squeaker wrote:[XAP]Bob wrote:Seems pretty free running when idle, it is internally geared, so it's not fighting the motor.
Excellent[XAP]Bob wrote:No idea about the torque curve, but it is soft start - makes main roundabouts easy to negotiate......
Actually not really sure how to measure the torque curve at the moment...
Wasn't expecting you to measure it
Where I'm coming from (and this will prove that I'm not an electrical engineer) is on steep hills a 250W hub motor is essentially operating at a speed well below its rated 15mph. For example, some simple maths shows that on my local, mercifully not too long, 18% grade my ICE trike (all up weight of 90kg) needs about 300W for 4mph (sorry about the units), so I'm curious as to what a hub motor would put out at 25% of rated speed. I've read that some will exceed rated power under such conditions, using temperature sensing to stop internal melting (!) on long hills, but I suspect that's going to be specific to individual designs. (There are likely to be mechanical limits too.) So what I really want to know is how much assistance would I get in practice on said b*st*rd hill, as hill climbing is undoubtedly the area of weakness for my aging legs (and lungs) and the area where much time is 'lost'. If the assistance as such low speeds were 'small' then it's not really worth the hassle / weight (and I'd be better off fitting a Schlumpf MD to get a suitable crawler gear). Will be reading your experiences with interest!
Nice to hear about the soft start - are you just using it in throttle mode or do you have a BB pedal torque sensor for pedalec operation?
I suppose I could try and blag an extended test ride from a local e-bike dealer....
Pure throttle operation.
Going uphill remember that you are providing some power as well. I tended to be doing 13+mph - but I doubt any of my hills are at 18%.
If you can provide 150-200W as well the you are up over 400W..
Of course the real answer is 'try it' and the other answer is that you can get differently geared hubs - get one rated for a 26" wheel and use it in a 20" and you'll get better low speed performance.
The other 'obvious' solution is to wait until next year when ICE make their BB drive available (it was really good when I tested it - the pedal sensor was torque based, and really made the system very elegant).