HOW IT’S MADE

STEEL FRAMES BY STARLING CYCLES

HAND-BUILT IN BRISTOL

We recently paid Starling Cycles a visit in their new Bristol, UK headquarters. While we were there, we thought we would take the opportunity to experience first-hand how a frame goes from the raw materials through to the finished product, and figured we would share that with you as we don’t imagine that many people are aware of all the little intricate steps involved in the process, and we think it’s pretty damn interesting. So, without further ado, let’s learn how to build a Starling front triangle.

First up, the raw materials are delivered to Starling. There are the Reynolds frame tubes in various different sizes and butting profiles for different areas of the bike; 4130 seat tube; machined head tubes, bottom brackets and main pivot junctions; laser cut gussets and cast cable guides. These are all taken through the quality control checks to ensure they’re up to Starling’s standards, before getting prepared to be manufactured.

The first manufacturing step is to miter the tubes. This shapes the interface at each end of the tubes so that they fit closely to the head tube and seat tube or bottom bracket, ready to be joined together. An abrasive notcher (essentially an accurate belt sander with adjustable cutting angles and diameters) sets the shape and length of these tube ends. This requires a manual set up each time a new tube size is going to be mitered, so Starling tends to do batches of ten of each frame size where possible to reduce the overall time spent.

Once the tubes are mitered and ready to be combined into a front triangle, a jig is set up to hold all of the tubes accurately in place. To increase efficiency, Starling uses the same positioning and angles for the seat tube, bottom bracket and main pivot. This only leaves the headtube position and corresponding angle and lengths of the top tube and down tube to be adjusted to create each different frame size and model in their full suspension range.

Each joint is first tack welded to keep everything in place, before being checked for alignment. The joints are then brazed together in a set order to create the strong connections between each tube, with a check for alignment following each braze to ensure there’s no distortion along the way. Brazing uses a brass based filler to join the components with a large and slightly flexible joint, which Starling favors over a TIG weld for the lower stresses and reduced heat distortion encountered during the process. The only exception to this is the joint between the bottom bracket and machined main pivot, where TIG makes more sense due to the thickness of these components and the corresponding heat and time that would be required to braze this junction.

At this stage, the frame is taking shape. The shock mount is brazed in place; and the head tube reinforcing gussets are brazed on using a different filler called Meta-Braze, selected to make the large brazing sections easier and more repeatable to manufacture thanks to its free-flowing characteristics. Starling selected their quite unique gusset plates at the headtube following some FEM (Finite Element Modeling) analysis, which proved that they were an effective solution to add strength to this area of the frame, working in the same manner as an I-Beam to promote the top tube and down tube bending together. The final pieces are added: the stealth routing port in the seat tube and the cable guides on the downtube are brazed in place; then the frame is given its finishing touches.

To ensure everything is perfectly aligned and any distortions that occurred during the manufacturing process don’t cause issues with fitting components, each interface on the bike is subjected to a clean-up operation. The head tube and main pivot are reamed and faced to give a perfectly circular and dimensionally correct inner surface and flat face; and the bottom bracket threads are chased to ensure a BB will thread in nicely. The seat tube uses an aluminum insert which is bonded in place, preventing issues with galvanic corrosion with seatposts inside the steel frame, and this is reamed with their lathe to ensure a perfect fit. After a final clean up of the brazing and check of tolerances and joints; the frames are good to go for paint.

While this manufacturing process is not much different to how a large scale factory would manufacture a steel frame overseas, Joe at Starling was keen to point out that the end product is higher quality when coming out of their Bristol workshop. Not only do Starling’s smaller batches of frames mean that they’re able to offer customization to their customers – from bottle bosses through to even custom sizing – but they’re also able to be considerably more reactive and constantly improve their product along the way. And from following the process along, it’s clear that the end product is of a high quality, and this translates to how they perform on the trail too: with a simple nature but high quality feel.

Joe left us with a closing statement “At the moment, this [Starling frame] as a product is lovely…as with all my bikes, everything is about simplicity and elegance and making it with as minimal effort as possible. I look at this and it’s as good as it gets basically, I can’t think of any way to make it better.”