Tender specifications for boom mowers have recently begun to include a requirement for “twin-pump (two-station) gearboxes”. It is worth asking, however, what exactly this solution is and what consequences – both positive and negative – it entails.
Let’s start with the advantages. This solution is in fact used by only one Italian company, which manufactures its mowers in China, India and Romania. The main advantage is the effective limitation of competition in the tender or RFQ process. Purchasing a boom mower with a cast-iron twin-pump gearbox also carries the risk of lacking access to service and spare parts.
Another advantage is that when replacing the large or small pump, the other pump does not have to be removed. Experience shows, however, that after ten to fifteen years both pumps typically need to be replaced, which increases the total number of removals required. So this advantage is at best moderate.
Now let’s move on to the drawbacks of this solution:
- The large size of the multiplier significantly reduces the working space available for hydraulic repair work.
- Irregular fatigue wear on the main drive gear is twice as high as on a classic multiplier. When using mulching heads, verge cutters or ditch cleaners, the service life of a twin-pump gearbox is measured not in years but in months.
- Dismantling is difficult because it requires removing the entire pneumatic-hydraulic system to reach the multiplier.
- Requires twice as much oil to fill the gearbox.
- Additional bends in the hydraulic lines lead to energy losses.
- The cost of replacing the gearbox is several dozen percent higher than for classic single-pump gearboxes.
To sum up, no reputable manufacturer of boom mowers uses this solution. ROLMEX produced a pilot series of several boom mowers with this configuration in 2007–2010. However, the problematic nature of the design led the engineering team to discontinue this ill-conceived project.
