David Roden wrote:
Interesting, but forgive me for saying that you're not quite answering the question.
The OP wanted to know what rating of motor to use for drive and what for mowing. However, you've given the TOTAL power USED by BOTH the drive and the accessories under certain conditions.
*Right*. That's why I included 3 numbers, one to drive and mow, one to till, and one to do big things like blowing snow. Because if I put an electric motor on my Craftsman 15.5hp, there's nothing preventing me from buying a snowblower attachment and giving it a go.
However based on my Elec-trak experience and numbers, a 5hp electric motor would probably not be able to handle the constant draws of blowing 2 feet of snow. That takes full power from the E20's main motor and full power from the blower mower to achieve.
And remember, you don't need a 12hp-rated motor go actually GET 12hp. Peak power of an electric motor is several times its rated power. I suspect a 2-3 hp motor would be more than enough to drive a tractor.
True, but there is also a bit more drag on a normal garden tractor due to things like the belt drives, indirectly-driven blades, and all the pulleys for the clutches. So I'd err on a slightly larger size (5hp) to more closely match the E20 and make it a happy tractor.
Technically you can get away with a 5-6hp gas motor on a normal tractor; my guess is they put 15hp engines on them to allow the use of bigger attachments and because it's not too much more difficult to make a 15.5hp single cylinder engine.
Chris