Table of contents:

How does the Bimota Tesi steering system work?
How does the Bimota Tesi steering system work?
Anonim

A few days ago, on the occasion of the article about the Bimota Tesi 3D RaceCafe, in the comments some of you asked how the front suspension scheme works without conventional fork. And since it is too interesting to explain in a comment, we are going to give it a little body with this article.

Next, in addition to explaining the operation of the alternative front suspension system Hub Center Steering, we will analyze the pros and cons. Because it has both, if they were all good things, I would not be the only one to ride it. Although… to tell the truth, she's not the only one either.

And where does this come from?

Ron Haslam Elf Honda

The origin of this peculiar front suspension scheme has its origin in competition. Looking for alternative solutions that would improve performance in critical situations and facilitate tire changes, Elf engineers developed a Grand Prix prototype that used single-sided swingarm on both suspensions. During the 80s and 90s Elf, with the collaboration of Ron Haslam and Honda, developed several racing prototypes.

Since then we have had intermittently in the history of production bikes some exceptions to the general rule of conventional forks. Perhaps the most popular is Yamaha gts 1000, a model of which you can still see units on the street.

Bimota Tesi Bimota Tesi 1d

Without a doubt, the most identifiable model with this peculiar solution is the saga that began Bimota with the Tesi 1D (on these lines), the materialization of two brand engineers looking for a point of exclusivity and sophistication. That first version used a conventional front swingarm and the steering rods went on both sides. Since then the model has been adapted to improve.

Gts1000

Today we have reached the sophistication of the Tesi 3D and the particular Vyrus that have many similarities with the current Bimota.

How does it work?

Well, the funny thing is that it is easier than it seems at first, because the Hub Center Steering It consists of a "fixed" front hub that is anchored to the front of the front swingarm and within which the steering is included.

In this way, to explain it in a simplified way, the body of the hub is in charge of managing the suspension, while the internal part is the one dedicated to the direction Through a few re-sendings that communicate the "directional" hub with the handlebars. As you can see in the video that heads this section.

And then we see the animated exploded view in a 3D render of how the Hub Center Steering system works which also uses the Bimota Tesi 3D. In this case there is a peculiarity and that is that it is a single-sided swingarm, but the principle is the same.

Pros

Bimota Tesi 3d

Getting into flour, this peculiar system bases its operation on a basic principle: separating the steering from the suspension and the braking forces. Because? Well for improve the performance of each system separately. Sharing steering and suspension as in conventional schemes causes them to interfere with each other. You already know what happens when you hit a pothole with the motorcycle lying down, that takes you out of the curve or that prevents you from braking correctly, or what happens when we brake in the middle of the curve.

As is normal, taking risks with a system of these characteristics is because it has to bring some benefit compared to conventional forks. To begin with, we have the aforementioned separation of functions, this means that potholes affect suspension exclusively, not the address.

Another great advantage is that eliminates sag during braking phases, keeping the geometry and making a more neutral direction by rolling to the limit. The rigidity of the set is also improved and much later and more intense braking is allowed.

Speaking of weights and inertias, with this arrangement we can lower the center of gravity of the motorcycle leaving the suspension arms in a horizontal position and a short distance from the ground, but we can also place the brake calipers below.

Cons

One of the weak points of the system, as demonstrated in the first Bimota Tesi 1D, is turning radius. Keep in mind that with a swingarm arm on each side, you have to find a compromise between compactness and manageability. If we put a swingarm whose sides are very open to allow turning space for the steering, we will have a very wide front part and we will challenge stability, while if we make a new swingarm we will have a limited turning radius.

As a curious fact, the Bimota Tesi 1D had a 17 degree useful turning angle. You would need a road as wide as an airstrip to turn. The current Tesi 3D has significantly improved these figures and can now turn at a standstill or at low speed like a conventional sports car.

Another drawback of the system is that being such an intricate system, without a direct connection between the handlebar and the front wheelIt cannot be taken to just any mechanic, although of course whoever buys a motorcycle from these very exclusive motorcycles will still have a full-time mechanic hired in their own garage.

Explaining this issue, with the union between the controls and the steering made through re-sendings, cams, crank pins and pushers, any play in the connections can produce direction inaccuracies. All the materials must then be of optimum stiffness and the joints extremely precise. In addition, the moving parts of the system are highly exposed in the event of a fall or impact.

At least in the case of the Tesi 3D the steering arms have been simplified so that they only run on the left side, whereas in the previous models they went on both sides of the swingarm. Even so, the system continues to evolve, because as you can see, almost in each photo the front shock absorber is in a different position.

I hope I have clarified any questions!

Popular by topic