Is it in here?
http://www.c5alive.co.uk/pub/downloads/C5-UnofficialServiceManual.pdf
...you're right, there are a few graphs etc in there - but not what we need . I'm after the power curve that gives torque figures at given revs etc.
tbh Karl, think you will have problems with getting this info, Hoover would be the ones or perhaps Adam.
but i'd wonder at the value of it even if available, the original setup has the motor is running via a reduction gearbox @ 12v, so we can work out the reduction ratio, we also know this setup has very little grunt running at this voltage especially at lower revs and soon runs out of puff on inclines.
if you again lower te ratio then you will have more grunt but lower top speed
my 2pth , i think you have to make a decision whether to run with 12 volts and same gear ratio as original, or go for 24v allowing marginally higher gearing.
if you go this route you might have to do some experiments on what damage might be done if the motor is stalled.
you already have a machine running 24v so you know how effective it is with original gearing which seemed very sprightly to me. you can't please all the people all the time so now you need to decide if that performance is enough for most, personally i think it is as these machines were never designed to be quick
.
if anything my advice would be make the standard ratio box as i'm sure these will sell in bigger quantities, then make a 'MKII' performance option with a higher ratio.
i've seen mods using sturmy archer hub gears, might be another way forward later on.
regs
alan