Wind Tunnel testing

Aptera Community Aptera Discussions Wind Tunnel testing

Aptera Community Aptera Discussions Wind Tunnel testing

  • Wind Tunnel testing

     Eric Caldwell updated 2 weeks, 1 day ago 13 Members · 17 Posts
  • DIRK WRIGHT

    Member
    August 29, 2022 at 8:28 am

    Aptera has spent a lot of money on CFD simulations but have apparently not put any of their vehicles into a wind tunnel to verify the sim. So, claiming a Cd of 1.3 is ludicrous until they actually put real wipers on the vehicle, with real, usable side view mirrors, and stick into the wind and measure the Cd. For those crying that such testing is absurdly expensive, guess again. The price as of 2019 I think was about $20,000 per day. You only need one day to get a number.

    Kevin Harvick on NASCAR wind tunnel costs – Racing News

  • BigSky Country

    Member
    August 29, 2022 at 9:09 am

    I think there is a good reason for this and many would not like the answer. They have the theoretical right to claim a Cd of 1.3 until they get new data to the contrary. There are so many variables they are managing and it doesn’t help their marketing claims to get new information early and risk what they are able to claim today. I suspect once Gamma is released, it will be time to do that test since the production intent is established and, theoretically, all of those Cd variables will be locked. There is little value in running wind tunnel tests that may jeopardize the 1.3 Cd hype unti that point. I’ve had the same curiosity on the 100 Wh/mi claim based on all the different battery sizes/weights. I would not expect them to be equal which would bring into question whether they will adjust the battery sizes to meet the 600 and 1000 mile variants to pull the additional weight. Maybe the claim is based on the 1000 mile variant and the results are better for the smaller batteries, but such a conservative marketing claim is not typical. I’m expecting some clarifications as they learn more, but I would expect them to be in the ballpark of what they are claiming.

    • Jonah Jorgenson

      Member
      August 29, 2022 at 2:09 pm

      You stated the wrong Cd in your post. The Cd claim is 0.13 not 1.3. You are an order of magnitude off.

      Similarly incorrect, gamma is not production intent. The delta prototype is production intent. There is one more prototype to go to establish production intent.

  • Jason Seymore

    Member
    August 29, 2022 at 9:33 am
    • John Trotter

      Moderator
      August 30, 2022 at 2:33 pm

      Jason. A twelve-year-old publication may not reflect the current state of the art. Have you run across something more contemporary?

  • Alain Chuzel

    Member
    August 29, 2022 at 9:53 am

    Many a solar car race team have learned the value of full scale wind tunnel testing.

  • Dennis Swaney

    Member
    August 29, 2022 at 12:10 pm

    Why don’t you pay for it then? Oh, you need to do two tests: one with those supposed external mirrors and one with the default side cameras.

    • OZ (It’s OZ, Just OZ)

      Member
      August 29, 2022 at 12:52 pm

      Dennis, Aptera will have both physical mirrors and cameras mounted as the side mirrors for the first production models, and until such time as the laws can be updated to remove the requirement.

      • Dennis Swaney

        Member
        August 30, 2022 at 7:11 pm

        But if they do both tests now, it doesn’t have to be redone when Aptera no longer includes the physical mirrors. Personally, I plan on removing the physical mirrors myself after a short period to get used to using the cameras.

        • Harry Parker

          Moderator
          August 31, 2022 at 6:57 am

          Not worried about getting a fine during a safety inspection or being pulled over by a cop? Where I Iive the friendly cops will give you a ticket (or at least a warning) for that or for having a tail light out.

          • Dennis Swaney

            Member
            August 31, 2022 at 8:02 am

            Nope, as I’ll just point out the cameras as I explain the design features for efficiency. I’ve seen lots of cars on the road with busted side mirrors but never have heard of that being a safety problem. Of course if you are suspected of something like selling drugs, DWB, etc., they’ll use any excuse to stop you. I figure when the first Aptera appears on the road, it’ll be stopped frequently due to its uniqueness since most police are car guys & gals.

  • Mark Salyzyn

    Member
    August 29, 2022 at 12:50 pm

    It is possible to measure the Cd by getting the vehicle to speed and let it roll to a stop measuring the speed/decel/time and putting it into the formula or models. The computer simulation on the other hand is great for finding the rough spots to smooth them out for the finer details, but nothing is better than reality.

    The only issue with this approach for Aptera is the cutting of the drive current would lead to some high voltages coming back into the drive electronics leading to breakdown or arcing on the cables, I am sure that they can get help from Elaphe on this. Or use only one motor (rear, set it up as a non-permanent magnet synchronous motor and cut the field windings) to get it to speed and just wheel bearings elsewhere, on a mule. A _lot_ cheaper than a wind tunnel, and will give them the data they need and they can break the runs between modifications as they please.

    They can setup the drive for non-interference station keeping on the PM motors, but there will always be FUD if they can not free wheel. This is where Elaphe can help I am sure.

    NB: my company has software to do this on an Android phone. Done.

    • Harry Parker

      Moderator
      August 30, 2022 at 7:35 am

      Mark, what you propose is how you would measure the total drag on a vehicle, including rolling friction and aerodynamic drag. That’s a useful piece of information, however the Cd is only a part of the formula for the total drag. Also included in the total drag is the drag of the tires on the road, the drag in the motors and bearings, and anything else.

  • John Trotter

    Moderator
    August 30, 2022 at 2:39 pm

    Who cares? I mean, unless there is a change to the machine, let Aptera claim whatever they have SOME basis for. Computer models are actually pretty good for evaluating design options and that’s what is more important. Save the money, time, and distraction.

  • Vernon Michael Gardner

    Member
    August 31, 2022 at 9:19 pm

    Dirk you seem oblivious to what is going on in the industry. https://www.youtube.com/c/JulianEdgar Is one very good and inexpensive way to learn about drag, or maybe you could watch some Rupaul’s Drag Race. He is very funny and educational.

  • Eric Caldwell

    Member
    September 15, 2022 at 9:10 am

    Lightyear just reported wind tunnel results of its Lightyear 0, which has already seen units hit the road. If Lightyear waited until now, it’s fair that Aptera is waiting until at least the Paradigm Editions hit the road.

    (For the record, the Lightyear 0 came in at 0.175, making it the current placeholder for most efficient production car.)

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