While I was opening the doors of the Café I was thinking about a conversation I had with a reporter of ‘LA MOTO’, a really good spanish bike magazine. I met him in MOTORLAND, the new MOTOGP racetrack. He came to test our bike, the Demonstener D1200R. We were sharing box with Álvaro Bautista and Loris Capirossi (Suzuki MOTOGP Team) that came also for an article . It was really a nice day!
The magazine article will be posted the 15th of this month so I´ll share it as soon as possible.
The reporter pushed to the limit the Demonstener and then he discovered that the limit was the BMW boxer engine. The cylinder was scratching the asphalt and making him loose the front wheel grip. He was annoyed because he felt that the steering and suspension system could go further.
Our bike has a type of steering commonly known as Center Hub Steering. He thoughts, as I do that this kind of systems have been underestimated and that their time is still to come. This idea keeps hanging on from the early 60s and may be it will never success. But let me think different, as I usually do. If we prove that it´s better it will success. And the only place we could prove this it´s of course the racetrack! Do you want to help us?? Soon you´ll know more…
This post plans to be the first of a series about alternative bikes suspension and steering systems, so let me start from the beginning…
At the corner of the Café, just under the pictures of some beautiful caferacer bikes there is an strange two wheeled piece of metal. is that a bike?
Well… let me introduce the V2R, friendly known as the StreetDumper. V2R is the Spanish acronym of Two Wheel Vehicle and it´s our first attempt to create an absolutely new vehicle (a bit ambitious may be!) . It was a low cost project that I lead in Vinci Innovaciones Tecnológicas that surprisingly worked well.
We started with an enormous report filled of differential equations and an old man patent about a steering system.
The report was made by CARTIF
The old man was Juan Elizalde.
The project was a Center Hub Steering scooter with a 150cc Scarabeo engine.
The bike he built didn´t work.
The CHS is a system were the steering is not in the headstock but inside or at least closer to the wheel hub. It´s normally mounted on a swingarm that extends from the bottom of the frame. This allows new settings in a bike like the antidiving or the variation of the castor angle while the suspension gets compressed among other possibilities. We´ll have time to talk about CHS.
Looking at the Elizalde´s patent we understood that it was an interesting start point, there were lot of good ideas even if the adopted solution was not so good. The steering was a complete chaos because was made of universal joints with angles of almost 45º between the axles. When you turned the handlebar for about 15 degrees the wheel didn´t turn. But if you turned a degree more then suddenly the wheel turned the 16 degrees. This phenomenon it´s called bump-steering and it was common (in a smaller way) to all the Center-Hub-Steering until we designed the StreetDumper.
The other big problem to solve in the Elizalde´s bike was the heavy swing arm that caused a bad sprung mass ratio. However it had a new interesting concept that was connecting both front and rear suspensions. In fact, as you can see, the idea of the project was unconsciously to put automotive technology on a bike.
The way we solved the bump steering was based on a phrase we used to listen in math class: ‘An straight line is a curve of infinite radius’ And that was the solution.
When the front wheel travel in a fork upwards it goes on a straight line. So we choose a point sufficiently far to simulate this. We choose an 1 meter radius front swingarm. It was big but light. To filter the small displacement we hanged the handlebar from a swinging connecting rod. So it moved back and forward in a negligible way. So we had the first non bump-steering CHS bike!
Next we did was linking front and rear suspension making front and rear swingarm work together. The bike is really comfortable, kind of new featherbed chassis! even though the studies shows that over 70 Km/h it becomes unstable. Only my dear friend and test pilot Guillermo de Oya Jiménez (A.K.A. Cuco) rode over that speed and I couldn´t see the fear in his eyes. At that time our resources to measure things were just our five senses.
In the Demonstener we have removed the suspensions link. You can never ride a bike like that under 70 Km/h!
The system worked. But it had a problem. When the rear wheel was compressed by a bump, it made front suspension to extend. It was surprisingly comfortable but risky. HERE you can find an old PowerPoint explaining the systems of the bike. It has lots of mistakes but it was the beginning. Hope you enjoy it as a museum piece!
This was the theory, in the next post you´ll see a young version of the Bikers Build Off! But this will be in the next coffee…
Carlos Beltrán Carrión
Follow also this links if you want to know more about CHS:
Our bikes: Demonstener D1200R
One of the inventors: Difazio
Other builders: the amazing Harrier , Tryphonos, Vyrus and Bimota Tesi
And of course: The guru Tony Foale
