Understanding the Tesla Model S Performance Motor

WeberAuto

498 миӊ. көрүүлөр50

    Join me for a deep dive into the details of the 18,000 RPM performance rear motor and drive unit from a 2015-2016 Tesla Model S P90D. This drive unit is similar to the one used in the 2017-2020 P100D. The video is divided into four sections showing: 1. The motor and gears. 2. The high-performance bearings. 3. The lubrication system. and 4. The cooling system.
    CORRECTIONS:
    Thank you to everyone for catching my errors. There are always errors ;)
    1. The Nissan Leaf ring gear is held on with 8 bolts, not 6.
    2. The fluid in this drive unit is Dexron 6 transmission fluid.
    3. Induction motor rotors do not have poles, just the stator. The 60 slot stator has four poles.
    4. Silicon Nitride is a ceramic material.
    TIMELINE:
    0:00 Start
    0:10 Introduction
    1:35 Gearbox housing
    2:10 Video Section 1 - Gears and Motor Rotor
    2:45 The giant differential ring gear with 16-bolts!
    4:20 The giant differential case bearings
    4:50 The differential case speed at 250 km/h (155 mph) = 1841 RPM
    5:15 MUST SEE Comparing the Tesla 213mm x 50mm. ring gear to a Chevrolet Bolt EV and Nissan Leaf EV
    5:40 A Chevrolet Bolt EV differential 198mm x 34.3mm ring gear with 12-bolts.
    6:10 A Nissan Leaf EV differential 200mm x 32mm ring gear with 8-bolts!
    7:30 The Counter Shaft (Jack Shaft) with 25 pinion gear teeth. 78/25 = 3.12:1 Gear ratio from countershaft to the differential case
    8:50 The countershaft speed at 250 km/h (155 mph) = 5743 RPM
    9:30 The motor shaft with 25 teeth drives 78 teeth on the countershaft for another gear reduction of 78/25 = 3.12:1
    10:08 The motor shaft speed at 250 km/h (155 mph) = 17,919 RPM
    11:20 See all three gears in the reduction gearbox with an overall gear reduction of (78/25) x (78/25) = 9.7344:1
    12:05 MUST SEE The AC Induction Motor Rotor with 74 bars
    13:25 Motor specifications for power, torque, and gear ratio
    15:00 MUST SEE Ceramic Bearings (Silicon Nitride) on the rotor from the SKF Group (skf.com)
    16:22 MUST SEE Close up view of silicon nitride bearing
    18:20 The motor rotor speed sensor reluctor wheel (tone ring)
    19:22 Must SEE The rotor installed on the drive gear and the functioning gearbox
    20:18 Video Section 2 - Specialized Bearings
    21:21 The 60 slot four-pole stator and housing
    23:05 The oil pump and how it is overdriven by the differential ring gear 23/78 = 0.2948:1 gear ratio (3.339 times faster than the ring gear)
    23:55 MUST SEE The function of the oil pump (it may surprise you)
    26:27 Motor shaft bearing reference speed and limiting speeds
    27:30 How to run bearings at higher speeds than their limiting speeds
    29:54 Video Section 3 - Lubrication
    30:25 Drain and fill plug locations
    30:50 Gearbox vent and inverter vents
    31:05 Sport model label
    31:39 MUST SEE Four different sealed areas in the drive unit
    32:46 Video Section 4 - Cooling System
    33:30 MUST SEE The coolant inlet port and the two paths coolant takes
    33:53 Up for rotor cooling and gearbox cooling
    35:03 Down for stator and inverter cooling
    36:05 Coolant from the rotor moves to the gearbox heat exchanger and the outlet port
    37:25 Stator temperature sensors
    38:10 Coolant from the stator to the inverter coolant passages
    38:28 Stator coolant temperature sensor
    38:35 MUST SEE Insulated-Gate Bi-Polar Transistor (IGBT) module coolant passages and flow through gearbox passages
    40:34 Inverter coolant outlet temperature sensor
    40:45 The gearbox oil-to-coolant heat exchanger
    41:38 Coolant outlet port to coolant pump and on-board charger module under the back seat.
    41:55 Drive unit cooling system summary
    43:04 IGBT inverter modules installed and inverter cover
    43:40 High voltage battery cable connections and low voltage connections at the inverter
    44:35 Video summary
    ABOUT US
    Weber State University (WSU) Davis Campus - Automotive Technology Department - Advanced Vehicles Lab. A technical description and demonstration of the Tesla P90D Rear Drive Unit (RDU). We teach current vehicle technologies to our automotive students at Weber State University and online. For more information visit: www.weber.edu/automotive
    This video was created and edited by Professor John D. Kelly at WSU. For a full biography, see www.weber.edu/automotive/J_Kelly.html
    Visit my other youtube channel kgup.info to see the amazing NVH app for vibration diagnosis!
    ADDITIONAL TRAINING FOR YOU
    Join us for hybrid and electric vehicle training with two online courses and in a 5-day on-campus boot camp with Professor John D. Kelly. See www.weber.edu/evtraining
    DONATE TO OUR DEPARTMENT
    Please consider a donation to the Department of Automotive Technology at Weber State University here: advancement.weber.edu/Automotive

    күнү жарыяланды 2 ай мурун

    Жорумдар

    1. Aravinth Kumar

      6:20 Nissan leaf's differential ring gear has 8 bolts instead of 6

      1. WeberAuto

        Yes, thank you. I was wrong

    2. Mitch Batten

      After watching this well delivered video I almost feel like I could be expecting a Certificate of Competency in the mail. Excellent job.

      1. WeberAuto

        Glad it was helpful!

    3. Puffers Paradise

      Love the video I wish somebody would help this guy out with his breathing problems

    4. Americannovice Twocentnovice

      If the bearings were submerged in oil, a pump wouldn’t be needed.

    5. Americannovice Twocentnovice

      Silicone bearings? Raw materials only found on Mars. No wonder why Elon wants to go to Mars.

    6. Americannovice Twocentnovice

      I’m sixty years old and feel like a 18 year old kid back in my automobile mechanic class in the 1980’s.

    7. Americannovice Twocentnovice

      The motor for the Cybertruck must be twice as big as this motor for the model S.

    8. PERRY JURGENS

      Wonderful teach-out - thanks!!!

    9. Johan Kuhn

      Silicon nitride IS a ceramic ;)

      1. Johan Kuhn

        @WeberAuto haha no problem, anyways really great video 👍

      2. WeberAuto

        Yes, thank you. I was wrong

    10. Turre Tuntematon

      Well done! I would like to see the Plaid plus motor after it’s launched. Must be crazy! 😊

    11. My Nguyen

      Watching it incoperate with my design. thanks

    12. Mr Pangy

      Great job. I would love to see complete comparisons to the competition.

    13. Hello Dolly

      I believe those knobbly heat exchangers are called pin-fins. Thank you for a great tear-down.

    14. Avelino Goncalves

      Nissan with 8 bolts...wight?

      1. WeberAuto

        @Avelino Goncalves Thank you

      2. Avelino Goncalves

        @WeberAuto After, I saw your acknowledge. Thank you for your care! BTW...great video!! Mainly because you showed that there are fluid to be exchanged ate roughly every 100K miles, top at those loads! But Dextron knows it better!

      3. WeberAuto

        Yes, I was wrong. Thanks

    15. Ayoub Boulehfa

      Excellent video

      1. WeberAuto

        Glad you liked it

    16. Didža Nazis

      Damn, those bearings!

      1. WeberAuto

        I thought the same thing

    17. Johan Grimm

      Hi prof. Kelly. Very interesting! Thank you! Have you seen this (deep dive but very short) kgup.info/get/lqqJk2y7q2yEnqU/video

    18. Philip Quinlan

      Excellent presentation. Thank you.

      1. WeberAuto

        Glad you enjoyed it!

    19. Mariusz Zaleski

      Another Wow!. High quality material. Thank you for sharing

      1. WeberAuto

        Glad you enjoyed it

    20. Sam Ehlers

      Thanks so much!

      1. WeberAuto

        You're welcome!

    21. Rudolf Wickond

      250 km/h ? That's fast enough on the Autobahn ... unless someone is in a hurry.

      1. WeberAuto

        True, Thanks for watching

    22. Amundsen

      Wow , excellent break down and analysis, SKF is a world leader in bearing technology, and the engineering and sophisticated machining required in this 500Hp power train is quit impressive to say the least. Fantastic explanation.

      1. WeberAuto

        Thank you very much

    23. Greatest Evar

      bet that motor survived the fire just fine.

      1. WeberAuto

        Everything survived that was not plastic or nylon

    24. JagiChan

      Wow, that is some serious engineering; and you did a fantastic job in explaining the whole drive train and the various components. Appreciate the amount of time and effort you dedicated to making such a great video.

      1. WeberAuto

        Thank you very much

    25. Learn Progress

      Is the lucid are motor better ?

      1. WeberAuto

        I haven’t seen one yet

    26. Lucian Mihai

      Would have been interesting to see the winding and inside of the rotor

      1. WeberAuto

        Thanks for watching

    27. Lucian Mihai

      The bearing technology is that used in the CNC machines spindle.ceramic are the best and can rotate up to 18000 rpm. They limited it under 18000 in order not to have surprises.

      1. WeberAuto

        Thank you for the information

    28. T. W.

      You can actually hear the motor and transmission whine if you sit in the rear seats on Tesla Model S P series cars when driving top speed on the autobahn.

      1. WeberAuto

        Awesome!

    29. Michael Jennings

      to start, its a rotor not a motor

      1. WeberAuto

        Thanks, yes.

    30. niceguy60

      Wait, the Model S has gears ???

      1. WeberAuto

        Four of them per motor

    31. Vasile Cretu

      On the third differential /gear box, there are 8 bolts, not six! ;)

      1. WeberAuto

        Yes, thank you. I was wrong

    32. Hank Hall

      SKF website (www.skf.com/caribbean/products/rolling-bearings/engineered-products/hybrid-bearings/permissible-speed) says rpm of silicon nitride bearings is limited, their equation gives rpm < 250000/(mean diameter of bearing). Estimating dimensions from your video it appears to me that the 17,900 rpm you mention for the motor is much higher than this limit. Correction: this comment is for grease lubrication.

      1. WeberAuto

        Thanks, I too was confused at first, but then I found the section of the catalog explaining how to safely exceed those limits. Thanks for watching

    33. Aaron Schwarz

      Thats a very complex cooling system // but keeping electronics & transmission oil cooler makes both last longer //

      1. WeberAuto

        Yes it does

    34. Aaron Schwarz

      20:16 there is something magical, no rare earths (china controls) permanent magnets (NdFeB etc) // induction motors are cooler than IPM for this specific reason & can be much much less expensive to make //

      1. WeberAuto

        Thanks for watching

    35. Huw Williams

      On the latest models there's something called the 'Octovalve' to manage the cooling systems as I understand it. It would be interesting to see how that works, because it is apparently unique to Tesla.

      1. WeberAuto

        Yes, coming soon. Thanks for watching

    36. your wife's boyfriend

      Wow such a simple motor.

      1. WeberAuto

        It sure is! Thanks for watching

    37. your wife's boyfriend

      Why didn't they just use 2 gears? 😐 why have not just have the differential gear contact the motor gear directly? Its both 78/25 isn't it?

      1. your wife's boyfriend

        @WeberAuto so basically just adjusting gear size will increase acceleration & torque?

      2. WeberAuto

        It would need to have gears with sizes relative to being in first gear on a chain driven bicycle. The gear that turns the wheel would have to be gigantic to get the same gear ratio as we have now with two sets of smaller diameter gears.

      3. your wife's boyfriend

        @WeberAuto how? Why? I don't understand 😕

      4. WeberAuto

        It keeps the gearbox size smaller

      5. your wife's boyfriend

        If less gear = more torque, why not just use 2?

    38. Buzz Pedrotti

      Fascinating. Thanks.

      1. WeberAuto

        Glad you enjoyed it

    39. Jon-William Murphy

      Crazy to me that the stator is welded to the other drive unit housings. I'm thinking about eccentricity, warp and tolerance issues, how did they get that to work? At 39:10, I'd call those pin fins. But buttons is definitely cuter.

      1. WeberAuto

        Good points, pin fins does sound better than buttons, lol, thank you!

    40. THE16THPHANTOM

      he uses mixed metric and imperial units... that's kind of a super power(to me). i could never get the feel of size with out translating one to the other.

      1. WeberAuto

        Thanks for watching

    41. kyimedical

      You can call nodule for those aluminium lump to increase surface area of coolant chamber ,

      1. WeberAuto

        Thanks

    42. Kimche TV

      PREPARE SHIP FOR LUDICROUS SPEED...lmfao i say that every time i drop the hammer...

      1. WeberAuto

        Lol. Thanks for watching

    43. A B

      Damn i wanna watch but his breathing is so disturbing to hear omg.

      1. WeberAuto

        Thanks for the feedback

    44. שמעון קופפרמן

      I must mention that I enjoyed every second of your video!! You explain excellently (even though I do not really speak English)... I'm glad you're recording with a microphone at a constant distance from your mouth - you sound great! And the video is really good and clear. Your effort and investment is evident in every detail! What could I have asked for more? Wish you the best! And glad to see such videos. I also sent to some friends.

      1. WeberAuto

        Thank you very much

    45. craigslist04

      John, another well-done presentation with great lighting and camera angles. You and Jack Rickard would have made for an awesome collaboration.

      1. WeberAuto

        Thank you very much

    46. Fedupwithfed forever

      So what ......I..... Will say ...as much as I'm against tne Uber lib Elon Musk and his TESLA....I DEFINITELY WILL...praise his company for his Quality that's put into the product his products......!

      1. WeberAuto

        Thanks for watching

    47. sarastro60

      Mr. John Kelly, I am writing to you from Argentina. I thank you for such a didactic explanation of the operation of so many mechanical and electronic-mechanical systems. I would like to know what is the voltage in volts and what capacity in ampere hours of the Tesla battery output which you refer to as high voltage. Thank you very much and best regards.

      1. WeberAuto

        You are very welcome. The fully charged battery is about 400V DC. It is a 90kWh battery, so 90,000 Watts / 400 V = 225 Ah

    48. Vita Quasus

      Best explanation of Tesla Motor I have ever seen. Thanks for this, it was informative and succinct.

      1. WeberAuto

        Glad you enjoyed it!

    49. TIYOL56

      this is goood stuff.

      1. WeberAuto

        Thank you

    50. Wolverine Windsor

      Magnificent video

      1. WeberAuto

        Thank you

    51. Brian Fretwell

      I keep wondering what performance S performance. All motor perform so I can't get it.

      1. WeberAuto

        Thanks for watching

    52. THE ELECTRIC SIDE OF THINGS

      Thank you for such a great video you explained it very well and I enjoyed watching the passion that you have for this electrical vehicle

      1. WeberAuto

        Glad you enjoyed it. Thanks for watching

    53. Greg Hoyle

      Why doesn’t this require any routine maintenance?

      1. WeberAuto

        The magic of marketing

    54. Mingyar

      Tesla are over engineer. Just bought more stocks after watching this video

      1. WeberAuto

        Thanks for watching

    55. Old Skeptic

      ... with professional background in Mechanical Engineering and Electronics I would like to thank you for this majestic presentation of the emerging technology... The makers of this car could have done it in a 'flashier' manner, but not with such a careful, detailed approach you have employed here.. Thank you, Sir..

      1. WeberAuto

        Thank you very much

    56. tadeusz czachor

      best videos

      1. WeberAuto

        Thanks for watching

    57. Kristian Jonsson

      Truck bearing on a passenger car differential!

      1. WeberAuto

        Thanks for watching

    58. Chrisso

      Wow and wow again! Does this professional professor know his stuff! Truly an icon on teslas and other motors i would have to say! Truly professional! Aussie Chrisso 🥇🏆

      1. WeberAuto

        Wow, thanks!

    59. fawzy moussa

      thank you , you are great,

      1. WeberAuto

        So nice of you

    60. Xavier Garonnat

      Great video. Is it the same motor or at least same technology on Model 3 ? If yes on which version/year ? Thanks.

      1. WeberAuto

        Not for the rear motor of the model 3, this is different. The front motor of the Model 3 is similar to this one, but much smaller.

    61. miguel goizueta

      Whoever designed this, deserved....What ???

      1. WeberAuto

        Thanks for watching

    62. Pulkit Jain

      Great. Now I just have to figure out how to make rest of the car!

      1. WeberAuto

        LOL, yes, me too

    63. Richard Wallinger

      My 1950 Westland Scout helicopter gearbox also used spray lubrication for the gears . I adopted this SECRET lubrication on my radio controlled model turbine helicopter .. Originally I attempted to tun oil bath lubrication which effectively fried the oil and overheated the gears due to hydraulic drag . Great video and super professional presentation .

      1. WeberAuto

        Very interesting, Thanks for watching

    64. watchinglosersagain

      So what he is saying at the beginning is that Tesla's balls are bigger than everyone else's.

      1. WeberAuto

        LOL, Thanks for watching

    65. Petter Nygaard Hansen

      Very good! My Tesla do 0 to 100km/h on 2,9 sek. No overheat, no vibrations, just 275km/h !

      1. WeberAuto

        Very cool!

    66. René V1971

      Very interesting and nicely explained!

      1. WeberAuto

        Many thanks!

    67. Mike Nelson

      Thank you for this enjoyable video . A clear presentation. I am in the process of expanding my limited knowledge and understanding of how EV's work and are built. This is a bit difficult for an old fart like me , but very, very, interesting and enjoyable journey. So, again, from an old bloke in Australia, thanks.

      1. WeberAuto

        Thanks for watching!

    68. Gsacni

      Thank you for an excellent presentation. Well done! It does however begs the question.... how did the car catch fire..? Was it related to the electronics and/or overheating of something in the motors..?

      1. WeberAuto

        Thanks, I do not know

    69. Gary Eisenzimmer

      Geart presentation.

      1. WeberAuto

        Thank you

    70. Girth Quake

      I'll be super interested to see the internals of not only the front motors, but also the core differences between the SynR Model 3 motor and the permanent-magnet based S motors. Great to see these layed out like this; I see where the motors needed "refinement" based on secondhand details of their performance limitations and where the coolant would leak prior to those bearings being replaced with those ceramics.

      1. WeberAuto

        No, the AWD model 3 still has an induction motor in the front. The model S still has an induction motor in the rear. I think they use the induction motors for maximum performance and the PM Synchronous reluctance motors for economy. I suspect they can use just one motor during steady state cruising. I am still investigating that theory.

      2. Girth Quake

        @WeberAuto Really? I wonder then if Tesla has completely switched motor production to a SynR type of AC motor; makes sense for economies of scale and parts sharing.

      3. WeberAuto

        Thank you. It is my understanding that the 2019+ Model S front motor and the Model 3 rear motor are the same unit.

    71. Not The weeknd • 25 years ago

      I will always much rather prefer the classic petrol/diesel engines, I can’t get enough of carburetor technology.

      1. WeberAuto

        Thanks for watching

    72. Jorge Suarez

      Good info. Your providing an incredible resource for us techs in the field. What do you think about the GM 2ml70 ECVT transmission?

      1. WeberAuto

        Thank you. It looked on paper, but it was so heavy that it almost made the whole hybrid project useless. They told us in the factory training class in Burbank, CA that they had to add aluminum body panels and improve aerodynamics to get an actual improvement in fuel economy compared to the non-hybrid.

    73. Richard S

      Very, >Excellent< explanation of this Model S Performance Motor..

      1. WeberAuto

        Thank you very much

    74. MFA

      28:28 the ball's expand... can cope with that...there are only 2 of them...

      1. WeberAuto

        Thanks for watching

    75. Krzywoprostydezerter

      They could use ceramic bearings because it is an electric motor, there are no vibrations or any loads from the crank and piston system. They have a higher allowable RPM and generate much lower rolling resistance. The density of the oil may be lower, so it is easier to cool it down. This is a well-engineered engine design. For maximum performance, the reducer also uses ball bearings, lower resistance and lower operating temperature due to lower pressures than tapered roller bearings. A nice thought-out drive ... simply. Great explanation, and great video Professor. Thanks. Greeting from Poland

      1. WeberAuto

        Thank you and thanks for the information

    76. FamilyFirstJ

      Incredible

      1. WeberAuto

        Thank you

    77. Michiel van der Meulen

      It feels strange two gears in the same box have an identical tooth count.

      1. WeberAuto

        @Michiel van der Meulen Yes, we call those "hunting gear ratios." That is very interesting

      2. Michiel van der Meulen

        @WeberAuto In printing machines one sometimes uses whole number gear ratios to have errors repeat over themselves. But then the consequences for wear and possible vibrations are taken for granted deliberately. Interesting.

      3. WeberAuto

        I thought the same thing. It works well

    78. Kim Hansen

      Great video, even for a non-engineer.

      1. WeberAuto

        Thank you

    79. CW Science Projects

      I have watched many of Professor Kelly's videos. They are well presented, informative and easy to understand. As a gear design engineer with many years experience on off-road vehicle gears I can make following comments 1. Model S final drive gear face width could be wider than required for durability or torque capacity. When the helix angle is low, more face-width is needed for higher overlap ratio and quietness when running (possible explanation) 2. Size of diff carrier bearings. Many times the half shaft spline size required for it's strength under side gear dictates size of bearings rather than load carrying capacity . Also the special bearing type might have a lower capacity than the standard type. Thus requiring a larger size bearing (possible explanation) Please continue making these videos - Good luck

      1. WeberAuto

        Thank you very much!

    80. Bob de Bruin

      Excellent quality video and content

      1. WeberAuto

        Glad you enjoyed it

    81. James LaRoche

      OooOoOooo! I clicked this super fast!

      1. WeberAuto

        Thank you for watching

    82. Johnny Voo

      Isn't that eight bolts at 6:18

      1. WeberAuto

        @Johnny Voo Thank you

      2. Johnny Voo

        @WeberAuto OK. Very good video. Thanks.

      3. WeberAuto

        Yes, I was wrong

    83. turk 182

      DID you read the small print? You are not aloud to open the gearbox. A Law suit is coming your way so make sure your hole is greased up good because you are in for a roller coaster of a ride.

      1. WeberAuto

        Lol. I guess not

    84. Paul Keith

      Two in a car, from different households, but not wearing masks. Different rules of course.

      1. WeberAuto

        Thanks for watching

    85. Alouis Schäfer

      The quality of their Drivetrain Components set the standard for everybody else. I hope they will apply that to commercial vehicles in the future because that is where the focus of the EV World should be. There are some potential issues in my opinion: -The oilpump setup looks very flimsy and cheap compared to the other components. Also the lack of an actual oil filter should be noted down. Sure the magnet will catch most of the worn off metal but pretty much all modern transmissions have a dedicated oil filter so why not Tesla? -Having multiple compartments with different fluids in them is a potential weak point. So I hope Tesla did their homework and used long lasting high quality seals. Failing seals are the Achilles Heel of any vehicle.

      1. WeberAuto

        It is impressive. Thanks for watching

    86. Henry Chen

      I disabled my adblocker and watched the entire ad for you. Keep it up!

      1. WeberAuto

        Thank you!

    87. Wilderness Music

      Maybe we should look at the bearings of the Kawasaki Ninjas of the year 2000. My 250cc Ninja had a redline of 14,000 RPM. 20 year old technology.

      1. WeberAuto

        Amazing technology! Thanks for watching

    88. Steve Brewster

      Great detailed explanation for somethiing not many of us electron heads get a chance to pull apart. Thank you for the insights.

      1. WeberAuto

        Thank you very much

    89. Darren Hwang

      1.25x speed playback is just right

      1. WeberAuto

        Thanks for watching

    90. Brandon Yarber

      8 bolts

      1. WeberAuto

        Yes, thanks, I was wrong

    91. mdimascio

      Great presentation and detailed analysis!

      1. WeberAuto

        Much appreciated!

    92. Sherman Morgan

      I really enjoyed watching the video. Very well presented. Thanks for making this very informative video.

      1. WeberAuto

        Glad you enjoyed it!

    93. D U V A C H

      kgup.info/get/enmgYoLHe4dil4s/video

    94. Dessin animé

      Excellent approch for E motors thanks . What does FSD tesla cars work ?

      1. WeberAuto

        Thank you. FSD is not my area of expertise.

    95. Drone.Camera.Action

      Would love to see a model 3/Y video to see the difference, especially as this is the future..

      1. WeberAuto

        Coming soon

    96. Sanket Devle

      Very nice video with detail information about powertrain.

      1. WeberAuto

        Glad you liked it

    97. Ancillary Sword

      Incredibly informative!

      1. WeberAuto

        Thank you

    98. John Henry Holiday

      Would You buy a Tesla ???? Im tempted and Im not "green"

      1. WeberAuto

        Yes

    99. John Henry Holiday

      Awesome.... Tesla in theory could go forward and reverse at 155 MPH.... that could be really fun....

      1. WeberAuto

        Thank you. It would be fun

    100. Garry Perrin

      Super cool, informative video Professor.

      1. WeberAuto

        Thank you!