In May 2016, Komatsu Forest launched their new 8 WD harvester 931XC at Komatsu days in Umeå, Sweden.
Komatsu 931XC is the eight-wheel harvester that closes the trending 8WD circle among midsize harvesters from leading manufacturers. The reason to go on eight wheels (four bogies) has been discussed lively in Scandinavia and other countries. Komatsu reason appears already in the model label XC which stands for Xtreme Conditions.
Why 8 wheels?
Xtreme Conditions in this case are mainly two types: soft, sensitive grounds where you get a lower ground pressure the more the wheel you have but also steep terrain where more wheels contribute for better traction and grip.
The circle is now closed with the 931XC in this segment where you find the major competitors as Eco Log Steephunter 688, Gremo 1050H, John Deere 1270G 8WD, Logset 10H 8WD, Ponsse Scorpion and Rottne H11.
In addition to these, there are both smaller and larger harvester with eight wheels, but they’re not really in the same league. Thinking of as Ponsse Bear 8WD, Rottne H21d (heavy final felling) but also Tigercat 1135 (thinning).
Still the Komatsu Way
The Komatsu 931XC is based on the same concept with stiff waist all Komatsu harvesters. Komatsu chose the solution to put a pair of bogie on its proven pendulum axle. This sets the 931XC apart from the rest of the harvesters above who use a stiff axles and a pendulum waist instead.
The pendulum axle has an axle oscillation of 16 degrees (same as 6WD version) and the rear, new bogie has a bogie range of 22 degrees. The front bogie has a range of 28 degrees.
Compared to it’s predecessor
The XC model has also got 10% more traction in the transmission and can now offer a maximum of 187 kN. Eight wheels usually means higher machine weight, and that’s the case here also. The “normal” 931 harvester has a start weight around 19.5 tons. The 931 XC weight 21.7 tons. But it seems to be a general opinion that the extra weight doesn’t make any negative influence in this context because you get a lower ground pressure when distributed on more wheels or even tracks.
The stability also increases. In the video below the operator demonstrate by provoking to raise and lower the 11 meters crane at full range with a C144 head at the boom tip and the machine stays put! Except for the specifications described above, the 931 XC has the same performance and structure as the conventional, six-wheeled Komatsu 931.