Dave explains how the rear swing arm of the FLIT-16 is manufactured… with footage directly from the factory!
Manufacturing the parts
These start their lives as round tubes, which are tapered and then curved into the shapes that you can see in the photo below.
Parts of the rear swing arm – Dave is holding the narrow tubular chainstays
The parts at either end of the chainstays (the yoke and the brake bosses) are manufactured by CNC milling. They start their lives as solid blocks of aluminium, and the shape is then gradually milled away.
As you can imagine, CNC milling is a pretty slow process (you can see in the video that tiny amounts of material are removed at a time). To give you an idea of how long it takes, we can manufacture four yokes (seen in the photo below) per CNC machine in one day.
A CNC-ed yoke (when riding, the suspension is compressed against the flat panel), seen being manufactured in the video above
Cleaning the parts
Before we do any welding or assembly, the metal parts have to be cleaned to remove any residue on the surfaces, to make sure that the weld is strong.
The parts are dipped in cleaning baths, which strips away impurities on the surface.
Cleaning the parts before welding
Loading the parts into a fixture
Once the parts have been cleaned, we then load them into a fixture.
The fixture keeps the parts of the rear swing arm in place for welding – ensuring that they don’t move around. Folding bikes are pretty complex pieces of engineering, so it’s essential that everything is aligned and in the right place otherwise the fold won’t work!
Fixtures are stiff, adjustable, and allow all of the parts to be clamped down temporarily during welding.
Parts of the rear swing arm clamped into the fixture
Welding the rear swing arm
T4 heat treatment furnace
To get all of the parts back in order, we place the assembly onto an alignment table.
On the alignment table there are various jigs that are used to hold the parts in the correct place. Other tools are then slid across the table to act as reference points for checking alignment. Parts that are out of alignment are bashed and bent with mallets and levers until sufficiently well aligned.
Aligning the parts of the rear swing arm on the alignment table
Heat treatment (round 2)
Once we’re happy that all of the parts of the rear swing arm are aligned correctly, the assembly is ready for T6 heat treatment.
T6 is an ageing process, which accelerates the ageing of the material in order to increase its strength, making for a strong and long-lasting frame!
When the heat treatment process is done, the part is then ready for painting.
Firstly, the surface of the part is prepped. This involves a phosphate coating being applied, which helps the paint to adhere better to the part.
Once the part has been prepped, the painting process involves three different coats being applied in a semi-automatic painting facility.
The first coat is a base coat, which is a white primer, then the colour itself (in this case our brilliant Blaze Orange!) is applied, and then finally a top coat is added. The top coat is a transparent hard coating, which contains a matting agent that gives Blaze his sleek matte finish. The top coat also acts to protect the paintwork from chips and scratches.
Once each coat has been applied, the parts are heated in an oven to cure. After the final coat the frame is inspected for flaws, and if all is well then it’s ready to go on the bike as a finished part!
Dave and Joe assembling the rear swing arm of Blaze at FLIT HQ
If you guys have any questions about the manufacture process feel free to drop us a line.