Hello;
In the dragonfly catalogue, there is no less than 6 different front section frame types prefixed with Part #29-???? for A,B,M group models, but no other information in the list, as to what part number for what model ect.
I'm trying to find out if there is a physical difference between ZB31 and ZB33 frames.
Are the B33 frames built obviously the same dimensions, but with a heavier construction? Also is there a way to tell, or a number stamped somewhere on a rigid rear section, identifying if it is correct for a ZB front section, B31 or B33 ?? Are these also a heavier construction.
Any help appreciated.
Merry Xmas to all.
Cheers Keith

email (option): keithatkinson@hotmail.com

Hi Kieth...The first postwar rigid B Series frame differs from the later one substantially..though none of these early ones will carry a ZB frame number prefix.

Post 47 rigid frame fronts which include ZB are identical dimensionally and in tube gauge etc. for both models.
However, there are some differences between rigid and plunger frame fronts (which both carry ZB prefixes.)....

These differences are detail differences and don't affect the ability to swap between rigid and plunger rear sections or between B31 and B33 models....

For example...Some plunger frames have the steering lock lug and the forging at the bottom of the front down tube is a slightly different shape..etc..

Each difference or series of differences will result in a different part number so it can get confusing just working off the numbers....

As stated though, the overriding principle is that ZB frame fronts will fit either B31 or B33 models and either plunger or rigid rear halves with only detail differences, all of which can be accommodated if necessary...ZB plunger models only carry an 'S' suffix to the frame number to indicate 'spring frame'..ie ZB31S 12345....Ian

email (option): ian@wright52.plus.com

Thanks Ian for the very informative answer. Excellent!!
I don't have Bacon's book with me at the moment.
Interesting about the steering lock lug, and the forging at the lower front frame tube.
I am aware of the smaller construction frames of the XB models, and the narrower B1 gearbox, and bantam steering head races ect.
Its good to know that post 47 ZB major components will work together without having to modify anything.
Cheers Keith

email (option): keithatkinson@hotmail.com

there was a discussion that the rack/angle of the steering head was different from the tele forks to girder forks

email (option): roger.beck@node6.com