For more than 50 years Kenworth’s venerable K-series cab-over has been a solid and dependable prime mover used for many tasks. However, there is a K-series Achilles Heel, which is ride quality. Sure, various measures such as parabolic front springs have been added which have made a dramatic improvement over earlier models. But the fact remains that the K-series ‘kick in the back’ is still evident on rough roads, which Australia has aplenty.
Wickham Freightlines knows as well as any this shortcoming of the K200. But rather than simply accepting the fact, the company decided to design and build its own solution in the form of an airbag cab suspension system.
Wickham Workshop Manager, Steve Lord explains that he set a time limit of three weeks to have a prototype K200 cab suspension built while Operations Director Graham Keogh was away in the States, to give him a pleasant surprise when he returned.
“The boys and I pulled out all stops and worked long days to ensure the prototype was finished, painted and sitting on a frame ready to install in the truck when Graham got back,” says Steve, proudly adding, “He was blown away when he saw it and was very excited to see it being fitted into the truck, which took about one day, and then around two days for testing.
“We didn’t outsource any of it, the fabrication boys did a fantastic job using spare steel that we had laying around and the end result was most impressive.”
Steve says the first couple of days of testing included making sure nothing was going to rub due to the cab movement, with the concept operating exactly as they had envisaged.
“The prototype worked really well, the driver loved it and said it felt like a completely different truck to drive,” says Steve.
He adds that the finished product was fully engineered and mod plated so that it became an integral and, most importantly, legal part of the vehicle.
“It was actually a relatively simple concept, we didn’t try to redesign the whole truck but just focussed on an area of the K-Series that we believed could and should be improved,” says Steve.
Some three years on, the original design has been updated to MkIII status, with various improvements including individual height control valves for each airbag instead of a single unit connected to both bags, along with structural design ameliorations to make it more aesthetically pleasing.
“The twin height control valves help keep the cab level by enabling the airbags to independently react to changes in the lean of the cab, such as when cornering,” says Steve.
Testament to the success of Wickham’s cab suspension, which is now fitted to four of the company’s K200s that have since collectively travelled well over one million kilometres, Kenworth asked the company if it could borrow one of the test units to evaluate the cab suspension as part of its new cab over development.
Over the years the K-series cab-over has been a solid and dependable prime mover, and now, word has it that the forthcoming release from Kenworth, due for an early June release, will feature Kenworth’s version of this cab suspension that will be yet another important evolutionary milestone in the lengthy K-series timeline.
All up, it’s a great example of a transport company with the initiative and wherewithal to fix an inherent foible in a prime mover; with the successful outcome leading to a similar fix in the new version for the benefit of all operators who subsequently purchase that particular model of vehicle.
