Main Frame

 

The first step of manufacturing the Main Frame was to join the correctly sized tubes, small sections on the edges had to be shaped into profiles according to templates developed on CREO. This meant cutting and filling down to shapes that would improve the contact area of the tubes to be welded. This was done to both the seat and chain stays and also to the top tube, since these were going to be welded onto the seat and head tubes respectively.

 

At this stage, further progress depended on receiving the bottom bracket from the technicians, though unfortunately this overran by over two weeks on their initial estimate. Having completed the steering column in the meantime, all stays and tubes were ready for welding by the technicians.

 

 

 

 

 

 

 

 

 

 

 

 

 

Having completed the welds, only two principal tasks were left to finish the frame, namely creating the rear dropouts and cutting the main tube to insert the hinge. The rear dropouts could not be manufactured before the seat and chain stays were welded in place, as they were highly dependent on the angles between them. Once the angles were measured and dimensions finalised, they were water jet cut from an 8mm steel plate, crimped and brazed onto the stays.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

With the dropouts attached, both wheels could be mounted to the frame, which allowed for the fitting and inflating of the inner tubes and tyres. The steering column was connected to the main frame via the headset, however, due to the non-standardised nature of the fork, this also proved difficult. Ultimately a hybrid of two headsets were used to apply adequate friction and hold the steering column in place.

This successfully allowed the handlebars to rotate freely inside the head tube. Unfortunately, the welding of the main frame had not been performed satisfactorily, and resulted in slag on the inside of the seat post. Practically, this had significant ramifications to the folding design, as the seat tube could no longer be inserted into the seat post, and therefore it was unable to drop-through as initially intended.

This necessitated a design change, and so separate seat clamps were purchased and were mounted to the frame. This introduced another step into the folding process, as the seat post had to be fully removed from the seat tube and inserted into these additional seat clamp to reduce the folded volume.

 

 

 

HINGE

 

After the angled sections had been returned by the technicians and the hinges had been cut to size, a final welding job was submitted to attach the latches and angles together. The position for the mid-frame cut was then decided by measuring the distance between the two wheels and cutting the frame at the middle distance. This way, when the bicycle was folded it would have both wheels side by side.

The incision was made perpendicular to the ground and the hinge welded to the two ends of the top tube afterwards. Another factor that had not been considered was that the non-standard front wheel was slightly larger than the rear wheel, although both were quoted as 16in. The result of two mismatched wheels, was that the rear wheel was raised off the ground in the fold, and so a solution had to be conceived that would hold the two sections of the frame together when folded.

 

A set of two neodymium magnets with 8.3kg pulling force were ordered and superglued in place at the left rear dropout. This had the effect of efficiently holding the frame together when folded as desired. The latches on the hinges were then adjusted and tightened to ensure that the hinges were being held securely closed when in riding position. An adhesive foam was then inserted inside the hinge to maintain a closed gap when the hinges were closed.