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Tesla's nerds are out of control -- In a good way

I've gotten into the habit of RainX'n my windshield on new cars. The MS has been a blast to drive so I got around to doing it this morning with about 500 miles on the clock. While wiping the RainX on I noticed a bend in the front glass. It was not the normal curve of the windshield but a deliberate bend from the vertical to more horizontal about four inches or so from the top of the glass. This subtle change in direction of the glass was surely designed to keep flow attached as the already raked windscreen transitioned into the roof line.

For anyone that has done FEA or wind tunnel flow analysis you will understand just how neat it is that Tesla chose to add another dimension to the compound curve of the wind screen in an effort to keep flow attached. Those guys are some serious nerds and that is a good thing where I come from.

@lolachampcar | FEBRUARY 12, 2013: I've gotten into the habit of RainX'n my windshield on new cars.

I used to Rain-X my windshields too, but now I've switched to Aquapel (http://www.aquapel.com). It lasts much longer than Rain-X (about 1 year for me) and doesn't interfere with the rubber on the windshield wipers.

Oh, and to stay on topic, I notice the hump on the windshield each time I clean my windows. I was wondering what that was for?

Airflow?

Could this curve explain the "stress fractures" in the windshields?

Brian H,

Sorry, airflow... Too much slang.

bsimoes,
I would not think so. All windscreens are curved so building curved laminated glass is not a problem. From a mechanical standpoint, compound curves strengthen structures so the added detail probably made it stronger. There is the (very) off chance that having curves in two different directions would "trap" the inner layer and allow stress to build on thermal expansion but I'd give that about a 0.1% chance of being the case.

Normally rocks cause cracks and they happen all the time, especially in the NE.

Would this make a replacement windshield significantly more expensive?

Obviously it would have to be OEM, but that would be the same for any car with such low numbers.

Don't know it the process for making compound curved glass would be much more expensive.

According to Tesla, the stress fractures were as a result of some issues with the install. I believe, but can't find the post, it referenced some issues with the robotic pressure and/or positioning.

I'll have to check out the aquapel product.

I don't believe it's a manufacturing issue IMO, as there have been reports of "people being on their third windshield", where the the latter two were not installed by robots but real people at the service center.

Most have reported the cracks occurring after a cold night and they are surprised by them in the morning. I think it is thermal stress caused by the high expansion of the alumiunm frame relative to the glass, and a mounting scheme that is not compliant enough to accomodate this. The curvature of the glass compounds the problem as the frame contraction creates bending stresses, similar to if you squeezed the windshield from both sides with a giant vice.

I was told last week by a TM employee that an "investigation was in process." I think they need to look at the low-temperature elastic properties of the adhesive that bonds the glass to the aluminum frame, and its thickness. There needs to be a more compliant connection between the two materials.

Just my opinion!

GAS;
Good WAG! Forgot about aluminum expansion. That definitely changes the picture.

Well thanks but I did use the word expansion once when I really should have used "contraction". However, if I'm correct this might be a problem at high temperatures also, but if the adhesive was cured at room temperature (say 70F), then the temperature delta is potentially greater with cold weather. Additionally, the windshield adhesive will get more pliable at higher temperatures which helps mitigate the "vice" effect.

Jeez I sound like a real nerd. :(

@GAS -- in a good way.

Yeah, cold→contraction, hot→expansion. I knew that. >:/


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