Schwinn Serial Number Stamping

[GTs58]

I thought a clue to the head tube being serial number stamped flat is that the serial numbers are on one side of the tube. Not going past the welded butt joint.

Another good point. So now the question is, when did the SN's first get stamped with this equipment in the 78 Reporter?

 

[Metacortex]

Anyone ever see the reversed stamping on a head tube later than 1970?

I have: http://www.bikeforums.net/classic-vintage/798805-rare-schwinn-error-serial.html

...when did the SN's first get stamped with this equipment in the 78 Reporter?

We know that headtube serials started in early to mid 1970. The article I pictured states that "frame heads are fabricated at Plant #4, Schwinn's newest facility, devoted exclusively to producing frames. In full operation by 1974." So it could have been functioning even earlier than that, and there is little reason to suspect they changed how headtubes were made.

I thought a clue to the head tube being serial number stamped flat is that the serial numbers are on one side of the tube. Not going past the welded butt joint.

They did sometimes go up to and even past the welded butt joint:

OK guys, did you read the article I posted? Again there is no way the serial would have survived on the headtube legibly after the pressing, welding, scarfing, grinding, sizing and polishing that happened after the flat plates were stamped.

 

[GTs58]

Weren't there many parts of the Tandem frame that were not EF and was filet brazed? Here is that same 1970 twinn that was double stamped with a SN.

I've also seen non EF head tubes on the road bikes where the serial number is near or centered in the head tube. Read all the reporter last night.
I work for a company that does light manufacturing and I use a grinder and flap sander on a daily basis. The head tube halves are rolled with high pressure stamps and it's not like they were hammered round so I see no good reason why a serial number would not survive a flash weld, grinding and polishing on sliver of metal slag in a single small area or the rolling by stamping equipment.

Can someone copy and paste that picture of the 1980 Cruiser from that other forum? I'm not going to join another forum just to look at one picture. Thanks!

 

[Schwinn499]

I think the font and size of the text changed with the change in placement as well. So probably not the same stamping equipment. Id have to go with Metacortex on this one, serials were almost certainly stamped as said in the reporter the entire run of these serials.

 

[momo608]

I'm sold, I already gave up on my theory after reading the Reporter.

For whatever it's worth the Chrome Moly filet brazed frames are number stamped differently. Many times the stamping is so light you can hardly see it.

 

[Metacortex]

Weren't there many parts of the Tandem frame that were not EF and was filet brazed?

That is correct, so not the best example in this case. Here is another much better example, taken from a '72 Varsity seen here: http://www.bikeforums.net/classic-v...ity-sport-chrome-fenders-worth-restoring.html

While that serial isn't centered, it definitely crosses into the welded area between the headtube halves.

Can someone copy and paste that picture of the 1980 Cruiser from that other forum?

 

[Metacortex]

For whatever it's worth the Chrome Moly filet brazed frames are number stamped differently. Many times the stamping is so light you can hardly see it.

I have seen some with lighter stamps, but that isn't the rule. These look pretty much the same to me:

1972 Varsity:

1971 Sports Tourer:

 

[Jeff54]

That is correct, so not the best example in this case. Here is another much better example, taken from a '72 Varsity seen here: http://www.bikeforums.net/classic-v...ity-sport-chrome-fenders-worth-restoring.html

There is a difference in the numbers by 1980. your green above is bold and is pressed so hard it pushes the post in, the other green previously has a slight bend too. While later, it's lighter, sloppier and perhaps a slightly different font. Sloppiest, in that blue upside-down set too. Either they've used the number press so much it's out, or an entirely different stamping mechanism.

This is 1980 Cruiser and the set is not close to front center.

 

[Metacortex]

There is a difference in the numbers by 1980...

I don't think you can ascribe that to a given year or a specific change over time. I'd say the stamps were affected more by the operator and machine settings, combined with wear on the dies. Given they stamped more than a million bikes some years I'd imagine the dies would have to be changed from time to time. For example here is a '73 Continental with a very light stamp:

 

[cds2323]

And here is a 1980 Cruiser 5 with a bolder stamp than the one posted by jeff54. (Edit: not sure why but I misread the serial number on jeff54s bike as BR not HR, still a deeper stamping). Not far apart either.