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Cargo connection points on Model X mule rear/roof?

Discussion in 'Model X' started by AnxietyRanger, Mar 28, 2015.

  1. AnxietyRanger

    AnxietyRanger Active Member

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    #1 AnxietyRanger, Mar 28, 2015
    Last edited: Mar 28, 2015
    One things where several Tesla people have gone on record is working on a solution to be able to transfer skis on a Model X. Traditional roof racks are probably out of the question due to the falcon wings... so how could this happen? The issue being, with falcon wings rising up, there isn't room for the racks or the skis, let alone a skibox.

    The most literal hints we have from the November update: "The optional tow hitch will support accessories and racks to transport skis and bikes with the minimum effect on aerodynamics. We’re also working with the best rack and accessory companies in the world to have elegant carrying solutions ready for Model X customers next year."

    We know from mule sightings Model X's are riding around with (now estimated) 2" hitch receivers. This seems to make it possible to attach bike racks on the back, but of course it could - and indeed would judging by the wording of the November update - be a part of a ski-carrying solution as well. It seems likely this is where the carrying solutions will be focused on, but before going to that, let's still consider the roof as well.

    Judging by the design of the prototype and what we've seen of the mules, there is an area in the middle of the roof before the falcon wings that is solid. Also, between the falcon wings in the middle of the rear part of the roof there is solid roof, where the wings attach to. It doesn't seem unimaginable a front part of a roof-rack could be placed in the front of the car. There was some speculation around the time of the alleged Model X leakster here that it could have come from the accessory side of things. Perhaps not surprisingly, Tesla's comment of working with best rack and accessory companies in the world came out quite near that leak. To work with accessory makers, you have to share drawings - at the very least it seems plausible.

    But where could a rear part of a roof transport solution go? There does seem to be a little room after the falcon wings, before the rear window, which has been covered quite well in the mules (something to hide?). Could there be room for roof racks that perhaps only have connection points in the middle, wide enough for skis that remain between the two falcon wings? Something like this perhaps (don't mind the car in the pic, just the idea)?

    model_x_rack_idea.jpg

    However, as seen in the November update email image, the space between the two falcon wings seems tight when they are fully opened up. The doors would have to be able to adjust themselves to this. Could the sensors on the door (some noted suspicious ones in the image below) allow the falcon wing to open outwards mostly when roof-racks are in place, thus allowing a ski box - assuming sensors note enough space on the side of the car to open outwards?

    attachment.php?attachmentid=76024&d=1427461140.jpg

    A more simpler option, of course, would be that only one door is allowed to open when a roof-based cargo solution is attached and make the rack solution such that stuff can only be placed on one side.

    2015-Tesla-Model-X-rear.jpg

    Now, finally, coming to the rear part of the car, it seems most likely Tesla might simply go for a traditional hitch-mounted solution and nothing happens in the roof area. Perhaps the solution will not be any more complicated than this - seems perfectly possible:

    hitch_mounted_ski_rack.jpg

    However, Tesla focus on aerodynamics suggests they might try go above and beyond in this area. This brings me to the final point that has been made, the changes in the Model X mules in the rear spoiler area. Could they either include connection points for some more aerodynamically friendly carrying solutions and/or a spoiler that would help aerodynamics in the case of an attached rack? Spoiler pops up to direct air away from a rack or somesuch?

    attachment.php?attachmentid=76027&d=1427464464.jpg

    See here for a pretty high-res look at this rear area of a Model X mule:

    Picture 16 - Spied: 2016 Tesla Model X

    All this, of course, well in the speculation territory - but I thought summarizing the ideas being bandied around in one thread might help move the conversation along.

    I'm looking forward to hearing other points and ideas. :) Thank you.
     
  2. Fanatic

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    #2 Fanatic, Mar 28, 2015
    Last edited: Mar 28, 2015
    I think that the rear glass will stretch all the way back.
    I will try explain why.

    When air travels over the paint it will be X amount of slippery and when it travels over glass it will be Y amount of slippery. Term:Skin Friction
    Because of the air generating more friction when over paint it will slow the air over the last edge and it will push some air up. More downforce but more drag. Also if the design is vary streamlined the biggest factor becomes the skin factor.

    http://en.wikipedia.org/wiki/Drag_(physics)

    Don't think I made myself clear but, I guess I could just say it would generate less drag.

    Spoiler would just increase drag there is no way around it.
    Some kind of top diffuser is what one should consider if u wanna reduce drag. Makes the air travel in linear patterns causing less turbulens.
    http://www.autospeed.com/cms/article.html?&A=3061
     
  3. Seesaw

    Seesaw Member

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    Interesting never heard of skin drag, gives credence to the rumours that the Model S will be losing its metal roof and having a fixed glass roof standard (with panoramic sunroof remaining an option).
     
  4. Fanatic

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    Its just friction of the surface but when I read about it I saw the term and thought it was kinda funny. A all glass roof would be nice. Which is more expensive do you think? Shaped glass och stamped aluminium? I have no Clue but would think aluminium.
     
  5. Liz G

    Liz G P03056

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    If they go with an all glass roof they are going to have to find a way to deal with heat loss. My car with the pano roof is always colder in winter than my friends with a solid roof. Not usually a problem until you're hypermiling 200 miles in 8 degree weather at night. I've managed to get ice to build up on the piano roof.

    So glad they put in the Springfield Super Charger.
     
  6. Fanatic

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    Maybe Insulated glass with a gas gap between multiple glass sheets? Would make it more silent as well.
     
  7. AnxietyRanger

    AnxietyRanger Active Member

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    Skin drag - just goes to show what diversity a good conversation can bring, something none of us could do alone. Great stuff. :) And indeed, it seems Model X may ship with an all-glass ceiling. Maybe this is why. Now, about the glass continuing all the way to the edge of the trunk cover, nothing in the photographs supports but also nothing prohibits that possibility - so very much a possibility, of course.

    What, I think, could support a spoiler there (hey, they could make it a thin glass spoiler...) is the potential need to add downforce at certain speeds for safety. What reduces drag and adds range on certain speeds, may also result in too little downforce on higher speeds?

    - - - Updated - - -

    Nothing would stop them from offering a glass roof (less friction on top) with fixed/covered/insulate interior option (less heat loss), though.
     
  8. Fanatic

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    Im not a fluid dynamics expert but what I would think is the best way to introduce more downforce is too make the whole shape of the car like an upside-down Airplane wing. That wouldn't increase drag in the same way as an spoiler and would increase downforce with higher speeds. Think of a spoiler as piloting an aircraft with the flaps down the whole time. A car is just like a "2d moving" airplane.

    I think that Mr.Musk would have a little knowledge about how to make a window that won't release to much heat in the cold and won't trap that much when sunny. Pretty essential when in space:p
     
  9. AnxietyRanger

    AnxietyRanger Active Member

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    True as that may be, could there be other reasons to avoid alternative solutions?

    After all, in very recent years when drag and CO2 have been very real issues worked on, at least three major car companies have introduced new car models that are not really sports cars, but with automatic spoilers: Porsche Panamera, Audi A7 and BMW 3 GT. Being able to lower the spoiler allows avoiding the drag it might create, while allowing raising it as necessary (depending on speed) for safety. If these companies are doing it, maybe Tesla would consider it too.

    It might be as simple as not wanting to introduce some fixed wing on top of the car for design reasons (like on more boxy SUVs), or more complicated, such as a wing not being effective if the rear isn't sloping fast enough - like it would on a traditional, boxy SUV - but instead is long and curvy, like on a coupe or coupe-like SUV/CUV.

    Mind you, I don't know if Tesla are adding a spoiler, your theory might well be right. But I'm not so convinced a spoiler would be something they could not at least consider enough to test on a mule... :)
     
  10. Fanatic

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    In low speeds lowering a spoiler may reduce drag but its in high speeds you really wanna reduce drag. When speed doubles drag increase by a factor of 4. Drag equation - Wikipedia, the free encyclopedia. Therefore a low speeds energy consumption is largely of the friction of the wheels and drivetrain when speed increases the drag is more prominent. Thats why Hypermilers drive so slow.

    Love this quote from Elon. "Physics is a great framework for thinking."
     
  11. AnxietyRanger

    AnxietyRanger Active Member

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    Fair enough, fair enough... But what if the spoiler is only needed for very high speeds? There, so that Tesla can safely say it can run at 150 mph on a German autobahn? Not there for normal driving - at normal motorway speeds it could stay lowered. Maybe only a Performance model feature.

    Moving away from Tesla Model X for a moment, or what they may or may not do, any thoughts:

    Why do car companies make new car models with automatic spoilers? Are you suggesting they don't care as much about drag or don't know what they are doing? :)

    I must say I haven't read nearly enough into the likes of Panamera, A7 and 3 GT to know the exact thinking behind their lowering spoilers, so I'm genuinely interested to hear.
     
  12. Fanatic

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    #12 Fanatic, Mar 28, 2015
    Last edited: Mar 28, 2015
    Because it looks cool and looks high tech and sporty and like the true sports cars where they can change inclination with higher speeds. But as for performance it would be better to have a more aerodynamic body with better weight distribution. The only reason as I see for having a spoiler is that you have a body shape that generates lift and to counteract this you need a spoiler. Lift coefficient - Wikipedia, the free encyclopedia is to high.

    Im wondering if Tesla is considering Gorilla glass on the cars.
     
  13. Saghost

    Saghost Active Member

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    Gotta say, I'm really surprised that we haven't gone to the pictures in over a page of discussion - especially since you linked a picture from the same set in the first post but focused on the lower hatch area. If you look at any of the pictures of the roof/falcon door interface, you'll see that the doors on the Mule aren't very close together and the hinge lines aren't parallel to the centerline of the car. Look here:

    Picture 17 - Spied: 2016 Tesla Model X

    model-x-spied-17_653.jpg

    You can clearly see a tapering gap between the doors - lots of real estate on the roof that isn't moving and could easily support a rack. Rear bars would have to be elevated enough to fit into the pocket between the falcon doors and the rear hatch if they aren't going to compromise the ability to open one, but the attachment won't be a problem.
    Walter
     
  14. AnxietyRanger

    AnxietyRanger Active Member

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    This, of course, what I suggested with this picture - red being roofracks, blue being skis (the car in the picture is not X, but it is representing it):

    attachment.php?attachmentid=76123&d=1427534531.jpg

    That said, I wonder how well it would fit when falcon wings open - unless the falcon wings use sensors or some such to steer clear by not opening fully.

    tesla-model-x-note.png
     
  15. Saghost

    Saghost Active Member

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    What I was attempting to point out is that the cutouts shown on the mule cannot match the geometry shown in the picture on the letter. There's at least eight inches between the front edges of the doors, and possibly more like a foot.
     
  16. AnxietyRanger

    AnxietyRanger Active Member

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    While that certainly seems true on the roof when the doors are closed, my point was couldn't the double hinge mechanism move the doors closer together in an opened position - as seems to happen on the November update image?
     
  17. Saghost

    Saghost Active Member

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    I would expect to see a gap at the roof level in that case, which isn't in the image. Complicated hinges seem unwise when supporting massive doors over people's heads, and are also likely to intrude into cabin space and add weight.

    What benefit would Tesla get from them that could be worth the cost, weight, and complexity?

    I think there's a fundamental disconnect between the image from the letter and the test mule - In my opinion they are quite clearly different configurations.
     
  18. AnxietyRanger

    AnxietyRanger Active Member

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    I base my assumption on the fact that the original Model X prototype had falcon wings that, when opened fully, intruded over the roof in the middle significantly lessening the free space that remained between them. The November update image seems to have the new style falcon wings of course, yet they seem to behave in a similar fashion as the original prototype in this regard. I have no reason to expect this behavior has changed from the prototype?

    The reason it works this way probably has something to do with keeping it sealed tight when closed and protection from rain when opened. They can't just put a door hinge on top of the roof that would simply open straight up...

    The way the hinges work and the roof is shaped, seems to allow wider room between the doors in the front of the wings than the back, but for storing skis etc. between them, it is of course the smaller side that dictates what fits...

    model_x_prototype_falcon_wing_open.jpg

    ---

    While we're at it, this old concept from TMC is nice:

    attachment.php?attachmentid=43497&d=1392672042.png

    Some discussion on TMF over it: Roof Rack and Falcon Doors | Forums | Tesla Motors
     
  19. Saghost

    Saghost Active Member

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    That's what I've been thinking for a while, though perhaps without the bolts. I expect that the doors will have motors driving both hinge joints, and the outer joints will be able to swing further outwards as well as the inwards they demo'd. You'd need a lot of space next to the car to open the door this way, but it looks like they've put sensors on the doors so the car knows if there is enough space - and if the space is a little tight, it could open the door partway and you duck under it - not really much worse than a conventional door in a tight space.
    Walter
     
  20. Gerasimental

    Gerasimental Member

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    #20 Gerasimental, Mar 28, 2015
    Last edited: Mar 28, 2015
    Can't say this for sure without running some basic CFD, but I think it's highly unlikely that the roof will be made of glass for skin friction reasons.
    Skin friction coefficient, Cf, is not that different for flow over glass or treated metal at these conditions. Plus, the area that would have metal replaced by glass is pretty small. Again, I can't back this up with numbers, but my engineering intuition tells me that skin friction didn't really come into the material selection.

    I like the idea of vortex generators on the trailing edge, but there seems little point in them so close to an abrupt corner at which the flow will inevitably separate anyway. However, a VG that close to the edge would add some vorticity that would tend to redirect the flow downwards after the edge, leading to quicker re-attachment with flow coming from below the car?


    [FONT=Verdana, Arial, Tahoma, Calibri, Geneva, sans-serif]In fact, I just looked at the pictures again and the rear has a very aggressive diffuser at the bottom as well, so it looks like they are really trying to make the rear as slippery as they possibly can. This car will have an absolutely absurdly low Cd for an SUV and I think it will beat most sedans/coupes.[/FONT]

    [FONT=Verdana, Arial, Tahoma, Calibri, Geneva, sans-serif]My new favourite: They're vortex generating pads that sit so close to the rear so that the flow turns down after the edge, but without the cost of adding skin friction because there is at (almost) no point turbulent flow actually passing directly over the surface. Combined with the aggressive rear diffuser this gives the car a nearly spherical rear, from an aerodynamic point of view.


    Disclaimer: take with many pinches of salt, I'm just having some fun here and indulging in our analysis/guessing game.[/FONT]
     

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