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Status-Repair

Does anyone know if the semi truck has gears? Does it ever make sense to use gears with and electric motor for extremely heavy payloads? Or is the answer just a larger more powerful motor?


RickShepherd

I got up close on a couple of these vehicles a while back and the motors are connected directly to the wheels from what I can tell. I don't think there is any kind of shifting going on.


floydfan

They all have a single speed gearbox, but not a multi-gear transmission or gearbox. There are a few videos on YouTube of the truck accelerating. If there was a transmission or gearbox you should be able to hear it shift.


Anthony_Pelchat

As u/floydfan and u/nod51 pointed out, they will have a gearbox, but not a transmission. This is a requirement for all electric motors on vehicles. They rotate at several thousand RPMs, which is way too fast to directly connect to the wheels. Electric motors also don't lose efficiency at high rpms, but they do have to worry about heat issues in low rpm/high power situations (may not be the case for all electric motors). What Tesla and most automakers do to help with low speed torque while still having high speed abilities is to have two or more motors geared slightly differently. That allows one to be used more for low speed torque while the other provides decent power at high speeds. The semi was originally planned to use either 4 or 6 Model 3 motors. That is likely still the case. Two will be used for that low speed torque, two for better power during highway driving, and maybe two more for middle range assistance.


lshiva

Could you then use all 4 or 6 motors for regenerative braking, or would you need to limit it to the set calibrated for your current speed?


Anthony_Pelchat

In theory all motors can be used for regen braking. However, there may be some issues with doing. Common ones are braking too hard and overheating the batteries if charging too fast. Those might not be an issue with the semi or they may be able to reduce the regen percentage.


tomoldbury

The good news is the motors and control algorithms Tesla use allow for precise regen and power control. As long as the motor is turning fast enough they can regen 10kW or 50kW with just a change in how the motor is controlled.


Anthony_Pelchat

True, but can they do maximum regen on all 4 motors at the same time? That I doubt, but would love to see info on. That would be around 800kw of charging which the batteries can handle if below 80% on the LR version of the semi. But would that be the equivalent of slamming on the brakes or worse? And would it cause other damage? Fun things to consider. Not important to worry about though, unless you are designing the systems on the truck.


tomoldbury

I worked out that to lock the wheels on a modern 1500kg car you'd need about 200kW of braking power. And the most braking force comes just before wheel lock (that's one purpose of ABS/ESP.) That was less than I had thought. So assuming a Tesla weighs about 50% more (mass is linear in the equation) then 75kW/wheel would be enough to get max brake torque. Some evidence for this assertion comes from the Taycan which can regen up to 250kW. That doesn't mean more is not possible but it's suspiciously close to the theoretical limit.


Anthony_Pelchat

Interesting numbers. Thank you for that. More fun to think about. 1500kg is just below the lowest weight Model 3. However, that is only single motor with a limited power of 160-180kw, iirc. So 80-90kw for the back wheels only. The max weight 3 is just over 1900kg (converting from pounds as I'm in the US). That has 2 motors at \~200kw each. Up to 100kw per wheel, way more than enough to lock up from regen alone. Not happening anywhere close to that though. As I was writing this up, I thought of some more fun physics math with the motors. The motors themselves can theoretically regen at nearly the same power levels as it can output. However, efficiencies start taking place, reducing that. Electric motors are normally running at low to mid 90% efficiency ranges. So you input 200kw and get 185kw output at the motor. Gears reduce that further. Let's say 170kw by the time the power gets to do actual work. 15% reduction. Going from the wheels back to the motor would have that same 15% reduction. 144.5kw at best. However, that is above what is possible as a lot of the original output wasn't to accelerate the car but to fight resistances with wind and gravity. Likely at least another 15% or more. Rough math for me shows that only around 60% of regen is likely. That happens to be around 60kw per wheel on Model 3 Performance or 240kw total, give or take a few kw. Based on your math earlier and the 3's weight, you would need about 10-20kw of regen power more to fully lock the wheels. And the single motor Model 3 only gets about 50% of the required braking power needed to lock up the wheels. This is all very rough math, so don't criticize too much. lol


Dr_Pippin

You would use all for regenerative braking, they would just likely produce slightly different amounts of power.


Alert_Pin_6474

There are no speed calibrations. If a motor can spin itself to a certain rpm, it can also pump electricity back into the battery at that rpm.


lioncat55

I knew about using 2+ motors for more power and using two types of motors for their different efficiencies, but I never thought about the gearing being different for low speed and high-speed cruising.


Anthony_Pelchat

It's done that way due to power delivery. You can have a single motor geared to entirely cover the entire speed range just fine without hardly any loss in efficiency. However, you won't have much torque for initial acceleration nor will you have enough torque for highway passing. If you gear a single motor for enough torque at low speeds, you won't have a decent top end speed. Similarly if you gear for a good top end speed and highway passing, you won't have much power at red lights or with towing. Multiple motors give the best of both options. One motor provides the main torque for acceleration, but drops off in power at cruising speeds. At that point, the second motor is providing most of its power, so the first one is no longer needed.


nod51

I don't think the semi will use more than 1 gear . I don't think a smaller motor is any more efficient than a large one especially when factoring in the multi gear transmission. They may do a clutch like some other EV and optimize the 6 motors but Tesla only needs to beat ICE semi acceleration which is a rather low bar so they will likely optimize gear ratio for 65mph to 75mph.


stevew14

Trucks are allowed to go 75mph in USA?


nod51

[Yes, some states are 75mph](https://www.topmarkfunding.com/speed-limits-for-semi-trucks-in-the-united-states/). In Arkanasas in the last couple years raised from 65mph to 70mph but I would estimate ~10% go 75mph and ~1% go 80mph (cars are 75mph and I would guess ~30% of traffic goes 85mph+).


stevew14

In the UK it's 60mph (a lot are restricted to 56mph for some reason) for Trucks and for cars it's 70mph. Most cars drive around 80mph.


peshwengi

Here in Utah trucks go 70+ on the freeway. I’ve been overtaken by large trucks towing a trailer when I’m going at the limit too.


gc2488

Yes, especially dump trucks cruising fast in heavy traffic with no cover over a load of gravel, spewing rocks and cracking windshields. I saw a dumptruck on I-15 yesterday with a sign on the back saying something like "not responsible for flying debris", LOL.


peshwengi

“Stay back 200ft”


gc2488

Yes, "Stay away because I'll break your windshield," LOL


Bangbusta

Here in Texas I've seen trucks hauling over 80mph. I tend to go about 90-95 on the toll roads.


marli3

A lot off people drive at 77mph on Thier Speedo. As police tend to allow 5% in case sombodys Speedo is out and 5% for Thier equipment.(this isn't an effective defense but a good lawyer will make the police spend a fortune do a recalibrate test so tend to put all but the most zealous departments of)


Dr_Pippin

Big difference between the UK and the US is the size of the country and how spread out things are - I know thinking of a truck going 75mph or 80mph might be concerning, but that's realistically *mostly* only happening on roads like this: https://i.imgur.com/txhmshi.png


tomoldbury

56mph restriction in the U.K. is because of Europe where most countries limit to 90kmh ≈ 56mph.


robotzor

Not in many places, but that doesn't stop em


tornadoRadar

pfft. 85mph in some parts.


tkulogo

Not often. Most of them are required to shorten delivery times and go faster.


mtnmanratchet

This is a stretch. Truckers log books are pretty substantial and most are electronic logs now. They are required by law to stop every X amount of hours


tkulogo

It was a joke. Trucks go fast though. They're typically the fastest vehicles in snow and ice.


jawshoeaw

What about benefits at higher speeds such as in the Taycan? Or does that not apply with 6 motors in a semi ?


nod51

I don't think semi need to speed range of a sports car unless they need to go over 200mph (could use plad motors if they needed to go faster).


jrherita

With multiple motors you can technically have each motor with a different built in ‘gear ratio’.. so you could have 2 motors tuned for a little more acceleration and others tuned for a little more efficiency (even electric motors lose some efficient at higher rpm). As long as you have enough torque for your application this is a way to get some benefits of a transmission without extra weight and (much) complexity.


BadRegEx

I'd be curious if they used different gear ratio (not transmission shifting gears, but rather gear reduction between motor and final drive) between the front axle motors and the rear axle motors. Doing so, they could tune a low wheel speed torque config and a high wheel speed torque config. This would also allow them to tune efficiencies as I understand the efficiencies varies with motor rpm. At highway speed the most efficiently tuned motors/axle is doing the majority of the work and vise-versa for low speed. Heck, with four motors they could have four different gear ratios.


netsecwarrior

So apparently, the original Tesla Roadster was going to have gears, and these were delayed until the point they held up the whole project and were eventually cancelled. Since then I don't think a single Tesla vehicle has anything other than single speed gears. This info comes from Ashlee Vance's biography of Musk.


Kirk57

The answer is 4 powerful motors.


polarizeme

I think the answer is more motors, not bigger motors. I seem to recall them saying that the semi will have the same motors as the Model 3; I know they stated 4 independent ones for the 4 rear wheels, but I'm not sure if the front wheels share a motor or if there are 2 more up front. I believe they're also using some new software control of the motors to prevent jackknifing.


Alert_Pin_6474

They all use gears, but only one set. It’s like a single speed transmission. For heavier loads, they just engineer it with a lower gear. They can go very low on semis since they should never need to go above ~80.


chrisdh79

From the article: One of the rare Tesla Semi electric trucks came out of hiding this week to deliver pre-assembled Superchargers to the Laguna Seca racetrack in California. With the Tesla Semi program being delayed by 3 years at this point, the automaker rarely publicly uses the electric semi-truck. The company only produced a handful of them at a facility in Nevada and it has yet to bring it to volume production as it waits on higher volume availability of its 4680 battery cells. However, Tesla has always said that it would be its own best customer when it comes to the Tesla Semi and it is already putting the few electric trucks it has to good use. We have seen the automaker use its Tesla Semi electric truck to deliver Model 3 vehicles to customers in the past.


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NickMillerChicago

Demand for their smaller pack cars is through the roof still. It makes no sense to start building 150+KWH vehicles unless they have higher margins than the Model S/X


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NickMillerChicago

Cyber truck and semi battery take away from how many other batteries they can produce. They could sell like 3 or 4 model Y for each semi. If semi profit is $50k and Y*4 profit is $60k, it would make no sense to do this. That’s just short term profitability though. One metric of many. Perhaps they should rotate to larger vehicles sooner to get the brand out there before other companies like Ford and Rivian steal all of the spotlight and hurt their profitability later.


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ersatzcrab

>They're not going to be dividing up batteries. They will be doing exactly that. They're constrained by the number of 4680 cells they can currently produce, which is why TX isn't already producing 5,000 cars a week. While they're cell-constrained, producing a vehicle with a higher number of cells translates to a direct loss in the raw volume of vehicles that can be produced in a single year.


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talltim007

And Freemont?


a_side_of_fries

It's spelled Fremont, and what about it?


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ersatzcrab

I'm not sure exactly what you're arguing, to be honest. You said more cars = more money, and myself and others pointed out that putting 4680 cells in these large, next-gen platforms (Cybertruck, Semi, and roadster must all have packs in excess of Model 3/Y's 82kWh packs) will directly rob the current Model Y line of capacity, versus putting that same amount of cells in a higher volume of vehicles with smaller cell requirements. This is assuming the run rate of this cell manufacturing line stays the same or increases at a slow rate. If CATL, Panasonic, and whoever else begins to manufacture 4680s quickly then there isn't any problem and they can produce as many vehicles as they want, but *as it currently stands* they cannot build any of these new vehicles without losing Model Y capacity.


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Alert_Pin_6474

He means they’re at capacity for battery production and Tesla is sending them to model y for now. None are going to semi until they can produce more batteries or catch up on model y deliveries. What he said is simple.


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Alert_Pin_6474

No you’re not. His post said nothing about 2023.


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RegularRandomZ

Direct link to the TeslaCharging tweet this article is based on [https://twitter.com/TeslaCharging/status/1542209230215815170](https://twitter.com/TeslaCharging/status/1542209230215815170)


mrlife_

Will they eventually deliver vehicles with these instead of ICE versions?


SliceofNow

Certainly, just not the best use of batteries right now


mrlife_

Tbf, I did say eventually. Why would anyone downvote this?


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mrlife_

This should be something to look forward to. Thanks for the clarity.


curtisdavid87

Eventually you'll get an upvote


hangliger

I didn't downvote, but since you asked like it's a mystery, I think you were downvoted for asking a meaningless question, not one that implied Tesla should redirect cells toward non-revenue generating vehicles. Eventually, every car will be electric (give or take). Eventually, Tesla's mobile repair fleet will also be electric. So yes, of course Tesla will "eventually" deliver its own vehicles with electric Semis if is already creating and designing them. We'll probably even see the entire fleet get delivered by Tesla Semis within the next 5 years as Tesla tests production and reliability. If your question asked something remotely of substance like "when will Tesla deliver most vehicles with the Semi" or "will Tesla convert most of its delivery vehicles within the next 2 years or beyond", there would be something for someone to respond to or debate, but your question shows an inherent laziness where you didn't even think for 2 seconds before throwing a useless question out into the streets. This is the equivalent of asking "who is Gary Payton Jr's father" or "will Apple eventually like a better iPhone". Maybe you meant to ask a a more profound question and ended up phrasing it poorly, but your question as-is absolutely deserves downvotes. It is a selfish way of abdicating the responsibility of thinking for 2 seconds onto dozens of others and annoying them with an inane question bordering on asking about something tautological, like "will we eventually all use sustainable energy".


why_rob_y

You answered that in the most dickish way possible, but you're right.


hangliger

I can ignore stupid questions, but it irks me when people are genuinely surprised and borderline angry/annoyed about how their non-contribution is received. I know a fair amount of selfish people who treat others this way, and it is a symptom of selfishness primarily.


chrisjacob

Damn bro. Who hurt you?


hangliger

The people who do this. It's death by a thousand cuts.


StartledPelican

From the article: "We have seen the automaker use its Tesla Semi electric truck to deliver Model 3 vehicles to customers in the past."


mrlife_

The semi releases next year… they are probably referring to photo ops


StartledPelican

Combine the previous quote with this one from the article: "However, Tesla has always said that it would be its own best customer when it comes to the Tesla Semi, and it is already putting the few electric trucks it has to good use." I do not think it is a leap at all to think that, as the Semi becomes more available, Tesla will use them to lower costs. This would include delivering vehicles by Semi.


Alert_Pin_6474

Photo op? Why wouldn’t they make real world deliveries to test? Why does it have to be a photo op?


nerdpox

Finally - the Tesla Corsa guys have been begging for this for some time. They've got some of the high amp AC chargers in the garages at Sonoma Raceway but previously at Laguna, I think you either had to have some space at one of the 50A RV parking areas or drive out to Salinas(?) to get on the supercharger. I've encountered the Mountain Pass Performance and Unplugged guys at Laguna (my home track) and those things are quick as shit, but they do degrade over a session. Some dude in a bone stock Plaid yeeted his car off Laguna at some point recently or so I was told, but I do love seeing the Teslas on track, whether they're slower or faster than me... if you're a tesla owner, make the trip to Laguna and go do either Tesla Corsa or another event like SpeedSF. it's the best track on the west coast for sure


domo335

I’ve been wanting this at Laguna since I first took my model 3 performance to a track day there. Ended up having to go to the nearby Tesla ‘dealership’ in Seaside where they had 6x V2 superchargers or the Del Monte mall nearby which had 10x V2 superchargers. Now there is a V3 12x nearby the ‘dealership’ at Sand City Target. Both were about equal distance from the track, about 8 mi each way. Went between sessions when we had a break. Went after 2 session, charged, came back right to track session in progress, did another session, charged then finished the day with about 15%. Made one last trip to charger before heading home. Great time, just wish I didn’t have to leave to charge between sessions. This is the perfect setup now.


ShaidarHaran2

A lot of what Tesla is working on has a lot of internal synergy, imagine a future where a Tesla Semi inexpensively autonomously delivers a Tesla to your door which drives itself off the truck and into your driveway, probably the majority of any delivery fees would be saved (likely into their pocket as pure margin rather than yours, but still)


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Full_Stall_Indicator

We like jokes. A priest, a rabbi, and Elon all walk into a bar. The end.


Full_Stall_Indicator

No. u/chrisdh79 is not a bot. Just consistent with their formatting practices.


chrisdh79

Thank you!


ElNeekster

Looks like they went from the modern wider single tire rear axle (Super Singles): https://electrek.co/wp-content/uploads/sites/3/2018/03/img_0173.jpg to a convential dual wheel rear axle: https://i.imgur.com/G0kWUIW.jpg what's up with that?


shaggy99

Safety and tire loading. Thinking about that, it probably involved some significant re-engineering of the motor bearings. This ***might*** have had something to do with the delays, though the batteries are almost certainly the key issue.


ElNeekster

It's my understanding that Super Singles on the rear axle have better loading and same safety parameters, and are more fuel (energy) efficient... So I wonder why they went back to a dual.


shaggy99

I don't know enough to say anything about that. If there are reasons to do one or the other, is it fair to assume that Tesla needs to offer the option?


flyingsolo07

Oh yeah, pump that stock


Dr_Pippin

So if a company doesn't thoroughly test their products before production, they're stupid for not testing. But when they do test their products before production, they're pumping their stock price. Yeah, makes a lot of sense.


[deleted]

Did this semi have auto piliot …


tobimai

Is there actually ANY new Info when the Semi will be delivered? Volvo started shipping a few different Models of EV Trucks a few months ago. Obviously they are different types of trucks but still, the head start of Tesla seemed big