Speedometers

[gerti]

I waiting for the day, when you buy a car and instead of the conventional instrumentation, you'll find an I-Pad plugged in. The driver will configure the instrumention to suit their own taste and it will include several choices for custom panels, including phone, GPS, etc.

A couple of weeks ago I was at the Doctor's office (he's a pilot) and there were several copies of AOPA magazine there. If I was interpreting the articles correctly it's not only feasible, but actually in use, I think they referred to it as a "glass cockpit". IIRC Burt Retan employs something similar in one or two of his designs. Not sure if it's actually an I-Pad, or something similar.

Tesla displays are all LCDs and can be reconfigured (within reason) by the user. Teslas also read speed limit signs and indicate the current speed limit with a red line on the speedometer.

[twistsol]

My 2014 Sierra truck has fixed instruments for the speedometer and tachometer, everything else is virtual on the display between those and there are half a dozen different dash styles. (Don't play with the settings while driving) I discovered this weekend when a trailer is plugged in, an additional "dial" shows up on the dash for transmission temperature. It's funny to see the virtual dials go through the traditional end to end range sweep test when the truck is powered on. I guess they're making sure there aren't any stuck pixels.

A big annoyance with our Volvo is that the speedometer seems to lag. Coming into town, you let your foot off the gas to slow down to 30 and the reading stays at 55 as the car is slowing down and then suddenly drops to 40 both on the analog and digital displays. The same thing happens as you slow to a stop. It reads 10-15 MPH then suddenly drops to zero. Not a big problem until we plugged in that driving monitor thing from Progressive. It kept recording "hard braking" and beeping each time and thus no discount for us.

[atgcpaul]

There are Apps that can be downloaded that do "some" instrumentation for you on the iPad and iPhone; Altitude, speed, distance traveled, time traveled and more.

I would love a HUD on my windshield. It would be even cooler if you could overlay GPS navigation onto the whole windshield almost like you were in a driving simulator. It seems like we're moving more and more towards self-driving cars. A totally aware car would not only identify the "threats" in front of you, but also identify cars/people/animals that are approaching perpendicular to you and react accordingly.

Tesla displays are all LCDs and can be reconfigured (within reason) by the user. Teslas also read speed limit signs and indicate the current speed limit with a red line on the speedometer.

There is a Tesla mini showroom in one of our local malls. My wife is totally in love with them. Not really because of the eco aspect but they are a beauty to behold. She says to me, "I like the S type, but I'll wait for their SUV to come out. It'll be more practical with the kids and dogs." I just looked at her like, Yeah, right, when I win the lottery.

[sailor55330]

Spedometers have accuracy problems. The problem is that they are dependent on wheel diameter and revolutions to determine the distance traveled.
the larger the diameter the farther it travels on one revolution. But they can only count revolutions and depend on assuming the tire diameter.

My tires are 225/55 R17.
http://tire-size-conversion.com/tire-size-calculator/
says that the diameter of the tire is 26.7", the circumference is 84 inches and turns 754.5 revolutions per mile.

However a tire has 10/32" to 11/32" of tread when new, you're supposed to replace it when down to 2/32 but some people drive til its bald.

So there's a difference of as much as 11/32" in radius and twice that in diameter when new vs old. That's a 2.5% difference in the diameter of the tire.
Furthermore there's the conundrum of inflation and load flatteneing the tire some, decreasing its effective radius. I don't have a figures on that but if its on the order of 1/2" due to load and inflation then variation the change can be another 3.7%

So I can account for a possible 6.2% error in spedometer readings just there alone and that assumes that the spedo is absolutely correct, I suspect they use a spedo with only approximate gearing to indicate correct speeds given the range of tire sizes and differentials available for vehicles. The same inaccuracies apply to your odometer.

I've had some cars that were right on and other cars which were 3 mph high at 60 mph. According to GPS and to time measurements on mile markers on the highway.

GPS will be much more accurate for instantaneous readings.

Now that's how an engineer responds......

[sailor55330]

My Volvo is 100% LCD for all gauges. I hate it. The speedometer is accurate by GPS, but there are no temperature gauges, only idiot lights and the gas gauge is just a series of bars. There is no way to tell when you are about to "drop down" a bar. On the flip side, the distance to empty is pretty much dead on. I ran it down once till there was about .8 gallons in the tank. The onboard computer said I had 20 miles till empty. I average about 25mpg.......not too bad

[JimD]

A way to get virtual gauges is with the Torque application. About $5 but you also need an OBDII to Bluetooth adapter, about $20. You can have a gauge for anything your car is measuring and you can choose the size and type of gauge. You can have several depending on the size. I did it on a tablet and could have 5 easily. It will also data log. And it reads and clears trouble codes.

I tried a heads up display when I drove a M5 and M6 at M school. It was not a normal driving situation but I didn't really like them. You still have to focus on them so when you do, you aren't really focusing on the road. Seems just as easy to look down slightly. They were also a little distracting since you can see the movement and want to look instead of at the road. Others really like them, however.