knucke frame

[hdhikaru]

hi,
please advise.
any difference between 37 and 38 frame?

[Chris Haynes]

Yes. One easy thing is the backup nuts on the tool box mount. 37 are rectangular and 38 are round. 38 has closed brake stay while most 37 have the end cap welded on, if they even have one.
Palmer's new book has all the details.

[hdhikaru]

Yes. One easy thing is the backup nuts on the tool box mount. 37 are rectangular and 38 are round. 38 has closed brake stay while most 37 have the end cap welded on, if they even have one.
Palmer's new book has all the details.

ok, thanks!!!

[3_7/16bore]

37 has a 7/8" upper strut and 38 has 1" strut ( behind gas tanks) ,,,,
the welded brake stay can be very well done and hard to decide if its added or if it is a forging.

[Steve Little]

3 differences in the foundry marks for 1937 neck forging
1/2" square for the first 37 VINs
After that they reduced the foundry mark to about 5/16" square
Then 5/16" square with number 2 for high VIN.
The number 2 revision neck had a larger spigot for the backbone brace. These necks started with 7/8" tubes with a sleeve over the tube to take it up to the 1" hole.
Then they had a 1" tube. All of these tubes were braised to the backbone.

All 37 frames had the narrow seat post cross braces.

[Chris Haynes]

37 has a 7/8" upper strut and 38 has 1" strut ( behind gas tanks) ,,,,
the welded brake stay can be very well done and hard to decide if its added or if it is a forging.

Early '37 is 7/8, Mid year became 1".

[Steve Little]

Braised front engine mount for 37. Electrode welded front engine mount for 38. Braised top engine mount 37. Electrode welded top engine mount for 38. Once upon a time I could rattle all this info in one shot. I will probably remember something else as it bubbles up.

[hdhikaru]

thanks you all!!