E-bike mid-drive motors hardly outperforms hub motors
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Jil
1 kW
I know, I used to have a BBS01 48V.sleepy_tired said:
I choose the BBS because it’s the only mid drive motor on Grin’s simulator.
On a Brose, a Bafang Mxxx, a Bosch, etc… you can fit a smaller front cog.
100 watts pedaling is what is generally considered doable by a standard individual on the long term.
Of course, on a 18% incline, it will be probably more.
But not for long. During the Tour de France Froome was able deliver 400 watts average on the Ventoux climb… for 1/2h.
Jil
1 kW
And for the same inclination, a mid-drive motor used on the right gear will be at ~80% efficiency.donn said:
The power limit in Europe is 250 watts nominal, but almost all mid-drive motors sold here have peak power above 500 watts (even some at 800 watts). But if you are on a long trip offroad and want to save your battery, you will better use 2 or 300 watts uphill (and your legs :wink: ) than 800.
classicalgas
100 W
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- 138
"The ideal e-bike drive is what you see on every EV in existence.. whether it's ships, or cars, or ships, or motorcycles, and that is single speed reduction drive. Automobile manufacturers largely abandoned multi-speed transmissions for EVs in the 1970s and for good reason, with very few exceptions. And they have to deal with producing a 1.5 to 3 ton vehicle that won't overheat in hills in congested traffic, yet will still happily accelerate quickly to 90 mph.
The challenges faced by e-bicycles is absolutely trivial in comparison."
Not exactly.
Tesla uses a front motor and a rear motor on several models, with different gear ratios, and uses software to feed more power to the one with the best ratio for the situation... to the high ratio motor when up to speed and cruising for efficiency, to the motor with the lower ratio when max acceleration is the goal.
A similar setup would work on an ebike...two small geared hub motors with different ratios, and software that would bias current toward the motor running most efficiently. Dual motors would also distribute torque loads..easier on spokes and dropouts.
https://cleantechnica.com/2022/08/17/why-simulate-a-manual-transmission-when-a-real-one-would-be-great-in-an-ev/
"Though, there is one problem. Electric motors do not generate the same torque from zero to maximum RPM. They all put out full power until a certain speed; then their torque begins gradually decreasing. Efficiency also varies speeds that the motor is capable of going. The sweet spot, where they are most efficient, ranges around ⅓ to ½ power at 30–40 MPH (50–65 km/h).
Even though an EV will operate from 0 RPM to the max speed of the motor, it won’t have as much power or range if its single gear is only meant for city driving.Fixing this by making the gear “taller” could theoretically help, but then the car’s performance and efficiency would drop in city conditions.
Most people are unaware that Tesla’s original plan for the Roadster was to have a 2-speed gearbox. This would provide optimized performance by having a lower gear for initial acceleration and then transitioning into a higher gear once the desired speed was reached. However, when compared to other EVs in development at the time, such as the Nissan LEAF with its 94 MPH (151 km/h) top speed or Chevrolet Volt which achieved around 101 MPH, it became clear that this idea wasn’t feasible.
The trouble was that Tesla couldn’t manage to create a multi-speed gearbox able to bear the torque of an electric motor. It was already struggling with cost delays, and had no choice but to give up on the multiple speed transmission. However, work on the “Whitestar” prototype for the Model S gave it another idea: by improving power electronics, it could stuff more electrons into it to make an even longer torque curve (i.e., more speed).
The inefficiency of that approach, however, is evident. Using more power to improve the performance tradeoff might work in theory, but it’s not feasible because current battery technology wouldn’t be able to support it for very long.
Tesla discovered that the best way to use two gears was by placing one in the back and another in the front. This created a powerful car that could maintain speed on highways while also being able alter power when necessary for city driving. Tesla’s implementation of dual motor drive units allow its cars, such as Models S, X, and 3, to have different gear ratios depending on whether it is needed for lower or higher speeds. In “range mode,” the computer directs more power toward the drive unit with the gearing that best fits the situation when cruising on the highway.
So, many Tesla vehicles do in fact have multiple gears and do get better range and performance by doing this. So, having a simulated manual instead of a real one would make less sense, because EVs can really benefit from having multiple gears."
The challenges faced by e-bicycles is absolutely trivial in comparison."
Not exactly.
Tesla uses a front motor and a rear motor on several models, with different gear ratios, and uses software to feed more power to the one with the best ratio for the situation... to the high ratio motor when up to speed and cruising for efficiency, to the motor with the lower ratio when max acceleration is the goal.
A similar setup would work on an ebike...two small geared hub motors with different ratios, and software that would bias current toward the motor running most efficiently. Dual motors would also distribute torque loads..easier on spokes and dropouts.
https://cleantechnica.com/2022/08/17/why-simulate-a-manual-transmission-when-a-real-one-would-be-great-in-an-ev/
"Though, there is one problem. Electric motors do not generate the same torque from zero to maximum RPM. They all put out full power until a certain speed; then their torque begins gradually decreasing. Efficiency also varies speeds that the motor is capable of going. The sweet spot, where they are most efficient, ranges around ⅓ to ½ power at 30–40 MPH (50–65 km/h).
Even though an EV will operate from 0 RPM to the max speed of the motor, it won’t have as much power or range if its single gear is only meant for city driving.Fixing this by making the gear “taller” could theoretically help, but then the car’s performance and efficiency would drop in city conditions.
Most people are unaware that Tesla’s original plan for the Roadster was to have a 2-speed gearbox. This would provide optimized performance by having a lower gear for initial acceleration and then transitioning into a higher gear once the desired speed was reached. However, when compared to other EVs in development at the time, such as the Nissan LEAF with its 94 MPH (151 km/h) top speed or Chevrolet Volt which achieved around 101 MPH, it became clear that this idea wasn’t feasible.
The trouble was that Tesla couldn’t manage to create a multi-speed gearbox able to bear the torque of an electric motor. It was already struggling with cost delays, and had no choice but to give up on the multiple speed transmission. However, work on the “Whitestar” prototype for the Model S gave it another idea: by improving power electronics, it could stuff more electrons into it to make an even longer torque curve (i.e., more speed).
The inefficiency of that approach, however, is evident. Using more power to improve the performance tradeoff might work in theory, but it’s not feasible because current battery technology wouldn’t be able to support it for very long.
Tesla discovered that the best way to use two gears was by placing one in the back and another in the front. This created a powerful car that could maintain speed on highways while also being able alter power when necessary for city driving. Tesla’s implementation of dual motor drive units allow its cars, such as Models S, X, and 3, to have different gear ratios depending on whether it is needed for lower or higher speeds. In “range mode,” the computer directs more power toward the drive unit with the gearing that best fits the situation when cruising on the highway.
So, many Tesla vehicles do in fact have multiple gears and do get better range and performance by doing this. So, having a simulated manual instead of a real one would make less sense, because EVs can really benefit from having multiple gears."
Ianhill
1 MW
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Have a look at a chain and deralier efficency and weigh it up against even the most efficent gearbox and you will see why the deralier system is still king of the hill, it loses the least power had a very wide ratio range and weighs the least.
Bicycle is applying a few kw of power at best so the need for a more stronger drive train aint there gearbox for cars has lots of weight and torque to deal with so a chain would stretch and xause maintence issues.
The old saying if it aint broke dont fix it comes to mind even still pawl engagement and clutched derailers have developed a system thats the best money can buy to date and foreseeable in my view.
Theres belt drives and geared hub for commuters that dont need such a wide gear ratio in exchamge for less maintenance.
Bicycle is applying a few kw of power at best so the need for a more stronger drive train aint there gearbox for cars has lots of weight and torque to deal with so a chain would stretch and xause maintence issues.
The old saying if it aint broke dont fix it comes to mind even still pawl engagement and clutched derailers have developed a system thats the best money can buy to date and foreseeable in my view.
Theres belt drives and geared hub for commuters that dont need such a wide gear ratio in exchamge for less maintenance.
ZeroEm
1 MW
Own a 2013 Nissan leaf it uses a CVT or Continuously variable transmission so it has a low and high gear. But it is still a belt.
I take my DD hub ebike to CO. in the summer and the hills eat up the battery super quick and the torque is real bad. I have never owned a middrive but know a friend who beats dirtbikes using one on steep hills. A 20" wheel will help the torque but I still get sad when feeling the limits of a DD hubmotor.
You need power, cooling and speed to take advantage of a DD motor on steep hills. If you want to climb a 20% hill at 35mph, then choose the DD motor.
Being able to climb faster can be an advantage. If you want to climb a 20% hill at 15 mph, like on a technical climb, then choose the mid drive. Being able to climb slower can be an advantage. In both cases, you want the motor to be spinning in an efficient part of the RPM range.
HillCruiser
10 W
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- Jan 19, 2022
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- 81
I climb true 19-degree hills with my 750 watt hubmotor with a 35a controller.
Pedalling like crazy , I use the mechanical gears to keep the motor from bogging down.
Every direction from home is uphill and I mean big hills rolling away towards the horizon.
10,000 km later and I'm rewarding her with new a freewheel, derailleur, chainring and a shiny new chain to replace the original components.
How can a guy get 10,000km on a chainset? Well, he could buy a hub motor and keep her lubed.
I buy big cans of Canadian Tire Chain Lube at C$8 and never let things run dry.
On the "other" forums there is a concerted push to get people to buy mid-drives. $$$$$$$$$$$
I always wrote it off as passive advertising for their bike shop/dealers.
If you want to ride around the block and look sveldt and sophisticated, buy a mid-drive.
If you want to get out and actually ride for miles and miles and miles and prefer minimum maintenance, get a hub drive.
Gravity is gravity...
Pedalling like crazy , I use the mechanical gears to keep the motor from bogging down.
Every direction from home is uphill and I mean big hills rolling away towards the horizon.
10,000 km later and I'm rewarding her with new a freewheel, derailleur, chainring and a shiny new chain to replace the original components.
How can a guy get 10,000km on a chainset? Well, he could buy a hub motor and keep her lubed.
I buy big cans of Canadian Tire Chain Lube at C$8 and never let things run dry.
On the "other" forums there is a concerted push to get people to buy mid-drives. $$$$$$$$$$$
I always wrote it off as passive advertising for their bike shop/dealers.
If you want to ride around the block and look sveldt and sophisticated, buy a mid-drive.
If you want to get out and actually ride for miles and miles and miles and prefer minimum maintenance, get a hub drive.
Gravity is gravity...
That must be offroad since there aren't many, if any, paved roads with a 35% grade. What kind of tires are you using?
HillCruiser
10 W
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- Jan 19, 2022
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It's an old tarmac road and is actually called "19 degree hill" (because nobody can pronounce the real name). When I want to test how things are working, I head over that way and challenge it. When I had only 500w to battle it with, it always won. The locals used to take their new cars packed with their buddies to see if they could make it to the top
I'm using stock tires in the summer and Cake Eaters in the snow...
PaPaSteve
1 kW
Take a look at the inside of a Leaf gear reduction
Nissan Leaf transmission - openinverter.org wiki
That must have been a challenge to pave. Are you in New Zealand?
The world's steepest street
Baldwin Street in New Zealand is the world's steepest residential road.
www.bbc.com
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Middrive is a great concept... it just have to be kept separate from human power.
Left-sided middrive single step reduction with short pitch chain or a belt can be much (~3x) lighter, yet more power dense, more efficient, can be force cooled easily if needed, needs no torque arms does not have long phase cables that cost efficiency and prone to damage, provides highly useful regen on demand
It just have to be integrated into bike construction to be most effective and easy to use... just like conventional 'crank drive middrive', incidentally! The fact that those you can buy are usually heavy and inefficient monstrocities is besides the point...
Add small light front hub motor and you have an awd system that weight less than one DD motor, highly efficient at cruise, can regen brake but can provide tons of torque on demand.
Left-sided middrive single step reduction with short pitch chain or a belt can be much (~3x) lighter, yet more power dense, more efficient, can be force cooled easily if needed, needs no torque arms does not have long phase cables that cost efficiency and prone to damage, provides highly useful regen on demand
It just have to be integrated into bike construction to be most effective and easy to use... just like conventional 'crank drive middrive', incidentally!
The fact that those you can buy are usually heavy and inefficient monstrocities is besides the point...Add small light front hub motor and you have an awd system that weight less than one DD motor, highly efficient at cruise, can regen brake but can provide tons of torque on demand.
Some mid-drives only weigh 4-6 lbs. That's the motor itself and crank spindle, not including the chainring, etc.
I've never heard of a hub drive motor being only 4-6 lbs.
If you are a weight weenie you buy a newer mid-drive motor for sure. If you just want power in back a hub drive is fine.
Mclewis1
1 W
The Bafang 310 series hub motors are 5lbs, the slightly more powerful Shengyi SX series are just over 6. There are other smaller hub motors in the same range. But I think we do also have to separate the integrated mid drives that use motor specific frames from the more generic add on mid drives.
I guess my point is that if you are building an ebike there are some weight savings from the mid drives but I don't find they are that big as you are essentially adding many of the same components - just in a different package. There does however now seem to be some better engineering (smaller, more efficient and powerful designs) on some newer mid drive kits - for example the CYC Photon at 7lbs.
I ride both front and rear hub motor (Shengyi SX) commuter and road bikes that are very similar in ride quality and handling to the analog versions (they are both ridden like "regular" bikes over longer distances). With integrated controllers and minimal wiring they add only about 7.5lbs plus the battery. I fully agree however if you are seriously trying to keep weight down then yes, a well integrated mid drive can offer substantial weight savings ... and especially so in the stealthy internal BB driven designs.
Retrorockit
1 kW
Grin Technology in Canada has an online Ebike Simulator. It seems to be pretty accurate. Mid drives are in an optional drop down menu. You can model whatever you like there. Be sure to model a battery with enough continuous Amps for the motor. No 20A. battteries on a 30A. BBSHD, This is not the same as Amp/hours.
ebikes.ca
Motor Simulator - Tools
Our ebike motor simulator allows you to easily simulate the different performance characteristics of different ebike setups - with a wide selection of hub motors modeled, and the ability to add custom batteries and controllers and set a wide variety of vehicle parameters you'll be able to see...
ebikes.ca
Chalo
100 TW
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That's 1.44 kg which is about 3.17 lbs. So you could use two of them and still be in the 6 lbs range.
Holy crap that is light. But would I get it...no.
For a really low-powered front hub, may as well buy some $500 throwaway folding bike that's 250W in the back, the whole bike weighs 36 lbs and once the battery dies, it's in the trash.
If you saw the Strava data offroad for the strong intermediate and expert riders with '250W' mid-drive e-bikes and 550W peak power, you'd quickly realize how much mid-drives have evolved. Yes, the complete bike is often $10,000 USD. Which means it's a really nice bike even without the motor. But these guys are putting up ridiculous mph numbers on very, very difficult offroad areas, places that on a normal bike I'd walk the bike up and down many times. They are just shredding up and down these steep hills with 'underpowered' mid-drives.
OK, these are extreme situations from a pavement point of view. But if a decent percentage of mountain bikers now have these mid-drives, then from an offroad perspective it's not extreme, it's becoming the norm. More and more mountain bikers are joining up in groups of mid-drive e-bikes to take on these black and double black trails that would physically wear them out on a normal bike. Now they do the whole mountain without getting winded. Could a 250W hub drive on a really nice mountain bike do the same thing? I don't think so. We'll probably never know because no MTB manufacturer would put a 250W hub drive on a really expensive bike; they would put on at least 1000W or more if it's a hub drive.
If you instead took the reverse argument and put a 250 mid-drive or hub drive on the cheapest mountain bike out there, like $200 USD, then the performance will start to converge, because either electric drive method is going to be hampered in performance by the cheap bike's suspension fork, brakes, tires, etc. So it will narrow the difference offroad between both types of drives because the performance of the bike itself becomes the main limiter.
Bottom line: mid-drives watt for watt have 2x the torque of geared hub drives, which in turn have 2x the torque of direct hub drives. You'd need 4 times the watts of a direct drive to get the equivalent torque of a mid-drive. You need torque offroad to climb technical singletrack; pure horsepower alone can't do it or the bike will be out of control on the turns and larger obstacles. So there is a qualitative aspect to this as well that can't be ignored.
hemo
100 W
My bafang G370 is 3.5lbs , although not a power hub it will gainly tow a 200lb load on a trail with little ascent .
North America diyers are biased (if not obsessed) with power and speed, not everyone needst power or speed. It is horses for courses and the small powered hubs provide options for a light weight set up.
North America diyers are biased (if not obsessed) with power and speed, not everyone needst power or speed. It is horses for courses and the small powered hubs provide options for a light weight set up.
When talking 250w mid drive vs. a much larger (1000w+) mid, the difference will be how fast you can climb that steep hill (not so much an "if" it will climb it), and how picky the bike will be regarding it being in the "right" gear at any given moment. The bigger motors are WAY WAY more forgiving in that regard!
As far as "out of control" if you take a rider used to a 250w bike and put him on a 1500w bike, yup, agreed, he's going to feel out of control. Give him several days of seat time with the extra power, and I'm betting you're going to see a pretty serious smile starting to appear....
One variable I forgot to mention is the externally (chain) geared hub drive. The e-dirtbikes typically have 2000-5000W on a rear hub, and either one or two chains --- one chain = single speed throttle only. Two chains and there can be one or more chainrings in the front and a cassette or freewheel in the back. Those bikes can shred up and down singletrack trails as good or better than a typical 50-55 lb mid-drive ebike, because of the chain gear reduction. And of course the power. The major problem is that they tend to weigh between 120-180 lbs and are illegal in many places. They are really an electric motorcycle with offroad tires and suspension. I'm not saying that's bad, but it's not the same as a bicycle. A 250W mid-drive e-bike is a normal mountain bike that has a motor and battery attached to it. The Sur Rons, Segways, etc. are not bicycles, they are electric motorcycles.
Which brings me to the question: if someone souped up their bike up to or past 2000W with a direct hub drive and large battery, and the bike is over 100 lbs, is it really still a 'bicycle', or has it become more like a moped in: weight, looks, performance, etc.?
Which brings me to the question: if someone souped up their bike up to or past 2000W with a direct hub drive and large battery, and the bike is over 100 lbs, is it really still a 'bicycle', or has it become more like a moped in: weight, looks, performance, etc.?
I have now tried out a hub motor of slightly less power then my mid drive build.
I've road both.
Where I feel a big difference, well for one. I feel more comfortable climbing and off-roading on a mid-drive.
Speed on pavement or asphalt. Well, I think a hub is really nice all day long. Over bumps you really feel the weight on the back rim.
The Mid Drive, Yeah sure the one I have is heavy. (Maybe kit is ~20 lbs) and battery in backpack doesn't effect me much. But I'd take it down over bumps. Climb over roots ext.
Where Mid-drive give some grief is potential to derail increases. Wear on drive components is a lot higher. You must maintain the bike more.
But the weight is better placed. Hubs I imagine to replace is fun to rebuild the wheel. I just did a new rim, not my expertise.
If you don't mind replacing chains and drive components a mid drive is not so bad.
If you don't mind re-spoking a rim then maybe hubs are the way to go.
But overall maintenance will be less of a choice as more is what kind of riding you do.
I've road both.
Where I feel a big difference, well for one. I feel more comfortable climbing and off-roading on a mid-drive.
Speed on pavement or asphalt. Well, I think a hub is really nice all day long. Over bumps you really feel the weight on the back rim.
The Mid Drive, Yeah sure the one I have is heavy. (Maybe kit is ~20 lbs) and battery in backpack doesn't effect me much. But I'd take it down over bumps. Climb over roots ext.
Where Mid-drive give some grief is potential to derail increases. Wear on drive components is a lot higher. You must maintain the bike more.
But the weight is better placed. Hubs I imagine to replace is fun to rebuild the wheel. I just did a new rim, not my expertise.
If you don't mind replacing chains and drive components a mid drive is not so bad.
If you don't mind re-spoking a rim then maybe hubs are the way to go.
But overall maintenance will be less of a choice as more is what kind of riding you do.
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