The timber grapple is the forwarder’s right hand. The operability and the reliability of the timber grapple have a great effect on the cost effectiveness of the machine. But how do you recognise a good timber grapple?
The structure must be of high tensile steel and must suppress peak stresses. Furthermore, it must be strengthened additionally to an adequate extent against the excessive loads experienced in the field. The steel structure must be welded to perfection if the plates are to be interconnected over large areas and with the minimum of internal stress. The optimal solution is when the various components are welded and form keyed connections.
A key component is the hydraulic cylinder, which may not exhibit any weakpoints and must undergo two million load reversals without leaking.
The bearings must be generously sized, and the pins be free of backlash at all times. Precision in all parts is a key prerequisite for a long service life and good driveability. “Driveability” may also be translated as “ergonomics”. The ergonomics has the greatest effect on the performance the timber grapple can attain.
If it is to attain a high performance, the timber grapple must fill quickly with a large volume averaged over all cycles. This applies to both the specific gripping of separate log and the takeup of multiple logs. A good filling ratio is obtained when the logs are rolled up together and aligned in the timber grapple. The shape of the claws must support this rolling and alignment. A round claw shape is also important for placing the sections at specific locations on the deck.
Building a longlife, productive timber grapple for a forwarder requires a lot of experience and years of further development in the design and manufacturing process. As a provider of professional timber grapples for forwarders, HULTDINS has been leading the field for many years.