4 ms·

I'm going to go ahead and guess here that Tesla is going to have to give up on launching the 4,785 pound Model S to 60 mph in 4.2 seconds. There might not be a

I'm going to go ahead and guess here that Tesla is going to have to give up on launching the 4,785 pound Model S to 60 mph in 4.2 seconds. There might not be a possible gearbox that can do that for the life of the car and fit the cost/size constraints of a sedan. Another case of "just because its possible doesn't mean you should". It will be fixed with 3 lines of code (to create a gear friendly torque curve) and a whole lot of PR to explain it.

Tloewald 12y ago
Gearbox?
- noonespecial 12y ago
  Teslas have a single speed gearbox that reduces the electric motor down 9.7-something to 1. This is likely the source of the "milling" noise. These gears degrade rapidly at the insane torque levels of an electric motor starting full blast from stop. Something they would never face from their ICE brethren.
  - scott_karana 12y ago
    Seems like something that could be fixed by a software update. Static friction is the same in equivalent spec'd ICEs, so if the Tesla is overtorquing, wouldn't they be able to back off on wattage for a few ms when starting out, and retain virtually the same accelerations?
    - seanflyon 12y ago
      There are not a lot of equivalent spec'd ICE vehicles.
      - scott_karana 12y ago
        The BMW 550i[1] has very similar size, peak power, and peak torque ratings compared to the Tesla[2][3], so let's use that as a comparison. Obviously, torque availability at 0 rpm with a flat curve is the notable difference, but remember that launch control in the BMW will also occur at peak power RPMs with a clutch or torque converter taking up the difference in road "RPMs", so it's not that dissimilar a comparison at least in regard to the strength of gearboxes, half-shafts, differentials, axles, CV joints, et cetera. (Consider too that the BMW has changeable gears, not a fixed ratio; the complexity should give Tesla a nod for transmission strength) BMW 550i (base) vs Tesla Model S P85 Cost: $63,900 vs $87,070 Curb Weight: 4277 vs 4647 lbs Peak Power: 445 vs 416 Peak Torque: 480 vs 443 lb-ft 0-60 mph: 4.5 vs 4.2 seconds Top Speed: 130 mph for both So I think my point stands; I suspect a software update in the Tesla could likely alleviate strain to the gearbox, without much tangible sacrifice in specs. I'm curious what "to the wheel" power looks like after the final differential ratio, but have to leave :) 1 http://www.bmwusa.com/Standard/Content/Vehicles/2014/5/550iSedan/Features_and_Specs/550iSedanSpecifications.aspx http://www.bmwusa.com/Standard/Content/Vehicles/2014/5/550iS... 2 http://www.teslamotors.com/models/specs http://www.teslamotors.com/models/specs 3 http://www.teslamotors.com/models/features#/battery http://www.teslamotors.com/models/features#/battery
        seanflyon 12y ago
        Thanks for the info. I think we can conclude that BMW is better at mass producing transmissions than Tesla. The BMW is only slightly lighter and slower to accelerate.

Tloewald 12y ago

Gearbox?

noonespecial 12y ago
Teslas have a single speed gearbox that reduces the electric motor down 9.7-something to 1. This is likely the source of the "milling" noise. These gears degrade rapidly at the insane torque levels of an electric motor starting full blast from stop. Something they would never face from their ICE brethren.
- scott_karana 12y ago
  Seems like something that could be fixed by a software update. Static friction is the same in equivalent spec'd ICEs, so if the Tesla is overtorquing, wouldn't they be able to back off on wattage for a few ms when starting out, and retain virtually the same accelerations?
  - seanflyon 12y ago
    There are not a lot of equivalent spec'd ICE vehicles.
    - scott_karana 12y ago
      The BMW 550i[1] has very similar size, peak power, and peak torque ratings compared to the Tesla[2][3], so let's use that as a comparison. Obviously, torque availability at 0 rpm with a flat curve is the notable difference, but remember that launch control in the BMW will also occur at peak power RPMs with a clutch or torque converter taking up the difference in road "RPMs", so it's not that dissimilar a comparison at least in regard to the strength of gearboxes, half-shafts, differentials, axles, CV joints, et cetera. (Consider too that the BMW has changeable gears, not a fixed ratio; the complexity should give Tesla a nod for transmission strength) BMW 550i (base) vs Tesla Model S P85 Cost: $63,900 vs $87,070 Curb Weight: 4277 vs 4647 lbs Peak Power: 445 vs 416 Peak Torque: 480 vs 443 lb-ft 0-60 mph: 4.5 vs 4.2 seconds Top Speed: 130 mph for both So I think my point stands; I suspect a software update in the Tesla could likely alleviate strain to the gearbox, without much tangible sacrifice in specs. I'm curious what "to the wheel" power looks like after the final differential ratio, but have to leave :) 1 http://www.bmwusa.com/Standard/Content/Vehicles/2014/5/550iSedan/Features_and_Specs/550iSedanSpecifications.aspx http://www.bmwusa.com/Standard/Content/Vehicles/2014/5/550iS... 2 http://www.teslamotors.com/models/specs http://www.teslamotors.com/models/specs 3 http://www.teslamotors.com/models/features#/battery http://www.teslamotors.com/models/features#/battery
      - seanflyon 12y ago
        Thanks for the info. I think we can conclude that BMW is better at mass producing transmissions than Tesla. The BMW is only slightly lighter and slower to accelerate.