Nimrod 6-8T Tilt Hitch
Background:Nimrod Engineering Ltd is a steel fabrication company specialising in the design, maintenance and repair of earthmoving attachments, including hitches and buckets. The development of a 6-8 tonne tilt hitch scaled from a 12 tonne model was experiencing problems in the initial prototype stage with hydraulic plumbing of the mechanism due to minimal clearances between moving parts.
Motovated Design & Analysis Ltd were employed to develop several alternate solutions using advanced 3D solid modelling. Seven concepts were generated and reviewed, and a novel single cylinder design accepted. This was then virtually prototyped, and the function and strength of the design verified prior to manufacture using finite element analysis (FEA).
The design specifications to be met were:
- Robust, simple hydraulic plumbing
- Tilt torque equivalent to existing designs and a tilt angle of ±45°
- Economical manufacture
- Minimum bucket to boom distance maximising breakout forces
- Components located within hitch for a slim-line profile and protection
A single cylinder design was chosen over a dual cylinder design due to space restrictions, and the direct cost saving of a cylinder.
Extensive mathematical modelling of the load cases was undertaken, and the results used to perform a Finite Element Analysis on the mechanism weldments (Figure 2). This highlighted areas that required strengthening due to the non-symmetric loading of the cylinder, and was used to verify the structural integrity of the design.
The final solution meets all the design criteria, with significant weight savings and reduced size compared to competitors. It also provides for 180% of competitors tilt torque in one direction and equal tilt torque in the other, or may be plumbed for equal torque and speed in both directions if desired.
Motovated provided manufacturing drawings using simple plate profiles and tabbing to allow accurate alignment on welding, resulting in a superior, cost effective design covering a wide variety of excavators.