A Steel Bicycle Porteur Rack.


This second Porteur rack design was made to fit the road bike and was slightly smaller than the first build to fit inside the drop handlebars.

The deck dimensions were 350mm wide x 280mm and the finished weight of the rack was 0.62 kg

 

Steel Tube Porteur Rack

The material chosen for the build was cheap 8mm diameter steel tubing from the local hardware store. Four lengths of 1000mm were used.

This tubing had a wall thickness of 1mm giving the possibility of bending it without the tube kinking.

To form the bends a small tube bender was purchased. This tool was made by Rothenberger and was recommended to be more successful than cheaper copies of the tool which would only bend the softest copper.

Making the first bend

 

 

 

 

 

 

 

 

The deck of the rack was made first. Rather than try and get four corner bends lined up so that they were all in the same plane and in the correct place, the rear of the rack was designed to be a straight edge with two brazed joints (see below).

The image on the right shows the two font bends complete and the back edge piece being positioned to make the location of the second cut, ensuring everything was square.

The deck outer frame

 

 

 

 

 

 

 

 

Each side piece was notched in the end by hand to make a joint suitable for brazing.

The corner of a square file was used to mark the centre line and orientation of the notch.

Then a round file was used to create the correct profile. If needed a piece of tube wrapped in grit paper was used to finish.

 

 

 

 

 

 

 

 

The deck had two bracing pieces added. There were cut to suit the frame dimensions and notched, before brazing into place.

Deck Complete

 

 

 

 

 

 

 

 

A back rail was added next.

Length of the rail was unimportant but it was made to be inset from each end, so that brazing wouldn't affect previous joints.

The rail had two bends as shown and care was taken to ensure that it was parallel to the deck and upright before brazing in place.

Back rail in place

 

 

 

 

 

 

 

 

A 6mm piece of steel rod was used to fix the back on the rack to the fork crown on the bicycle.

The rod was brazed in place and had a washer added to give the rack the correct position on the bicycle leaving clearance for brake cables etc......

The rod was threaded with a M6x1mm metric thread and was bent in-situ on the bike to make it exactly level.

Back mounting

 

 

 

 

 

 

 

 

The two front stays were cut slightly over-long and an eye suitable for the front axle diameter was made from 3mm steel plate. This was cut and filed to shape and included a 10mm long tang to fit inside the 8mm tube.

The tube was squashed slightly in the vice to make an oval to take the tang. Then the parts were brazed together.

Front Stay Detail

 

 

 

 

 

 

 

 

With the rack mounted on the bike the front stays were cut to length and notched. Then with the front wheel removed they were brazed in-situ to create a perfect fit.

A quick load test at this point showed the rack to be quite sturdy and rigid with a low tendency to vibrate.

Brazing Front Stays to Rack

 

 

 

 

 

 

 

 

For the lightest rack, construction could end here, but to ensure the front says would not buckle under load it was decided to add some extra bracing using the remaining tubing.

The bracing pieces went from mid-point on the front stays up to the back of the rack, but they were also angled outwards towards to top to give triangulation in more than one plane.

A threaded spigot was also added to the right hand front stay to take the dynamo light.

Extra bracing stays (arrowed)

 

 

 

 

 

 

 

 

Images of the finished rack painted in black enamel paint and with the dynamo light fitted.

 

 

 

 

 

 

 

 

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