Grammariosbikes (Gramcarbon.com)

Γενικές πληροφορίες

Our company is A. Kitselis & T. Theodoridis G.P. and it is located in Athens-Greece, 4 Tilephanous Street, post code 10442, VAT EL 998546183 and it has three sections. A commercial department, Grammarios Bikes, which is distributor and sales point of many top end cycling bikes and parts, a research department which conducts research for composite materials and a manufacturing department in which the ideas of our research department come to life and its name is Gram Carbon.

Gram Carbon is a team of people specialized in the design and evolution of products made of composite materials. The members of the team happen to be cyclists as well and this is how we got evolved in the cycling equipment design business.

Being fanatic with high end technology we wanted our bikes to be made of the best possible quality and performance specifications humanly available. The solutions in the market did not cover us because mass production and aerospace grade quality do not match. Smaller companies or even family businesses making custom bikes were a much better solution but they did not cover all our requirements. The solution was one. Since what we wanted did not exist we would have to design and construct it ourselves! But how can you create something that does not exist? The answer is by research. We would have to make studies not only in design level but also in technology lever. In order to proceed with our goal, the Μechanical Εngineer and the designer of the team, Alexandros Kitselis, started a Phd in the National Technical University of Athens with a subject “Catastrophic vehicle failures with specialty in composites and application in bicycle frames and parts!” The road was difficult but the time in which we would ride our own bikes kept us from quitting.

The objectives were simple but conflicting

We wanted a frame which would be stiff and compliant
We wanted an aerodynamic but also light frame
We wanted a frame which would be absolute and yet easy to drive
May we add that we wanted the frame to have very long life time as well?
In order for the frame to be able to have all these properties together, it would have to be a true monocoque. It should come out of the mold in one piece. True monocoque and not “Monocoque something” which is a result of marketing. A true monocoque like the chasis in Formula 1 or other various aerospace type components. Very difficult and very expensive. This did not fear us and we followed this road.

The design started together with the problems. The only part which was not so difficult was the decision to use prepreg carbon fiber since this is the only way to have high reliability and long service life.

The driving behavior would follow since it is a true monocoque and has a geometry from analytic measurements from BikeFitting it would have a unique driving feeling. It would feel like an extension of the rider’s body, it would change direction just by… considering it and it would be stable in all conditions.

After this point every parameters was cancelling another. If we made it very aerodynamic from the front it would lose performance in crosswinds. When we made it as stiff as we wanted we would lose in comfort. If we made it superlight we would lose in stiffness. In one word: Chaos!

After hundreds of tests in tubing shape and different layups, research from thousands materials we saw that we could combine stiffness weight and aerodynamics but the comfort would be lost and the bike would be tiring after a few hours of riding. We looked up in scientific books and publications and we saw that we could alter the comfort if we could change the way the material is cured and processed. By changing the pressure and the temperature the frame would have another viscoelastic behavior, which means it would absorb vibrations from the ground.

If we changed the temperature and the curing cycle (curing less time or at lower temperature) we would have problems in some countries and the very hot weather. The problem was solved by using a special epoxy in the prepreg we chose because it can alter its behavior if the frame would be postcured after initial curing and would gain both properties.

The other part was pressure. If we cured with low pressure the final product would have air bubbles inside which could cause in failure. If we cured in high pressure the bubbles would be removed but the bike would be harsh. And here starts the difficult part. We should keep the pressure low but remove the bubbles!

The idea for a solution came from disk brake bleeding! When you bleed disk brakes you tap or shake the cable so as to guide the bubbles to the exit. Our there was our idea: What if we shοok the mold during curing while we have liquefied the epoxy thanks to the temperature control? This is how we started countless experimental and theoretical processes which created the Vibratech technology which is used exclusively by our company. By using resonance during curing, even with low pressure we do not have air bubbles inside the material!

Vibratech along with the tremendously detailed layup, the shape of the frame and all our “Secret recipies” create AStech, our truly Aerospace Technology used in Gram products. It is this unique combination that creates one of a kind results. In the case of the bicycle, when you ride a Gram, you “ride in another dimension”!

This technology along with other techniques is used in other applications apart from cycling. The applications are numerous and start from sporting goods, other transportation means, furniture, decoratives and more.