Tuesday 24 February 2015

Theory that Gearshift Lever's Design Contributed to Horrific Accident


A New York newspaper is looking at the design of a Mercedes gearshift lever as the potential cause of a horrific car-and-train collision earlier this month.

On February 3rd, 49-year-old Ellen Brody's ML350 was struck by a commuter train north of New York City. The car exploded, the train pushed it for 1,000 feet and the first train car burst into flames. Brody was killed, along with five passengers in the train.
 
So what role could the gearshift lever have played? These days when I hear of a car accident, I usually wonder if the driver was texting rather than suspecting some ergonomic fault with the car's design. But the gearshift argument makes sense given the following information and the eyewitness account:
Brody was in a line of heavy stop-and-go traffic, waiting to cross the railroad tracks. This was an unfamiliar route for her; traffic had been detoured due to an earlier accident on the nearby highway she normally traveled on. As Brody's turn came and she inched her car forward, the crossing gate suddenly came down onto the back of her car and she stopped. The car behind her then began to reverse, assuming Brody would do the same to free her car of the gate.
 
According to an eyewitness account, Brody got out of the car to see what had happened. She touched the gate but did not, or was not able to, remove it off of her car.
Brody then entered her vehicle and sat there for a moment, which the witness described as “enough time to put on her seat belt.” The witness said Brody then suddenly pulled forward, directly onto the tracks, and the train struck her car.
"I just knew she was going to back up—never in my wildest dreams did I think she'd go forward," the eyewitness said.
 
It makes no sense—until you consider what must have happened. Brody gets back into her car, presumably pauses to put her seatbelt on, then puts the car in reverse, to back up and snap the gate off if need be. Instead the car moves forward directly into the path of the train.
Take a look at the stalk-style gearshift lever in the ML350:
 
With this arrangement, when it's in "Park" and you pull it down one notch, it goes into "Drive," i.e. forward.
 
Brody was 49 years old. Thirty-three years ago, when she was sixteen and presumably first learned to drive, column-mounted, automatic-transmission lever-style shifters were common in America. They looked like this…
 
…and the sequence was always the same: P, R, N, D. In other words, one notch down from "Park" was "Reverse." I believe Brody, like most Americans of that age who learned to drive on such a car, had it hard-wired into her brain that when you're shifting something mounted to the column, one notch down from "Park" is "Reverse." I think she meant to back her car up away from the tracks, muscle memory took over, and she unwittingly lurched the car forward. There was no time for either her or the train driver to react.
 
Records show that Brody had registered the car in December, meaning it was new-to-her and perhaps she hadn't gotten the hang of the transmission yet. But even if she had, that may not have made a difference. In an online forum for Mercedes owners, one owner of a GL-series—which has the same shift lever arrangement as the ML-series—writes:
I have [13,000 miles] on my GL and really don't like the stalk shifter. I still must consciously think about shifting, especially going from either R or D into park, unlike the automatic motions I use with a center console mounted shifter. Even the standard column shifter of days gone by and which are still on some vehicles is more intuitive. I think it's because the position of the shift lever, be it on the floor or the column, is an obvious visual indicator of shift position rather than the not so obvious lights on the dash.
The type of shifter in Brody's car—which is a function of drive-by-wire and is not mechanical—is not unique to Mercedes; some BMW models have an identical arrangement. But given that these are for drive-by-wire systems, it must be a relatively recent convention.
Older European cars had predominantly manual transmissions, and in my own anecdotal experience, every older European I've met that can drive learned on a manual. In automatic-transmission-crazy America, however, most older Americans learned to drive under the P, R, N, D convention. Perhaps we cannot expect a European car company to adhere to a convention not of their making. But to a generation of drivers raised on column-mounted P, R, N, D, the newer design approach seems a very poor one indeed

Wednesday 4 February 2015

The History of Engineering Design Tools: Engineering 3.0


There have been four great stages of engineering and design tools leveraged over the past 250 years to account for all mechanisms, inventions and designs that we have used to simplify our lives. This post will take a look back at the third phase, Engineering 3.0 which occurred from 1985 to 2015 roughly 30 years. This was the second phase to take advantage of computers which became increasingly powerful (Moore’s Law) during this time period. Missed parts one and two of the History of Engineering Design Tools series? Click the links for a looking back at Engineering 1.0 and Engineering 2.0.

Engineering 3.0 (1985-2015)
The second generation of CAD offered a new paradigm of creating and inventing. The emphasis this time was on building designs (models) more like the world we see and live in (3D) versus simply mimicking the 2D drawings of the past.
rich1Early 3D systems were again (like Engineering 2.0 2D CAD systems) based on mainframe computers and available only to larger organizations, such as aerospace and automotive manufacturing companies. Over time, workstations based on UNIX operating systems brought the price down to the medium-sized companies.

Finally, personal computers (PC’s) based on DOS, UNIX and then Windows made 3D CAD possible for the mass market.

Some early 3D CAD users originally learned to create 3D models based on Boolean geometry, which they could put together like puzzle pieces in 3D and add, subtract or merge to create new images.
Later, the ability to create 2D forms that could be extruded, revolved or swept allowed more flexibility and speed in creating 3D models. Over time more powerful tools, such as fillets, chamfers, mirroring and holes, were made available to 3D users.
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Users typically engaged with a digitizer for an input device. These could range in size from 11×17 inches to as large as an old drafting board providing a certain level of comfort to users that had just moved from traditional paper drafting to CAD. A cursor with 2-16 buttons similar to a mouse was used which provided more accuracy then the mice of that generation. Some users preferred a pen feel and used a stylus which looked and felt like a pen and was still very accurate in resolution.
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As these new tools evolved,many significant benefits were realized by utilizing 3D modeling versus the previous phase of 2D tools including:
  • Better Visualization – rendering, animations
  • Interference and Clearance Detection – piping, routing, complex assemblies
  • Engineering Calculations – volume, weight, surface area, center of gravity
Designs could be communicated to customers, suppliers and others more quickly and easily and understood by users who did not fully understand how to read 2D drawings.
rich63D spatial challenges could be solved by creating multiple 3D parts or even entire buildings. Imaging determining if the HVAC ducting would interfere with the Electrical Conduits or Lighting Fixtures before getting to the construction phase of a project or piping in a power plant.

Due to tradition and lack of alternatives, most 3D models were converted to old-fashioned 2D drawings to enable manufacturing. The benefit to designers was that the tedious and time-consuming part of creating communication tools could be highly automated, as top, front, right side, isometric and detail views could be created semi-automatically once a 3D model had been created.

As 3D became more and more powerful and prevalent among engineers and designers, users were able to improve designs by running simulations in order to validate designs. Initially known as Finite Element Analysis (FEA), users could test the strength of their designs based on different materials, part thicknesses, radius selection and load and constraint conditions. Analyses could be run and easily understood and communicated using color coding where red indicates the highest level of stress (von Mises)
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Now, parts and assemblies could be analyzed for a greater variety of failure modes including:
  • Linear Stress
  • Non-Linear Stress
  • Fatigue
  • Thermal
  • Frequency
  • Buckling
  • Drop Testing
  • Dynamic
  • Motion
  • Cost
  • Flow
  • Plastic Injection Molding
  • Sustainability
With 3D CAD becoming mainstream and the primary tool at most companies, the challenge of managing the data had to be solved. While the system of record for many years had been physical paper based on 2D drawings either manually drafted or converted from 3D models electronically, the more common method today is to rely on the original 3D model. This is the master model for drawings and the relationship between 3D and 2D must be maintained in order to easily affect design changes during and after the initial creation.

In order to effectively manage the large amount of data, first Engineering Data Management (EDM) and then Product Data Management (PDM) tools were implemented which could track and maintain relationships between parts, assemblies and drawings, even if files were moved from one storage location to another.

PDM systems added features and capabilities such as:
  • Viewing
  • Annotations
  • Bill of Material Creation
  • Engineering Change Order (ECO) Management
  • Workflow and Routing of Documents
  • Version Control
  • Revision Control
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As the Engineering 3.0 era comes to a close, it is important to note that the three capabilities that were pioneered, perfected and mass enabled:
  • 3D CAD
  • Simulation (Validation)
  • Product Data Management (PDM)
These three (3) pillars will serve as the foundation for the next revolution in Engineering, stay tuned!
The next engineering paradigm, Engineering 4.0, extends design data to downstream departments in the right format at the right time; resulting in a more efficient product development process. Read our article and infographic to learn how you can stand out with Engineering 4.0.