Introduced in 1989 to replace the SH30, the Reco Mengele SH40 trailed forage harvester remains a popular machine, with few changes made to the original design. Although this is one reason why these foragers make a sound used buy, another is their potential output: With the right amount of power up front they can reliably chop 25ha a day, with 30ha+ performance regularly reported. James de Havilland reveals all