CFD analysis to support the bike designer

Have you ever wondered why some people seem born on their bike, while others struggle to find a comfortable and efficient position?

The answer, largely, lies in two fundamental concepts: sizing and fitting.

Defining the optimal dimensions of a frame it’s always a fascinating challenge. Even more so is calculating the optimal measurements of the entire bicycle, that is, that set of geometries that lead to a total harmony of ergonomics and handling, from the saddle point to the hoods (hand points) and to the pedal (shoe points).

Traditionally, designing custom bicycles requires the physical presence of the cyclist at the manufacturer’s headquarters or the retailer, which can be limiting and can make the tailor-made accessible to a very small subgroup of amateurs, not only for economic reasons but also for logistics and time.
The world of bike fitting has developed over the years a series of “recipes”, empirical methods refined and handed down over the years, evolved as new equipment has entered the bike fitter’s study, but often oriented towards the ultimate goal of adapting the athlete to an existing frame. Usually, replacements and/or micro-adjustments of the saddle, stem and handlebars are proposed to improve the posture, rarely achieving perfection only when the starting point already falls within the ideal values… it is certainly not possible to compensate starting from a frame with inadequate measurements.

Here’s why sizing of the frame is important, whether it’s identifying the most suitable standard size or, better yet, starting from a blank sheet of paper and setting up the project for a new tailor-made special.

But what is Gregario’s proposal on this subject? Well, it all depends on your starting point…

Case A) Do you already have clear ideas?

Chances are you already have a trusted bike fitter or a dealer equipped and capable of defining your ideal contact points… or let’s say you have an old bike that fits you like a glove and you want to replicate that exact positioning on a modern monocoque but does not match with standard sizes… or let’s finally suppose that you already have your ideal measurements in your head because your great-great-grandmother told them to you in a dream. Well in all these cases no sizing method is necessary, you’ll just have to communicate us these essential data clearly, i.e. those reported in the following table in reference to the diagrams below:

If necessary, also provide information on the driving style you prefer, so we will take this into account during the design phase to set the length of the stem. Our cockpit also provides the possibility of adjustment of the stem angle, but the basic reference is with horizontal stem (parallel to the ground) and any variations in the angle are intended for micro-adjustments (e.g. seasonal) as well as the saddle adjustments: up to ± 3 cm in height and the classic forward/backward depending on the chosen saddle model. These are the reference schemes for the measures to be provided if you already have all the tools to define them independently.

At Gregario, we have always cultivated esteem and respect for the artisanal frame-building tradition of our beautiful country, which is dedicated to a niche of timeless “classic” products, primarily made from steel, but also incorporating wrapped carbon and other techniques specific to small workshops.

So long live frame builders and anyone dedicated to preservation and pass on a noble and fascinating ars technica !

That said, we recently came across some social media posts from several respected bicycle craftspeople who, while rightly praising the (undoubted) qualities of their frames, contrast their “handmade” products with “moulded” monocoque carbon frames. On the face of it, this seems like a legitimate claim, but this narrative leads to significant misinformation about HOW such “moulded” frames are actually produced… namely, with manual work that is decidedly more demanding and onerous than any technique for joining eight tubes.

Yes, because we are not talking about printing cookies, but rather about carefully arranging over 200 fabric shapes (pre-impregnated carbon) inside a mould. These pieces range from 40 cm strips to tiny stamps, all positioned by hand according to a precise plan (the ply-book) with meticulous overlaps, folds to manage and fibre orientations to respect. And this is only half the work, because then, depending on the resin curing technology used, there are a further series of steps involved, always rigorously by hand.

In the case of autoclaves (the most common technique in Europe), it is necessary to carefully position the internal bags, close the two half-moulds without pinching anything, arrange a series of auxiliary materials, close the external bag, apply the putty to connect the internal bags with the external and so on until the whole thing is cured under high pressure and temperature. Furthermore, once the curing is finished, it’s back to manual work for mould opening, part extraction, and finishing. All this with a series of possible variations we won’t go into now.

In short, there is nothing more “handmade” than a carbon monocoque frame.