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The Physics and Economics of Moving 44 Tonnes at 56mph

mikeayles.com

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Re: The Physics and Economics of Moving 44 Tonnes at 56mph

#61

Post by [deleted] »

mschuster91 wrote: post #13
mikeayles wrote: post #2

I was reading the NASA truck aerodynamics thread earlier and realised that commercial freight is one of those fields that touches everyone's daily life (everything you own arrived on a truck) but sits in a complete knowledge blindspot for most people. I work in fleet fuel efficiency and wrote up the foundational mental model, covering why trucks weigh what they weigh, why they're all doing exactly 56mph, why diesel i…

A very well written article! I'd add a few things though. > Every kilogram you add to the vehicle is a kilogram you can’t carry as freight. That is only relevant when hauling bulk loads, think ore, soil and the likes, or you're carrying a trailer full of IBC liquid containers. I worked in stage lighting stuff, our trailers were at least 3/4 foam by volume, they didn't even come close to maxing out their weight. > A b…

[deleted]

Re: The Physics and Economics of Moving 44 Tonnes at 56mph

#62

Post by jcgrillo »

ReptileMan wrote: post #60
jcgrillo wrote: post #57

Earlier quoted context omitted.

A Cat 3406 weighs around 4000lbs and an Eaton 18spd weighs around 1000lbs. So rounding up a bit for accessories and other equipment say 6000lbs total (~2750kg).

throw 350 kg of diesel. So the extra weight is 3 tonnes, not 6. Not peanuts, but I think it is manageable and the math could work, especially if they charge on off peak or surplus electricity.

A diesel electric hybrid, at least naively, makes quite a lot of sense to me. Your generator can be sized such that at full output at its torque peak it's making enough power to push the truck at highway speed up a slight incline (just slightly overpowered for maintaining highway cruise). Batteries take up the slack for starting, pulling hills, etc. Remains to be seen whether it actually works.

Re: The Physics and Economics of Moving 44 Tonnes at 56mph

#64

Post by mcdonje »

Long haul trucking should be illegal or effectively eliminated by a carbon tax. Use trains for long hauls.

He even said the problem with trains is last mile. Last mile short haul trucks can be and are electric.

It's weird he laid the groundwork for this argument, but he isn't making this argument.

Fix the infrastructure issues that make transferring from rail to truck difficult. Yes, that's challenging and expensive. Guess what else is? The status quo, and the effects of climate change.

Re: The Physics and Economics of Moving 44 Tonnes at 56mph

#65

Post by mikeayles »

jillesvangurp wrote: post #52

> A diesel fuel tank for 400 litres of diesel weighs roughly 350 kg (the tank itself is relatively light; diesel is 0.84 kg/L). A battery pack storing equivalent energy would weigh on the order of 16 tonnes at current lithium-ion energy densities. That’s not just additional weight. It’s 16 tonnes of payload that disappears. And yet, electrical semis exist that come without 16 ton batteries. The fallacy here is that m…

Fantastic comment, thanks! A review of the state of BEV's was actually going to be one of my next articles (hopefully after the additives).

Are you happy for me to drop you an email to review a draft when I'm ready?

Re: The Physics and Economics of Moving 44 Tonnes at 56mph

#66

Post by JoachimS »

cbdevidal wrote: post #59
matsemann wrote: post #46

Earlier quoted context omitted.

> Most assume the truck driver is being inconsiderate. From the article. Then goes on to show exactly how they're inconsiderate with maths. How they're not seeing it is baffling.

Seems to me that the slower truck is really the inconsiderate one here. If you’re already slower, tap the brakes a little and let the other guy slide in.

Or just take the foot of the pedal for a while.

Re: The Physics and Economics of Moving 44 Tonnes at 56mph

#68

Post by GeertB »

The article makes it sound like the Tesla Semi is physically infeasible. Yet, it is in active use on a sufficient number of long-haul routes that ignoring this proof of existence undercuts some of the central points the post tries to make.

The combination of higher efficiency, regenerative breaking, and some regulatory wiggle-room such as slightly higher allowable gross-weight (2000 lbs in the US, and 2000 kgs in the EU), together with reduced maintenance cost and time significantly affect the economics of trucking.

As regulatory frameworks price in more externalities of internal combustion engines, such as the climate and health effects of their emissions, burning diesel will no longer make economical sense. All road transport will end up being battery-electric. The declining cost of owning and operating electric vehicles compared to internal combustion ones will reach this point even without regulatory changes, just at a slower pace.

Re: The Physics and Economics of Moving 44 Tonnes at 56mph

#69

Post by dgacmu »

jjk166 wrote: post #58
secult wrote: post #28

For people that want to make the calculation: A truck does not need a 15 ton battery. In Europe, we have mandatory breaks for truck drivers. So you need a battery pack for max 400km of range, let's say 500km. When you have a break, you charge. For this, you need like 1500kWh battery pack, which weigths like ... wait, 15 tons. But this is not entirely correct, the real values reported are between 120-150Kwh/100km, tha…

Those mandatory breaks are 45 minutes long. You're not charging 750 kWh in 45 minutes. With a fast charger 750 kWh is 2 to 7 hours. At the far more common level 2 chargers it's 18 hours. Either mandatory breaks need to be substantially longer, you need a substantially larger battery than just that required to go between breaks, or you need some sort of specialized technology for dramatically speeding up charging rate…

Tesla is, in theory, deploying a handful of 1.2MW charger sites: https://electrek.co/2026/02/24/tesla-megacharger-64-location...

Assuming some amount of tesla over-hyping there, Tellus is doing 600kW chargers: https://chargedevs.com/features/inside-tellus-powers-600-kw-...

So _if_ your route had those, you could charge in somewhere around 1.25h. Not enough for break time, but you can imagine starting with, say, a 1.1MWh battery with one +500kWH boost mid-day being enough to get you to an overnight full recharge. Lots of "ifs" there, since you might not always be able to get full charge rate from the charger, might not time things perfectly, etc., but it doesn't seem completely out of scope for a few years from now.

(And who knows, perhaps tesla will come through with those megachargers. Seems more likely than, say, building an autonomous humanoid robot.)

Re: The Physics and Economics of Moving 44 Tonnes at 56mph

#70

Post by hulitu »

JoachimS wrote: post #66
cbdevidal wrote: post #59

Earlier quoted context omitted.

Seems to me that the slower truck is really the inconsiderate one here. If you’re already slower, tap the brakes a little and let the other guy slide in.

Or just take the foot of the pedal for a while.

Or just step on the brakes. This will teach him about safety distance.
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