JK Cross:
Anatomy of the Kirk Frameworks cyclocross frame

Part One
Frame design, fork and seatstays

When I build a frameset I do it in more or less a specific order and in every case I start by creating the design for the frame and the rider. The frame design provides all the rider-specific numbers like top tube length and also has the dimensions needed to cut the tubes to the right length and to properly set the jig for the construction. The JK Cross uses the same tubeset as the JK Special and has geometry suited to cross racing in a variety of conditions. The JK Cross has a level top tube for ease of shouldering the bike and uses lugs to allow for that.

When the design is complete the raw materials are gathered and a quality control check is made of every piece. Once that is done I start into the “subassemblies.” This means doing all the prep work of joining dropouts to chainstays and capping and shaping the seat stay tops. Once complete these subassemblies are set aside until needed later. I also build and finish the fork at this stage.

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Computer image of complete bike including all jig and cut dimensions.

All major raw materials laid out and ready to cut:

Lugs – Sachs Singer
Dropouts – Breeze Hood Style
Top tube – Reynolds 953
Down tube – Reynolds 953
Seat tube – True Temper S3
Chainstay – proprietary Reynolds
Seat stay – proprietary Reynolds
Fork Crown – Sachs
Fork Blades – Reynolds lightweight
Steerer – Reynolds butted lightweight

“H” tools used to make front dropout faces parallel and concentric

Stamping serial number

Fork ready for alignment

Seatstay Caps

This type of cap is labor intensive so it’s seldom done now but it’s also the lightest and strongest type. Most caps are solid cast steel plugs that are brazed into the end of the stay. The inverted tube type I make are hollow to the very end.