Long-Tail Cargo Bicycle.


This project was an extended bicycle designed to carry a greater load than a standard cycle.

The cycle was built initially for personal use but was to eventually be sent to Africa as a donation to 'World Bike'.

 

 

 

 

 

 

 

 

 

The donor bicycle was steel framed mountain bike with 26" wheels. The bike was being discarded by a friend and was kindly given to me for this project.

Donor cycle

 

 

 

 

 

 

 

 

 

The plan was to extend the rear frame of the bike by 250mm (10") along the chain-stay. It would therefore require a longer chain and longer gear and brake cables.

This PhotoShop image gives an impression of the design.

 

 

 

 

 

 

 

 

 

Key Features

Chain stay extended by 250mm (10").

Front frame triangle retained for strength.

New frame tube from rear axle up to seat post or cross bar near seat.

Rear brake retained for simplicity.

Long load deck of 700mm.

Load deck part of frame structure to allow rear brake to be retained.

 

 

 

 

 

 

 

 

To extend the chain-stay some 16mm steel tubing was used. The chain-stay was tapered and so it was measured to find the place where its diameter was 16mm. Here it was cut on both sides.

The seat-stay was cut as close to the seat post as possible.

Joining pieces were turned from steel to enable the chain-stay and 16mm pipe to be joined flush.

Measuring Chain-stay

Cutting Seat-stay

Chain-stay joiner

 

 

 

 

 

 

 

 

This photo shows the chain-stay assembly brazed. The spacing at the rear was set using some threaded rod to ensure it would fit the rear axle. A piece of tubing was also brazed between the chain-stays to hold this width.

Chain-stay Brazed

 

 

 

 

 

 

 

 

To complete the extended rear triangle, two lengths of 14mm rod were brazed from the rear axle mount up to the cross-bar.

The cross bar was drilled to take the 14mm rod and was then filed to allow it to be inserted at an angle. The 2 tubes were also pre-bent using the pipe bender to get the right angle down to the rear axle.

Rear frame triangle complete

New seat-stay before fitting

 

 

 

 

 

 

 

 

A freewheeling test run at this stage confirmed the frame to be strong enough and handling to be unaffected by the change.

 

 

 

 

 

 

 

 


The height of the cargo area of the cycle was set by the end of the original seat stay. A 140mm length of bar was brazed to the top of this feature. This 140mm dimension was chosen to allow the pipe bender to form the rear curved section.

Next 2 long bars were bent at one end to form the sides of the rack. These were cut and filed to join both the new 140mm bar and the new seat stays, as shown.

 

 

 

 

 

 

 

 

 

The rear, curved section was formed on the pipe bender using the larger wheel as the former to create a 140mm diameter 180 part. This was brazed to the 2 side sections using and internal joining piece of steel tubing.

Rack frame complete

 

 

 

 

 

 

 

 

To finish the extended loading area, two stays were attached between the rear of the rack and seat stay. Also an additional cross brace was added.

Rack complete and painted

 

 

 

 

 

 

 

 

A load deck was cut from 9mm exterior ply. The width was left short from the side frames of the rack to allow the fitting of panniers. The wood was attached with self-tapping screws to the frame cross pieces, it was finish in Teak oil to make it weather proof.

Load Deck

 

 

 

 

 

 

 

 

 

The bike finished with extended chain, rear cables.

(Standard brake and gear cables were just long enough).

 

 

 

 

 

 

 

 

 

Finally these 2 images show a typical loading for the bike. It was designed to take 2 child seats one behind the other or as shown here, one seat and some luggage.

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