Should Tesla 're-design the wheel' for CyberTruck?

[go99s]

To cut-to-the-chase, my opinion is that Tesla should absolutely consider a 'First Principles' evaluation of the hub, wheel and tyre for CyberTruck.

We have not really changed car wheels, other than the transition to alloy for the wheel structure verses steel, for about 100 years.

For almost all vehicles we still use a pneumatic inflated rubber tyre mounted on a wheel that then mounts onto a hub using threaded fasteners. Yet, Formula 1 and some other race cars have advanced hub/ wheel mounting systems, several of the worlds premiere tyre companies have air-less prototype tyre/ wheel systems (often protected by patents but I'm sure they would 'partner' with Tesla) and finally, we could have the opportunity to have the tyre/ wheel combo behave dynamically in response to the huge variety of load cases that they are subjected to.

For example the current prototype air-less wheels use internal structures to provide bump absorbtion whilst retaining lateral stiffness but I feel sure that Tesla engineers could develop that to include speed related fuctionality such as creating a smaller contact patch at higher (60 - 90mph) speeds to reduce friction but that would flatten back out instantaneously on braking. The moment you lift off the accelerator, the load map within the wheel/ tyre combo changes, even more so if you then apply a braking force. I recently watched a video suggesting using wider tyres on a Tesla MY to improve NVH - which had me attempting to think like Tesla!! (Youtube: The Automotive Fanatic, watch?v=szSAnY59A_Q)

Another scenario is for the central tread pattern, contact patch and rubber formulation to be optimised for smooth pavement which would give reduced rolling resistance for range improvements and for the outer quarters to be optimised for off-road. In normal road use, especially at speed, the outer sections of the tyre might barely touch the road and thus reduce friction and road noise. These outer quarters, made with a softer compound, more suitable for softer terrain, loose gravel and dirt are able to engage with the ground on softer surfaces... You could even have an active element (equivalent to the partial deflation of regular off-road pneumatic tyres) that can switch between smooth pavement and off-road optimisations.

However, I am not suggesting that any of the above content is anything other than a template for the sort of discussion that I would be interested in hearing about as I am certainly no expert on hub, wheel or tyre design. So please try to avoid your reply simply being a hit-job on me!

I would be interested to hear what others on the forum think about this. With CyberTruck, we are soon to have the most revolutionary vehicle in the last 100 years, I would love to see it with equally revolutionary hubs, wheels and tyres.

Kind regards, Go99s.

 

[Crissa]

That's cool, but...

-Crissa

 

[Dids]

But, that's cool...

 

[Dids]

My understanding of how a tire works is that the hub weight is suspended from the portions of the tire currently not in contact. This means that a tire is an oval and it isn't only friction that causes rolling resistance but the oval shape, therefore a wheel like a steel wheel which maintains it's round has lowest rolling resistance.

 

[go99s]

My understanding of how a tire works is that the hub weight is suspended from the portions of the tire currently not in contact. This means that a tire is an oval and it isn't only friction that causes rolling resistance but the oval shape, therefore a wheel like a steel wheel which maintains it's round has lowest rolling resistance.

I'm not sure that I follow your argument... Are you saying that a steel wheel is more able to retain its shape and is therefore better for rolling resistance?

 

[go99s]

By the way, I chose my picture of the wheel/tyre because it looked pretty, not because it was technically suitable for a CT!

 

[firsttruck]

I'm not sure that I follow your argument... Are you saying that a steel wheel is more able to retain its shape and is therefore better for rolling resistance?

The issue is more the inflated tire against paved ( asphalt / concrete) road.

steel wheels on steel rails has some of the lowest rolling resistance possible that is why trains can be so efficient by weight on moving loads compared to trucks on paved roads.

----------------------

Rolling resistance, sometimes called rolling friction or rolling drag, is the force resisting the motion when a body (such as a ball, tire, or wheel) rolls on a surface.
https://en.wikipedia.org/wiki/Rolling_resistance

.....
Any coasting wheeled vehicle will gradually slow down due to rolling resistance including that of the bearings, but a train car with steel wheels running on steel rails will roll farther than a bus of the same mass with rubber tires running on tarmac/asphalt. Factors that contribute to rolling resistance are the (amount of) deformation of the wheels, the deformation of the roadbed surface, and movement below the surface. Additional contributing factors include wheel diameter,[3] load on wheel, surface adhesion, sliding, and relative micro-sliding between the surfaces of contact. The losses due to hysteresis also depend strongly on the material properties of the wheel or tire and the surface. For example, a rubber tire will have higher rolling resistance on a paved road than a steel railroad wheel on a steel rail. Also, sand on the ground will give more rolling resistance than concrete. Sole rolling resistance factor is not dependent on speed.

.....

 

[CyberGus]

I'm pretty sure "tyre" is pronounced "tire"

 

[JBee]

I'm not sure that I follow your argument... Are you saying that a steel wheel is more able to retain its shape and is therefore better for rolling resistance?

To follow on from firsttruck's comments:

Tyre deformation, that is how much the tyre changes shape around the contact patch to the ground, is the primary cause of rolling resistance. Hence a steel train wheel on a steel rail has less such deformation and therefore less rolling resistance.

Airless tyres are predominantly a gimmick for off road use only where punctures are a problem. Anything caught in the side wall openings of those airless tyre will cause such a imbalance in the wheel at highway speeds that the vibrations would make it un-driveable.

A much better option is CTIS (Central Tyre Inflation System) where you can change and refill air in pneumatic tyres. Tesla apparently poached Mercedes Unimogs CTIS engineer and made some patents recently, so I'm super hopeful we'll see it, at least as an option on the CT because it is a game changer.

CTIS solves a bunch of problems with tyres.

Punctures, adapting tyre pressures to terrain and surface conditions, flotation for sand and snow, optimal pressure for highway cruise rolling resistance, adaptability to vehicle loads per wheel etc.

But there is limited scope for using tyre air pressure to deform tyres to the degree required to change the part of the contact patch of the tyre with the road that exposes different tread patterns. The reason is that most modern tyres are designed to have fairly rigid sidewalls and a flat tread across the bottom. You can embed some extra tread on the sidewall so when you deflate it for offroad, but otherwise its fairly limited on road.

I remember a while back someone suggesting the same sort of thing to improve wheels and tyres to EM, and his response was that they are already highly optimised and in particular cost effective components, that can only be incrementally improved.

In saying that I had some ideas around how to "reinvent the wheel" some decades ago, but never got it is past an simple proof of concept. It was a combination of flapping "flying carpet", hovercraft and alternating track deformation that combined the best properties of each, that used the incoming air underneath the vehicle as a air cushion, and also as a skirt to provide traction as required. Anyways, something for another day.

 

[rr6013]

As ex-roadbiker(pedal) 25yrs, thin skinny high bar pressure reigned. Until science educated a bike aficionado who tested rolling resistance.
Science-speak I can’t but simple-man translation is “contact patch” matters. And smallest contact patch lost. The ability of bigger, wider, softer lower psi tires to rollover, roll-on and do so with the least amount of resistance out-tested traditional narrow hi-pressure slick tires.

Cybertruck dynamic suspension even though featured as lift-kit, similarly provides Tesla the opportunity to tackle efficiency destroying dynamics in suspension geometry, energy counter-absorbtion and voodoo AI PUREvision electro-magnetic innovation goodies that render whatever owners buy to put on the CT, pointless.

 

[Cybertruckee]

I'm pretty sure "tyre" is pronounced "tire"

I prefer tyre. I don't feel my energy zapped after reading it.

Interesting too but I think a cost-benefit study will point to a no-go.

 

[JBee]

Cybertruck dynamic suspension even though featured as lift-kit, similarly provides Tesla the opportunity to tackle efficiency destroying dynamics in suspension geometry, energy counter-absorbtion and voodoo AI PUREvision electro-magnetic innovation goodies that render whatever owners buy to put on the CT, pointless.

Do we know if we are getting electro-mechanical suspension for the CT? I only heard of air suspension which by itself lacks the real time response rate for active damping and control. Citroen's hydraulic over air used to work a treat, except for carsick inducing oscillations for some people, but Bose style electro magnetic suspension would be supreme.

As I pointed out previously, the CT rear suspension setup must be a pushrod arrangement to keep it under and out of the way of the bed. What I'd like to see at least is air suspension for ride height and load adjustment and a kinetic rollbar setup like on my Landcruiser, that produces zero body roll and no pitch either. Then add some electronically variable viscosity shock absorbers and we could start getting FSD to sample and predict road surface conditions and modulate suspension settings to suit.

 

[Crissa]

Modern material are more 'squishy' which reduced the resistance to changing shape, allowing a larger contact patch.

It's a balance of forces that are needed. We need other things than just low rolling resistance.

-Crissa

 

[CyberGus]

I prefer tyre. I don't feel my energy zapped after reading it.

Interesting too but I think a cost-benefit study will point to a no-go.

I'm tyred of this debate

 

[Zabhawkin]

I have only seen airless tires on bicycles and tractors, so nothing high speed.