Unfortunately, i am not able to keep creating new videos in my current situation. Visit: evtolinnovation.notion.site/eVTOL-innovation-TH-cam-Channel-054d7bae8e344a0b8851f4be18600498?pvs=4 Email me: request.0207@gmail.com I'll be evaluating offers and ideas. Thanks.
This the only detailed video I ever seen that is not treating viewers as brain dead. Thanks for such detailed explanation of how propellers keep aircraft in air! :)
Mind Blown! The Gyroscope system and the counter rotation of blades to eliminate counter rotation without a tail rotor was smart! By using the cross direction blades on same rotation
That would mean a death in every street every day, think about that. Im a drone builder and flyer using the exact same principals as this. Another thing to consider is that this model has 8 motors instead of 4. Do you have any idea of why that is? Someone with your limited knowledge would say more power but this is simply wrong as there are way bigger motors available right now that you yourself can buy. The reason it has 8 motors is because if 1 motor fails in flight the motor above or below increases rpm to compensate for the loss of thrust. You must land immediately for safety without looking for a safe spot to land, just get it down. If you had 4 motors only that are capable of producing more thrust than 8 it would still not be able to carry a person because the law would not allow it as one single failure on a 4 motor setup no matter how powerful the motors are will result in failure and a crash killing the pilot. So no, we dont want this on every driveway. You remind me of the people who saw the very first adverts for flying cars, where are they, how come you dont have one?
@@OzFPVflyer I feel the same way. These things will be nothing more than flying missiles waiting to come through a home. On my commute to work I see peoples front yards and fences destroyed from crashes. These things will go right into the home. You'd have 911 potential times 1 million. Just look at all the drunks and people on there cell phones. Do you want that in the sky? Are these people insane or dumb. The answer is both. Look at all the rust buckets on the road. Do you think these flying missiles won't start dropping like crazy from failure as people don't up keep them? I look at people that want these things as the dumbest people on the planet.
Fantastic exciting stuff !! While I have no advanced education in any of these concepts, when something is explained to me, I usually ‘get it’ without much confusion. The following thoughts don’t contain any intentional sarcasm. They are honest wondering. This video mentions that if the distance between upper and lower props is a bit increased, efficiency rises. It also mentions a problem of the lower prop having some difficulty with the increased velocity of air flow from the upper prop. What if the following concepts were combined. 1. Increase distance between upper and lower prop. 2. Give the lower prop a more aggressive pitch to take advantage of the already faster airflow. 3. Enclose both in a tubular shroud to further increase efficiency. 4. Double the number of motors/props to 16 (8 shrouds) increasing the safety factor of failures of motors and greatly reducing the diameter of each. 5. Raising all of them to completely above line of sight to the ground, not only greatly improving visibility, but also lowering the center of gravity, making the computer’s job easier with more inherent stability. I hungrily await an education on these thoughts, preferably from those who actually know, not from those who think they know. No offense intended. EDIT: HOLEECRAPOLEE !! I just saw your video about the Adaptive ducted fan and it answers some (but not all) of my questions above. Great stuff ! EDIT AGAIN: HOLEEGUSTAVWHITEHEAD !! I just watched your video of the Lillium jet. Disregard all of my questions above. Astonishing ! 😳 🤜🤛
There is an ideal distance between coaxial propellers, I have built a coaxial helicopter and researched the distance I should use, the figure of 10% rotor diameter was right for me, any closer or any further away and lift would be reduced. In order to balance torque on both rotors the pitch of the lower rotor had to be increased by 1 degree. A single larger prop is more efficient than two smaller ones, it's more efficient to move a large amount of air slowly than a small amount of air fast. Helicopters with larger diameter rotors will produce more lift using the same power. Increasing the height of the props I do believe will increase stability
Fantastic video, never gave it too much thought, but thanks for explaining brush less vs brushed motors....NOW I get it! Great video and great instructions, loved it!
A few years ago I watched a few videos on how to fly and repair my rc drone and one of the videos where almost the same as this one. So I guess it's basically the same as building an rc drone just on a larger and more dangerous scale. Pretty damn cool.
I just discovered this channel and I must say, the content is absolutely fantastic. So detailed and the graphics are spot on. Answered many of my questions about this vehicle. Thank you!
@@wildlifewarrior2670 no I produced it years ago. They didn't I was the one that had the original design of a book from them. I made it they bought it off of me. Nobody's going to take credit for my word just like Apple. The credit amongst me.
@@wildlifewarrior2670 I don't still work just like they still medical equipment. They don't have medical over there but they can say that they can construct. It's always and will always be me. Don't play me
Thank you for all of the amazing details and specs. I have been interested in the Jetson One for over 6 months and this video answered must of my technical questions. Great Job!
There could be designated flight paths that the onboard computers would recognize and adhere to if they were ever used as mass transit. Even sensors that would automatically make minor adjustments to the crafts flightpath to avoid collisions.
Возможно будут трассы/коридоры и пути ухода. Плюс радары и компьютеры будут договариваться между собой о порядке расхождения за доли секунды. А полное ручное управление отменить.
Thank you so much for your explanation of rudder authority. It could use foot rudders like an aircraft or helicopter. If you also had foot control for pointing authority it could help if the pilot were wounded in the right shoulder or wrist. In say a combat condition in say the Ukraine carrying a Carl Gustav for anti armor. With axial flux electric motors it could lift more for a higher battery load with 48" propellers. With dynamic wing support it could also double that range.
they don't give any info on anything. it's probably scam and can only fly 3 minites that's why they need to edit their videos so heavily and can't just show a normal test flight.
@@jackwilliams7738 if it was possible to cram all that energy into such a small battery it would be an explosion like the Oklahoma Federal building if it shorted or fell from the sky. this is a very inefficient way to fly.
I like the ballon idea coupled the the motor and uneven size propellers I believe that a specialized cap cover style streamed lined designed ballon cap cover for rain cover in bad weather could be useful and stylish
10,000 feet? What in the world? This thing can barely lift the weight of the pilot. And, with the flight time I've calculated at 2-4 minutes, do you really think there's a chance of getting to 10,000 feet?
Basically a scaled up r/c drone - the flight computer does the same thing that the small drone's does, the difference being the pilot on the ground uses a controller to remotely pilot it, and in the Jetson One the pilot and controls are in the aircraft directly connected to the flight controller. Just hope battery chemistry gets better and better so that we have even more long term power with lower weights in the future. 20 minutes is a long time, but it's also very short - fly a drone and see.
you got scammed. there isn't even proof it can fly longer than a minute. they are all jump cut edits. I don't believe you ordered anything I tried to and they want me to be an Investor.
@@pradeepchandra1734 he should upload any battery and motor specifications and talk about the contract they have. all these people didn't buy one not knowing anything about it and never seeing any of its claims proves. I think this will end up being a scam like so many crowd funded quadcopters only bigger. do you think that many people really ordered it?
15-20 minutes by battery will not enough, we need hydrogen one, that fuel cell, IC (specialy wankel like liquid piston) or mini jet engine, battery is for child and hydrogen for adult pilot.
I think I heard something about a gas generator being in the works to increase flight time, which is currently at 20 minutes (you could probably squeeze out one or two more but you're likely damaging the battery), it can fly at 60 mph and cover 20 miles, which if you know anything about drones is an extremely respectable flight time, but a gas generator would greatly increase that, by at least double. It requires enlarging almost everything though so it's going to be a little beefier of a craft and will be a lot louder too. But with all that supplemental power from a generator along with it's batteries it will also have a lot more oomph as well, it should be able to reach a little higher top speed along with a longer flight time.
3 or 4 minutes max. they would show a continuous five minute flight if they could. they need to heavily edit every video to make it look like it's good. if it could fly 20 minutes they would show that and be the first in the world to do it. if they would release the specs we could do the math.
This thing is a Ninja Juicer for humans!!!!! Would you lose lift or power from wrapping a composite tube just big enough for the blades to fit inside. It must not Jive with it. How in the hell does a Giant sized Human Ninja Juicer even make it to market? Nice job on the video.
The only technology difference compared to a small drone is the joysticks lol Btw. the prototype flights were done using a remote system just like for small drones, suggesting that the platform is using some top shelf flight controller (FC) meant for small drones. The motors are probably from T-MOTOR something like U15Ⅱ KV80. The motors, propellers and ESC total to around $12k I think you could DIY it for like $20k
One thing that really bothers me, is the blades being so exposed and next to the pilot. The blades can be super dangerous when landing, and the pilot fail to see a person next to it. Maybe it needs a cover for the blades, and some type of grade under and over it, that allows air flow, but keep people from touching the blades.
I was more thinking about the fact that aircraft props have been known to come off from time to time. With that many spinning in such close proximity to the pilot it seems like it would only be a matter of time until someone gets sliced up by a broken prop.
@@donaldengel4128 I'd be much more concerned about exposed blades striking something - a power line or a tree branch or whatever. This thing needs "brush guards" of some type surrounding the prop blades, like what you've got surrounding the tail rotor of a helicopter. Thin, wire mesh, or something like that. It doesn't have to be complicated...!
I think when something is new people are more worried. Helicopters are super unstable and people fly in them with less of an issue, and plane engines fail and new software messes up and there have been multiple plane crashes recently due to that. And many people even text and drive and plow their cars into stuff then they see this and are like wow this seems dangerous.
Good design. When you have material failure or a prop strike and the prop disintegrates, the fragments will get safely embedded deep into your brains so they can't harm anyone.
I feel that engineering isn’t hard but research is a completely different animal. Anyone with enough resources could create an aircraft but most people can’t design an aircraft from scratch, that requires extensive knowledge.
Unfortunately, i am not able to keep creating new videos in my current situation.
Visit: evtolinnovation.notion.site/eVTOL-innovation-TH-cam-Channel-054d7bae8e344a0b8851f4be18600498?pvs=4
Email me: request.0207@gmail.com
I'll be evaluating offers and ideas. Thanks.
just explain the name eVTOL please. And let us know if we can help.
@@curtcoller3632 Electric Vertical Takeoff And Landing vehicle
@@curtcoller3632Vertical Take Off and Landing
This the only detailed video I ever seen that is not treating viewers as brain dead. Thanks for such detailed explanation of how propellers keep aircraft in air! :)
Thanks for explaining how it works. Kudos to YOU and JETSON one team.
Great description of how Jetson works!
Mind Blown! The Gyroscope system and the counter rotation of blades to eliminate counter rotation without a tail rotor was smart! By using the cross direction blades on same rotation
Nice video! Well done on the explanation of the design and function of the Jetson ONE. This gives one much more comfort and confidence in the vehicle.
Jetson should be in every driveway. SCREW TRAFFIC! Lets go!
That would mean a death in every street every day, think about that. Im a drone builder and flyer using the exact same principals as this. Another thing to consider is that this model has 8 motors instead of 4. Do you have any idea of why that is? Someone with your limited knowledge would say more power but this is simply wrong as there are way bigger motors available right now that you yourself can buy. The reason it has 8 motors is because if 1 motor fails in flight the motor above or below increases rpm to compensate for the loss of thrust. You must land immediately for safety without looking for a safe spot to land, just get it down. If you had 4 motors only that are capable of producing more thrust than 8 it would still not be able to carry a person because the law would not allow it as one single failure on a 4 motor setup no matter how powerful the motors are will result in failure and a crash killing the pilot. So no, we dont want this on every driveway. You remind me of the people who saw the very first adverts for flying cars, where are they, how come you dont have one?
FAA: Hol up.
Disaster!
@@OzFPVflyer I feel the same way. These things will be nothing more than flying missiles waiting to come through a home. On my commute to work I see peoples front yards and fences destroyed from crashes. These things will go right into the home. You'd have 911 potential times 1 million. Just look at all the drunks and people on there cell phones. Do you want that in the sky? Are these people insane or dumb. The answer is both. Look at all the rust buckets on the road. Do you think these flying missiles won't start dropping like crazy from failure as people don't up keep them? I look at people that want these things as the dumbest people on the planet.
Car Wars. 🤔🤭
To be fair this is basically how all drones work, but i still like this.
Great video!!
Fantastic exciting stuff !!
While I have no advanced education in any of these concepts, when something is explained to me, I usually ‘get it’ without much confusion. The following thoughts don’t contain any intentional sarcasm. They are honest wondering.
This video mentions that if the distance between upper and lower props is a bit increased, efficiency rises. It also mentions a problem of the lower prop having some difficulty with the increased velocity of air flow from the upper prop. What if the following concepts were combined.
1. Increase distance between upper and lower prop.
2. Give the lower prop a more aggressive pitch to take advantage of the already faster airflow.
3. Enclose both in a tubular shroud to further increase efficiency.
4. Double the number of motors/props to 16 (8 shrouds) increasing the safety factor of failures of motors and greatly reducing the diameter of each.
5. Raising all of them to completely above line of sight to the ground, not only greatly improving visibility, but also lowering the center of gravity, making the computer’s job easier with more inherent stability.
I hungrily await an education on these thoughts, preferably from those who actually know, not from those who think they know. No offense intended.
EDIT: HOLEECRAPOLEE !!
I just saw your video about the
Adaptive ducted fan and it answers some (but not all) of my questions above. Great stuff !
EDIT AGAIN:
HOLEEGUSTAVWHITEHEAD !!
I just watched your video of the Lillium jet. Disregard all of my questions above. Astonishing ! 😳 🤜🤛
For someone with "no advanced education in any of these concepts", your quite inquisitive; kudos to you
There is an ideal distance between coaxial propellers, I have built a coaxial helicopter and researched the distance I should use, the figure of 10% rotor diameter was right for me, any closer or any further away and lift would be reduced.
In order to balance torque on both rotors the pitch of the lower rotor had to be increased by 1 degree.
A single larger prop is more efficient than two smaller ones, it's more efficient to move a large amount of air slowly than a small amount of air fast. Helicopters with larger diameter rotors will produce more lift using the same power.
Increasing the height of the props I do believe will increase stability
Fantastic video, never gave it too much thought, but thanks for explaining brush less vs brushed motors....NOW I get it! Great video and great instructions, loved it!
Yeah, you can buy electric weed-whackers with brushles motors and build your own :)
It is very good explanation.
Thank you.
A few years ago I watched a few videos on how to fly and repair my rc drone and one of the videos where almost the same as this one. So I guess it's basically the same as building an rc drone just on a larger and more dangerous scale. Pretty damn cool.
I just discovered this channel and I must say, the content is absolutely fantastic. So detailed and the graphics are spot on. Answered many of my questions about this vehicle. Thank you!
it is German made......
@@1bluemoondj even cooler 😁
@@1bluemoondj Swedish made
@@wildlifewarrior2670 no I produced it years ago. They didn't I was the one that had the original design of a book from them. I made it they bought it off of me. Nobody's going to take credit for my word just like Apple. The credit amongst me.
@@wildlifewarrior2670 I don't still work just like they still medical equipment. They don't have medical over there but they can say that they can construct. It's always and will always be me. Don't play me
Thank you for all of the amazing details and specs. I have been interested in the Jetson One for over 6 months and this video answered must of my technical questions. Great Job!
I cannot imagine when this thing will have massive production. With no roads and traffic signs, there will be massive numbers of deadly accidents.
There could be designated flight paths that the onboard computers would recognize and adhere to if they were ever used as mass transit. Even sensors that would automatically make minor adjustments to the crafts flightpath to avoid collisions.
Возможно будут трассы/коридоры и пути ухода.
Плюс радары и компьютеры будут договариваться между собой о порядке расхождения за доли секунды. А полное ручное управление отменить.
thank you, now i can make my own
Thank you so much for your explanation of rudder authority. It could use foot rudders like an aircraft or helicopter. If you also had foot control for pointing authority it could help if the pilot were wounded in the right shoulder or wrist. In say a combat condition in say the Ukraine carrying a Carl Gustav for anti armor. With axial flux electric motors it could lift more for a higher battery load with 48" propellers. With dynamic wing support it could also double that range.
This is an important video show show the buyer how complicated this vehicle is and show the homework was done
Finally the drone unveiled....Great works
❤ Love your explaining this Star-Wars vehicle 👌
Does anyone have info about Jetson's Flight control computer? Do they make their own hard and software or do they use opensource ones?
Probably using a DJI setup.. pretty easy to configure esc and motors to to a higher voltage output…
they don't give any info on anything. it's probably scam and can only fly 3 minites that's why they need to edit their videos so heavily and can't just show a normal test flight.
@@fairyphotography they need to develop a better battery that can fly for a few hours at a time.
@@jackwilliams7738 if it was possible to cram all that energy into such a small battery it would be an explosion like the Oklahoma Federal building if it shorted or fell from the sky. this is a very inefficient way to fly.
@@fairyphotography they might be able to make a bigger better battery.
polycarbonate wind screens would prevent slicing, but also it's dangerous if flown near other. Remember the chariot race in Ben Hur?
Brilliant, thank you very much for your beautiful video ❤
Yes! I too cannot wait to sit between 8 spinning propellers 😂
Thank you.🙌
Absolutely brilliant machine!.... I want one!
I like the ballon idea coupled the the motor and uneven size propellers I believe that a specialized cap cover style streamed lined designed ballon cap cover for rain cover in bad weather could be useful and stylish
The brilliant engineering of the quadcopter on display. It has rotors and they spin, creating lift. The end. Super revolutionary stuff.
I love it. I wish i could afford this. This would be a dream come true for me. I would love to own one.
Wonderful explanation. I would love to have one of these.
You can for $92,000
Very good video..my like
Very informative thanks for the info on the brushless and the brushed and the propulsion system. Great Contant.
Every video I've seen of Jetson flight tests show it flying nape-of-the-earth. What is the effective flight ceiling of this vehicle?
For a 22 ( Y/O) probably 10.000 ft then again they could carry ox tank , this is a beautiful machine though 😁
@@Bigfoots777 Thank you again for that information.
10,000 feet? What in the world? This thing can barely lift the weight of the pilot. And, with the flight time I've calculated at 2-4 minutes, do you really think there's a chance of getting to 10,000 feet?
Very good presentation..
This is it. Thank you! 😊😊
Excellent stuff bro, keep it up
Gratuluję świetnego projektu i życzę powodzenia !
Basically a scaled up r/c drone - the flight computer does the same thing that the small drone's does, the difference being the pilot on the ground uses a controller to remotely pilot it, and in the Jetson One the pilot and controls are in the aircraft directly connected to the flight controller. Just hope battery chemistry gets better and better so that we have even more long term power with lower weights in the future. 20 minutes is a long time, but it's also very short - fly a drone and see.
How many minutes does it fly? on one charge
The ballistic shute is probably the most required feature
I just saw the Xpeng2 please make your interiors and finishes look that nice!
Evtol enn great job evwry one🌐🌏🌏🌎🌍👍👍👍👍👍☝️☝️☝️☝️☝️
This is really cool
Excellent video.. I’be ordered one of these for my Dad.. we get it next year hopefully. This is the best video I’ve seen on it so far.
wow please upload its flight once you get it
you got scammed. there isn't even proof it can fly longer than a minute. they are all jump cut edits. I don't believe you ordered anything I tried to and they want me to be an Investor.
@@pradeepchandra1734 he should upload any battery and motor specifications and talk about the contract they have. all these people didn't buy one not knowing anything about it and never seeing any of its claims proves. I think this will end up being a scam like so many crowd funded quadcopters only bigger. do you think that many people really ordered it?
Sir, What is the max.height the craft can achieve?is it possible to make a four seater version craft, with the same dynamics?
it can't reach it's ceiling without running out if battery so it doesn't matter. it goes as high as you are brave.
so, i'm assuming around 15 to 20 minutes of flight time? How long for a charge?
Are the batteries swappable?
15-20 minutes by battery will not enough, we need hydrogen one, that fuel cell, IC (specialy wankel like liquid piston) or mini jet engine, battery is for child and hydrogen for adult pilot.
I think I heard something about a gas generator being in the works to increase flight time, which is currently at 20 minutes (you could probably squeeze out one or two more but you're likely damaging the battery), it can fly at 60 mph and cover 20 miles, which if you know anything about drones is an extremely respectable flight time, but a gas generator would greatly increase that, by at least double. It requires enlarging almost everything though so it's going to be a little beefier of a craft and will be a lot louder too. But with all that supplemental power from a generator along with it's batteries it will also have a lot more oomph as well, it should be able to reach a little higher top speed along with a longer flight time.
3 or 4 minutes max. they would show a continuous five minute flight if they could. they need to heavily edit every video to make it look like it's good. if it could fly 20 minutes they would show that and be the first in the world to do it. if they would release the specs we could do the math.
@@fairyphotography stop spamming with that bs everywhere nobody believes you
@@Ducky69247 they never did
Great video
This thing is a Ninja Juicer for humans!!!!! Would you lose lift or power from wrapping a composite tube just big enough for the blades to fit inside. It must not Jive with it. How in the hell does a Giant sized Human Ninja Juicer even make it to market? Nice job on the video.
Great video and detailed info. Thanks and please go on.
What company is that boxwing aircraft in the very beginning of the video?
The Jetson is still my favorite vetol aircraft!
Excellent! You know what you are talking about. Why ... what is your current situation? Can we help?
Great video!!! Thanks:)
Have those propellers been tested against bird strikes?
How high can it climb and what controls ascent and decent??
hi there. can´t find any info about possible hight of flying.
DJI have this brilliant engieneering a long time!!
Amazing
This is awesome. Thanks
Jetson One is the right one!
How high and how far can it go?
Do the lower motors run at a faster speed ? or are they on the same axil ?
For sure the Jetson One is mega cool!
BTW, I just uploaded a video to my TH-cam channel that explores a possible application of the Jetson.
Solid 💯👍🏼🤙🏼
What’s the flight time at what output?
How about engineering the rotors above the pilot?
Toroidal propeller(s) or the combination of both? ....
Super really ,information!Thank's you ,good.
I love this, oblivion inspired movie
It's an upscaled RC quadcopter/octocopter. There. Video done in 2 seconds.
Awesome
Love thus new byrd but be carefull spinning blabes when on ground
hmm... you could ADD a BLIMP like Balloon filled with Helium to help undo the weight.
What altitude can it operate ?
The only technology difference compared to a small drone is the joysticks lol
Btw. the prototype flights were done using a remote system just like for small drones, suggesting that the platform is using some top shelf flight controller (FC) meant for small drones.
The motors are probably from T-MOTOR something like U15Ⅱ KV80.
The motors, propellers and ESC total to around $12k
I think you could DIY it for like $20k
R u fucking crazy
Looking forward great 👍 😊
Amazing 👍 and innovative ❤️
One thing that really bothers me, is the blades being so exposed and next to the pilot. The blades can be super dangerous when landing, and the pilot fail to see a person next to it. Maybe it needs a cover for the blades, and some type of grade under and over it, that allows air flow, but keep people from touching the blades.
agree, maybe Ducted propeller more safe
I was more thinking about the fact that aircraft props have been known to come off from time to time. With that many spinning in such close proximity to the pilot it seems like it would only be a matter of time until someone gets sliced up by a broken prop.
@@donaldengel4128 I'd be much more concerned about exposed blades striking something - a power line or a tree branch or whatever. This thing needs "brush guards" of some type surrounding the prop blades, like what you've got surrounding the tail rotor of a helicopter. Thin, wire mesh, or something like that. It doesn't have to be complicated...!
weight is the deal killer there
Maybe use a pool without water to land and nobody enter there. The small size of the vehicle and easy to land make this possible.
Excellent
What is the altitude max on this?
qual e metragem d coprimento e largura
Do they have a model with throttle/yaw on the left stick and Pitch/roll on the right stick?
it's probably an open source software and you can do whatever you want.
Amazing!
weight requirements?
What is the range?
How long is the flight time.? How far an you fly.
感謝分享 太棒了 !!!🤩
What is the current flight time duration ?
Nice ride
If I was strapped into such an aircraft, I would definitely want redundancy over efficiency.
I think when something is new people are more worried. Helicopters are super unstable and people fly in them with less of an issue, and plane engines fail and new software messes up and there have been multiple plane crashes recently due to that. And many people even text and drive and plow their cars into stuff then they see this and are like wow this seems dangerous.
how soon will these birds be available to the public and at what costs, thank you for a great video
I like Jetson One except I wish it had floats for landing on water. Is that something i could safely add without screwing up the aerodynamics?
How much weight can it lift?
I bet the pilot could weight shift for fine control.
That said, what's the surface area of all blades combined? Equivalent to a small helicopter?
Any applications on Toroidal concept
Good design. When you have material failure or a prop strike and the prop disintegrates, the fragments will get safely embedded deep into your brains so they can't harm anyone.
Yes, correct. It is called a Coup de Grâce 😊.
Yep, now go get in your deathtrap car and experience the same . 😂
How do you practice driving this ? Is there a simulator with joysticks that mirror the unit
I feel that engineering isn’t hard but research is a completely different animal.
Anyone with enough resources could create an aircraft but most people can’t design an aircraft from scratch, that requires extensive knowledge.
Range? Achievable altitude? Max speed?