PUTC Interview with Honda Ridgeline Chief Engineer, Gary Flint
A bunch of car guys designing and building a pickup for the first time? It was quite a challenge but the inexperience may have been a blessing for the Honda engineers since they weren’t bound by traditional rules or honoring a current model. For a closer insight into the development of the new Honda Ridgeline—including the decision to build a unibody structure—PickupTruck.com sat down with the truck’s chief engineer, Gary Flint.
Also joining editor Mike Magda were Kevin Thelen, who was in charge of testing, and Jim Keller, in charge of design.
PickupTruck.com: Talk about the early steps in the timeline when you reviewed the competition.
Gary Flint: We started looking into trucks many years ago, just started tearing them down. Really, the essence of the original project was: How are trucks put together? What is their cost structure? What’s the supplier matrix?
Kevin Thelen: What’s the level of their technology?
Flint: Yeah, where should we fall in this array? The initial investigation was really not focused on anything other than truck construction.
PUTC: How long ago were the basics of the Ridgeline’s configuration set?
Flint: Leading up to the actual full development we had identified a lot of the marketing information, started to put together the business case and where we wanted to be with the package. That was about a year out in front of the development.
PUTC: When you started tearing down the competitive vehicles, I understand you found some surprises.
Flint: Surprises? I guess it’s that they were remarkably simple; really not a lot of technology implemented on any truck.
PUTC: I heard there were some surprises out of your static tow test.
Thelen: We did test some of the competitors to what we internally set as a benchmark. The interesting thing there is one of the competitors didn’t meet the internal spec at that time. But the thing we found in the next model year was that vehicle had counter measured the same problem. So it was a surprise that it made it into production with that problem but it also affirmed to us that our tests and approach to quality were probably similar to what the competitors were running.
PUTC: Regarding the unibody construction, explain your approach to addressing bending and torsion dynamics.
Flint: Bending lends itself to customers’ general impression of ride quality where torsion tends to manifest itself in handling. You want to keep the body stable and let all the work be done by the suspension.
Jim Keller: If the body structure is moving—of course, the suspension is attached to the body structure—and the alignment of the axles is all related to the alignment of the body relative to the axles. So if the body flexes, that means the [suspension] mounting points are moving. And when the mounting points are moving, the axle is moving. So the control of the vehicle is being affected by flex.
Flint: You may get steering or some other strange things happening in the axle because the body is moving so much.
PUTC: Talk about the analysis and computer modeling you did before you came up with the final direction of the truck.
Flint: One of the things we first started with was an optimization program to give us more of an empirical recommendation of where’s the best place to put structure. It doesn’t design the car for you. It tells you what direction should you go with and what could be the optimal, most weight-efficient way to achieve a bending or stiffness target. That really led us into the architecture you see executed on the vehicle. We did, in fact, have the most complete model ever put together that early in a development. But we did have an advantage in that we were springing off from other model developments—both Pilot and MDX—where we had some of the structure modeled. We used that as a base to start building what we targeted as additional truck structure back into the vehicle. We actually did three complete iterations of the body model before we were finished. We did a lot of full validation work with them.
Keller: That was even after we did the initial unibody versus body-on-frame comparisons. We did full modeling. We had a competitive vehicle that we used for a total vehicle test. Then we took that vehicle apart and measured it and created a computer model. We kind of reversed-engineered that vehicle into a computer simulation model that allowed us to do a comparison.
PUTC: Forty-four percent of the structure is made from high-strength steel. Did that number come from the computer modeling?
Flint:You try to get a balance between weight and performance. That’s another level of optimization. You start looking at gauge (thickness of the steel) reduction. You’ve got the basic geometry of the components identified. If we allow some of these materials to go to a higher stress-level material, what can we do by reducing gauge and not causing failure?
PUTC: You claim the Ridgeline is 20 times stiffer than a body-on-frame pickup. Where are traditional pickups losing it?
Thelen: First you start with their frame structure; it’s a flat-plane frame. That frame structure, honestly speaking, is not conducive to torsional restraint. But our frame is integrated with the upper structure. The rear panel in our cab is all integrated with that section to create not only a box section, but a reinforced box section.
Keller: If I can demonstrate. (The engineers then used small, empty milk cartons to show how a box structure is stiff and resists twisting. But when the carton is crushed flat; what essentially is the same amount of material or mass can easily be twisted. They also show how the traditional pickup body is based on three separate sections—front clip, cab and cargo bed—that follow the movement of the frame while the unibody design acts as one unit and is a stronger piece.)
Flint: If I take a box, like a truck frame, and put a torsional load into it. Now I take that same piece and slit it. Now it’s a C-channel. It’s 15 times stiffer as a closed section. So we’ve got that going for us because they’re all closed-box sections. Plus we’ve got the additional benefit that it becomes a bridge structure. It’s more like a truss. It’s a more efficient way to handle loads because I’m forcing loads into the upper superstructure of the vehicle. If I’m trying to make the lightest possible structure in a space-constraint, stiffness-critical application; any computer optimization program is going to immediately explode a cross-section area to the maximum possible space that you’ll let it go to and the thinnest possible wall stock. That’s the most efficient way to make a structure. If you want to do a whole lot of work in a small area, which is what a truck frame is, it gets real heavy and real inefficient. We’ve made use of all those elements that a normal truck construction doesn’t do because they aren’t connected.
PUTC: You carried over the basic design of the suspension from other models but what adjustments did you make to handle the extra loads?
Flint: We knew we were going to have a significant difference between the laden and unladen condition but we didn’t want a Jekyll and Hyde characteristic of the vehicle. So in the loaded condition, we needed to get some pretty significant damping forces back to the damper, so we needed an efficient lever ratio. In the previous suspension design, the damper is more horizontal. It’s very difficult to increase the damping force and get any kind of effective utilization of that damper output because the lever ratio is so poor. With an upright damper, it has a huge benefit because everything is going right into it, plus it has a better layout for the torsion bar. It’s just a much better suspension package to handle this significant swing in loads and maintain a stable, flat ride.
PUTC: The Ridgeline tow rating is set with two occupants in the vehicle and 175 pounds of cargo. The footnotes for most other trucks say the rating is based with only a driver in the vehicle.
Keller: We decided rather than having a numbers game, we wanted a real world rating. We thought if we were towing something it would be a guy and his buddy.
PUTC: Let’s talk about the body design.
Thelen: The first goal is Cd (coefficient of drag).
Flint: Let’s go back further than that. The major goal is fuel economy. In order to have fuel economy targets, it affects a lot of attributes in the vehicle. So it goes back to predicting and maintaining aerodynamic drag. It was a very high target for us.
Thelen: The question everybody asks is what’s better: the tailgate up or down? If you engineer the truck correctly, by far the best aerodynamics will be with the tailgate up. You design it so the airflow comes off and misses the tailgate. We actually tested on competitor where the air came off the roof and hit the tailgate. But for the most part they are designed so air comes off, misses the tailgate but then reattaches as soon as possible behind the vehicle to keep the slipstream as long as possible.
Flint: All the gains we made were on the back of the truck. Very little if anything we did up front.
Keller: For the fuel economy, it was important we set the basic body shape, especially before the styling was fixed. Once that was done, we used the wind tunnel to tune for NVH (noise, vibration and harshness). Details like the mirrors and A-pillar shape. It was more refining at that point.
PUTC: Did you design the angle of the bed rails to make it distinctive for Honda?
Keller: Early on we had two competing designs for the exterior and they were different in that regard. One was more horizontal and didn’t have the buttress shape. This one (pointing to the Ridgeline) won. We could’ve executed either one but the styling drove the shape of that C-pillar and the bed. As it turns out, this is a pretty efficient structural shape but it wasn’t the driving factor.