Oshkosh TAK-4 Independent Suspension System

In 1999 Oshkosh was awarded a United States Air Force (USAF) contract to supply P23 ARFF trucks. These, and the earlier P23 supplied to the Air Force between 1994 and 1996 by Teledyne and Emergency-One (E-One) were fitted with independent suspension designed by Timoney Technology of Ireland. The success of the P23, and subsequent interest in an independent suspension solution for US Army and Marines 5-ton truck upgrade projects led to Oshkosh (and the then Rockwell) approaching Timoney with regard to a licence arrangement for the suspension. Following discussions with both, Timoney opted to enter into a licence arrangement with Rockwell (now Meritor). Oshkosh then developed two, possibly three independent suspension systems, including the set-up that came to be marketed as TAK-4 independent suspension system. The first use of TAK-4 independent suspension system was on an M939 5-ton truck as part of the Marines’ plan to upgrade its M939 fleet. The upgrade approach was ultimately abandoned, this replaced by a new-build approach for which the Oshkosh Medium Tactical Vehicle Replacement (MTVR) was selected. The first production contract for the MTVR was awarded in February 1999 and the type remains in production for the US Marines. The MTVR is fitted with TAK-4 independent suspension system independent suspension and was the first US mass-produced military truck with fully independent suspension (Tatra had been mass-producing independently suspended military trucks since the 1930s). Oshkosh has since fitted TAK-4 independent suspension system to its Palletized Load System (PLS) trucks, Logistic Vehicle System Replacement (LVSR) trucks and M-ATVs (MRAP – All-Terrain Vehicle), and the system has been retro-fitted to US Army/Marines General Dynamics/Force Protection Cougar MRAPs, BAE Systems’ RG-31 and RG-33 MRAPs. Oshkosh business units Pierce Manufacturing and Oshkosh Airport Products fit TAK-4 independent suspension system systems to a large amount of its fire trucks. Most recently the latest TAK-4i intelligent independent suspension system has been fitted to Oshkosh's L-ATV (Light Combat Tactical – All-Terrain Vehicle), selected to meet the US Army and Marines JLTV (Joint Light Tactical Vehicle) requirement. Oshkosh remains the market leader as of 2024 for independent suspension systems above the 5000 kg threshold, almost exclusively for large commercial vehicles, and excluding Striker and Pierce products, has equipped in the region of 30,000 military vehicles with the TAK-4 independent suspension system set-up. This figure will increase as JLTV production ramps up. To date the TAK-4 independent suspension system has accrued in excess of 1,000,000 actual durability test miles, most of these in extreme conditions. ==Description==

The Oshkosh TAK-4 (and TAK-4i) suspension is known as double wishbone independent suspension. This is an independent suspension design using two wishbone-shaped arms to locate the wheel. Each arm has two mounting points to the subframe and one joint at the knuckle, and in the case of TAK-4 independent suspension system these arms are of unequal length. The shock absorber and spring mount to the lower arm to control vertical movement. The double-wishbone suspension can also be referred to as ‘double A-arm,’ though the arms themselves can be A-shaped, L-shaped, or even a single bar linkage. The complete TAK-4 independent suspension system set-up also includes a subframe which contains the axle differential, half shafts, and wheel ends with steering attachments and brakes. TAK-4 independent suspension system accepts various spring mediums, but the vast majority of systems supplied by Oshkosh to date have been fitted with coil springs. Exceptions are the rear axles on the LVSR and the wrecker variant of the MTVR which are hydro-pneumatic struts with Hendrickson components. The light version offered as a potential HMMWV upgrade has a GVWR of 10,000 kg and offers around 14-inches of vertical wheel travel. In all cases the operating profile of the system is 70% off-road, 30% on-road. The new Oshkosh TAK-4i intelligent independent suspension system suspension provides 20-inches of wheel travel, and again a 70% off-road, 30% on-road operating profile. TAK-4i intelligent independent suspension system suspension is fitted to Oshkosh's JLTV/L-ATV. TAK-4i intelligent independent suspension system suspension is an ‘intelligent’ independent suspension, providing variable ride height through gas springs. ==TAK-4 Applications==

(coil springs unless stated) • M939 5-ton: Development for potential upgrade which evolved into MTVR procurement • BAE Systems RG-31 Mk5 MRAP: 97 TAK-4® independent suspension system upgrade kits supplied from February 2010, 21 new-build vehicles in early 2011 ==Gallery==

File:M939 with TAK-4.jpg|The first use of TAK-4 independent suspension system was on an M939 5-ton truck as part of the Marines’ plan to upgrade its M939 fleet. File:MTVR TAK-4.jpg|Oshkosh's MTVR is fitted with TAK-4 independent suspension and was the first mass-produced military truck with fully independent suspension. File:Pierce TAK-4.jpg|Oshkosh's TAK-4 independent suspension system is an option on the Pierce Arrow (F), Enforcer (F), Impel (F/R), Dash CF (F/R), Velocity (F/R) and Quantum (F/R) custom chassis. File:U.S. Air Force Staff Sgt. Ryan Vanterpool, an aerial porter with the 455th Expeditionary Aerial Port Squadron, chains down a mine-resistant, ambush-protected vehicle aboard an Air Force C-17 Globemaster III 131002-F-YL744-098.jpg|Oshkosh's MRAP – All-Terrain Vehicle (M-ATV) is fitted with TAK-4 independent suspension. About 10,000 M-ATVs have been built to date File:Five days, two pairs of socks later, Marine convoy operations in Afghanistan 131022-M-ZB219-479.jpg|The front axle pair of Oshkosh's Logistic Vehicle System Replacement (LVSR) 2022 are fitted with TAK-4, the rear axles are hydropneumatic struts with Hendrickson International components File:Stryker (3561270493).jpg|Oshkosh's Striker range of specialized Aircraft Rescue and Fire Fighting vehicles are fitted with TAK-4 independent suspension File:Hillcrest NY 2002 Pierce Dash Midmount Platform.jpg|Oshkosh's TAK-4 independent suspension system is an option on the front or rear axles of the Pierce Dash File:Oshkosh-TAK-4.jpg|Oshkosh's TAK-4 independent suspension system has been retro-fitted to US Army/Marines MRAPs including the General Dynamics/Force Protection Cougar File:Ridgback TAK-4-crop.jpg|A single example of the British Army's Ridgback MRAP (UK-specific version of Cougar) has been fitted with Oshkosh's TAK-4 independent suspension for evaluation ==References==