E-bike mid-drive motors hardly outperforms hub motors

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Re: E-bike mid-drive motors hardly outperforms hub motors

Post by donn » May 05 2021 11:12am

ferret wrote:
May 05 2021 9:26am
As I wrote before, running 2 identical motors at identical RPM at identical road speed will give nearly identical efficiency regardless of where they are installed.
According to the 0 degree slope example, this motor's peak efficiency is at 320 RPM. The rear motor setup will only operate at peak efficiency at 30 kmh. The mid motor's peak efficiency at 320 RPM can be used at several different speeds, Therefore the amount of time spent riding at peak efficiency is potentially greater with a mid motor.
That's in his graphs. The simulated crank drive is more efficient, since it's operating at 320rpm the whole time. It just doesn't make a really big difference.

Actually, I'm not real sure what he's up to there. The "remains constant at all travel speeds" would require the simulated gearing to approach an infinity ratio at the beginning, which seems a little silly - and doesn't match the graph, as I interpret it anyway. The simulation apparently does use some gearing advantage, because the outcome is different from the hub motor.

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Re: E-bike mid-drive motors hardly outperforms hub motors

Post by Ianhill » May 05 2021 11:31am

Tell that to the guys running belt drive and big power middrive scooters and they will piss themselfs the belt loses a good 5% of the power before it even hits the tyre wall theres loses all along the system while a hub drive just loses power to the tyre flex alone.

Theres some serious scooters kicking about taiwan that push out 50kw and spin a 12inch hub to 3.5krpm thats pushing the limits of whats capable but that same inout power even on a chain drive wont be as efficient.

Torque advantage has its place but a well sized hub motor can be so torque heavy that it will pull hard enough to break traction hold a wheelie and power on to crazy high speeds with FOC.

I seen a video of a guy revving his dualtron in Thailand and the liytle 6.5 hub expands its tyre like a drag car i was impressed with that but that 50kw scooter i talk about looked damn scary i wouldnt go near it if that went wrong it will take out half the block its a 20kg flywheel basicly spinning over 3krpm i dont wont to work out its kinetic energy because oneday i wouldn't mind having a pop at something simular myself.

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Re: E-bike mid-drive motors hardly outperforms hub motors

Post by MadRhino » May 05 2021 1:54pm

Yep. Hubs are simple, efficient, durable, and easy to build.

Mid drives are for extreme requiremrnts
Extremely low or extremely high power
Extremely light weight
Extreme terrain

So many bike manufacturers are building with BB drives nowadays because of the low power legal limitations and the light-weight marketing in bicycle industry. They are making very good ebikes for the bicycle sport crowd, but very poor commuters that are high maintenance and low performance.
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Re: E-bike mid-drive motors hardly outperforms hub motors

Post by neptronix » May 05 2021 2:07pm

MadRhino wrote:
May 05 2021 1:54pm
So many bike manufacturers are building with BB drives nowadays because of the low power legal limitations and the light-weight marketing in bicycle industry. They are making very good ebikes for the bicycle sport crowd, but very poor commuters that are high maintenance and low performance.
Yes, it's kind of a dumb trend isn't it? for the typical commuter it would be much better to use a dual geared reduction hub motor. Those motors are butting heads with the power density of most mid drives, and a 5-8lb hub has a really small impact on rear suspension performance.

Many of these commercial mid drives are overengineered, hard to get parts for, and lock you out of modification. They may be sleek and have great weight balance, but unless you're offroading or hill climbing, you won't see the benefit.
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My first major build: 1.6kW 8T MAC motor on a Trek 4500 MTB.
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Blue Dream: Maxaraya FS semi recumbent and high efficiency mid-drive - under construction.

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Re: E-bike mid-drive motors hardly outperforms hub motors

Post by donn » May 05 2021 3:05pm

What I think is funny is that when recumbent riders start thinking about an electric drive, practically every one of them decides it's got to be a crank drive. Because of the obvious efficiency advantage - just like the obvious aerodynamic advantage that sold them on recumbents. You can't tell them it isn't real - because it is! It just isn't nearly as meaningful as they think it's going to be.

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Re: E-bike mid-drive motors hardly outperforms hub motors

Post by neptronix » May 05 2021 8:25pm

Actually the right sized hub on flat ground will be 5-10% more efficient regardless of bike.
3 less gear and chain reductions makes a difference.
This is why electric cars generally don't use gears. Friction loss is a bitch even if you have a super efficient motor at the end of it.

The only thing that can swing the efficiency picture is a non-optimally chosen hub motor in a recumbent which has a small wheel. However, in smaller wheels, the continuous power of every motor will increase, so that's a big benefit ( you can use a smaller motor for the same power you'd use in a 26" wheel etc. )
"Love and compassion are necessities, not luxuries. Without them, humanity cannot survive." - Dalai Lama

My first major build: 1.6kW 8T MAC motor on a Trek 4500 MTB.
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Re: E-bike mid-drive motors hardly outperforms hub motors

Post by MadRhino » May 05 2021 9:37pm

Well, riders who don’t care about efficiency and beat the crap off their bikes day after day, are much better with hubs because mid drives are making them more time tempering than riding.
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Re: E-bike mid-drive motors hardly outperforms hub motors

Post by Ianhill » May 05 2021 10:38pm

I not saying gearing doesn't have its place like when moving very slow and its in practical for a motor to spin so slow.

For example a mobility scooter travels mph must carry 150kg load and all in a small wattage footprint then i agree gearing is a better use than a massive motor to output the torque figure that would never spin on to any faster.

But those mopeds they can put out all the torque thats needed to flip in the air on a massive hill and then iy will go on to higher speeds needed so it makes sence to add the motor mass because it will be used for torque to pull off and high speed situations.

I suppose you could go the otherway with a big enough chaindrive motor and small bike to start turning the wheel more times than the motor shaft but that would be like a 4kw 138qs motor on a 30kg bmx or simular.

Efficiency is balance im no expert but id say in general daily driving on off power there wouldn't be alot in a well balanced system of all varieties few WH here and there and as one regens better its controller driven too a cheap setup wouod prefer the chain druve but money well spent on a vector foc controlller and powerful hub would see it even out maybe turn in favour of the hub in general driving.

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Re: E-bike mid-drive motors hardly outperforms hub motors

Post by fatty » May 06 2021 2:25am

neptronix wrote:
May 05 2021 8:25pm
This is why electric cars generally don't use gears. Friction loss is a bitch even if you have a super efficient motor at the end of it.
All electric cars use gears. 1-speed fixed gears, but gears nonetheless. Certainly not direct drive.

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Re: E-bike mid-drive motors hardly outperforms hub motors

Post by fatty » May 06 2021 3:23am

avandalen wrote:
May 04 2021 6:39am
I would like to know how others think about this.
Excellent quantitative analysis.
For completeness, I've attached the Excel from which these conclusions were drawn.

You are likely receiving pushback in this thread because your title and conclusions are both mislabeled. Per your GitHub project, you evaluated efficiency vs speed, comparing the same motor in a hub-drive and mid-drive configuration -- not nebulous "performance". It is no surprise that the same motor exhibited nearly identical stead-state (cruise) efficiency -- this is a characteristic inherent in electric motors. Efficiency is at the bottom of the list of criteria to select a drive configuration anyway.

You're also receiving pushback because your 250W analysis is foreign to most enthusiasts here. I would expect the starting power here is an order of magnitude higher.

To the former, mid-drive is used in power-limited scenarios to leverage the existing bicycle gearing. 20Nm from the same motor can be geared down (via 32T chainwheel to 52T cog) to 32.5Nm. This is very noticeable.
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E-bike hub and mid-drive motor simulation.xls
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Re: E-bike mid-drive motors hardly outperforms hub motors

Post by neptronix » May 06 2021 8:24am

fatty wrote:
May 06 2021 2:25am
neptronix wrote:
May 05 2021 8:25pm
This is why electric cars generally don't use gears. Friction loss is a bitch even if you have a super efficient motor at the end of it.
All electric cars use gears. 1-speed fixed gears, but gears nonetheless. Certainly not direct drive.
I know that and you know that; i meant gears other than the reduction itself :P
"Love and compassion are necessities, not luxuries. Without them, humanity cannot survive." - Dalai Lama

My first major build: 1.6kW 8T MAC motor on a Trek 4500 MTB.
Monster MTB: Leafmotor 1500w @ 4kW on a Turner O2 full suspension.
The monster scooter: Heavy duty Cannondale semi recumbent - under construction.
Blue Dream: Maxaraya FS semi recumbent and high efficiency mid-drive - under construction.

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Re: E-bike mid-drive motors hardly outperforms hub motors

Post by Manbeer » May 06 2021 9:45am

neptronix wrote:
May 05 2021 2:07pm

Many of these commercial mid drives are overengineered, hard to get parts for, and lock you out of modification. They may be sleek and have great weight balance, but unless you're offroading or hill climbing, you won't see the benefit.

Honestly, I think that's just it. We are seeing the trend of things being shifted more into dealer/authorized service requirements. Literally everything nowadays has some type of proprietary cable and software for diagnostics… Air conditioner units, pool heaters, cars it's just the beginning. We already know performance can be Matched or surpassed for much less but these are well integrated systems that ensure little to no user serviceability and a steady stream of revenue for years to come till they're forced into planned obsolescence

edit- Had to turn down a customer that wanted a rear shock rebuild on a newer Cannondale Jekyll. It's a fox dyad pull shock, So far as I can see the only place we are parts are available for me to buy are in Europe And it looks like such a pain in the ass I just told him to go elsewhere

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Re: E-bike mid-drive motors hardly outperforms hub motors

Post by TDB » May 12 2021 8:50pm

avandalen wrote:
May 04 2021 6:39am
I wrote an article where you can read that a mid-drive motor hardly outperforms a hub motor.

https://www.avdweb.nl/solar-bike/hub-mo ... ive-vs-hub
Image
In practice there is no significant difference in performance. You can clearly experience this yourself during test drives with both kind of motors, I did this myself too. Because I wanted to know the cause, I researched this subject extensively. The conclusion is that the advantage of mid-drive motors is only noticeable in extreme situations, on steep slopes while the cyclist pedals only a little or not.


I would like to know how others think about this.
Well, I understand what you're saying and where you're coming from.

I ride under similar rules. Local 200W with no speed limit or EN15194 pedelec (which are purposely designed to lock people out of modification).

On the road hub drive offers me best overall weight, efficiency and range. The only performance deficit is on long steep climbs that most of the FFs (that's fat fellows) here wouldn't get up under there own power. :P
Last edited by TDB on May 15 2021 4:51pm, edited 1 time in total.

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Re: E-bike mid-drive motors hardly outperforms hub motors

Post by TNC » May 15 2021 4:48pm

neptronix wrote:
May 05 2021 2:07pm
MadRhino wrote:
May 05 2021 1:54pm
So many bike manufacturers are building with BB drives nowadays because of the low power legal limitations and the light-weight marketing in bicycle industry. They are making very good ebikes for the bicycle sport crowd, but very poor commuters that are high maintenance and low performance.
Yes, it's kind of a dumb trend isn't it? for the typical commuter it would be much better to use a dual geared reduction hub motor. Those motors are butting heads with the power density of most mid drives, and a 5-8lb hub has a really small impact on rear suspension performance.

Many of these commercial mid drives are overengineered, hard to get parts for, and lock you out of modification. They may be sleek and have great weight balance, but unless you're offroading or hill climbing, you won't see the benefit.
I work at a bike shop where we sell Trek and Specialized emtb's. I'm a long time mountain biker, but these emtb's at the suspension quality level I require were too rich for my blood. I tried a Bafang BBSHD in an older Santa Cruz Nomad with very good fork and shock components. I didn't expect much, but wow!...I'm pretty darned pleased with the finished product for real mountain biking with proper programming.

So, while I know nothing about hub motors, I'm thinking you're right about the mid-drives being the only real solution for real mountain biking. I cannot imagine the effect of the unsprung weight of a hub motor on handling and suspension performance. That benefit of having gears, centrally located weight, and some apparently decent power seem a fairly large benefit IMO. I see the mention of simplicity and durability on the hub motors, but I guess being somewhat mechanical doesn't really scare me off of a mid-drive.

I'm definitely with you on how Trek and Specialized...especially Specialized...are very protective about what elements you can work on their motors. However, the Bosch stuff in Treks seem to be getting more liberal with info and even a little programming latitude.

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Re: E-bike mid-drive motors hardly outperforms hub motors

Post by MadRhino » May 15 2021 8:20pm

Yep, mtb cyclists will definitely prefer a BB drive. Hub motors are closer to motorsport in the mountain. You can’t ride them as fast on technical sections or downhill because of the rear suspension and weight are a handicap. They can’t be good jumpers as a lightweight, well balanced bike does. But, they are faster overall, with much better reliability. It is easy to build them so fast climbers and hard pack speeders, that the time lost in technical and DH is not significant. They never experience drivetrain fails in the trail. So, it is not the same kind of fun ride of course, but there are many good reasons to ride a hub motor in the mountains, including leaving all mid drives in the dust.
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Re: E-bike mid-drive motors hardly outperforms hub motors

Post by markz » May 16 2021 7:43pm

More complexity to the mid drives and if your motor chain breaks, or something (power, trail dmg) breaks your drive train have fun walking.

Changing gears on full power can break things - there is the sensor you can install on some of the m.d's. I've noticed on some hill climbs on my dd hub I need to change gears. When I am getting to the hill at w.o.t. in rear 34T and get half way up on w.o.t. and need to change to a 20T half way up then lowest T of 14 or 11T rear gear still at w.o.t. to get to the top - any pause in the power applied while going up the hill to reduce power on mid drive to change gears will have great affect on getting up the hill. It comes down to make or break getting up the hill. But yeah sure I've done C4K from a standstill on a 20% hill, and able to climb in the right gear.

Besides all that, "mountain bike riding" is a very broad term.
- Goat trails with rutted roots, cut tree trunks
- Dirt bike trails
- Tight trails
- Easy swooping corners of a ski hill bike trail, like velvety trails of green/blue runs
- Big jumps like drops off made platforms of ski hill bike trails.
- Small jumps
- Back country forestry roads, typical gravel that any mtb can do
- Single track with various conditions from technical turns, to easy lumbering look at the birds trails.
- Large chunky rocks, like dry river beds or puddled or riding across a river/stream.
Heck "mtb riding" could even mean riding high altitude in the resort towns easy bike paths/sidewalks/roads, hey your in "the mountains"

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Re: E-bike mid-drive motors hardly outperforms hub motors

Post by dogman dan » May 17 2021 6:16am

Remember who they sell those bikes to. People who used to pedal up 15%, but now have bad knees and COPD.

ES folk, we often used to ride motorcycles, and build bikes that ride like one. To us, performance is raw horsepower.

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Re: E-bike mid-drive motors hardly outperforms hub motors

Post by Ianhill » May 17 2021 8:16am

For me nothing replaces the day i get the 200mm front fork blasting down the stone rutted path and feel hardly any bump smooth as a solid fork on chippings i realized then hiw the downhill world cup nutters habe so much pace.

The geometry and refinement of thier bikes make them carry speed so well i just csnt recommended them enough to turn into an ebike that is where the daddy bike lies and mamy get it wrong trying to pump loads of kw in add tons of weight and the bike losses all its charm aim is to keep the ride close to possible as stock and noine does that better that the production ebikes but £6000 is alot considering they move as fast as mobile phones 2-3years max and your out of date.

(still nothing wrong with the bikes parts can be found etc) hotrodding the shimano ep8 or e8000 would be a good shout you may think but they have optimised them so well theres little meat left on the bone to pull any extra power out so the bafang motors and a downhill 2017ish frame make sence then its the middle man bit fatter bit heavy bit mote powerful less agile takes more energy to move about exactly like a pairing wrong weight division boxers different areas they shine.

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Re: E-bike mid-drive motors hardly outperforms hub motors

Post by dogman dan » May 18 2021 5:42am

Couldn't agree with that more. Nothing sucks like the bikes I used to ride. So so fork, old y frame, too much big hub motor weight, no good way to carry the battery, but they did roar up the steep ass hills here nice.

Would have been much nicer with a frame designed to carry a battery, and a decent fork. I had no money then though.

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Re: E-bike mid-drive motors hardly outperforms hub motors

Post by qwerkus » May 18 2021 12:53pm

I've built mid drives, dd and geared hubs. Efficiency highly depends on usage, as others pointed. The definite argument in my opinion is not so much how much battery power you can save, but more how much maintenance can you save. Besides chinese after market kits like bafang bbs - which are still very expensive to repair - ALL mid drive are basically locked black boxes you cannot touch. Only take the entire thing out and send it back to the manufacturer. Bosch, Brose, Yamaha, Shimano - all the same. You need a shop with the right partnership for any repairs, which is a big no-no for me. The amount of grey energy sunk into the logistics of the modern ebikes defies my intellectual capacities; hard to call it "green" anymore.

An the other side, i've taken apart every single hub I have (out of curiosity), cleaned old ones, greased them, replaced gears for $15 and mounted them back. 2h job, only problem I ever had was accidentally destroying hall sensors, which is an easy fix, or braking cables.

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Re: E-bike mid-drive motors hardly outperforms hub motors

Post by MadRhino » May 18 2021 4:28pm

Yep. BB drives had brought up a very neat and stealth looks, and bike manufacturers had built vey good light weight sporting ebikes with them, but they are also made to tie the users to their service dept.

Still, riders whom riding style and terrain do require mid drives can build their own with solutions that are much better than BB drives, in terms of power and ease of maintenance.
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Re: E-bike mid-drive motors hardly outperforms hub motors

Post by Ianhill » May 21 2021 10:56am

Anyone seen theses floating about like they down a manhole with IT the clown.
Screenshot_20210521-165016_Alibabacom.jpg
Screenshot_20210521-165016_Alibabacom.jpg (197.62 KiB) Viewed 118 times
3kw nominal 12kw peaks ive seen it wheelie on a youtube video guy flipped it looked like it had loads of bottom end and its 4 speed with clutch.

Not the best solution from engineering stand point but it looked a blast dip the clutch and drop a hurt bomb on the wheel.

They been used on big bikes with 19inch front tyres but id like to see this on a pitbike 14 inch front wheel 12 in the back the smaller wheel would make it mental and it would ride exactly like a normal bike rear foot brake etc.

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Re: E-bike mid-drive motors hardly outperforms hub motors

Post by john61ct » May 21 2021 2:15pm

> like they down a manhole with IT the clown

sorry I do not understand the meaning of this

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Re: E-bike mid-drive motors hardly outperforms hub motors

Post by Ianhill » May 21 2021 2:34pm

john61ct wrote:
May 21 2021 2:15pm
> like they down a manhole with IT the clown

sorry I do not understand the meaning of this.

Floating about like they down a manhole with IT the clown.

He was consealed only seen by the few not the many not a mainstream clown same for these motors its the first ive heard of them but they actual perform decent from the vids ive seen just as scary as the monster down the drain.

Not many get me so no comcern if you dont. No harm.

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Re: E-bike mid-drive motors hardly outperforms hub motors

Post by john61ct » May 21 2021 3:04pm

OK, did not realize "IT" was a name, clown, book or film. Clueless wrt pop culture, not my sort of jam

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