The new Welte
Welte Fahrzeugbau actually wanted to show the third generation of its special forestry tractor W130 at the KWF-Expo in Hessen. Because this did not work out for known reasons, our author Johannes Sebulke had the machine explained to him shortly before delivery in the Welte factory in Umkirch.
The new W130 looks as compact and agile as the old one, although the bonnet has become larger. Welte has decided to fit the fine dust filter required for exhaust gas stage 5 under the hood in addition to the SCR catalytic converter. There it is protected and does not disturb forestry work. When you open the cover, all you can actually see are components of the exhaust aftertreatment system - the diesel moror is hidden somewhere underneath.
The larger bonnet drops sharply towards the front. This is why the view from the cab has remained good even when driving on the road. The same applies to the view through the panoramic window to the rear when the driver is working with a crane and to the clamping bench. Although Welte Managing Director Joscha Nühnen expects the new emissions standard to result in slight savings in fuel consumption, Welte has nevertheless increased the tank capacity for diesel by around 30% in order to increase the vehicle's operating time without refuelling.
The particulate filter of the new engine has a pleasant side feature: it also dampens engine noise. According to head of development Armin Riesle, the TÜV has measured better values in the cabin than in the previous model. The newly designed vibration damping between the diesel engine and frame and the new cab suspension also played a part in this, however. Welte has gone its own way here. Other manufacturers offer active cab suspensions, which tend to require more and more sensors, hydraulic valves and controls for the hydraulic cylinders. Welte, on the other hand, relies on passive cab suspension without electronics and hydraulics. The result is a combination of coil spring and shock absorber, similar to that used in a motor vehicle. "This enables us to achieve a noticeable reduction in vibrations," explains Nühnen, also referring to the "reasonable price" of the solution.
The SIB gearbox remains
In the further development of the W130, Welte considered in detail whether the continuously variable SIB transmission (shifting in motion) should be further developed or whether a CVT transmission would be the better choice. In the end, the Umkirch-based manufacturer stuck with the proven SIB. The reason: CVT transmissions are predestined for vehicles that often have to drive longer distances, for example agricultural tractors or forwarders. However, because they are also hydro-assisted or purely hydraulic, depending on the type of transmission, the effort involved is higher.
Welte's SIB transmission is mainly suitable for reversing tractors, for which hydrostatic starting, braking and reversing is still the main stress. At the same time they often want to drive fast without excessive hydraulic losses. "Drivers try to avoid long transfers on their own axles," says Nühnen with conviction. This is why Welte has decided to stick with its SIB solution, but to redesign it completely.
As a reminder, the SIB drive system is a purely hydrostatic drive with a downstream purely mechanical two-speed transmission that can be shifted while driving. Shifting is possible in the green overlap area and is done automatically after the driver has selected a gear. When shifting in the green overlap area, the load is reduced, neutral is engaged, the hydraulic speeds are readjusted, the new gear is engaged and the tractive force in the new gear becomes effective. The whole process takes only one second. This is enough for adjusting the diesel engine, Hydraulic moror and pump, gearbox, sensors, CAN bus data transfer and CPU runtime. The tractive force-torque diagram shows a quasi stepless progression from zero to maximum speed over both driving ranges. "By changing gear quickly while driving, we can always keep the hydraulic motor in a fuel-efficient speed range," says Nühnen. The transmission offers additional safety because in an emergency, it also functions without the automatic shifting system: You can continue working in any case, but with a standstill shift instead of SIB.
The heart of the SIB 3.0 drive is a new hydraulic motor in double design. These are actually two hydraulic motors, which are located in one housing and operate on a common adjustment disc. The piston pressures are partially supported on each other, which reduces friction on the supporting surfaces and increases efficiency. The new motor also made it necessary to redesign the gearbox. The gearwheel design now corresponds to the next higher gearbox design stage. The results of the redesign for the customer are:
- The tractive force is 25 % higher than before. This means that you can now work longer and more powerfully with second gear even when reversing.
- When driving on the road or over longer distances, you can select the Eco mode, in which the diesel engine turns slower and thus more fuel-efficiently than in working or slope mode.
- You can now drive continuously variable 0-14 km/h in first gear
- The desired gear can be preselected, automatic shifting takes place when the driving speed is within the green range and when there is partial load.
S-Series of Epsilon
Welte has built the S120R72 jib crane from Epsilon on the first W130 of the new generation, with a reach of 7.2 m, a net load moment of 114 kNm and a slewing moment of 36 kNm. "Our new W130 corresponds well with the S series from Epsilon," says Nühnen. There is now a clear allocation: for the W100 the M series, for the W130 series the S series and for the W210 the X series. The W130 from the third generation onwards is now suitable for mounting the Epsilon S110R and S120R cranes. It thus achieves net load torques of up to 119 kNm, slewing moments of up to 36 kNm and ranges of up to 9.6 m.
WelControl 2.0 is the control system for the entire machine, i.e. it regulates the diesel engine, the travel drive and the working attachments such as crane and winch. It now has two displays. The smaller one on the front windscreen is intended for road travel and only shows the functions that are important for this, such as travel speed.
The larger display is located at the rear of the cabin. The driver can move it to the left or right depending on his preferred working position. Welte has dispensed with the rotating display on the swivel seat to give the driver maximum freedom of movement. In the rear display, the driver can call up a wide range of masks, from operating data and setting data to a help mode. A special feature is that all functions can be set either by touch screen or with a rotary knob. When the service technician at Welte dials into the system for remote maintenance, he sees the same screen in front of him as the driver on site. This facilitates diagnosis and communication. The following new functions are also convenient:
- When leaving the vehicle, you can automatically leave a headlight on for a few more minutes (Coming home),
- or as an option switch on remotely when coming (Leaving home),
- or have the battery switch off automatically (so that you do not have to wait until the AdBlue lines are pumped empty).
The practical test
Welte delivered the vehicle to forestry contractor Michael Hund in mid-May. In the Ortenau region he has to deal with wetlands in the Rheinauen and slopes in the nearby Black Forest. The distances to the rear of the lake are often 200 m and more. He therefore appreciates SIB and quickly changes to second gear even for these short distances. Because of the stronger tractive power of the machine, another thought comes to his mind: In the rather flat terrain, you can stay in second, economical gear for long distances when working backwards and don't need to shift gears at all. The first gear then functions as an off-road reduction gear, which can be engaged quickly if necessary.
The complete article by Johannes Sebulke was published in the magazine "Fost & Technik", issue no. 6 June 2020