"RGF" French bottom bracket shell?
03-24-06, 12:42 PM
#1
Old Skeptic
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"RGF" French bottom bracket shell?
Can anyone offer info about the maker of a bottom bracket shell on a 1970s bike I recently bought. Bike has pure French tubing dimensions and French threading. The BB is fairly simple (no fancy feature-cuts like a Nervex Pro) and has "RGF" within an oval, cast/forged onto the top left side. The rest of the lugs on the bike appear to be a Prugnat "Professional" set with long spearpoints. I'm sure I had once seen this BB logo on another bike, but cannot now find an example on any of my other French bikes.
03-25-06, 07:39 AM
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I’m pretty sure RGF bottom bracket shells were made in France. I used them on most of the frames I built in England through the 1970s, and bought them from Ron Kitching who imported them along with the Prugnat lugs. These BB shells were “Bulge Formed” which is an interesting process and I will explain for the benefit of those who have not heard of this.
A steel tube with the diameter and wall thickness of a bottom bracket shell is fed into a special machine. A mold clamps around the tube that has internal sockets that form the down tube, seat tube, and chainstay sockets. The ends of the tube are sealed and hydraulic oil is pumped inside. The pressure causes the steel to blow into the sockets like a bubble.
The mold opens, the tube slides sideways to clear the mold and a saw cuts it off. The machine repeats whole process automatically. In a separate process the sealed ends of the sockets are machined off making the finished sockets for the tubes. Finally the BB shell is faced and threaded.
I used these BB shells because they were the best available at that time. By the late 1970s investment cast bottom brackets, which are far superior, became available. I’m sure the bulge forming process is still being used for lower end bikes.
A steel tube with the diameter and wall thickness of a bottom bracket shell is fed into a special machine. A mold clamps around the tube that has internal sockets that form the down tube, seat tube, and chainstay sockets. The ends of the tube are sealed and hydraulic oil is pumped inside. The pressure causes the steel to blow into the sockets like a bubble.
The mold opens, the tube slides sideways to clear the mold and a saw cuts it off. The machine repeats whole process automatically. In a separate process the sealed ends of the sockets are machined off making the finished sockets for the tubes. Finally the BB shell is faced and threaded.
I used these BB shells because they were the best available at that time. By the late 1970s investment cast bottom brackets, which are far superior, became available. I’m sure the bulge forming process is still being used for lower end bikes.
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History, photos and tech articles on "Dave's Bike Blog." 'dave moulton' Registry including a Picture Gallery https://www.davemoultonregistry.com/
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03-25-06, 08:27 AM
#3
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I believe the manufacturer is Gargatte. They also made (or still make?) investment-cast BB shells.
03-25-06, 10:17 AM
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Somehow "EX" framebuilder does not sound right with "Dave Moulton"---but anyway I have that BB on a mid 50s Maclean,thanks for the insite on it.HarleyDavision uses this bulge process,they call it hydro forming,to make the bends on their new superbike frames because regular tube bending could not get the curves needed for the frame .
