Ok I've tried to simulate 250W from a typical direct drive motor on the chart. If you look at the red line you see the power is about 250W-400W which I would say is typical for such a motor with 400W being peak, they don't peak anywhere as much as a mid-drive motor. You can also see the Newton metres peak at 38Nm which I would say again was typical for such a direct drive motor they don't go as high as fairly meaty mid-drive motor even 250W. You can also see the drop off at 25km per hour which again would be typical of such a motor. I've had to set the throttle to 60% in order to keep the watts as per a 250W configured motor as the original motor is more powerful. I've set the bike to the highest overall weight of 170kg which is the maximum setting unless you choose custom so a heavy ebike, heavy rider and a lot of touring luggage mounted. So as you can see from the chart at 8.8km per hour you start at about 44% efficiency and you peak at about 84% efficiency as you go faster so the average is about 64% efficiency. The issue is how much effort you put in, if you put in a bit more than 150W then speed and efficiency climbs but if you put less than 150W then efficiency and speed drops. However I have used an excessively loaded bike as the example at 120kg total load the average speed goes up significantly and the efficiency starts at 64% with this increased average speed. If you stay at 120kg total load and have a rider who can only produce 100W then the efficiency starts at 60%. There are no gear restrictions at all with a hub motor ebike so you could have a 3x11 setup if you wanted to to give you full control of your cadence and optimise your power levels in addition to the motor power. On very heavy ebike like that when you come down the hill you will get probably the full 15% regen so if the bike was expected to have assisted distance of 30 miles without regen you could get 34.5 miles. However the lighter the load of the bike the less the regen.
The All Axle motor takes the simplicity and robustness of the direct drive hub motor, and optimizes it for the modern bike platform. This hub is fully compatible with all quick release and thru-axle bike forks, it is over 30% lighter than standard generic hubs of similar power (4kg vs 6kg), and...
ebikes.ca
You are more than welcome to make a comparison with a mid-drive motor the point I would raise is going up the hill would significantly add additional wear to your drivetrain components and going down the hill would significantly wear your brake pads and inside the mid-drive motor itself as you climb you would have continued to wear down the gearing significantly if a steep hill especially with a load of 170kg.
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I appreciate the effort you are going to! I spent a fair time on the Grin Sim when deciding what the bike part of my solar plan would be, and for my requirements, which were influenced by the 1500km of long touring rides I did last year, and my plans for this year, I could not see a hub motor solution that worked, let alone a direct drive one.
My red lines are:
1. Properly UK pedelec rules compliant, not hiding lots of power behind a fake motor label. This gives some latitude, which I cap at short term power up to 500W, measured as electrical input not mechanical output. I have seen up to 470W on my Shimano, which makes me feel comfortable stretching it that far. I'm not willing to go to 750W or more.
2. Rider input constant, regardless of gradient, and limited to 100W. That is what I need, it will not be what everyone needs. As I mentioned some time ago, ebiking to me is biking with the hard work taken away. I don't mind going slowly up a hill, but I do mind working hard when I have a motor to do that for me!
3. Terrain: gradients of 1 in 5 must be possible albeit in bottom gear, without the need for rider effort to rise above 100W. This essentially means the bike can go up 1 in 5 without change in rider effort until the battery runs out, which it won't, because I'm towing a 330W solar trailer...
4. All up weight 125kg. That's bike, me, trailer, luggage.
I could not find any hub motor, geared or direct drive, on the sim that could meet my requirements, which is why I have a TSDZ2 sitting in a box for my old mountain bike, once I have finished learning about how to make a Shimano bike run on the sun!
I may be a special case for drivetrain wear too, as I am generally riding at human power of no more than 100W, and in lowest assistance level which is 140%, so my drivetrain is transmitting less than 240W. I have not gone looking for studies, but at a smidgen under 4,000km, 1400km of which has been in touring trim of 125kg or so, and 600km at an ill advised 150kg+, my first chain shows 1% stretch. I don't think that is too bad. Likewise, just about to replace brake pads for the first time.
The one thing I would like to have that the mid-drive cannot do is regen, and when I have time I may look into something like the Revos friction drive concept.
A lot has been said already, but I'll just add another little bit of 'from first principles' calculation:
At 250W motor output power plus 100W rider input, so 350W power, at 125kg mass so 1250N weight, rate of climb ignoring aero losses and rolling resistance is only 350 / 1250 = 0.28 vertical metres per second.
On my 1 in 5 requirement, that is a forward speed of 1.4m/s, or a tad over 3mph. That's the condition I would need a hub motor to manage. With a 700c wheel, that is about 38 rpm.
