How well-built and engineered is the Model 3?
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Last week Sandy Munro gave us an exclusive walk-through of his shop’s racks and tables strewn with Tesla Model 3 parts his team had meticulously dismantled and scrutinized. The Munro team had conducted a 6,000-hour teardown of one of the most closely watched new-vehicle launches in history—and the evaluations were mixed. Although the Model 3 received praise for its many technological advances, the Tesla build quality and body engineering left much to be desired.
This week Munro & Associates formally presented its results to the Automotive Press Association, with Munro’s vehicle manufacturing and electrical engineering experts presenting their comprehensive findings. Most of the “eye-catching features” these experts presented fall into the category of industry-disrupting innovation. Then there’s the body, which is another matter altogether. Channel your inner geek for all the nittiest, grittiest details.
Read more about the Model 3:
- Tesla Model 3 Teardown: Deconstructed 3
- Tesla Model 3 First Test
All-Wheel-Drive Prep—This photo shows the front knuckle, which clearly has a hole machined for an axle input (then plugged). The lower end of the shock would need to be forked or dog-legged to accommodate the half-shaft. The front cradle also protects space for the motor. Note the control arm at the top and the two links at the bottom that provide stiff lateral bushings for handling precision and compliant longitudinal bushings for ride. Also note that the rear suspension carrier is isolated; the front is hard-mounted for handling precision. Perhaps the front motor will be isolated from the hard-mounted cradle?
Front Upper Control Arm—These are formed of thinner-gauge stamped steel then reinforced by having plastic webbing molded inside. This plastic also provides attachment points for routing the ABS sensor wiring. The oddity: Note the ingot of iron that is glued in place (held by zip-ties while glue sets). Munro reckons this is to dampen a troublesome natural frequency. It remains to be seen if AWD Model 3s will require this.
Upper Shock Mount Casting—This unusual casting incorporates both the upper shock mount and the upper control-arm bushings and mounts. Munro guesses this unusual approach simplifies the procedure for marrying the front suspension module with the body.
Electric Power Steering—The control board shown in the Ziploc bag controls the electric steering assist motor. It appears to feature two separate 12-volt power inputs, probably to provide the redundancy required for fully autonomous driving.
The entire pack contains 4,416 cylindrical Panasonic 2170 cells (21mm diameter, 70mm length). These are divided into four large modules (each with its own voltage-monitoring circuitry), one of which has been removed from the battery pack shown here. Subgroups of 46 3.5-volt individual cells are connected in series via ultrasonic wire bonding to stamped aluminum current collectors. Each of the four modules connects 24 of these subgroups in parallel via copper ribbons (shown under green tape). The aqua-green stuff is “potting compound,” which bonds cells to one another and to the cooling passages. It also eliminates any possibility of vibration that could break the fragile ultrasonic wire bonds. Tesla holds more than 90 patents on this class-leading battery pack.
Charging Board—This large, complex board filters electricity coming in from the charger with the tall and modular board at right. This board is tailored to suit the electrical service of the vehicle’s destination country. This U.S.-market car is prepped for three-phase current, so there are three big copper donuts under that board that look like the one on the left side of the board (that one handles the conversion to 12 volts). This approach is unique and deemed quite savvy relative to the Chevy Bolt and BMW i3 Munro has also analyzed.
Multilayer Bus Bar—High-voltage current basically takes a short trip in a Model 3, exiting the back end of the battery, flowing directly into the power electronics and on to the rear motor. One of those short trips involves this heavy gauge bus bar composed of numerous bent bits of sheet copper.
Pyrotechnic Battery Disconnect—This Tesla-patented device uses airbag/seat belt tensioner technology to instantly disconnect the battery in the event of a short circuit or other battery voltage spike event. The current shunt sensor helps trigger it.
Batman & Robin—Perhaps just to show that the Tesla electronics geniuses have a sense of humor and/or are DC Comics buffs, several circuit boards feature these images, and some are even labeled “Robin.” Munro figures they may be chips serving redundant functions.
Luggage Well—This well is composed of numerous metal stampings that are time consuming to form and assemble. Munro recommends replacing this well with a simpler structural composite tub.
Alternating Self-Piercing Rivets—These closely spaced rivets are alternately installed from the top and bottom. The Munro team is unaware of a structural benefit brought by this added complexity.
Overpowered Spot Welds—These resistance spot welds in steel show evidence of too much electrical power, which has caused molten metal to spray out. This issue may have since been resolved, as Munro was evaluating an early-production example, but Tesla could not confirm if that was the case.
Self-Piercing Rivet Stud—These are commonly used fasteners; less common is attempting to mount them on a curved surface like this. Such an operation is very difficult to control. (Perhaps the location is not critical in this case?)
Rear Door Opening—There is a curious mix of sine-wave tig welding along the roof rail, spot welds along the B-pillar and rocker, and self-piercing rivets along the (extra large) flange near the wheel opening. The rivets may be necessary to join steel and aluminum, but a simpler design overall would save cost.
Munro & Associates is in the “lean design” business, as its web address attests: leandesign.com. Sandy Munro spent a decade at Ford helping optimize the company’s design for manufacturing processes, and while there he met the famous W. Edwards Deming (“In God we trust; all others bring data”). Deming’s theories on improving quality by reducing variation resonated with Munro, and in 1988 Deming convinced Munro to leave Ford and start his own consultancy to spread the lean-design gospel to multiple companies.
Munro is very impressed with the Tesla’s design, ride/handling, electrical and electronic architecture, and myriad innovations sprinkled throughout the Model 3. He made little secret that he would like to assist Tesla in the areas where he sees room for improvement. As we go to press, Tesla is not yet a Munro client.
We asked Tesla for a follow-up response to this more detailed summary of the Munro teardown. After our initial exclusive, Tesla gave a general comment regarding build quality and safety. At the time of this subsequent story’s posting, Tesla declined comment.