champion striking fork gears (and later, other types of Super Champion gears they imported).
The reason that the vertical dropout was included in these rear ends was, as Peter, states, to be able to get the rear sprockets as close as possible to the striking fork (necessary for efffective operation of the gears) and still be able to remove and replace the rear wheel quickly. This would not be possible if the wheel had to be slid forwards in a normal dropout to remove it, since the sprocket would then foul on the striking fork.
Some riders who used Osgears did so successfully on frames with track ends, rather than Osgear ends, since the wheel is, of course, removed to the rear and, therefore, away from the striking fork.
Norris Lockley said:
At first glance...and second for that matter...it could have been a 1930s-40s English handbuilt machine. Close scrutiny of the rear drop-outs however, virtually precluded that possibility, as any English frame built to use a Super Champion Osgear would have had either Stallard "Osgear" drop-outs, or Claud Butler, or Cyclo. I cannot recall seeing any English frame with genuine Super Champion drop-outs, but no doubt there are plenty...somewhere.
The drop-outs on this machine appear to be the genuine Super Champion articles, but although I have quite a collection of French frames using the ST Etienne company's frame parts, I have never seen a pair of drop-outs of this type and design.
I did begin to wonder whether they might actually be Simplex-made ones, but that company's catalogue for 1939 does not show anything resembling this pattern, not even for use with their own striking arm derailleur.
Super Champion did manufacture a less well-known rear derailleur that resembled the design of the Simplex "Tour de France", so I have been wondering whether these drop-outs with their gear boss was a short-lived and rare Super Champion model. Does anyone on the List have a Super Champion catalogue from the late 30 - early 40s?
Clearly this Edge frame was never intended to use an SC "Osgear" type striking arm derailleur, otherwise there would not be a cable stop on the chainstay. All striking arm derailleurs were activated by a cable running under the chainstay not along the top. There is the possibility, of course, that the frame was originally built for use with the "osgear" and then at a later date converted to a Simplex or other brand of piston type mechanism. The gear boss could simply have been brazed on to the original Osgear drop-out . My own belief is that the boss was added at the outset of the frame-building process to provide an unusual pair of drop-outs.