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As mentioned elsewhere on this site, the most important stage in building a custom fit bike, is, to transform all the measurements and data supplied, and produce a bicycle design that will both fit the rider, and comply to the riding style as well as possible.
The Build Process.
The Steps Involved In Producing One Of Our Frames.
Spirit Cycle Works


Mark uses two methods to build superior frames. Lugs and Fillet Brazing, we feel that these methods, despite being more time consuming than the more common TIG welding, are the best ways of building high quality bicycle frames.

A lot of care is taken at this stage, regardless of the fixing method, to eliminate any distortion of the frame, or sealing into the frame any stresses.This is accomplished by fixing the joints in an order that has been arrived at through experience and a mastery of the art of fillet brazing and lug construction with an acetylene torch. This ensures that the frame remains straight and true when it is released from the confines of the jig, and therefore, will require no cold setting.

When the frame is completed, including the chainstays, seatstays and all bottle bosses etc. The frame is cleaned of all flux, and once we are happy that everything is as it should be, a final alignment is performed and a last comparison is made with the full size drawing.

Lastly we prep the frame. Seat tubes are reamed, head tubes are reamed and faced, bottom brackets tapped and faced, and all threaded bosses are cleaned with a tap.

Now the fun part. PAINT...
To that end Mark will produce a scale drawing. From this they will check for any design conflicts, such as with the chosen components or things like toe overlap etc. Once satisfied, the design is passed for production, and a full size drawing is made. This drawing will be used as a reference through the entire build process, from checking mitered and cut joints, to checking the geometry of the completed frame. These drawings are sent to you with the completed frame, and make interesting conversation pieces for your garage or workshop...

Once the tube set has been chosen the cutting and mitering begins. Each joint is worked on until the desired fit is aquired. This requires lots of old fashioned work shop time, involving the disapearing art of hand filing...

After all the tubes have been mitered, they are all placed in a special frame jig, and checked to make sure all the joints are correct, and that the angles and frame geometry match the design.

When satisfied all is well, vent holes are drilled where necessary, and the tubes are thoroughly cleaned and prepped for joining back in the jig.
This little cartoon dude shows some of the measurements that we need to fit a bike.
Check out our page on bicycle fitting.
A lug. We use investment cast, stainless steel lugs. This one is in its raw state and requires some file and cloth work before it is ready to be brazed. The lugs can also be polished to a high mirror shine.
A fillet brazed head tube assembly. The fillets are bronze and produce a lovely contoured joint.
Sometimes we blend the two methods together. Here we have a seat tube joint waiting to be fillet brazed, then the seat collar, which is cast stainless, will be silver brazed on like a lug.
A completed 29er mountain frame overlaid on the original design sheet, just waiting for some paint and a rider...
The Build Process
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