Anatomy of the new Kirk Frameworks cyclocross frame
Part Four
Final machining : Alignment : Studio photos of the unpainted frameProceed to Part 5 - Final AssemblyIn the penultimate installment of this series, I’ll give you an idea of what the final steps look like as the frame is made ready for Joe Bell’s paintwork.
Before any time is put toward the final finish work the frame must be machined and aligned. The first step in this process is to tap and face the bottom bracket as the bottom bracket faces are used as the reference for the alignment. The procedure is the same as it was when the front triangle was faced before adding the rear triangle. The threads are cleaned out with the bottom bracket taps and then the taps are left in place to act as guides for the facing tool to ride in. This assures that not only are the faces parallel to one another but that they are concentric. This important for the frame alignment as well as the life of the bottom bracket bearings. If the bearings do not run perfectly parallel to each other they will wear more quickly and make more friction when you spin the crank.
Cleaning threads in bottom bracket
Facing the bottom bracket to assure accurate alignment
Next the head tube is reamed and faced for the headset. Just like with the bottom bracket the faces of the head tube need to be perfectly parallel to each other so the fork will spin smoothly.
After the headset is reamed I move onto cleaning out all the threads on the frame to be sure they are up to specification. I also stamp the serial number into the bottom. The serial number is a simple code and in this case the number is 11 08 33 where “11” stands for the month and the “08” stands for the year and “33” is the sequential number for the year. So this frame was built in November of 2008 and was the 33rd frame built that year. This number is valuable to me beyond the obvious need to keep track of the frame. The number also lets me know what batch of raw material the frame was made from. So if for some reason there was a problem with the frame in the future I can contact the tubing manufacturer about the exact tube that was used in that bike.
Reaming the head tube for proper headset fit
Cleaning threads on braze-ons. In this case it’s the front derailleur pulley mount. All braze-ons are cleaned this way to assure quality threads
Cleaning gear hanger threads
Stamping serial number in bottom bracket
Serial number 11 08 33 stands for November 2008 and the 33rd bike made this year
Next I cut the seat tube slot. The slot is done by hand as you can see and the cut is made down into the key hole that will prevent cracking at the bottom of the slot. The inside of the seat tube is cleaned and smoothed so the seat post will fit just right and not get scratched when it is slid into place.
Slotting seat tube
Seat tube slot and key hole
With all the machining done I can now move onto the final alignment. Since the handling and stability of the frame depends on its precise alignment I am extremely particular about it. The frame is clamped onto a machined bottom bracket post and suspended out over the flat surface plate. Then I use a height gage to check that the various parts of the frame are the right distance from the plate assuring that the frame is straight and true.
Machined frame on alignment plate
Checking the distance from head tube to plate
Next I focus in on the rear dropouts and the rear wheel alignment. The rear wheel needs to not only point perfectly straight ahead but also needs to stand vertically so the bike will not pull to one side. The first step in this process is to be sure that the rear dropout faces are parallel to each other and this is done with “H” tools. The gap between the faces of the tools must be even and concentric.
With the dropout faces parallel to each other I then move on to checking the rear wheel alignment. This is a simple but time-consuming procedure where a perfectly dished and true rear wheel is installed in the frame and is checked to be both pointing forward and to be standing vertically. If this is off at all it can affect the high-speed handling of the frame and I pride myself on bikes that go down hill with ease regardless of the speed. If due to any distortion from the brazing process the wheel is anything but right on then the dropout axle slots are ground ever so slightly to bring the wheel into perfect alignment. This requires much patience and cannot be rushed as the entire build is depending on it. Measurements are made with calipers to be sure that the wheel is centered between the stays.
Inside face of the rear driveside dropout checked with alignment tool
Rear end alignment bar checking lateral location of the driveside dropout. The non-driveside dropout is then checked relative to the driveside to set the proper rear spacing
“H” tools being used to check that rear dropouts faces are parallel to one another and concentric. This assures that the frame isn’t stressed when the rear wheel is clamped in and that there is no bending load to the rear axle. This important for the long term health of both the frame and the hub bearings.
Checking to be sure that the rear wheel rim is centered between the seat stays
The final alignment step is checking the rear derailleur hanger alignment. This assures that the rear derailleur will hang in the correct orientation and shift properly.
Using the “DAG-1” to check that the rear derailleur hanger is properly aligned so that the derailleur will be in the correct alignment with the centerline of the frame and the front chainrings
Derailleur hanger tool checked against rim
Final Finishwork and Studio Photos
Only after all the machining and aligning is complete do I move onto the final finish work. The first step in this is to clean the frame of any cutting oil or residue from the machining. I then move onto the handwork of sanding and polishing the frame to get it clean and ready for paint. There is no sand blasting used to clean the frame. After the finish work is done I let the bike sit overnight so I can look at it with fresh eyes in the morning to double check my work. I also take one last look at the paperwork to be sure I didn’t forget anything and then a few photos are taken before it goes into a box and off to JB.
Driveside of completed frameset
Polished and ready for Joe Bell paint
Full deck on the fork ready for special colors
Sachs lugs
Side tack hollow cap seat stays fully wrapped
Rear brake cable hanger and rear view of seat stays
Full wrap hollow caps
Bottom bracket and front derailleur pulley mount
Fillet brazed dropouts. The strongest, stiffest and lightest way to go.
I hope you’ve enjoyed getting a little glimpse into what goes into building a frame. This frame was built for the North American Handbuilt Bicycle show, but nothing was done differently with it. It was built using the same care, attention to detail and time that I use on every frame. All of the frames I bring to the NAHBS show are normal customer bikes that are on loan from their generous owners. You won’t find any unrideable show specials in my booth. I prefer to spend my time building bikes for people to actually ride rather than making something that is fancy but ultimately unusable. So if you find yourself at NAHBS I hope you’ll stop by and see this one and the other bikes I’ll have there.
The next and final installment of this series will be posted when the frame comes back from JB with its fresh paint. At that time I will prep it for assembly, hang the parts on it and finally take some photos. Continue to Part VThanks for reading.