Trucks & Trucking – Page 2 – Vadnais Engineering

March 12, 2017September 15, 2018

Truck Acceleration SAE Technical Papers

In March 2016, friends and colleagues Wes Grimes (http://cea-az.com/), Greg Wilcoxson (http://www.wilcoxsonconsulting-llc.com/), and I conducted a series of heavy truck acceleration tests using tractors with automated manual transmissions (AMTs) in full auto mode. In auto mode, the transmission chose all shift points without input from the driver.

These were straight-line acceleration tests from a stop using two different truck tractors and two different test drivers. For each truck and driver combination, we ran tests with empty, partially loaded, and fully loaded van semitrailers. The drivers were asked to do half of the runs at what they felt was a “normal” acceleration. The other half of the test runs were at full throttle acceleration. There was a slight slope along the 300-foot test distance, so runs were made in both upslope and downslope directions. Our tests showed the slope, load, and throttle position all influenced when the transmission chose to shift. (Click on image to enlarge, then click on back arrow to return.)

Panning during Kenworth Acceleration Test (ZEISS 50 mm f/2 macro lens on Nikon D810.)

Technical papers describing the results of both test series have now completed the peer review process and have been published by SAE. We presented these papers at SAE’s World Congress Experience WCX 17 in Detroit on Wednesday, April 5, 2017. SAE has these paper available through these links:

2016 Kenworth T680: http://papers.sae.org/2017-01-1418/

2016 Freightliner Cascadia: http://papers.sae.org/2017-01-1426/

Special thanks to Contract Freighters, Inc. (CFI) and XPO Logistics for the generous use of their tractors, trailers, loads, scales, facilities, and test drivers at their facility in Joplin, MO.

February 19, 2017September 16, 2018

Effects of Wide Angle Lens on Vehicle Photo

Often, a vehicle we need to photograph will be crammed in between other vehicles or in a small garage or storage area. I’ve encountered the same problem when trying to photograph a whole tire in a small conference room. A wide angle lens then becomes necessary to capture an overall photo in a single frame. But doing so will inevitably cause the vehicle or tire to appear distorted. (Click on image to enlarge, then click on back arrow to return.)

Van with Normal 50 mm Lens. (ZEISS 50 mm f/2 macro lens on Nikon D810.)

Van with Wide Angle Lens. (ZEISS 25 mm f/2 lens on Nikon D810.)

These two images show the same van, but the top one was made with a ZEISS 50 mm lens, while the bottom one was with a ZEISS 25 mm lens. To fill the frame with the van, I made the photo with the 25 mm lens much closer to the van than with the 50 mm lens. The photograph made with the 25 mm lens looks like the van was the long wheelbase version while the 50 mm photo looks like it had the short wheelbase. This closer distance to the subject caused the wide angle lens to stretch the appearance of the van.

The best solution is to try to capture as much of the subject as possible with a lens as close to a 50 mm “normal” lens as possible. This might entail getting a higher vantage point, or shooting between obstacles. When that’s not possible, take the wide angle shot, then normal lens shots of parts of your subject.

Other effects of using wide, telephoto, and normal focal lengths for vehicles, accident sites, and for tires will be discussed in future posts.

February 18, 2017February 21, 2017

Don’t Move That Truck!

After a truck has been involved in a wreck, driving it even a couple feet at the crash scene without first disconnecting the vehicle speed sensor (VSS) will almost certainly destroy any last stop data recorded by the Heavy Vehicle Event Data Recorder (HVEDR), whether it is an Engine Control Module (ECM), an Electronic Control Unit (ECU), or some combination. This loss of digital evidence has often been cited as evidence spoliation, which can have serious repercussions.

This situation is easy to avoid by locating the speed sensor near the transmission output shaft, and disconnecting the electrical plug from the speed sensor. Let the plug hang free. The truck many then be driven or towed without danger of overwriting and losing important data.

It is important to make this common knowledge for truck drivers, wrecker drivers, investigating police officers, and truck service and maintenance personnel. This information can be disseminated through training classes and service bulletins. Labels on trucks near the VIN, near the toll-free number decal for the trucking or adjusting company, and on the accident packet can also help at the crash scene. Here’s a suggested label:

After a crash, do not drive or move vehicle at all without disconnecting vehicle speed sensor.

February 12, 2017September 16, 2018

Out of Service (OOS) Brake Defects and Brake Force Calculations

Various CVSA (Commercial Vehicle Safety Alliance) Out of Service (OOS) violations may be found when inspecting heavy trucks. These can be maintenance or safety items that fail to meet the criteria in Appendix G of Subchapter B of the FMCSR (Federal Motor Carrier Safety Regulations) (40 CFR §396.17). This post will focus on brake issues only.

CVSA uses the term “defective” to denote a brake condition that does not meet specific criteria. CVSA declares a vehicle OOS if twenty percent of the brakes are defective. A common three axle tractor with a two axle semi-trailer will have ten brakes total. Twenty percent of ten brakes means the truck would be put OOS if two brake defects were found. (Click on image to enlarge, then click on back arrow to return.)

CVSA brake defects often result from inadequate maintenance. One important purpose of a CVSA inspection is to catch maintenance issues before they adversely affect the stopping ability of the truck. While it is essential to properly maintain vehicles for safe operation, the presence of one or more OOS brake defects does not necessarily mean the braking ability of the truck was compromised at the time of the accident. So there are two separate, but related issues: -1- Were there any problems with the truck? -2- Did any of those problems affect the truck’s ability to stop during this particular incident? Continue reading “Out of Service (OOS) Brake Defects and Brake Force Calculations”