I had no idea that the 'mechanical' workings of a Grand Piano and an Upright Piano were so different. Yes, a Grand Piano has three pedals and an Upright Piano doesn't have the middle one; and the 'soft' pedal (the left one) operates differently on a Grand and on an Upright. There is information about both these things here:
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http://www.tierce-de-picardie.co.uk/viewtopic.php?f=404&t=6354
But also it would appear that the way the 'hammers' work is different on the two types of piano. Obvious really if I had thought about it, as the hammers on a Grand Piano are striking the strings 'upwards', and on an Upright Piano the hammers are moving horizontally. All is explained in this video.
Hugh