Schwinn Serial Number Stamping

[Metacortex]

Referencing this topic showing an upside-down serial number stamp (and I've seen and heard of several others http://thecabe.com/forum/threads/someone-please-explain-this-photo-for-me.85709/

I just acquired the May 1978 Schwinn Reporter filling in a gap in my collection and finally have located definitive documentation about how and when the serial numbers were stamped in the frame manufacturing process:

As the article states the serial number was stamped as part of the very last operation in the headtube manufacturing process (along with drilling the badge holes). Considering the shape of the headtube and the stamping process you can see how easy it would have been to stamp some upside-down.

Thinking about this further, I've never seen or heard of a fillet-brazed bike with an upside-down serial number. The fillet-brazed bikes would have had this stamping and drilling done on a bare tube with no protrusions (meaning no up from down other than the serial number location). Since in that case the serial number would be the only indication of up or down and since they were subsequently hand-brazed it is no wonder you never see a fillet-brazed bike with an upside-down serial number. Comments anyone?

 

[GTs58]

Very interesting. I was close, real close. :=)

 

[Schwinn499]

I saw those reporters in the sold listings...I had a feeling it was you. Thanks for sharing. Cool stuff right there. Schwinn bikes are the best!

 

[Dale Alan]

That is great info,good to see the facts . Thanks for sharing.

 

[momo608]

Great stuff!

I hope you make a habit of putting these articles up.

So much for my theory of stamping while a flat plate.

No scanner? I had to zoom in quite a bit to read some of it. Our friends with small screens might not be able to read it.

 

[Jeff54]

Just about how I expected reverse, up-side-down serial numbers got there. Cept, I hadn't imagined it would have been done before the whole frame was assembled.

That is, I wouldn't put numbers on a part, alone, until it reached the last stage of whole assembly, Quality control inspection and serial number stamp, before painting. Because, the number would be lost if any error occurred before completed.


So, good ol'Hangover Mondays', Jamie Marquet did it!

 

[Metacortex]

According to other Schwinn documents when the serial numbers were on the LH rear dropout, those dropouts were also serial number stamped before being welded into the frame. That is also why in early 1970 when Schwinn moved the serial numbers from the dropout to the headtube there were some frames built with serial numbers in *both* places, and the numbers did not match.

In the case of the headtube manufacturing process you can now see why the number was stamped last, if it had been stamped on one of the flat plates at the beginning of the process it probably wouldn't have survived the pressing, welding, scarfing, grinding, sizing and polishing that followed.

Here is a pic I found online that shows one of the headtube halves being stamped in a press:

Unfortunately I don't have access to a scanner right now but I did make sure the full-page pic was sized so the text was readable zoomed in, and that's what counts.

 

[Jeff54]

Here is a pic I found online that shows one of the headtube halves being stamped in a press:

.

Well that photo also splains why they'd gone on strike and virtually killed Schwinn's business. The strike must have been an attempt to abolish their slave trading business too. [grin]


Alternatively, I'd guess that chain and wrist band pulls the worker's hand clear of the press. 'Hang-over Mondays' safety prevention

 

[GTs58]

Some food for thought on this subject. I'm still believing the SN's were stamped flat, at least for 1970 when all these upside down and wrong side stampings occurred. The serial number location was changed to the head tube in early 1970 and prior to that all the stampings were done on flat steal. So it's very possible Schwinn started stamping the head tube numbers while it was flat since their original equipment was for stamping serial numbers on flat steel. This Reporter was from 1978, so when "exactly" did Schwinn install this new serial number stamping equipment for round tubing? Anyone ever see the reversed stamping on a head tube later than 1970? Any news in the Reporters saying when Schwinn upgraded their stamping equipment?

 

[momo608]

Some food for thought on this subject. I'm still believing the SN's were stamped flat, at least for 1970 when all these upside down and wrong side stampings occurred. The serial number location was changed to the head tube in early 1970 and prior to that all the stampings were done on flat steal. So it's very possible Schwinn started stamping the head tube numbers while it was flat since their original equipment was for stamping serial numbers on flat steel. This Reporter was from 1978, so when "exactly" did Schwinn install this new serial number stamping equipment for round tubing? Anyone ever see the reversed stamping on a head tube later than 1970? Any news in the Reporters saying when Schwinn upgraded their stamping equipment?

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.