Neige-Quad

[tieflieger]

If you want to put this trike in a fairing, it will be quite a large Fairing. In a normal Velomobile the top of the nose is at about 60 cm from the floor. That's about the top of the 26 inch tyre, without accounting for suspension travel. Average seat hight is at about 10 cm from the ground, this is about 30cm. The frame on this also sits quite low, but it needs to be within a fairing.

The behavior of a velomobile shell in wind can be a bit like a weather vane. Like the Rooster Tail, a big tail will push the nose in to the wind, a long nose overhang will do the opposite. The side surface is pushed on by the wind, wich results in forces working in the other direction. adding to that you can get a very clean airflow over the fairing resulting in an underpresure on the side away from the wind, sucking it in that direction. The both result in forces working together to push/suck the VM in the same direction. And what does one do instinctivly? Steer in the other direction, the wind direction, wich results in lifting forces on the wheel at the wind side, and extra presure on the other side. The shell should have a shape that balances the forces out over the wheelbase.

Adding to that, steering geometry and attachmentpoints also play a part in how a shell reacts on sidewinds.

If this has an 80 cm trackwidth, and you have 20 cm extra seat hight, you add 80x20cm frontal surface. Also with these steering and inclining big wheels the front wheelwells will end up quite big.

Adding a shell might offer weather protection, but with this base it won't result in much extra speed. The resulting shape is simply to big.

 

[Velocoupe]

Hi tieflieger.
Your above post is important to this dialogue. Tilting trikes generally require larger wheel wells, and once enclosed, the shell is bigger than low, narrow, speed optimized velomobiles. In cross winds, the added surface area can introduce unwanted effects. It's not without it's challenges.
The difference for me, comes down to design priorities.
If the goal is practical, everyday transport - especially in mixed urban infrastructure - other factors start to matter more than minimum frontal area etc.
With e-assist now common, aerodynamic efficiency can be less critical for many riders. Average speed, comfort, stability on side slopes, and composure over uneven paths can matter just as much. Tilting designs, by keeping the rider aligned with gravity when stopped or traversing camber, can reduce the lateral "tippy" feel that rigid vehicles can produce in bicycle infrastructure. And as Stefan M mentioned Tilting is pure fun.
From my experience, adding a shell doesn't deliver any real gains in speed, and I agree that the shell shape should ideally balance the forces out over the wheel base. But it can provide weather protection, practicality, a broader balance of stability, and year-round usability, which hopefully, for many short to medium distance commuters, is a meaningful measure of performance. For distance, efficiency, and speed, the low, narrow, velomobile makes perfect sense.
I think there's room for both approaches.
Cheers.

 

[tieflieger]

Yes there is room for many approaches and often each has its own benefits and drawbacks. But by wandering down a certain path you may be heading in the wrong direction to reach certain goals. By reaching for a certain goal, you get further away from its opposite.

E assist at the moment is often limited to minus 25 km/h. Wich is slow for a fast velomobile. They would only benefit from e-assist on the uphill sections. Yet most velomobile riders use their vehicle also as an everyday mode of transport. The extra speed extends the radius in wich one can move everyday with your vehicle. Without range anxiety. Because it's a very energy efficient vehicle. And on many factors the design decisions are made with speed efficency in mind.

In many designs the priorities are in other directions, wich lead to vehicles that are not so energy efficient, move at a slower speed and thus benefit from e Assist. If the design has a large frontal surface, it will be less energy efficient and the rider won't be able to deliver the energy needed. That can come from a battery, but that needs recharging.

The design decisions made at the start lead the project in a certain direction. That direction might suit users with a certain profile, demands. For some users comfort means arriving at their destination without being sweaty. For others comfort means being able to travel 200km a day on their own power. Result may also change depending on your range of travel. With trips under say 10 km, a fast vehicle like a velomobile might be less than ideal, i do not take it for the 2 km to the local shop. I take the upright with bags and an easy lock. But i would not take my upright to visit the Outdoorshop 25 km away, i'd rather take the VM, as it gets me there in half the time. Everyday usability is a very wide goal, depening on what you want to use it for.

I do not see a right or wrong path to travel down. But i can see that a certain path might not be enjoyable for user profile X, while it might be ideal for user profile Y. It's good to think further, not everything one envisions at the start of a project turns out as one hoped. You need dreams, ideals, as a motivation with such a project. But wishfull thinking alone won't get you there. Sometimes feedback can be usefull to reflect, and perhaps readjust. Sometimes it also steadies, i am on the right path to achieve what i want. That other path might also lead to a nice destination, but that's not where i want to go.

 

[Velocoupe]

I agree - different riders prioritize different things and that conceivably shapes which features are considered worthwhile. Likewise, although I followed a zig zag design path, my priorities also shaped my project's outcome that includes some unconventional constructs and arrangements which may not be sufficiently understood or trusted by every-day riders.
When a construct differs from what many of us are familiar with, it's natural to question whether it behaves as effectively as conventional approaches. So, I'm going to ask again. Does anyone else use FTC Steering governed by a human powered or alternatively powered DTC setup?
Cheers

 

[Velocoupe]

Greetings.
Having received no responses to my request for any hands-on experience with FTC Steering governed by a DTC setup, I googled FTC. It seems there were a lot more FTC related posts when I was starting my project. Yet even then, there's a noticeable lack of first hand experience. With that in mind, it might be useful to share my experiences.
After more than a dozen years of design, build, test, re-design, rebuild, etc., I can confidently claim that, compared to bicycle wheels, all of my hub-centered constructs offered good to excellent directional control at low to higher speeds, while the zero degree rake steering axis of the non-rotating hub provided the best sensitivity to lean inputs throughout the tilting range. My takeaway is that some constructs clearly work better than others. For the sake of fairness and clarity, I'd like to focus on a point raised in Dr. Cornelius's review - the suggestion that FTC Steering is inherently unstable at slow speeds, and the comparison to riding a bicycle with no hands .

That framing doesn't really match my experience on the Tilt4orce, nor what's visible in the Velocoupe videos which show it tracking straight at walking speed, crossing side slopes, negotiating uneven surfaces, and cornering cleanly on both dry pavement and snow. I think the disconnect comes from viewing FTC Steering in isolation, rather than as part of the Tilt4orce's overall control architecture.
The Tilt4orce is a Direct Tilt Control vehicle. Lean input is coupled to a continuously engaged fail-safe tilt apparatus based on a Vertical Force Design which derives it's leverage from the resistance at the contact patches of both rear wheels. This 3 part mechanism facilitates the play of force/counter-force between each reciprocating hand lever as well as the force/counter-force between my weight shifts and both hand levers. That's a very different setup from a no-hands single track bicycle where balance and steering is dependent on speed and the air-shifting of the rider's arms and upper body .

On top of this, FTC is just one of two steering inputs. The other is manual steer, with the shoulder actuators (as shown in the "Tilt4orce Gets Radical Upgrade" video). And, because I don't have to reach for them, I can apply slit second steering input layered on top of the mechanical lean control when I encounter unavoidable potholes, slippery surfaces, etc. At this point I have dual tilt control (Direct TC + Steer TC) active at the same time. Thus, as long as the rear tires retain surface contact, I retain tilt control - even when traction is lost on the steered wheel due to loose gravel or ice.

So, instead of asking whether FTC is inherently stable or unstable, it might be more useful to ask how the total design handles tilt and steering inputs as a system. And, what mechanisms can provide fail-safe control as well as contribute to a velocar embodying a height-to-width ratio which makes it feel safe in traffic (in all seasons) when returning home with the essentials.






Cheers.

 

[tieflieger]

If a vehicle is just a free tilter, there is just the riders body, cornering forces, influencing the ammount of tilt. There is no mechanism, no lever or button to work with. If things go wrong, somehow, it might be very difficult to correct, as there is no lever to work with. In your design there is a lever to push, with your shoulder. If you fall to far in the curve, pushing with the other shoulder might help you up. If that is physicaly possible, the lever ratio correct. But there is something, even two levers that can be used to correct tilting angle errors, if i understand it right.
From what i have seen from your machine i assume both levers can even be operated instinctivly.

It's important to consider what would be likely scenario's for things to go wrong, and the sollution or way out of those situations. Simply pushing yourself back up, or a bit further inclined if needed might be a very simple cure in some situations.

It's very wise to be familiar with the factors influencing the stability of your vehicle. How do they work, what is the relation between them, wich can you alter, and wich not. What happens when you go over an edge, and how to prevent things from going realy wrong.