A Bicycle Porteur Rack.


This page details a simple home-made front Bicycle rack or Porteur rack.

It was made from tubular steel formed and welded together, with wooden planked deck.

 

 

 

 

 

 

 

 

The daily commuter bike was fitted with a back rack and a crude front wire rack.

With the addition of a child seat at the back the front rack was no longer large enough to carry the workbags and so a new larger front rack was required.

Original Front Rack

 

 

 

 

 

 

 

 

This rack design was made from a triangular frame on each side of the wheel and a wooden slatted deck on top. It was designed to take the work bag which measured 400mm wide by 300mm tall.

 

 

 

 

 

 

 

 

The height of each side triangle would need calculating to ensure that when angled away from the wheel, it would be just taller than the wheel.

The chosen height of the rack above the front axle was 360mm.

 

 

 

 

 

 

 

 

Some quick Trigonometry showed that the angle of lean of each side would mean that the actual height of the triangular frame would need to be :

X = Sqroot(1452 + 3602) = 388mm

This assumes a deck width of 400mm and takes into account the fork spacing of 110mm.

The other thing to consider with the design is that from a side view, the rack would not be centred about the front axle. It would stick forward and so the triangle would need to be asymmetric.

 

Angle A = Inv Tan (388/80) = 78 Degrees

Angle B = Inv Tan (388/220) = 60 Degrees

 

 

 

 

 

 

 

 

The triangular side frames were bent from 14mm steel tube from the hardware store. This was bent in two places to the required angles using a homemade tube bender.

An alternative might be to use plumbing copper which can be formed over the knee with a bending spring.

The tube was left over long at both ends and then the front tube squashed in the vice to for a flat section at the end.

 

 

 

 

 

 

 

 

 

To finish the triangular side frames, the "non flattened" leg was cut at an angle to meet the neighbouring part and welded into place.

Brazing could also be used but because this was a welding project a MIG welder was used.

Once the weld had cooled the flattened section was drilled 10mm to fit the front axle and shortened as appropriate.

Completed side frame

 

 

 

 

 

 

 

 

Legs in position on the bike

Two legs were made - the second one a close match to the first.

The mounting points had to be angled to give the required deck size at the top. This was done by bending by hand with the part held in the vice.

One leg was formed first and the second to match, ensuring that the parts were 'handed' to fit correctly.

Measurements and fine adjustments were made on the bike so that the rack would sit centrally.

 

 

 

 

 

 

 

 

A cross bar was added at the front to give the rack some rigidity and also to give somewhere for tie downs or bungy ropes to be attached to the rack.

This was a straight piece of 14mm steel tubing cut to length and filed to match the angles of the side frames.

Front cross bar in place

 

 

 

 

 

 

 

 

The deck was made from a plank of thin wood found in the garage. There was enough wood for three lengths, so these were cut and sanded to leave safe edges and then spaced evenly along the top.

Each plank was drilled and countersunk to take some self-tapping screws into the side frames.

 

 

 

 

 

 

 

 

U Bracket to attach rack to forks

The rack also needed to be attached to the top of the forks to provide secure mounting. This could be done is a variety of ways but because of the cantilevered brake arrangement on this bike and the fact there was some tube left over, a U shaped part was made to fit as shown.

It was secured via a single hole and used the mud guard fixing screw.

A longer part could have been welded to the front cross bar and this would have been a much stronger design; but the cross bar was slightly too low (poor design). So instead the deck planks we used to hole everything together.

 

 

 

 

 

 

 

 

The finished rack looked good and was plenty strong enough.

 

 

 

 

 

 

 

 

To finish the rack it was painted to prevent it rusting and the deck was treated to some teak oil.

The finished Porteur Rack

 

 

 

 

 

 

 

 

With the 5kg work bag loaded up the bike was found to handle a bit differently. It was still easy enough to ride but the inertia on the steering was noticeable.

The self centring characteristics were also different although once again - perfectly acceptable.

An alternative design might have been to attach the rack to the frame rather than the forks to reduce some of these effects.

Bike loaded and ready to go

 

 

 

 

 

 

 

 

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