To mid drive or not to mid drive

sannder

sannder

10 mW
Joined
May 11, 2016
Messages
20
Location
Switzerland
The Shakespearean e-bike dilemma - at least for me - is weather should I give away the simplicity and reliability of a DD hub for the smoothness, the torque and the weight distribution of a mid drive.

And I am not talking about Bosch, Panasonic or Yamaha mid drives, but about replacing a 350W BionX with the BBS02.

What I do like about my DD hub
- quiet operation
- it has torque sensor
- regenerative braking
- console with hacking codes :)

What I dislike:
- the unsprung weight on the rear wheel - weight distribution is not ideal.
- the struggle to keep momentum while climbing steep hills.
- having to ride above certain speed to keep the engine 'happy' and vibration-free.

In terms of efficiency, mine doesn't get hot even when climbing and I am still able to run about 20Km per charge with a fairly old 350w/h battery.

If I am to upgrade, will a mid drive be able to serve me a couple of thousands km trouble-free or should I expect to grease it and replace the nylon gears every once in awhile ? :)
 
I am afraid you will just need to bite the bullet and try one. I have DD hubs, geared hubs, BBS mid drives, and friction drives. All have their various advantages and dis advantages but I enjoy riding them all. If you said to me i could only have one, it would be the Mid drive.
 
Do you ride a lot in the city, stop and go?

If so, you might like a 500w rated geared motor a lot. Light compared to most DD's, though maybe close to same weight as your bionix DD. Much better on starts, or steeper hills, than your bionx. More torque than similar wattage DD motors, for sure.

On the other hand, if you really do ride up killer hills, stuff above 8%, then you will love a mid drive. The downside, is you might end up riding in a slower, lower gear than a hub motor if you have a stop sign every 1/4 mile. Mid drive kills the hill, that is certain. But if you put the mid drive in the highest gear it has, it will struggle and make heat, wasting energy, just like a DD motor does.

I'm not saying it will over heat and die,,, not at all. But it will spike amps, make heat, and reduce your range when the riding is stop and go inner city riding. AND, you leave it in a too high gear. So you might end up shifting a lot, or riding in a medium gear instead of your highest one.

This only applies to nasty, inner city rides with a light or stop sign every damn block. That kind of ride is where a moderately powerful (850-1000w) geared hub motor really shines. Quick and efficient take offs, riding leaving it in high gear all day, if not for years.

I'm with Kepler,, in the end you want 3-4 kinds of e bikes. But pick one,,, a mid drive makes a ton of sense these days, for an MTB or a cargo bike.
 
Dogman Dan makes some good points. It really depends upon the type of riding you intend upon doing. I would recommend DD hub if most of your riding is on the streets. Mid drives takes a bit of shifting to make use of its power and tend to be harder on the chain, derailleur, and sprockets. I have two bikes one is a rear and other a front DD hub systems, to keep the CG low I mounted the batteries as low and in the middle of the frame. The DD hub systems are a bit slower on the hills, but I like the reliability of the DD hub system, it has proven itself over the past three years and about 10K miles of riding. When climbing hills, and if the bike slows to less than 18 MPH, I leave the bike in mid to higher gear and just add some old fashion pedal power.
 
The sinewave controllers that you get these days make geared hub-motors fairly quiet - at least as quiet as a BBS02. A 500w one will give all the torque you need for climbing very steep hills. With a downtube mounted battery, weight distribution is very good. The Q128 at 48v and 20A is very light, quiet and it produces good torque. For serious hill-climbing, choose the 500w Bafang CST.

The main downside to middle motors is the constant gear-changing and crunching when you get caught in the wrong gear. I personally find that it can make your riding a bit tedious compared with the hub-motor, which will help you out when you get stuck in the wrong gear. The upside is the ability to make good torque at low speed and high speed in a high gear. Contrary to popular belief, the tests I did showed that efficiency is about the same.
 
I have a direct drive, a geared hub, and a mid-drive.
I enjoy riding the direct drive with the sine wave controller the most.
Mid-drive is good when I'm towing or when I'm expecting to climb steep hills.
 
Thank you all for the insightful answers.
Shifting and replacing transmission parts it's not a problem - I already have some spare parts awaiting to be employed.

I am tempted to start with the 36V unit and a small pack of lipo batteries just to get the lightest setup possible. I could even use the programming cable to run display-less.
However, I am not so sure that the weight difference between 36V and 48V version will be more than 1/2 kg - case in which it's hard to consider the 36V for anything else than the legal matters.

Tested with the amp meter, my BionX is approaching the 1kW mark when it's pushed to the max. On flat, at the top speed of 32Km/h, it's consuming about 200W (I am using slick tires).

I am wondering if BBS can do a much better job energy-wise.
On paper, 120Nm of torque with ~5:4 ratio (34T cog) is about 3 times what my current BionX is capable of doing. In reality, the output torque curve for each engine is needed for a decent comparison.
 
On the flat, once running at 32 kph,, both systems will have close enough to identical efficiency to not give a shit if one is better than the other. that is assuming your pedaling input remains the same, no differences caused by bike gearing differences, wheel size differences, aero differences, etc. 32 kph generally takes about 400w, so you are pedaling hard, around 200w worth, compared to some.

The mid drive of course, if you shift about three times, can get from 0 to 32 kph more efficiently.

Or, either one could be pedaled to 15 kph, then start using the motor, and both again have close to equal efficiency.

In short, the reason to use your mid drive is primarily to take advantage of the gears in situations where they are needed the most, heavy loads and steeper hills.


DO build yourself a mid drive bike,, I never said don't. I'm just saying that in stop and go city riding, you may come to still prefer the DD.
 
In building my midrrive, I had concerns with the constant shifting and getting stuck in the wrong gear. To overcome that, I paired the BBSHD with an IGH. Specifically, the SRAM G8 allows for shift under load, coasting and while at stand still. I think that's the only way to have a mid-drive and not have to be spot on with your shifting on deceleration. NuVinci can also do that, but can be expensive.
 
To clarify, particularly on the flat, you can stay in top gear with todays version mid drives. You just lose the one big efficiency advantage of the mid drive if you don't shift down a gear or two. Should never really need those lowest gears again, except in mountains.

Old school mid drives had to be shifted down. I'm referring to stuff like the brushed motor 250w e bikes of the 90's. Those would pop the controller over and over if you took off in high gear.

Though mid drives rock, and are going to dominate the ready built e bike market in the near future, there is still a place for a rear hub motor bike. Just nice to have a durable, simple bike that stays in high gear, and takes off nice from a stop in the big city ride.
 
you're right. my mid drive rides nicely in high/highest gear, but sometimes has some unfunny hickups when accelerating hard - with high rpm delta. so going from a zero rpm to high rpm at high current.
and for a mid drive to work REALLY nice i recommend a torque sensing bottom bracket. i wish i had one installed in my bike. it makes such a pleasent ride.
 
I have a rather heavy bike with panners and do all of riding on the street, so ease of maintenance and reliability is my main issue so I went to a DD system.
 
Thank you guys for your input.

I've finally got my hands on a BBS and had a test ride. Even though it was the 500W model with stock setup, I found it quite powerful.
Just as I started pedaling the engine pushed a great deal of power. Compared to my DD, the BBS acceleration from standstill was almost uncivilized :)

The acceleration kicked in brutally and almost got kicked off the bike in a slow U turn. I also felt that it works like an on/off switch.
Maybe I can get used to it or it can be changed in the software but the first impression was a bit nasty, like riding a horse or smth. :lol:

The wattage meter on the console was very optimistic, as I did not manage to get much past 500W with a half charged battery, by climbing a very steep hill.
Not changing the gears properly gives a feeling of running out of juice. I am sure once you get used to it and it can become fun to drive - like being on a some kind of small motorcycle.

My personal opinion is that cvt systems like nuvinci can really shine with the BBS kit. Maybe Bafang could include more clever sensors in the engine to create a perfect gear changing experience.
If I will be buying this kit, I would probably limit the power delivery with a function of time + speed - if possible. Meaning that once you start pedaling or accelerating, the power will increase gently.

Otherwise, I will be just naming the bike "The wild horse". :oops:
 
Sannder - I have the same experience as you. I built my BBS02 750W mid drive about 6 months ago. I'll preface this by saying I haven't tried programming it yet, and I know you can do so to get different characteristics, but -

Like you've noticed, the motor (using cadence sensor) is on/off' and can almost buck you off if you're not careful. It's a monster and you've really got to learn how to ride it. My wife (who doesn't cycle much) is thinking about an ebike, for example, and there is no way I'd recommend this to her.

I have an 8 speed internal rear hub. If I had the cash I'd drop it on a nuvinci. Unfortunately my rear hub can't change under power, so I'm forever feathering the brake or stopping peddling to change gear. Ability to use gears on hills is magic, and I cannot complain about top-end in top gear either. I can easily cruise at 40kmph and hit 50kmph at maximum cadence in top gear (for a minute or so, at least) on an upright 'dutch' style bike.

I'm now used to the mid drive. I hardly ever use pedal assist - I use thumb throttle only. It allows me to control that crazy power when taking off, and gives way better control than that extremely poor on/off that the cadence sensor has.

I personally am sold on the mid drive, but would pair it with a nuvinci, or at least a hub that can shift under power. In order to use pedal assist it really needs a torque sensor, but as far as I'm aware the BBS does not support one? Only the more expensive Bosch and the like do, I think?

Just my 2c anyway.

Enjoy your own adventure!
 
I installed the 'gearsensor' add-on for BBSxx (lunacycle has them) to sense my shifting and cut-power momentarily. I find it to be very effective. There is a slight delay, but I don't find it too annoying. I'm at about 500 miles on my BBS02 and it has been awesome. I highly recommend the 42T bling ring also.
 
I'm a couple of weeks into owning my Gtech eBike (UK), it's 250w geared hub drive, single speed with Gates carbon drive. Lovely to ride and excellent for commuting through town (multiple stop/ start).

I'm looking to convert my mountain bike to BBS02 or BBS-HD mid drive, got a Nuvinci hub for the rear so I can shift under power and also when at a stop. Will be interesting to compare the two when done!.

The Gtech is just so easy to use though, no gears and perfect for just getting to work with no issues. Mid drive will just be for messing about with at the weekends..
 
For the record I am still riding my bionX at the moment. The extra weight on the rear wheel makes the bike feel heavy.
I was thinking that I could save weight with BBS02 but that might not be the case.
With the same number of battery cells, BBS02 will probably only improve the weight distribution.

So I've been starting to look to Xiongda 2 speed and even Q100 instead + a small custom 10S3P /14S2P battery.
I would really like to preserve the handling/agility + look and feel of a normal bike as much as possible.

There are any other (lightweight) options out there to be considered ?
 
So you are thinking about staying with a Hub Motor.

Well I am still riding hub motors, since I do not have enough $$$.$$ for a mid-drive to test, to see if I like it better for going up hills.

I really would like to see the % of inclines you are going up , and for how long are those inclines ?

Every month there is an ongoing debate/discussion about weather to get a mid drive or not , and most ( not all ) say for mountains / long inclines with high slopes the Mid-drive is the only way to go.
But
There was recently a thread, by someone who traveled from Canada to Mexico, on/in the mountains ... using a hub motor . I would not have thought it possible before, But he did it, and the Mac survived, he is not sure if he used the Mac 10T or 12 T since he bought two and forgot which one he laced up to his fat bike.
https://endless-sphere.com/forums/viewtopic.php?f=3&t=84351

With the Two Hub Motors I have , I can go up inclines up to %14 for a short while.
Like 1-1.5 km or less with the little Q100c CST 201 Rpm laced to a 650b/27.5 wheel. Higher inclines to perhaps 0.5 km in distance.
And
On the Mac 6 T ( fast wind version of the Mac ) I can go up longer and steeper inclines .
I am now debating on getting a 12 T Mac , and lacing it up to a 26 inch or even a 24 inch wheel, to climb up steep and long inclines ( like 1,200-2,000 foot climbs )
Since I already have the controller and Cycle Analyst set up for the Mac 6T )

There is going to be a couple of testers of the Xiondga 2 speed hub motor within the next couple of months, since there is a vendor here in California that is now importing them.
Unfortunately , I was not picked as one of the Testers for the Xiondga , and that is a shame , since I live in the perfect area for testing any motor to go up hills of endless differences of length and % of grades. Endless Possibilities of both where I live, more than most any other place I can think of .
So there is still a big question as to weather it would work for where you live, since from what I have seen of Switzerland it is much the same as where I am.
Sure the Xiondga 2 speed hub, would work in Paris ( reports a vendor/seller there ), or the slightly rolling coutryside near by to Paris.
But ...(
I have not found any reports of testing of it with the challenging terrain where I live and places like much of Switzerland .

How long before you think you will buy a kit and build your next e-bike ?

So for a summary ,
I have a 201 rpm Q100c CST on a Road/Gravel bike
and
A Mac 6T on a hard tail Mountain Bike , that is heaver by 8-9Kg in weight than the Q100 Road Bike,
And I have now gone back to Riding the Heaver MTB with the Mac on it. ( 48 volt @ 20amp Max )
There just is no substitute for Power . Better Speed, and about the Same / Little better climbing than the little Q100c , even though it is a faster wind ( high speed/low torque motor ) . Q100c 201 is 201 rpm motor and my Mac 6T is 410 rpm motor, and it still climbs the same or a little better than the Q100c 201.
So , if , you do stay with a hub motor the Mac 12T would be one of your options.

Edit : for your post below, the Mac motor is a Geared Motor,
However
I Do , as well , have interest in the Xiondga 2 speed motor , I just do not know if it will perform much, or if at all, better than my Q100c that is over volted at 48 volts , I already climb some short hills with that right now.
I would like to see testing of the Xiondga on the climbs that the Pro's do at the Tour De France .
Since I have not been picked to test the Xiondga , I will have to see some tests done on three to five of the different of the Mountains of the TDF , in the Alp's and Pyrenees , that be the needed testing ground to convince me since I will have to rely on others, at the present time , for test results .
 
Yes, only that I will be switching to a geared hub motor - much lighter and less dramatic at low speeds than my bionX.

I was rather impressed by the range and the torque of a small 250W geared hub - pretty fun to drive in the city too.

I am tempted to try the The Luna version of Xiondga 2 https://lunacycle.com/double-gear-double-torque-motor/ + 14S2P-30q battery

The manual shifting feature + thermal protection + plug-and-play connectors are a nice package. This setup will end up being 1Kg heavier than the Q100 CST.
If this hub has upgraded nylon gears and follows better specifications it's probably reliable enough and it's worth a try - but I am unsure if the climbing abilities are very different compared to an overvolted Q100 201rpm.
 
I live in the mountains too,, but the desert. I quickly kill a small geared hubmotor, if it's in a larger wheel like 26".

Love the 500w rated geared motors though,, Can't seem to break one riding off road. But not for heavy cargo, above 300 pounds total weight, they start to really suffer on the steeper hills.

What is your use? Trails? city commute? Trekking with a trailer? What's the entire weight going to be? Under 300 pounds, take your pick of nearly anything.

Riding the divide,, I believe he towed a trailer too. But he can PEDAL,, because of age and illness, I can only put out about 75w now. Bottom line, if you can keep a 10t motor turning at 10-12 mph, it won't fry. If it bogs to 8 mph like mine did with a 400 pound load out, it will cook off. Not sure if 12t can stand 8 mph, but it might.

Faster winds need to stay closer to 15 mph up steep hills, in 26" wheels, which they easily can do if the load is under 300 pounds.
 
As long as you DON'T ride a BBSxx like a motorcycle it will be a good ride! The o1 and 02 like running at high RPM and you MUST use your gears to keep it happy. The BBSHD can be left in mid range 42Tx 20T and run by throttle like a MC with few problems. It's do around 25MPH at that.
 
Thank you all for your insightful advices and useful thoughts.
After months of research, my mid-drive is installed.

Went for a test drive and... what a joy this kit is compared to my former DD.
It's quiet and refined too. My old battery is rather pleased with it.

Now, I will need to replace my old battery with a custom pack made out of some low resistance cells.
Programming cable is on its way :)
 
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