CigTech

Is a Hub or mid drive system beter?

I like the idel of putting all the motor power through the bike gears instade of just having 1 gear (hub motor). Just sounds like it would be more efficient. What do you guys think?

Allen

I'm firmly in the mid drive camp.

cerewa

I've seen claims that hub motors usually operate at 60% to 80% efficiency. Due to losses in the gearing that is needed to use a mid drive system, i suspect they top out at about 80% efficiency too.

For reliability, hub motors have an advantage because they don't have any more moving parts than a regular bicycle hub. They are also much more common, and therefore cheaper

As far as performance hub motors are superior in high power / high speed situations. Their larger motor size (and surface area) makes them hard to overheat. For bikes that need a lot of torque at low speeds (as a tandem bike going up steep hills probably would) a mid drive seems like a good choice.

crackerdog

Hub motors would not be superior in high power or high speed. Mid drive just uses the gears so the motor can be smaller and lighter. Try driving your car around in just one gear and see how well it does on starts or high speed. It would be fine once your car got up to a certain speed but getting there would be tough. With a mid drive motor you just change your gearing until it fits your situation.
Hub motors are easier to install and some are very quiet and that is their best features. A mid drive is a bit of a hassle to set up on a upright bike because of the question of where to put the motor. On a recumbent with that long chain line, they are ideal. Lots of torque for hills or load and lots of high end speed if you gear it correctly.
Electric motors don't like going slowly which is why hub motors aren't very efficient until you get up to a certain speed range and you are cruising. We have lots of short steep hills all over so hub motors don't do well here. If you have a longish commute and not stop and go traffic, hub motors are fine though quite heavy compared to mid drive. Hub motors are just so easy to install though.

EBikeFL 

Here's a good description and vendors for mid drive motors: https://www.electricbicyclesmagazine....ang-page1.html

Shouldbeworking

Mid-drive! It's so smooth, and I can climb really steep hills, and it doesn't overheat like the hub motor did. I'm visiting Europe and I see mid-drives all over the place. On brands I've never seen before, like "Flyer". Mid-drive is fab.

On the other hand, if you are riding on flat land maybe hub is enough. Depends on your purposes.

fietsbob

Stoke Monkey worked out a mid drive, it turns a cross over chainring on the left side, tandem parts,
but only on long tails, Xtracycles & big dummys, since, motor goes behind the seat tube
then the final drive uses a whole MTB type drivetrain to have the torque to climb hills with a load.
a hub motor out of the wheel..

cerewa

(((Hub motors would not be superior in high power or high speed. )))

Here's what i'm talking about. I read on endless sphere about people running hub motors at 4 horsepower (3000 watts). I also read about the RC-airplane-motor powered bikes. At such a power level, using a smaller lighter motor may sound nice, but it's also easier to overheat.

You're comparing an ebike to a car (and a gas or diesel car really DOES need gearing). Tesla motors doesn't use multiple gear ratios for their electric cars, because it's quite unnecessary.

But Tesla's vehicles are a good illustration of what is ideal when you have a huge budget to pay engineers. You can solve the reliability problems, have motors built specifically for your application, and have gearing designed for you that's efficient and light. Given those circumstances, Tesla chose a single speed design, but they used reduction gearing because reduction gearing really is useful (again, assuming you have reduction gears that are efficient and reliable).

Gearless hub motors bring with them about 10 pounds of weight that would be unnecessary with the right gearing. But they are reliable and 10 pounds isn't such a big deal for me when i have a big battery and heavy, durable mountain bike (the whole rig probably weighs 80 pounds).

I had a geared cyclone motor system and it gave me way too many problems. Not saying every geared system will have the 'you better be a mechanic to use this' lack of user friendliness of Cyclone. But it takes highly skilled (expensive) engineering effort to do any better.

350htrr

I thought that's the beauty of electric motors, 100% of the torque right from the first RPM right up to 12,000 RPMs or what ever... No real need for gearing if you have the right motor for the application you are using it for...

Apache Thunder

Well yes. But the way we gear up/down when the motor hits high speed feels alot like how manual transmissions feel in a motor vehicle. Due to how most derailleur systems on bikes work, it's generally not good to try changing gears on full torque as it results in chain slips and more wear and tare. Especially when a motor is driving the system with more power then a human usually puts into it.

I throttle down (but not completely) just before changing gears and it feels a lot like shifting gears in a car. That may be one factor that drives more people to prefer this system over hub motors. More control. That's the key there. Plus it makes it feel more like a cool "combustion" engine system, but without the dirty gas burning and not so environmentally friendly stuff that comes along with it. Plus my motor has a gear box so it has a slight noise to it when it's under load. When the load goes away (like when I throttle down), the noise the gear box makes is much less further contributing to that "engine" like feel to it.

Sure I could get a beast of a motor and never have to use lower gears to get more torque from a stop and go, but where's the fun in that!

Don't forget it's most likely more efficient then strapping on a 1000+ watt motor on and never changing gears with it. Think about all that excess current that is getting pulled from the battery every time you go from a full stop to full speed. It will take more torque to get the bike to the motors full speed if it was always on one gear. Unless you got a 72+ volt system where the motor can be free to spin crazy fast on first gear and still get a high travel speed off of. But anything above 48v would be a budget buster, not only that, it would be dangerous to work with under the hood since that voltage level starts to get to the point where it's high enough to electrocute you with. I don't know the exact voltage it takes to conduct across the human body but 72v and up is starting to push it.

And what about if someone here has used a middrive system with a wheel that has one of those internally geared hubs? Those are rare in the wild to begin with (geared hubs with more then 3 speeds that is) and I would love to know how they would fare in a mid drive system since they are known to be able to change gears under power. They may lose a little bit of the cool factor since one would not have to throttle down, but it may be more efficient since the acceleration curves from shifting gears is much smoother.

So the main point is that mid-drive systems are more tailored to getting better range out of the battery and for those who want more control over how much torque their bike will put out.

Allen

I've got a mid drive and a NuVinci IGH hub. I used to run the system with a Rohloff.
I don't have a throttle though, torque sensor in the BB.
With an IGH it can be shifted under power but it can be difficult to shift with a lot of torque on the gears. I coast when I shift. Derailers are easy to shift under power.

Apache Thunder

Ah so they do exist!

Harder to shift under load with an IGH hub would be a bit of a deal breaker for me. I think I may stick with the classic derailleur system then. Either way, we're both technically coasting when changing gears. Also, my bike doesn't have one of those higher quality chains that have to be oriented a certain way and are super smooth at changing gears. Mine's strictly a budget machine. My step dad had a $1200 road bicycle and that thing was super smooth on gear changing. I could only wonder what kind of performance I could get out of a bike like that if it was converted to electric. It's got titanium rims with a magnesium alloy frame. Only thing better then that is those carbon fiber bikes I've been hearing about. Some pricy stuff right there!

Allen

You pedal when you change gears with a derailer. The pedaling action is what moves the chain from one gear to the next. When I change gears with an IGH I just break stride for a moment when I shift. Only takes a few tries to get used to it.

Apache Thunder

Oh I see. Currently my system doesn't have the chain going through the crank chain wheel. Thus for now I can't pedal it. But I will be ordering some spacer rings to alter the alignment of the mounting bracket with how it's mounted on the bottom bracket. Currently it's not perfectly straight due to the rear forks being slightly wider then the bottom bracket. (one end of the mounting bracket is held on by the bottom bracket screw on mount and the other end is held to the rear fork via u-bolts. So far it is quite stable)

If I had connected the pedal chain wheel with it like that now, it would de-rail the chain off the motor cog and would then cause the chain to derail off the pedal chain-wheel which would get real nasty real quick. The motor cog needs to be lined up with the chain wheel first.

Once I got it lined up right, I will reinstall the motor's freewheel cog (which I think has 13 teeth on it compared to the current 9 tooth fixed cog) and run the chain through with the pedal chain wheel as part of the system. Sometime next week is my time table on that. I've already got the freewheel crankset installed so the spacers are the last thing I need.

I will keep that in mind once my bike is 100% done. I'll explore that method for when I'm shifting it. Thanks.

Kevin Harvey

tried a 500 hub motor from e bay sold it to a guy in a city with no hills ( perhaps a geared hub motor might have been better butthis thing was usless ), now I;m a cyclone fannatic ( Taiwan ) real goodto deal with, make my own LIFEPo4 battery packs but easyier to just buy, most popular is 500 w . I now have a NuVinci hub & man what a buz when riding round town. Need more mechanical skills with cyclone but you pick these things up as ya go .I Sell a few & suply parts to some other riders & fit new BMS etc to young blokes who get stuck with rip offs.Hey & there is even blokes who on U tube Use the hub motor as a crank drive so if thats not telling you what can.Advice ----get the right BMS to suit motor.

Kevin Harvey

tried a 500 hub motor from e bay sold it to a guy in a city with no hills ( perhaps a geared hub motor might have been better butthis thing was usless ), now I;m a cyclone fannatic ( Taiwan ) real goodto deal with, make my own LIFEPo4 battery packs but easyier to just buy, most popular is 500 w . I now have a NuVinci hub (960wsame size motor illegal so who can tell)& man what a buz when riding round town. Need more mechanical skills with cyclone but you pick these things up as ya go .I Sell a few & suply parts to some other riders & fit new BMS etc to young blokes who get stuck with rip offs.Hey & there is even blokes who on U tube Use the hub motor as a crank drive so if thats not telling you what can.----the one fault with Nuvinci is having to take the power off to change gear.Most blokes biggest mistake is getting a BMS that doesn't take enough Amperage as web site start from the cheapest ie for less than 300w.

dumbass 

I've been running a mid-drive on hardtails for several years but have never tried a hub setup. I've run with derailers and Nuvinci hubs and prefer to use the Nuvinci. I use a twin chain setup whereas, the Nuvinci is driven by 2 seperate chains (crank & motor). Works great but you do have the small problem of not shifting under high power loads. But it will shift under light power loads especially if down shifting. I am doing a new build this winter and will start out with a derailer to see how it works out for me. But I have one of the Nuvinci 171n develipment kits (auto electric shift) that I may install on it to compare. If I use the electric shift setup I may modify it to a manual electric shifter. I tend to prefer to be in control of what's going on. The electric shift is said to shift under any load up or down. We'll see!

Bob

Allen

You have to shift while coasting with any IGH (internal gear hub) not just the NuVinci.

magic carpet

Hi everyone, this is my first post.
I test rode a Polaris ebike yesterday. After reading a couple of misleading press releases, I had to see one in person.
What they are calling 'Duo Drive' is actually a combination mid drive AND geared hubmotor! I didn't get a chance to ride it off-road, but on the flats it is a quick accelerating bike. Good luck trying to figure out the specs of the two motors on the Polaris! The brochure is deliberately mis-leading, for some inexplicable reason. They definitely don't say 'the bike has two motors', but indeed, it does.
My own bikes are a BionX, DD 350 SL DT XL on a Swiss army style Opus Zermatt and an Epik Whistler, mid drive mountain style bike, with 8spd cassette and rear derailleur. I say 'mountain style' because 8 speeds does not make a MTB.
I enjoy both the mid drive and the hubmotor bikes and can compare them to a standard transmission Corvette and an Automatic Cadillac.
For touring I like the ease and smoothness of the BionX hubmotor and for sportier or off-road riding, the Epik is superior. I expect the simpler, direct drive hubmotor to be more reliable, due to the lack of any moving parts and the mid-drive to be more maintenance heavy, due to the loads it places on the gear train. I'm only speculating because both bikes are new this summer and are working perfectly.
If I had to choose between my two bikes, I'd pick the BionX. But that's because at Double Nickles I'm not as aggressive a rider as I once was. If I was twenty years younger, I would go for the mid-drive, Epik.

turbo1889

You are correct that unlike an internal combustion engine an electric motor develops its full torque at lower RPM's and this is an advantage in that it does allow for single gearing direct drive. However, it only allows for it as opposed to being the ideal situation. Long story short, it is a question of efficiency. If you are running a 1000W direct drive hub motor and I am running a 350W cyclone motor through an 8-speed rear cassette hub where the ratios have been optimized to match my pedal cadence across the entire gearing and speed range. Yes, on the flat you will pass me and get out on ahead of me since you have more watts of power at your disposal and your direct drive is just slightly more efficient without the approx 2% power loss through the roller chain drive and approx 10% power loss through the planetary gears on the cyclone motor power head that my set-up has to contend with. However, when we get to a big long hill with almost 1/3 the power at my disposal I have the potential not only to keep up with you up that hill but if it is steep enough and long enough even pass you going up that hill while all the time using 350W instead of 1000W. Reason being is that when I shift down through the chain gearing system I make an even swap between RPM's and torque. In other words if I shift down from the 12 tooth rear cog I was using on the flat to a 24 tooth rear cog to climb that hill I cut my sped in half but I doubled my torque while still only using 350W. In your case, however, with a direct drive hub motor if your motor gets bogged down going up that hill so that you are only going half the speed you were going before you have cut your speed in half and have gained nothing in additional torque and your motor is still putting out the same torque or in other-words while going up that hill because you can't change the gearing between your motor and wheel you have taken a 50% loss in efficiency and you are now using 1000W worth of power at 50% efficiency while climbing that hill so since you can't change your gearing you are now wasting half of your power output. Steepen that hill up to the point where you are slowed down to 1/3 of your flat ground speed and guess what, you and I are both going up that hill at about the same speed but you are using 1000W at only about 33% efficiency because you can't change gears but I can change gears and am climbing that same hill at the same speed but am only using 350W to do it.

Long story short, if you live where there is a bunch of hills to climb the ability to change the gearing between the motor and the drive wheel allows you to keep your motor operating at the top of it's RPM range where it is most efficient and you don't end up wasting a whole bunch of watts.

chi6er

here is a build on new mid drive kit
https://endless-sphere.com/forums/vie...p?f=28&t=42785

here is the kit, looks easy and not that expensive and fast

https://www.gngebike.com/450wbrushless.htm

Greg_d

Hub motors are likely better for the higher wattage due to the size of the coils (I'm not enough of an engineer to say for sure), but in the consumer market, mid drive is generally better. The geared transmission is a big step up over hub planetary gears. That being said some bikes with hubs we stock have regen braking that helps compensate. That same bike is intended as a 350 watter and it shows in the motor size but is downspecced for the UK. The KTM guys are using a hub for their flagship electric motorbike pretty much, as are the Phaser builders. For some reason high power hubs seem to be a trend amongst 'power users' and I think this comes down to comparative ease of build. In terms of range the answer is normally to throw more cells into the chassis and draw even more power from the motor!

One of the big points in favour of a hub drive amongst cyclists has been because there's no crank freewheel system to get in the way of a stack of gears. Both the Storck Raddar and BH E-Motion bikes are 24 speeds if I recall correctly but they are often somewhat redundant apart from exceptional cases. We change the chainring size on the Bosch system bikes as and when to suit customer requirements too and normally the 9 speed cassette or whatever it is is outfitted with is more than enough.