I need some one to help me determine the age and type of bike I have.
#1
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I need some one to help me determine the age and type of bike I have.
All I have is the frame. But the numbers are 40431. I don't know anything else about it.
#2
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The frame design dates to the late thirties and was patented by Schwinn. It is known as a cantilever frame because the seat stays are carried all the way forward to join the down tube just behind the head tube/down tube joint. Any dynamic twisting forces that would normally twist the head tube out of plane with the seat tube are resisted by one of the carried forward seat stays going into compression while the other goes into tension, maintaining the head tube and seat tube aligned in the same plane.
After the Schwinn patent expired in the 1950s, many other manufacturers copied the design. Millions of bikes from several manufacturers have built frames like this over the past 75 years or so, and the date it was made and the manufacturer will likely remain a mystery.

After the Schwinn patent expired in the 1950s, many other manufacturers copied the design. Millions of bikes from several manufacturers have built frames like this over the past 75 years or so, and the date it was made and the manufacturer will likely remain a mystery.


#3
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Better close-up photos of details like the rear dropouts and the tubing joints may be helpful.
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As makers made more bikes the serial numbers quickly became more complex with alpha-numeric combinations that vary between brands.
The joints appear to be plain welds instead of brass fillet brazing, which eliminates Schwinn from the long list of possible makers.
If there is no head badge, might there be an outline of the shape remaining in all the partly removed paint?
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Well it's definetly not a Schwinn and not a true cantilever frame and is 60's or newer., The chain stays braces are seperate pieces and welded. The cripped dopouts and lesser welded construction would indicate a fairly low end 60's-70's frame made to look like the classic Schwinn pretty common during the 60's. In current condition no paint no fork it basically has nominal value.
#7
Senior Member
The way the chain stays approach and connect to the bottom bracket is like a 70's Columbia was put together. But no exclusive to that.
I agree with others, 60's to 70's most likely.
A project to learn with but not an investment.
I agree with others, 60's to 70's most likely.
A project to learn with but not an investment.
#8
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Here are fifties ads for similar frames from Huffy and Columbia made after the Schwinn patent expired.



#9
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Thanks Scooper. Looking at the seat stays at the bridge… Columbia might be it. but expand the possible dates back a decade or two.
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#11
Decrepit Member
I think the bike is being suspended from the ceiling by thin wires.

#13
Decrepit Member
For anyone interested, here's the patent drawing from the 1938 application and some of the introductory information describing the ability of the frame to resist twisting strains.

It's no coincidence that many early mountain bikes were built up using old Schwinn cantilever frames.

Originally Posted by Frank W. Schwinn in U.S. Patent 2,151,533
My invention contemplates and provides a bicycle frame of novel and graceful construction which is particularly well adapted to resist certain strains, resultant from accidental or other overloads, which frequently destroy bicycle frames, - i.e., those strains which tend to twist the axis of the steering head out of the plane which includes the axis of the saddle post mast, and those strains which tend to disrupt the union between the steering head and the reach tube which, in the normal use of the bicycle, constitutes a tension member acting between the steering head and the crank hanger.
The primary object of the invention is to provide a bicycle frame of neat and sturdy appearance which is so constructed as to be well adapted to resist the destructive strains to which reference is made in the preceding paragraph.
A secondary object is to provide a bicycle frame which, as an incident to its being greatly strengthened to resist the aforesaid strains, provides a natural pocket for a battery and/or tool box.
A salient feature of the frame of the present invention is that the upper stays of its rear wheel fork, after being welded to the upper portion of the saddle post mast, are extended and curved forwardly and downwardly in parallelism to the lower reach tube, and are welded to the latter, - in such a way as effectively to resist those strains which tend to twist the axis of the steering head out of the plane of the axis of the saddle post mast.
The primary object of the invention is to provide a bicycle frame of neat and sturdy appearance which is so constructed as to be well adapted to resist the destructive strains to which reference is made in the preceding paragraph.
A secondary object is to provide a bicycle frame which, as an incident to its being greatly strengthened to resist the aforesaid strains, provides a natural pocket for a battery and/or tool box.
A salient feature of the frame of the present invention is that the upper stays of its rear wheel fork, after being welded to the upper portion of the saddle post mast, are extended and curved forwardly and downwardly in parallelism to the lower reach tube, and are welded to the latter, - in such a way as effectively to resist those strains which tend to twist the axis of the steering head out of the plane of the axis of the saddle post mast.
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