Dib-Dob: The Story of a Roadie for Dobie – Part 1

DIB-DOB: THE STORY OF A ROADIE FOR DOBIE – PART 1

Many readers of this blog may know my friend Daniel Dobinson. He’s the brains (and brawn) behind iRideAfrica. As a professional cycling guide he spends a lot of time on his bikes. And because of his odd body proportions he’d always found stock road bikes to be a little stretched out. Whereas most cyclists spend the majority of their road time on the hoods, Dan found himself comfortable on the flats – the hoods were reserved for special go-fast situations and he found the drops on most road bikes so far away that he didn’t bother journeying there.

Dan has long legs and a relatively short upper body. Having come into cycling from a mountain biking background he was used to a more upright riding position and hadn’t (mis)spent his youth contorting his body into aero shapes over the top tube of a road bike. As a result most modern road bikes feel very long to him – to compensate he’d used shorter stems but these weren’t ideal for getting weight onto the front of the bike and made descending feel sketchy. Using smaller frames also wasn’t a solution as he’d end up using a gazillion spacers under the stem to get the bars to the right level. This offended his sense of aesthetics.

In the past, many road bikes were shorter than today’s models. European bikes were typically ‘under square’ – this meant that the top tube was shorter than the seat tube. American bikes on the other hand tended to be ‘over square’ sporting top tubes that were longer than their seat tubes. Sizes were offered in 1cm increments starting at 51cm and going up to 66cm. The head tube length was entirely governed by the level top tube but the quill stems could be adjusted a few centimetres up or down to get a comfortable bar height. It was thus perfectly feasible for Dan-like cyclists to take a size or two smaller than their inseam would suggest and to have the stem a centimetre up to compensate. These days most bikes are offered in tee shirt sizes – S,M,L and XL. As such, unusually proportioned people may find it harder to get a good fit without compromising the handling of their bike.

In considering the geometry for Dan’s new road bike I encouraged him to ride my beloved Eddy Merckx Corsa Extra. This bike was built in the early 90’s out of skinny Columbus SLX tubing. By today’s standards it is a little on the heavy side but it handles beautifully with an extra-low bottom bracket, slackish head angle and the classic ‘under square’ proportion. The seat-tube length is 58cm from centre of the BB to centre of the top-tube, whereas the top-tube length is only 56.5cm long. It sports an 11 cm long quill stem. Dan took the bike around the peninsula on a long road ride. For the first time Dan found himself able to rest comfortably on the brake hoods – he took exception to the Merckx’s extra low BB as he’d had some pedal strike issues and I think he was a little dismayed at the meagre performance of the 22 year old groupset still hanging on the bike – but overall he was comfortable.

Now we had a starting point from which to draw up a custom frame to fit Dan.

I decided to keep the seat-tube and top-tube lengths the same as on the Merckx but in deference to Dan’s complaint about the bottom-feeding Bottom Bracket I raised this a full centimetre. The Merckx has old-school style horizontal dropouts that offer a couple centimeteres fore and aft adjustment – I made the chainstays the equivalent length to the Merckx in it’s shortest setting. I drew the frame with a 73 degree head angle and a 74 degree seat angle. We decided early on to go for an after-market carbon fork.

We settled on Columbus Zona Road Oversized tubes with a 1 1/8″ steerer to provide a little future proofing and endless stem and headset options. Zona is not the lightest tube set available but it is a sensible tubeset with moderately thin walls and a relatively forgiving composition. Initially Dan didn’t want any flashy lugs but I managed to convince him that lugs could be very understated and elegant.

I placed an order and a few days later a cheerful chap in a yellow DHL van arrived at my doorstep with a parcel from the UK. The bits for Dan’s bike had arrived.

In the past lugs were pressed from sheet steel and then folded into shape – they required a lot of filing and shaping just to enable the tubes to fit into them. These days lugs are “investment-cast”. This is an expensive process: A model of a lug is used to make a plaster mold that in turn is used to make wax replicas of the lug. The wax replicas are then dipped into plaster and once the plaster has hardened molten steel is poured into the new mold – the steel melts out the wax filling the lug-shaped space inside the mold. Afterwards the plaster molds are broken open to release the newly cast lug. As a process this requires some heavy investment and thus the term “investment-cast’ came into use. The short of it is that cast lugs require a lot less finish work than the older pressed lugs did. Most of the filing done on lugs these days is purely ornamental and offers the builder some ways of distinguishing their work from other builders.

I was no different in this regard except that I have very little experience with lugs. I wasn’t about to start cutting crazy shapes into these things but I couldn’t leave them alone either. I decided to gently shape the lugs – accentuating the curves cast in them and tapering and thinning the points (tapering and thinning also serves a structural purpose in that it helps prevent stress risers along the edges of the lug).

In the picture alongside are two bottom bracket shells. The shell on the left has been cleaned up – the points have been accentuated and thinned and all casting marks and numbers have been erased. Out of sight, under the shell the BB has also been stamped with the frame no.

The one area that I did spend a lot of time on was the seatlug. The standard seat lug was visually very heavy with straight lines around the binder bolt area – this seemed to clash with the otherwise swoopy nature of the long points and I felt it needed redressing.

 In the image on the left are two seatlugs. The lug on the right is how they are supplied – the one on the left is one that has had a lot of sweat equity. While the other lugs only took around half an hour each to clean up – this one had me sweating (and bleeding – in future I’ll sharpen the points last) for two hours! I was very happy with the end result.

The next step was to cut all the tubes to length and to mitre the tube junctions

Dan had decided early on that he wanted internal cable routing. I’d never tried anything like this before but was excited to give it a bash. The internal routing consists of a length of brass tube brazed into stainless tubes at either end. The whole assembly is then bent and fed through a slot cut into the top tube at either end. The stainless tube was the fillet brazed with silver solder to the top tube for a seamless junction. After a little cleanup the end result was rather pleasing.

Before long the front triangle was assembled and it was time to start work on the rear triangle. This is an exciting time as this is when things really begin to resemble a bicycle. As a result of how exciting I found this I have few photos to document it.

In the image on the right are freshly brazed chainstays with Breezer dropouts. The fillets here have not yet been filed smooth but have only had the flux soaked off them.

After putting the chainstays in it was time to prepare the seatstays. I have always admired seatstays with long scalloped tops and I wanted to emulate this on Dan’s bike. I scrounged some off cut top tube for the scallops and brass brazed them into place. The edges of the scallops were then ground flush with the seat stay.

In the image to the left is the finished seat cluster. 

All that was left was to add a brake bridge. I had planned to use a nice aero section brake bridge. I even spent an hour filing till it pleased me with its shape. It turned out that it was too narrow to span the gap between the seatstays and I had to fabricate something from scratch. I turned down some bright steel on the lathe to make a new brake mounting and then attached this to two pieces of bent stainless tube. This was fillet brazed in place.

After reaming head tube and seat tube and chasing and facing the BB shell, Dan’s bike was almost ready for painting.

There was just one tiny detail missing: I made a little brass name tag with Dan’s schoolboy nickname punched into it. This was affixed under the BB shell opposite the frame no. DIB-DOB  

It just so happened that the day I finished Dan’s frame happened to be the day before he went into hospital to have both his feet broken. Maybe this explains the photo quality of his excitement at seeing his frame for the first time. He wouldn’t stand still. This is the clearest picture I have of him seeing his bare, naked frame for the first time:

I hope all my customers get that excited.

Thanks for reading,click here for part 2 – a visit to the painter,  the build and Dan’s first ride.