As a simple quick check at home, sort of like checking the oil dipstick, is
the accuracy & repeatability of a smartphone yet sufficient to check
automotive camber?

On Fri, 24 May 2019 21:00:25 -0500, Elder Jones wrote:
As a simple quick check at home, sort of like checking the oil dipstick,
is the accuracy & repeatability of a smartphone yet sufficient to check
automotive camber?

I'm sure it depends on how accurately you park the vehicle on the phone. :-)

Jon
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It seems that recently said:

I'm sure it depends on how accurately you park the vehicle on the phone. :-)

The three measurements that we need to accuracy & precision of about a
tenth of a degree are caster, camber, and toe.
o Caster is a function of camber at ±20 degree angles
o Camber has a range of from 0 to about ~±6° ~±10'
o Toe has a far smaller range of about 0.05° to about 0.1° per wheel
[https://blog.bavauto.com/11758/bmw-a...wear-diy-kit/]

Since toe can be more easily measured linearly, only tenths of a degree
accuracy & precision would be required for measuring Caster & for
calculating Camber.
[https://forums.bimmerforums.com/foru...eel-Alignment]

For toe, we can obtain linear equivalents simply by converting a factory
given front total toe spec of 0°5'±10' and a factory given rear total toe
of 0°22'±4' to a non-angular linear distance given just the tire diameter
a. P235/45R17 = (235)(2)(0.45)(1/25.4) + 17 or about 25.3"
b. Factory total front toe = 0°5'±10' & factory total rear toe = 0°22'±4'
c. Toe from tread centerline to vehicle centerline is half that
d. Individual toe to centerline is 1/2 of 0°5' = 0°2.5' (halving may not be needed though)
e. 0°2.5' divided by 60' is ~0.0417 decimal degrees
f. 17" diameter rims * tangent ~0.0417° = 0.0124"
g. 0.0124" is roughly about 3/256ths" (or about 0.3mm)
[https://www.bmwcca.org/forum/index.p...nt-specs.979/]

The rears, calculated similarly, would be ~0.33" for total toe in.
[https://robrobinette.com/ConvertToeDegreesToInches.htm]

We could also use the sine instead of the tangent if we consider the radius
of the tire to be the hypotenuse (the linear measurements are likely to be
taken at right angles to the centerline of the car, or an imaginary line
through the steering axis parallel to same) not at right angles to the tire
centerline; but at these tiny angles sine and tangent are basically the
same anyway so that makes no significant difference where the major linear
measurement error is likely in the gravitational bowing of the typical tape
measure. Hence the toe measurement accuracy & repeatability is due more to
the fact that the tire isn't very large, and the factory-specified angle is
very small, causing even a miniscule difference in distance with the tape
measure to translate to a fairly large portion of the angle.
[https://forums.pelicanparts.com/pors...ees-help.html]

Given that both toe and caster can be derived from other measurements, the
only question at hand is for Camber degrees to be measured by a smartphone.

For Camber, tenths of a degree in repeatability & accuracy would be nice.
Does anyone here know if a typical smartphone can achieve that feat yet?

If not...
When do you think phones will be able to achieve that accuracy & precision?

On 5/25/19 10:13 AM, Elder Jones wrote:
If not...
When do you think phones will be able to achieve that accuracy & precision?

Nice try, but most of us have enough sense to have this done
by someone with the correct equipment.


--
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Jeff-1.0
WA6FWi
http:foxsmercantile.com

On Sat, 25 May 2019 10:13:43 -0500, Elder Jones
wrote:

For Camber, tenths of a degree in repeatability & accuracy would be nice.
Does anyone here know if a typical smartphone can achieve that feat yet?

The MEMS accelerometer used in many smart phones is capable of 0.06
degrees of resolution (not accuracy). The device will need to be
calibrated against a 0 degree horizontal flat surface (easily done by
vertically rotating the MEMS sensor and adjusting for zero change) to
obtain such levels of camber accuracy. The limiting factor is the
sensor noise level.

ADXL213AE datasheet
https://www.analog.com/media/en/technical-documentation/data-sheets/ADXL213.pdf
The typical noise floor is 160 µg/vHz, allowing signals
below 1 mg (0.06° of inclination) to be resolved in tilt
sensing applications using narrow bandwidths (60 Hz).

Note that this MEMS sensor currently sells for about $32/ea which
makes it an unlikely candidate for a consumer grade smartphone.
https://www.digikey.com/product-detail/en/analog-devices-inc/ADXL213AE/ADXL213AE-ND/669792
There are probably better and cheaper sensors available.

If not.
When do you think phones will be able to achieve that accuracy & precision?

When someone finds or creates a market for such a device.

You can try it yourself to see what can be achieved. There are many
electronic bubble level apps for Android and iPhone:
https://play.google.com/store/search?q=bubble+level&c=apps
Most seem to display in 1 degree resolution, but there are a few that
will display 0.1 degree resolution:
https://play.google.com/store/apps/details?id=com.jonyups.poziomicagen
I tried to use various Android apps for aligning satellite dishes,
where +/-0.5 degrees or better accuracy is the norm:
http://www.learnbydestroying.com/jeffl/antennas/dish-new-install-project/
but found that a digital angle level was more useful:
https://www.google.com/search?tbm=isch&q=digital+protractor

These look interesting:
https://express.google.com/u/0/product/15900634407707968640_0_6099994
High accuracy ±0.005°, high resolution 0.001°.
https://express.google.com/u/0/product/KKmoon-DXL3/12101973972988473742_13025317009461916407_6099994
High accuracy ±0.05°, high resolution 0.01°.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Why does this idiot troll have any traction in this group whatsoever?

Any idiot that would use a cell-phone or any similar device to check critical measurements in a vehicle deserves exactly what it gets. The sad part, of course, is when it gets what it deserves, it is more than likely to take one-or-more innocents with it. Of course, one is entirely and fully entitled to compete for a Darwin Award, but not to threaten others in the process.

Peter Wieck
Melrose Park, PA

On 5/28/2019 2:05 PM, wrote:
Why does this idiot troll have any traction in this group whatsoever?

"Like"

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Jeff-1.0
wa6fwi
http://www.foxsmercantile.com

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