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Aluminum MS and traffic light sensors

brucet999

Active Member
Mar 12, 2015
2,694
1,500
Huntington Beach, CA
Given that MS has all aluminum body and frame, with just a little steel in the motor, gear reduction, axles and brake rotors, is it able to be sensed by traffic light magnetic sensors or will I have to wait for a conventional car to join me before the traffic light controller knows anyone is there and changes the light?
 

Lloyd

Well-Known Member
Supporting Member
Jan 12, 2011
6,324
2,125
San Luis Obispo, CA
Given that MS has all aluminum body and frame, with just a little steel in the motor, gear reduction, axles and brake rotors, is it able to be sensed by traffic light magnetic sensors or will I have to wait for a conventional car to join me before the traffic light controller knows anyone is there and changes the light?

There appears to be enough metal to trigger the lights. I have not had any issues in 4 years.

Actually that is a misconception that iron is required. From wiki


Detection of Bicycles at Demand-Actuated Traffic Signals

Shared via the Google app
 
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ACVolt

Member
Feb 12, 2015
23
2
Greenwood Village, CO
There are two types of traffic light sensors. one type uses cameras to detect cars at an intersection. The other type uses an induction loop buried in the roadway and detects cars by the change in loop inductance. Aluminum should change the inductance similar to a steel car.
 

breser

AutoPilot Nostradamus
Aug 28, 2014
2,314
94
North Bend, WA
Given that MS has all aluminum body and frame, with just a little steel in the motor, gear reduction, axles and brake rotors, is it able to be sensed by traffic light magnetic sensors or will I have to wait for a conventional car to join me before the traffic light controller knows anyone is there and changes the light?

Battery casing is steel and is a very large component. So I don't think there's any issue here.
 

NoMoGas

Supporting Member
Supporting Member
Given that MS has all aluminum body and frame, with just a little steel in the motor, gear reduction, axles and brake rotors, is it able to be sensed by traffic light magnetic sensors or will I have to wait for a conventional car to join me before the traffic light controller knows anyone is there and changes the light?

These are all over LA. Works just fine.
 

scaesare

Well-Known Member
Mar 14, 2013
8,536
14,730
NoVA
Battery casing is steel and is a very large component. So I don't think there's any issue here.

Source for this?

Several sources have indicated aluminum, specifically Tesla has indicated the bottom "ballistic shielding" is 1/4" aluminum plate. Also, as I recall the structural frame appeared to be aluminum as well in the several tear-down accounts/videos that exist...
 
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jgs

Active Member
Oct 28, 2014
1,581
934
Ann Arbor, Michigan
Also, as I recall the structural frame appeared to be aluminum as well in the several tear-down accounts/videos that exist...
I don't know about the battery shield, but http://www.teslamotors.com/sites/default/files/tesla-model-s.pdf says:

This unique positioning both lowers the car’s center of gravity, which improves
handling and minimizes rollover risk, and replaces the heavy engine block with impact absorbing boron steel rails.

Side impacts are met by aluminum pillars reinforced with steel railsto reduce intrusion

So there are at least some chunks of steel in there per Tesla's own marketing collateral.
 

scaesare

Well-Known Member
Mar 14, 2013
8,536
14,730
NoVA
I don't know about the battery shield, but http://www.teslamotors.com/sites/default/files/tesla-model-s.pdf says:

This unique positioning both lowers the car’s center of gravity, which improves
handling and minimizes rollover risk, and replaces the heavy engine block with impact absorbing boron steel rails.

Side impacts are met by aluminum pillars reinforced with steel railsto reduce intrusion

So there are at least some chunks of steel in there per Tesla's own marketing collateral.

Correct, steel rail up front ahead of where engine would have been. Boron-steel pillar inserts (although it's thought those may no longer be there with a re-design).

Neither of those are the battery casing, which is Breser's assertion I'm questioning.
 

jgs

Active Member
Oct 28, 2014
1,581
934
Ann Arbor, Michigan
Correct, steel rail up front ahead of where engine would have been. Boron-steel pillar inserts (although it's thought those may no longer be there with a re-design).

Neither of those are the battery casing, which is Breser's assertion I'm questioning.
I see. I was reacting to "the structural frame appeared to be aluminum as well" which I took to mean the auto frame. I guess you meant the battery pack frame.
 

breser

AutoPilot Nostradamus
Aug 28, 2014
2,314
94
North Bend, WA
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scaesare

Well-Known Member
Mar 14, 2013
8,536
14,730
NoVA

Yeah, I believe that "steel case" comment is likely wrong too...

I was remembering this comment where wk057 mentioned aluminum as well as his teardown pictures which appear to be aluminum as well. But he never states there wasn't also steel.

Also I note that the Tesla Ballistic Shield Patent also does state that the shield may protect a steel structure.

So I guess, although we know there's a lot of aluminum in it, it's not been proven to not also contain some steel.
 

AmpedRealtor

Well-Known Member
Jun 30, 2013
6,414
3,398
Phoenix, AZ
Battery casing is steel and is a very large component. So I don't think there's any issue here.

Battery casing is actual aluminum and one of the reasons why it can be penetrated easily by a toe hitch. That's why the battery shield was needed, which is made from aerospace-grade titanium or something.
 

ecarfan

Well-Known Member
Sep 21, 2013
19,351
14,020
West Vancouver, British Columbia
Battery casing is actual aluminum and one of the reasons why it can be penetrated easily by a toe hitch. That's why the battery shield was needed, which is made from aerospace-grade titanium or something.
I think it is an exaggeration to say the Model S battery case can be penetrated "easily" as it takes considerable force to do so, but it certainly can be penetrated.
 

scaesare

Well-Known Member
Mar 14, 2013
8,536
14,730
NoVA
The bottom of the pack has always had the 1/4" aluminum plate "ballistic shielding". Tough stuff.

The tow hitch that caused the famous battery fire appears to have punctured the non-protected vertical front surface of the pack. That appears to be thin-gauge non-armored material:

tesla-3a-600x337.jpg


It was a bit of a fluke as that means the object came up and penetrated the area under/behind the frunk (where steering rack, coolant lines, etc... are) and hit the front of the pack. The new titanium plate covers that small under-frunk area to prevent similar events.
 

brucet999

Active Member
Mar 12, 2015
2,694
1,500
Huntington Beach, CA
Thanks, Lloyd. I had not known that electrical conductivity was the requirement. I assumed that magnetic conductivity was the necessary trigger.

Reminds me of my time aboard a minesweeper where everything possible was done to minimize disturbance of the earth's magnetic field in order not to set off magnetic mines. All iron components were surrounded by degaussing cables to counteract their effect, even galley storage lockers. For that reason, empty tin cans were returned to the storage so as not to change the magnetic signature. Standing rigging on the mast was interrupted every few feet with insulators so that as the ship rocked, steel rope swinging through the earth's magnetic field would generate the smallest possible currents. The diesel engines themselves had aluminum blocks, monel steel crankshafts, stainless steel heads, copper oil lines, etc.
 

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