NYSI.org.uk - Bicycle Design

The results are listed below. Angles of 16° to 18° are fairly typical for modern bicycles. The large angle measured on the Courier indicates that, compared with contemporary bicycles, its saddle is significantly further aft of the crank.

27° - Courier

16° - Ammaco Nova

18° - Apollo County

18° - Mountaineer

16° - Trek 7.3FX

18° - Raleigh Monterey

Indeed, the relative crank/saddle position of the Courier makes its layout more akin to that of a vintage bicycle. The overlay illustration below shows how the 'Ordinary' Bicycle (1880) and 'Rover Safety Bicycle' (1886) have near-identical saddle positions - as measured from the crank location. These relative crank/saddle positions are very close to that of the Courier bicycle.

The Courier's performance suggests that, with regard to cycleway riding, some vintage design features are still advantageous.

While it's easy to assume that modern bicycle design is a well-informed, highly technical process, the reality is possibly closer to 'rule of thumb' and fashion.

In the magazine 'New Scientist', 28th May 2011, a feature entitled 'Easy Rider' explained that a formalization of the mathematics of bicycle design has occurred only fairly recently. In the article, Andy Ruina of Cornell University stated, modestly, that "the equations started being written in 1898 - we just finally wrote them down clearly and definitively".

In the same article, Rob van Regenmortel, then R & D manager of Batavus BV said he anticipated that the newly formalized mathematics would probably lead to future changes in wheelbase, seat tube angle and head tube angle.

The above research is very interesting but is something of a digression from the project in hand. Although bicycle handling and performance is influenced by a number of factors such as wheelbase, steering axis angle, fork offset, and trail it was decided to keep the project simple. The Courier has demonstrated a very comfortable, upright riding position. It was decided to take two existing bicycles and use different approaches to replicate the Courier's relative handlebar, saddle and crank positions.

The first subject for experimentation was the Ammaco Zone (pictured right), purchased from Hawk Cycles. The saddle / crank angle was already 23.5 degrees and so it could be modified relatively easily to achieve the desired geometry.

The major change for the Zone would be the handlebars. Due to the variety of proprietary handlebars available it was considered probable that a suitable unit could be purchased, however, the geometry must be known to be correct. The solution was to manufacture prototype handlebars in copper using a copper pipe bender.

The photo above shows the prototype handlebars fabricated from copper tube. It was not possible to bend the handles into their ideal position since the radius of the required bend near the handles was smaller than the pipe bender could produce, however, it was sufficient to indicate the required geometry.

It was found that cut-down BMX handlebars (that is small BMX handlebars with approximately 1" cut off each end) were a very close match to the geometry of the prototype copper handlebars. The BMX handlebars have the advantage of handles bent to the correct position. With suitable handlebars purchased the project became one of simple assembly. The new components included a short-reach stem, new road tyres and a repositioned saddle.

By rotating the saddle clamp such that the nuts were aft of the seat post and by sliding the saddle all the way back along its rails, the handlebar/crank/saddle could be made to match the courier's geometry exactly (shown in yellow below).

The result - the finished bicycle is wonderful to ride with its upright seating position.

The second project used a Raleigh Monterey. Modifying the frame by cutting and welding new tube was considered initially. The proposed modified frame design is shown in green in the figure below.

To test the design concept, the Zone's copper handlebars and a newly manufactured copper layback seat post were fitted to the Monterey. The test showed that the concept was a good one although the twisting moments that cycling would induce about the layback seatpost meant that the fitting would have to be very robust. At this point it no longer appeared necessary to modify the Monterey frame. A purpose-built steel layback seat post and modified steel BMX handlebars were used to create the required geometry.

The layback seatpost was cut from a scrap steel chair frame. Originally, it was envisaged that the correct bend in this 1" steel tube would be achieved by cutting a series of slots (see photo below), bending the tube to the desired angle and then welding it using a MIG welding machine (right).

However, the chair frame was cut in such a way that it made use of a bend already incorporated into the frame. As chance would have it the angle was perfect for the Monterey's layback seat post.

The only downside to using this pre-formed tube is that the metal is 'drawn' around the bend (i.e. the tube is thinner in the vicinity of the bend). This means that the seat post clamp is less effective and hence a self-tapping screw was required to fix the post in the tube and prevent the layback seat post from rotating. A second screw was used in the saddle clamp to prevent the saddle rotating about the seat post. The clamp itself had been cut to fit over the 25.4mm post (the clamp was originally 22.2mm). The finished bicycle used a new BMX stem, modified steel BMX handlebars and a new steel layback seat post

From the photo on the left it can be seen that the new Monterey layout matches the Courier's geometry (in yellow) reasonably well. With the frame itself unmodified, the handlebars are slightly too far forward, however, this is more than made up for by the ease with which the task was achieved and the fact that the original configuration can be regained with the minimum of work.

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