Cybertruck Frunk

Ogre

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1627869387698.png

A side view from a second source from a different F150 looks like about 6 inches taller and 4-6 inches closer to the ground. That’s pretty consistent with what you see in my image.
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Crissa

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The bumper is not a grill. I don't doubt that the bumper on the F150 doesn't come as high. But we're talking a couple inches, not a massive thing to life over.

-Crissa
 

Ogre

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The bumper is not a grill. I don't doubt that the bumper on the F150 doesn't come as high. But we're talking a couple inches, not a massive thing to life over.

-Crissa
I’m just looking at total frontal surface area. Bumpers cause drag too.
 

Ogre

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Looked so lopsided I thought I might have goofed the scaling up, so I scaled it up a bit more so the CT is actually taller than the F150. Result is pretty much the same. The F150 (not surprisingly) has a huge frontal area. The “Grill” on the Tesla ends at the light bar, roughly in line with the Ford logo.

1627871782776.png
 

JBee

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Looked so lopsided I thought I might have goofed the scaling up, so I scaled it up a bit more so the CT is actually taller than the F150. Result is pretty much the same. The F150 (not surprisingly) has a huge frontal area. The “Grill” on the Tesla ends at the light bar, roughly in line with the Ford logo.

1627871782776.png
Great job. Those front views show the problem exactly.

So now completely ignore what is front grill, bumper or windscreen and just look at the total area of each vehicle you see including the wheels. That total "section area" is used in the aero calculation, not just the front grill/bumper.

That is why it doesn't matter if the front hood sticks out forwards or not, the air still has to move out of the way of the whole area you are pushing through it. Think of it as "displacment", more like buoyancy in water.

Note I didn't say the total sectional area of the CT is the same as the Ford, because I know the roof is lower so its also smaller, despite sharing the same width. (Btw the CT and F150 have the same body width not wheelbase). I said the size and protrusion of the Ford bonnet assembly made no difference to the total sectional area the air has to go around in the Ford. Likewise on the CT the shape or configuration of the nose does not reduce the total sectional area or air that needs to be displaced.

This is also why they want to get rid of the mirrors, because they add drag but no internal space, plus they can't have a taper to the rear which causes yet more turbulence and drag.

Btw just for reference airflow does not strictly adhere to the vehicle shape. Typically it creates local turbulence and the main airflow goes around that instead. It can "self smooth" as such. (like the one in the ford bed that smoothes some of that out) If done right you can get a straight surfaced Stealth fighter to fly too.

In this case the CT creates an aero turbulence effect in front of the nose of the vehicle caused by its flat grill, that seperates the air before getting to the vehicle itself. This has the effect of making the front less square and more rounded which can reduce the Cd. Same applies for many other grills, Ford also have aero designers, its just proportionally less important for range in a ICE because of the much higher energy density of fuel. That is also why a CT won't be able to compete for range with and ICE truck when towing.

This is a interesting video to watch regarding aerodynamics. Note he also only uses the total sectional area, in this case the area of the trailer because that is the biggest section, and ignores the car in front that is smaller (just like the Ford hood can be ignored).

 
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JBee

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The Cybertruck does not have an exposed grill.

It has a bumper.

Also, remember the F150 doesn't change height, but the Cybertruck does.

-Crissa
Nobody said it has an "exposed" grill.
(I'm assuming you mean an semi open "grill" to let air through and protect a radiator behind it?)

But it has a front area where the "grill" would normally be.

But being a "exposed grill" or a flat wall doesn't necessarily make either better for aerodynamics though. Many cars have louvres that can close to reduce aero drag. Others have carefully sculptured ducts behind them to direct airflow and minimize drag. Yet others use that airflow to create underpressure envelopes to create downforce, or cool brakes or both. It mostly depends on each vehicles cooling requirements. (BTW the lightning has a mostly closed "grill" as well - it's just plastic and you can clearly see the CT and Lightning cooling openings in the photos above.)

In the case of the CT it still has a radiator like an ICE, but it is used in conjunction with the HVAC heat pump for cabin, battery and motor heat/cooling. This radiator is mostly cooled with forced air from a electric fan, and only partially from airflow created from driving forwards, from the gaps in the bumper under the "grill" area. This means that whilst driving at normal speeds a little airflow will suffice to keep everything cool, with most of the thermal load coming from the cabin demand. But as soon as more motor/battery performance is required the fan can speed up and move enough heat to meet demand for acceleration/deceleration or charging whilst stationary, where driving airflow is not available.

This is no different to ICE cars, except that the amount of engine cooling on a ICE is the dominant heat producer. It's typical for northern cold climates to put a cover over the entire grill so the motor can stay warm in winter.

It has been proposed the 4680 pack might also cool directly to the floor under the CT, meaning it might have a smaller HVAC setup and radiator. But the problem there then is being able to actively manage the battery temperature to keep it within the best operation range regardless of outside temperature. It also needs to be heated in winter, so unless they can de-couple it from the batteries and actively control it, it won't help much. Also the surface area of the bottom of the vehicle is insignificant in comparison to the surface area and capability of the fan forced radiator. (the modern radiator is the only reason modern ICE engines even came about - they always had a cooling problem)

This is an interesting video I came across recently, where they have to keep the cars running whilst parked otherwise they would freeze up inside 30minutes. I don't think EV's could survive there, which is btw similar to the average surface temperature of Mars.


As for height adjustment, that is a more dynamic matter, because of the in ground effect, and how that changes with vehicle speed. Technically the CT shape will also create lift along with a flat floor bottom. That might reduce rolling resistance at the expensive of a little induced drag.
What I was hoping was that the suspension forward angle can also be adjusted so that we can chose between lift or downforce, but it might not have much effect because even at the lowest setting it has a huge clearance underneath (8-10") because otherwise the wheels touch the arches. Which means that needs to be dealt with, with diffusers or something, to keep it in check and not let it increase drag too much.

I'm expecting the ride height to change with speed automatically, and they might tweak it by pitching forward and backwards as well. (as other vehicles have done before the CT)
 

John K

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The condition in the statement is low velocity. If both vehicles travel low velocity, the low being undefined, drag will be negligible between the two vehicles.

the other sid of the discussion is
I wrote this in another thread explaining why if you're interested:

https://www.cybertruckownersclub.com/forum/threads/any-updates.3293/post-55628

Basically the length of the vehicle or hood is not relevant to aerodynamics at car velocities. Because there is not much skin resistance at those low speeds, unlike a Blackbird at much higher speeds where it causes the wings to heat up. The dominant factors are total width x height = cross sectional frontal area of the vehicle and Cd which is the drag coefficient that incorporates how the airflow flows accross the shape.

The total frontal area cross section of each vehicle is not increased by the bonnet size, because at the roof apex its always bigger on both vehicles. So you could make the CT or Ford into a van if you wanted too, with the windscreen up front (in fact the CT does this more than the Ford) or put it all the way back, and you would not change the front sectional area of either. Things at car speeds don't need to be pointy to be aerodynamic. Take Tesla semi as an example.
http://www.aerospaceweb.org/question/aerodynamics/q0231.shtml

I am perplexed since this part of the post, “ and Cd which is the drag coefficient that incorporates how the airflow flows accross the shape” agrees with other postings the drag coefficient will be lesser in the CT compared to F150. The CT’s shape yields a smaller truck.

The vehicles do travel at sufficient speed where their drag coefficient affects their performance. Agree on skin resistance + velocity not making an impact.

Are we all saying the same thing?
 

JBee

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The condition in the statement is low velocity. If both vehicles travel low velocity, the low being undefined, drag will be negligible between the two vehicles.

the other sid of the discussion is


http://www.aerospaceweb.org/question/aerodynamics/q0231.shtml

I am perplexed since this part of the post, “ and Cd which is the drag coefficient that incorporates how the airflow flows accross the shape” agrees with other postings the drag coefficient will be lesser in the CT compared to F150. The CT’s shape yields a smaller truck.

The vehicles do travel at sufficient speed where their drag coefficient affects their performance. Agree on skin resistance + velocity not making an impact.

Are we all saying the same thing?
[IMG alt="Computer drawing of an airliner. Drag equals the drag coefficient
times the density times the area times half the velocity squared."]https://www.grc.nasa.gov/WWW/k-12/airplane/Images/drageq.gif[/IMG]


Nearly.

The "aerodynamics of the shape" is mostly determined by the Cd but the "total cross section area" of the car is the total area of air that needs to be displaced by the car, no matter where on the vehicle (bonnet/windscreen/tailgate/wing/parachute etc) it is displaced. Both of these are also subject to vehicle/air velocity and air density. (which is why airliners go higher to fly faster and further with the same fuel)

Both the CT and the Lightning have their own Cd values, of which I'd strongly expect the CT will be better than the Lightning. Ford doesn't list the Cd however so its not a known quantity as such. The CT also has a smaller overall section area., because it has a little lower roof line. Both of which means the CT will have less drag. But this does not mean the CT truck "shape" is "smaller" as such. Just that it has less drag.

I only mentioned skin resistance because that is often what people imagine to be the larger "drag" component, which as you agree is not relevant at car velocities, even at highway speeds. Cd most definitely is relevant at highway speeds.
 

BillyGee

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Fun fact: John DeLorean insisted that his car be able to transport two sets of golf bags, or they wouldn't be able to sell them to executives. I can confirm that the shelf behind the seats will accommodate two golf bags.

Fortunately, there is no place to put a hard-sided suitcase, so I can avoid having to pick up anyone at the airport. Once I'm a CyberTruck owner, however, I'm going to need an excuse to avoid helping people move ("It's illegal to transport furniture in electric vehicles, I swear")
I've found that friends ask less about moving than they do about towing, but I also live in a more rural area so everyone already has a truck.

What I'll need to figure out is a way to explain why I have "that funky city folk truck" despite the fact that it beats a regular gas truck on every metric.
 

Frank W

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ICE truck wins on faster refueling and perhaps towing long distance but I certainly wouldn’t put either of those as a priority when buying a vehicle. Performance, safety, durability, functionalities, over the air updates win over ICE easily.
 

chalupacabre

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The only image I've seen is the one displayed during the event in 2019.
imgj_1574790480.jpg

Kinda low res as it's a picture of a smaller picture on distant screen. I'm not sure what the light colored thing is, SS reflecting? Idk!

As a point of interest, there's also wheel well pillars for storage! These always get forgotten about.
have-you-noticed-that-the-tesla-cybertruck-has-sail-pillar-storages.jpg

Nice! Multimission storage
 

Jhodgesatmb

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Looked so lopsided I thought I might have goofed the scaling up, so I scaled it up a bit more so the CT is actually taller than the F150. Result is pretty much the same. The F150 (not surprisingly) has a huge frontal area. The “Grill” on the Tesla ends at the light bar, roughly in line with the Ford logo.

1627871782776.png
Interesting. Is that with the Tesla at nominal ground clearance (12"), low ("8"), or high (16")? The drawing overlay would be best with the 2 trucks at the same groud clearance.
 

Ogre

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Interesting. Is that with the Tesla at nominal ground clearance (12"), low ("8"), or high (16")? The drawing overlay would be best with the 2 trucks at the same groud clearance.
I’m honestly not sure. In the photos, the Ford’s bumper is a little lower than the Tesla’s and the Tesla’s hood is quite a bit lower. But exactly what that height is is hard for me to guess.

… the air suspension is one of those features that just touches so much of the functionality of this truck. I’m just blown away that when they talk about comparing this to the competitors this isn’t top of any article.
 

jerhenderson

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The bumper is not a grill. I don't doubt that the bumper on the F150 doesn't come as high. But we're talking a couple inches, not a massive thing to life over.

-Crissa
unless you like to complain, then its something to complain about. and by complain, I mean how the CT frunk is lower than the Ford frunk.
 
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