These 1992 observations by G. Glenn Gardner, general manager of Large Car Platform Engineering, largely refer to the origin of the original LH series (Intrepid, Concorde, Vision, LHS, New Yorker) but apply generally as well.
Recently, I was asked about the 'chicken or the egg' theory relative to vehicle design and packaging. It's really not which comes first ... design or package.. .because, basically, it's an interactive process between Engineering, the Design Office, Manufacturing and Purchasing.
The human body doesn't change and when we start to develop a new car ... in this case, the LH we begin with a specific set of package criteria for the driver. The design has to work itself over the top of those hard points (fixed dimensions).
Everybody must be in agreement on these hard points. The designers, for example, know the hard points represent the brick and mortar and they can put a facade over it, but they cannot violate these hard points.
These are the critical things. Here's where the guy's hands go. Here's where the steering wheel is. Here's the critical point on the A-pillar. Here's how far the roof rail can come in on the sides, how far the header can go. The driver must sit within those parameters. The designer knows he or she cannot go fore or aft of these. They can go above. They can make them bigger, but not smaller. The designers then go off and do their thing ... to develop a skin around those hard points.
As engineers, we normally speak of the vehicle package in a multiple framework . . the interior, the size of the engine compartment, the packaging of components such as the engine, transmission, heating, air conditioning, venting controls ... all in the room provided by the overall vehicle package.
When you think of the interior package, the major challenge is to create an accommodating driver environment. You start with the driver and everything we do works itself around a driver package that is tied into the kind of vehicle it is.
All humans are the same, although they may vary a little in size, of course. All vehicles are different. In the case of the LH, we knew the driver had to have a comfortable upright seating position. He couldn't have his feet straight out in front of him like you would in a sports car. After all, LH is a family sedan, not a sports car.
A second criteria, the driver must have easy access in and out of the vehicle. In the case of the A-pillar, it's getting the head past the pillar conveniently, whether going in or out of the car. That is a key point.
The driver should feel very comfortable relative to the position of the front header, the windshield, sun visors and all that. You don't want him or her to feel crowded. In sports cars, we're happy to be scrunched up. But you can't do that in 4-door sedan. The basic dimensional aspect of the car sets the target point for the header. In the side view, it's crucial for driver ingress or egress. In the front view, the header location -- fore and aft -- must provide a comfort zone for the driver's head.
Another important aspect of the interior package is where the driver sits in relation to the inboard location of the left-side roof rail. The driver doesn't want to move his head sideways and immediately hit side glass. That's side view packaging, proper location of the roof rail. It's all part of vehicle width.
Once you've done that ... put the driver in place ... physically he is packaged.
Now, you take those dimensions and ask yourself, how do I handle the taller person who moves his or her seat rearward to the farthest point, but still demands comfort? And a shorter person, perhaps a woman .... who positions the seat all the way forward and up?
Add a steering wheel to that environment and you say then, how do I accommodate these people? The steering wheel is on the center line of the driver. So you put the steering wheel in its proper place. Now, you have the elements of the basic front-seat dimensions that must be addressed.
The passenger side of the package more or less goes along with the driver's side, although there will be some different criteria ... foot room, for example. The passenger is not driving, of course, and tends to be in a more relaxed position. In contrast, the driver must have comfortable relationship with all of the pedal controls ... accelerator, brake, clutch, transmission and so forth. That's why the driver must be the primary focus of the front-seat package.
Once the driver/passenger front-seat relationship is determined, we overlay that with new criteria the safety aspects of the interior package in the event of a vehicle crash or collision.
The instrument panel must meet certain criteria relative to the knees of the front-seat passengers. The crush capabilities of that panel must be such that the knees don't come into contact with an immovable object. Otherwise, you might crush a knee cap. Instrument panel surfaces have to be far enough away and collapsible enough so that they meet the basic safety criteria.
Next, the controls a driver must see and handle are factored in. They must be convenient, natural locations and tactilely familiar. The instrument cluster must be positioned in such a way that the driver is able to see all the gauges from any seating position he or she wants .. ..up and down, fore and aft.
In the case of LH ... when we talk Cab Forward.... we were able to meet all the basic criteria of the package and create this nice environment for the occupant. We wrapped most of the cluster and controls around the driver to create a bit of a cockpit type of feel. We wanted to get a sort of sports car, 'wear it' feel for the driver -- without confining or scrunching him up.
We wanted to emphasize not only the ergonomics, but the importance of the driving position. So we orchestrated it in such a fashion as to position the controls ergonomically where the driver could reach them easily and handle the driving. We wrapped them around the driver so any per
son who drives feels very important. All the controls in the LH are attuned to that. Once that's accomplished, you can take the windshield and do a lot of things with it.
In the case of LH, we pushed the bottom of the windshield out and flattened it in order to improve the car's aerodynamics and also to reduce wind noise because NVH (noise, vibration, harshness) was a major priority in this car. The faster the windshield, the less buffeting at the corners.
The Cab Forward design of LH, with the bottom of the windshield touching down at the center point of the front wheels, may create an illusion of a short overhang. But, in fact, the distance from the base of the windshield on LH to the front bumper is not that unusually short. Also, having a north-south engine arrangement helped immensely with the package design.
The secondary aspect of the interior package is the width. With LH, we went up to 59 inches of shoulder room, which gets us more into a full-size car dimension. By comparison, consider today's Imperial, New Yorker and Dynasty are in the 56-inch range.
Packaging the rear compartment presents an entirely new set of issues. You must ask yourself, how do I get someone in and out at the opposite end of the cabin? And is the head of that person going to go past the C-pillar easily and safely? It's a function of how wide you can make the rear doors because the tumblehome (curvature) of the glass figures into it, too. Another point to consider, what is the width between the rear seat cushion and the 'B' pillar so you can easily move your foot through that area?
In case of LH, we wanted a very large, commodious rear passenger compartment. We had large dimensions between the front seat back and rear seat to give lots of room. We also had a door that opened almost perpendicular to the body, allowing an entrance that was very open and spacious. With the Cab Forward design of LH, the front wheels were only slightly moved ahead, but we moved the rear wheels back to an even greater degree.
A longer wheelbase may be primarily related to ride and handling, but this allowed us to maximize the rear door openings and get rid of the wheelhouse intrusion you find in the rear compartment of most cars today. We were able to eliminate any contact between rear-seat passengers at the wheelhouse.
Once a person is seated, we also had a roof rail, rear header and backlight sufficiently up and behind so there was more than enough head clearance. The width of the rear seat goes right along with the front seat width, of course.
Computers are wondrous, indispensable tools in today's car design process. But once in a while, an engineer has to rely on his basic instincts, despite what the numbers say.
Take the front and rear floor pans of the LH, for example. We went through all the package designs and the actual vehicle mockups. Everything seemed perfect. Then we went out on the road with the earliest of our prototype vehicles.
What we found was that the driver's seat position -- the driver's hip point to heel -- relative to the floor seemed strange. It didn't feel like the driver had command of the road. It wasn't as comfortable as the numbers said it should be. It may look good on paper, we told ourselves, but it just doesn't feel right. We wanted the same comfortable feel as a driver gets in a minivan.
We went back and took a look at it. This was very late in the program and we knew we couldn't change the styling. We were too far along.
But we found a way to drop the floor pan ... front and rear ... by 9/10 of an inch to improve the occupant seating position. And this was way after the package design was approved. We already had prototypes out for testing.
We went to Dennis Renneker, our executive engineer for Body-In-White and Chassis, and asked him if we could do it. He said he could if the change didn't interfere with the sills or the catalytic converter. The welds also had to stay the same.
In my opinion, if it were not for the LH Platform Team, we never would have accomplished that goal. We would have interfered with too many other people, organizations. In the old days, they would have said it's too late, we can't do it. But with the LH team we did it and the driver is the beneficiary.
LH cars: Intrepid, Vision, Concorde | Interview with Francois Castaing
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