loopernow said:
Maybe I should start a separate thread for this, but I was wondering if someone could explain some basic concepts. Since starting this thread, I read elsewhere that more volts roughly translates to more speed and more amps to more torque. Torque = hill-climbing ability. And I understand higher rpm = higher top speed but less torque. I also get the impression that low-powered hub motors in particular, and hub motors in general, are not the absolutely best for hill climbing, because they are running at one particular gear ratio, and that gear ratio is not particularly low, in fact is generally pretty high.
Okay. So here's something I'm wondering. I also read in another thread where a guy was running a 328 rpm Q100 in a 700c and it was great for high speeds but he wouldn't operate it below 7-10mph because the motor struggled too much. Makes sense to me. What I'm curious about is, at what speeds (cadences?) are the various builds recommended to me...usable? Would the ebikes.ca calculator show me that? Having not ridden an ebike before, I'm struggling a little bit to understand. The way I envisioned my ebike is that it still handles/feels roughly the same, but that the same amount of peddle power from me would result in higher top speeds because I'm getting assistance. That's how I plan to use the bike: always assisted, never just the throttle. I guess it's just going to feel like it assists me about the same no matter what speed I pedal at (other than perhaps a low speed that is too low for meaningful assist) on flats, and then less and less the more of an incline I'm on?
If I dial back how much power is going to the motor with one of those LED/LCD panels or with the throttle, will that help the motor help me on hills? The ebikes.ca calculator seems to say that I can burn out one of these guys on a 5% grade in about 4 minutes at 100% throttle, but if I dial back the throttle to about 33% on that grade, the bike will go something like 3 mph without ever burning out. I don't know how much assist that would feel like, but I'm guessing it will be somewhat useful.
Motomech (sorry I got your name wrong previously, motomech) mentioned my legs spinning like a cartoon character's with a 13T smallest rear gear and a Q100H 260 rpm build...why would that be, and in what contexts?
I installed Cyclemeter on my iPad last night and went for a quick spin on my donor bike to see how fast I was going. I rode around a completely flat linear park near my house. I was surprised how fast I went at some points. I got up above 20mph (the 2nd line from the top) 5 times, went 27-28 mph twice (the top line), and mostly stayed in the 12-20mph range. It was an 8-minute, 1.67 mile trip, punctuated by slow-downs for stop signs, speed bumps, turns. I was trying to go fast, but in a fun way. Probably exerted myself to 85-90% capacity at top speeds.
host image online
Here's a graph of the elevation changes on the 10-mile commute to work (NOT the same trip as the graph above!):
upload image online
I hope that's not too many questions. I appreciate all the suggestions so far and I realize I have to settle on something. Just want to understand a little better how the bike will actually perform with different setups. I'm also thinking of taking the Cyclemeter app with me on a commute to work, to perhaps post here before making a decision.
Maybe I should start a separate thread for this, but I was wondering if someone could explain some basic concepts. Since starting this thread, I read elsewhere that more volts roughly translates to more speed and more amps to more torque. Torque = hill-climbing ability. And I understand higher rpm = higher top speed but less torque. I also get the impression that low-powered hub motors in particular, and hub motors in general, are not the absolutely best for hill climbing, because they are running at one particular gear ratio, and that gear ratio is not particularly low, in fact is generally pretty high.
All good questions, and your assumptions are correct. The concept of torque as applied to electric motors is more complicated than say, "the ability to climb", but we will just leave it at that for now.
And yes, hub motors have a limited range and will always be most efficient as the motor approaches it's no-load(top speed)point. That's why the 260 mid-speed mini-motor is the best compromise for the vast majority of riders. The larger hub motor in a more powerful system is less constrained and can widen the "powerband".
But the simplicity of the hub motor makes it attractive when not too much is asked of it.
I also read in another thread where a guy was running a 328 rpm Q100 in a 700c and it was great for high speeds but he wouldn't operate it below 7-10mph because the motor struggled too much. Makes sense to me. What I'm curious about is, at what speeds (cadences?) are the various builds recommended to me...usable? Would the ebikes.ca calculator show me that?
Yes, the Ebike sim. is very good to understand the relationship between motor speeds and road speeds.
Use these three mini motors;
MXUS FXO7-201
Outrider std.-260
Cute 328-328
These are supposed to be no-load speeds, on the test stand @ 36V, but only the 260 rpm motor are actual. The 201 rpms are actually in the 220 to 230 range and the 328's are usually around 280 to 290. I know, don't ask why, it's complicated.
Plug in the Outrider on 36V and note that the top speed is 20 mph using around 330 Watts. Now I have read that racers can put out more than that, but realalisticly, for the avg. rider, sustaining even 200 W over a long time will be a chore. So let's add 200 on top of the motor and see what we get. Move the dashed line to where the difference between required load and motor power is 200 Watts and we get 21.8 mph. 100 Watts might even be a better load for a rider to get a workout and not arrive sweaty and exhausted and that would be 21 mph(Of course, hills and head winds are going to change things).
This describes why the perfered way for most of us who like to assist use a method of setting the speed with the cruise at a speed 1 to 2 mph lower than you want to go and add with the legs. This works very well with low powered motors, but the other option is to use PAS. On a mini motor, the top speed most likely will be the desired cruising speed, so a simple speed-limited PAS system works fine. But on a larger, more powerful system, the rider is likely going to want to limit the speed to a lower setting. But what happens now is, once the PAS is engaged, the motor "torque" is not limited and the bike "blasts" up to the set speed
Not good. This is where the expensive "torque-based" systems shine, or even the "torque imitation" systems like the sine wave SO6S/SLCD-3 set-ups like BMS Battery sells.
The other thing to notice is the last and highest part of the efficiency curve is actually past the no-load speed and mostly out of reach. This tells us that maybe this motor speed is not a perfect to the Volts in terms of max efficiency.
So lets look at the 201 MXUS on 48V(cause we know it will be too slow on 36V). A little better efficiency(81% vs 79%), but not enough to make a difference if one considers that a 36V battery will have more capacity for the same money and size of a 48. Still, if you really wanted to go 21.5 mph....
And lastly, the 328 on 36V. We see efficiency has fallen to a poor 74.6 % with the meat of the efficiency band well past the no-load speed. This system would only be good for a serious racer that can put in a sustained 200 to 250 Watts and bring things up into a reasonable efficiency range.
I f I dial back how much power is going to the motor with one of those LED/LCD panels or with the throttle, will that help the motor help me on hills? The ebikes.ca calculator seems to say that I can burn out one of these guys on a 5% grade in about 4 minutes at 100% throttle, but if I dial back the throttle to about 33% on that grade, the bike will go something like 3 mph without ever burning out. I don't know how much assist that would feel like, but I'm guessing it will be somewhat useful.
What's missing here is the reality that, partial throttle settings won't sustain a slow speed. Once a mini falls to half of the no-load speed, the speed just drops like a rock irregardless of the throttle setting. When it happen to me, I just cut the throttle a little before and get off and push. The idea is to hit the bottom of the hill as fast as you can and try and maintain as much speed as possible.
Motomech (sorry I got your name wrong previously, motomech) mentioned my legs spinning like a cartoon character's with a 13T smallest rear gear and a Q100H 260 rpm build...why would that be, and in what contexts
I run a 11T/48T combo and can pedal along up to about 25 mph. How fast were you pedaling at 20 mph? Go to the Sheldon Brown website for his gearing ratio charts.
I installed Cyclemeter on my iPad last night and went for a quick spin on my donor bike to see how fast I was going. I rode around a completely flat linear park near my house. I was surprised how fast I went at some points. I got up above 20mph (the 2nd line from the top) 5 times, went 27-28 mph twice (the top line), and mostly stayed in the 12-20mph range. It was an 8-minute, 1.67 mile trip, punctuated by slow-downs for stop signs, speed bumps, turns. I was trying to go fast, but in a fun way. Probably exerted myself to 85-90% capacity at top speeds.
While you can hit higher speeds as a pedal bike and think, "this isn't that fast or unsafe", the difference when it's an Ebike is, you will be doing it all the time. The odds that you will get cut off by a car, or hit something in the road(maybe in the dark) are expodentuialy higher. Plus your butt is more likely on the seat and the bike is now carrying extra weight.
In time, you will yern for a full suspension mountain bike with hydro brk.s to soak up the bumps and will stop on a dime.
These are mine;
https://endless-sphere.com/forums/viewtopic.php?t=48004&p=706056#p706056
Not nader's(I wish), but the two halfway down the page.
Whenthose pics were taken, they were both frt. whl. drive(which is what I would do if I were you).
The Rocky Mountain is now two whl. drive.
