To my way of thinking, applying car/motor vehicle logic to this, when talking about rotovators, quoting HP numbers is pointless. The number quoted will be the maximum output from that engine at a given RPM. With the single-cylinder motors fitted to most 'vators this normally occurs at about 45-5000 rpm, which is quite high. Most of the time you hear a tiller at work it's chugging along at about 3-3500 rpm, so producing less than maximum power.
Anyhoo, big-number HP is not what you really want, it's torque, which is the turning force the engine can produce. Most petrol-engined cars on the road produce roughly the same numerical amount of torque HP e.g. 200HP with 200 lb/ft of torque. The bigger artic lorries you see on the road produce around 8-900 HP from a 16-litre engine but around 1800 lb/ft of torque, which is what they need to lug 30-odd tonnes along. Same with a 'vator, you need turning force to drive the tines through the soil.
I'll take me anorak and go away now
