mid drive hub motor advantages?

[cajunjay]

I have at my disposal 3 different ebike kits one is a 36v 250w hub motor a 36v 500w hub motor and a cyclone knock off kit rated 48v 450w.

The 36v 250w motor is okay as I run it at 48v but is really just for commuting as it hasnt got much power at all, need to pedal on start up to get the bike moving as to not bog down the motor to much, hill climbing is non existent without pedaling obviously.

Now the 36v 500w kit run at 48v isnt really that bad, along with pedaling it can get upto speed pretty quick and i like this setup the most, the cyclone knockoff is the best performance wise but is a bit noisy for my liking as I prefer something more stealthy.

I have seen a decent thread where a guy made a mid drive hub motor running through some freewheeling cranks just wondering if anybody knows the advantages of running a hub motor this way instead of in a wheel? seems very stealthy and might have alot more torque aswell as being able to run through the gears.

This is the thread I saw and it does look pretty easy (for some) to implement a build like this.


http://www.endless-sphere.com/forums/viewtopic.php?f=28&t=17070&start=15

 

[Whiplash]

Yes, it will give much better climbing ability and a bit more top end if geared correctly. You want to set it up with the highest rpm does you feel comfortable with at the cranks to keep the motor happy...

 

[iperov]

Better than cyclone - because no gears and overheat.
Better then motor-wheel because spinning weight removed from wheel - more effeciency and removed gyro effect.

 

[neptronix]

A geared mid drive is going to help you on hills. On flats, not really. A motor is most efficient at it's top cruising speed. If you ride in your fastest gear with a mid drive.. then you've just got a hub motor with a tiny bit of friction added from the extra chain / freewheel / linkage needed.

 

[cajunjay]

So running the bike through the gears will help with torque and acceleration to an extent, also using the gears will keep the motor running at a more efficient speed.

Kind of the opposite of how a car or motorbike would work, you want to get max rpm out of each gear before changing this will prove more efficient whereas doing this in a combustion engine would empty your gas tank real quick.

Seems like a really cool concept, getting to rev the hell out of each gear before needing to change

 

[amberwolf]

If you do lots of complete stops and starts, like in city traffic, it will probably be more efficient to run thru the gears, especially if you and the bike are pretty heavy, and the bike's normal top speed is fast (>20MPH). If you haul cargo and have the other two conditions, it would almost certainly be better to go thru the gears.

If all you do is ride WOT for long runs without stopping, there's not much point in the gears.

 

[cajunjay]

Hi

My bike isnt really heavy at all neither am I, im like 75kg and the bike is about 30kg. I wouldnt be doing many complete stops just slowing down (braking) then accelerating back upto top speed.

From the answers I have here so far some say the hub mid drive is better than in the wheel others say its roughly the same thing :?


They guy who I pointed out in the original post said the mid drive hub puts out a surprising amount of torque which in a wheel is definately not the case.

 

[cajunjay]

I have at my disposal 3 different ebike kits one is a 36v 250w hub motor a 36v 500w hub motor and a cyclone knock off kit rated 48v 450w.

The 36v 250w motor is okay as I run it at 48v but is really just for commuting as it hasnt got much power at all, need to pedal on start up to get the bike moving as to not bog down the motor to much, hill climbing is non existent without pedaling obviously.

Now the 36v 500w kit run at 48v isnt really that bad, along with pedaling it can get upto speed pretty quick and i like this setup the most, the cyclone knockoff is the best performance wise but is a bit noisy for my liking as I prefer something more stealthy.

I have seen a decent thread where a guy made a mid drive hub motor running through some freewheeling cranks just wondering if anybody knows the advantages of running a hub motor this way instead of in a wheel? seems very stealthy and might have alot more torque aswell as being able to run through the gears.

This is the thread I saw and it does look pretty easy (for some) to implement a build like this.


viewtopic.php?f=28&t=17070&start=15

 

[dogman dan]

Through the gears doesn't get you more power, but it can get you up steeper hills on the power you have. Gearing down means slowing down of course, but it's the way to climb steeper hills.

The question is, do you need it? Most direct drive hubmotors on 48v are quite capable of climbing 7% grades for long distances, or even 10% with lots of pedaling help.

So what are your needs? Towing 3 kids at a time to the top of hills to skate down? then you need the gears.

 

[deardancer3]

You asked for the advantages, but you might want to conside the downside of each configuration.

There is no debate that running lots of power thru the chain and derailur make for lots of drive line issues that have to be attended to, vs a hub drive which takes stress off the chain. you will lube, adjust and change chains a lot more often. And you must use the gears all the time or the motor advantage is lost.
emergency stop in your highest gear and the motor is useless until you can downshift.... not true on hub motors.
You learn to shift smoother or you go thru drive line parts faster.

I run a chain drive cyclone because i have to.. big loads, start /stop, lots of hills. This was all a great advantage back when big batteries cost mega bucks to support 600 watt hub motors for max power and long range.

Now, one need not run a chain drive unless the loads/terrain are very demanding and it is important to keep the motor close to peak efficiency for those widely varying loads and issues.

At 225 lbs in the mountains carrying lots of loads, I have no choice. But I spend 4 times as much time on drive line service as i do on everything else.. tires, brakes etc.

I met a guy on the bike path that used to have the niftiest recumbent chain drive... 30mph 70 mile range... he swapped for a lesser efficient hub motor just because of the constant chain line problems.

my two watts worth

 

[DrkAngel]

Proper link to "referenced" post. - Hub motor BB drive
Note: Build required wider BB, for proper clearance of hub motor.

Running through the bottom bracket, could effectively produce a multi-gear ebike.
With a 7 speed 11-34T rear sprocket, a 3:1 torque ratio is available at the "bottom end".
At the "top end" "gearing" could apply additional speed for downhill, tailwind, drafting, crouched etc.

I would highly recommend a chain guard, for any type of mid-drive!
Getting a pant leg caught in the motor chain could be extremely painful-dangerous!

 

[Whiplash]

I will admit my chainlike takes more effort, cleaning and such, but if you want climbing power AND less power consumption to doing it there is only one choice to make...

 

[pdf]

I have one bike that drives through the BB and one hub motor. The hub motor is a 9C 2810. If all you need is a bike to carry yourself and you are similar in weight to me (around 165 lbs), then this set up will sprint up a steep short hill or do around 20 or a little better up a shallow (7-10%) hill for a long time. This is running on an 18FET controller at 72V LiPO. If you want to carry a lot of weight up steep hills, you need to go through the cranks. However, I have been amazed at how well the 2810 does on 72V LiPO. And it was cheap. Top speed of the 2810 is around 28 mph for me.

My crank-driven bike is a StokeMonkey on an Xtracycle conversion. It runs on 36V and can pull a very impressive load up a steep hill (15-20%) with surprisingly little power, but of course, it doesn't do it in a hurry. If you want to run a lot of power through a bottom bracket drive, you will need to be careful of the components and how you shift. With a chain-driven setup, you can put a lot of torque through the system and you can't shift under power with a deraileur setup, same as with pedaling. I have gone through one BB bearing, one chain, and one rear sprocket in around 4000 miles with this bike. The ability to send more torque through the parts was partially the reason, although the components weren't top of the line either.

I'd say that unless you want to pull a big load up a big hill, the appropriate hub motor on 72v LiPO and a decent controller will surprise you. I have a 20% grade that I have to go up every day and when I ride the hub motor, bike, it flies up it. The BB drive bike goes up on much less power, but at about 1/4 the speed. This has nothing to do with the BB drive, but the fact that this bike has low C 36v LiFePO4.

 

[amberwolf]

he swapped for a lesser efficient hub motor just because of the constant chain line problems.

That is why CrazyBike2 has a hubbie instead of the powerchair chain drive, basically. But I still want to do the chain drive on the newer version frame if I ever get it finished.

 

[MadRhino]

A mid drive that is built to use the bicycle gears is a fail waiting to happen. I wouldn't like having to shift through the derailer range either, that is too many gears for the need of a powered bike and too weak for any interesting power to last. The best way to build a mid drive IMO, is to drive the disc side independently from the bicycle drive train. This would need two speed at the most, only one with enough power, and can be made with components that are reliable for the kind of torque that a motor can produce.

The advantages to build a mid drive using a hub motor are obvious, but the design and fabrication required to make it a good ride is such, that one has to really need it to make it worth the trouble and investment.

 

[John in CR]

A mid drive that is built to use the bicycle gears is a fail waiting to happen. I wouldn't like having to shift through the derailer range either, that is too many gears for the need of a powered bike and too weak for any interesting power to last. The best way to build a mid drive IMO, is to drive the disc side independently from the bicycle drive train. This would need two speed at the most, only one with enough power, and can be made with components that are reliable for the kind of torque that a motor can produce.

The advantages to build a mid drive using a hub motor are obvious, but the design and fabrication required to make it a good ride is such, that one has to really need it to make it worth the trouble and investment.

I don't need it and I'm still building one. 2 reasons:
1. To gear the hubby down slightly for more acceleration
2. To retain all the benefits of a hubbie (silence, durability, etc) while reducing the unsprung weight in that wheel by 70% or so.

 

[flyinmonkie]

I have run nothing but chain drives through the rear hub and dérailleur. I don't spend any more time on maintenance on the drive train than I do on my standard non motorized bike. I also have not had any issues with chains or sprockets wearing out faster yet. If you get your alignment correct, then everything wears nicely and runs smoothly.

The biggest differences are starting with installation. The hub in the wheel is going to be the quickest and easiest to install. Lace it in the wheel, come up with some torque arms and wire it up. Anything that drives the rear wheel with a chain is going to need a mounting bracket and time will need to be taken to align chains. That is extra cost and fabricating.

For both systems you will need to figure a way to mount your batteries. A hub in the wheel may give you more room in the triangle, depending on where the motor goes for a non-hub drive.

As for performance, that has really been covered. If you are hauling lots, or have a lot of hills, or want lots of low speed torque and a high top speed, then a non-hub drive is more suitable. If you live where it is flat and you can just cruise at top speed for a long time then a hub drive may be more suitable.

You have to weigh up all these factors to decide what is best for you, or what you want.

Clay

 

[deardancer3]

Flyin NZ, what motor and wattage you running? do you have a standard type bike with short chain lnes or extended length?

My 360w cyclone was running fine for quite a while till i bumped the cyclone idler wheel shaft, then a few days later I had to make it home without any pedalling (my Health), motor only. Spent weeks trying to find out what all went wrong, found the bent idle shaft, some fried lube in the cyclone xmission, and that 5000 miles on bike components designed for a weekend rider.

Everything is now upgraded, chains, cables, idlers, lube, motor heat sync, derailuer.

I think that a nuVinci or Nexus internal hub would make life much simpler for chain drives.

d

 

[John in CR]

Cajunjay,

If you're living in cajun land, and you're not planning on swamp riding your bike, then a direct drive hubmotor in wheel is all you need, since the biggest hill around is just a 15ft high indian mound.

Eat a couple of sacks of crawfish for me. It's been way too long since I've been home.

John

 

[cajunjay]

Well the Indian mound is at least 25-30ft high, you cant have been back home for over 10 years my friend.

The craw fish as still as good as ever but my wife is away and I cant make em the way she does. I'll probably just stick with the hub motor in the wheel as theres not much use going up the mound anymore anyway as the view isnt that good.

 

[flyinmonkie]

Flyin NZ, what motor and wattage you running? do you have a standard type bike with short chain lnes or extended length?

My 360w cyclone was running fine for quite a while till i bumped the cyclone idler wheel shaft, then a few days later I had to make it home without any pedalling (my Health), motor only. Spent weeks trying to find out what all went wrong, found the bent idle shaft, some fried lube in the cyclone xmission, and that 5000 miles on bike components designed for a weekend rider.

Everything is now upgraded, chains, cables, idlers, lube, motor heat sync, derailuer.

I think that a nuVinci or Nexus internal hub would make life much simpler for chain drives.

d

I was running a brushed currie motor with and average of 2500w and a peak of 5000w. I burned the motor up by running 100amps through it. So now I am running a cyclone 1200w and I am seeing around 2500w peak or so. I am using a Kona dirt jump frame and I drive the rear wheel through the dérailleur after a gear reduction. I DO NOT drive through the cranks.

 

[DrkAngel]

Mid-Drive, through the bicycle gears (sprockets)...

A mid drive that is built to use the bicycle gears is a fail waiting to happen.

A typical healthy male is, briefly, capable of outputting 900w+ of power into the bicycle gears. (NASA 1964)
(Probably alternating between 1700w and 100w surges, per pedal stroke?)
A much smoother, continuous, 500w motor input should hold up nicely, ... tho I would recommend reducing throttle during shifts.

If the motor is placed in front of the Bottom Bracket, then there would actually be less stress on the BB!
The torque to the rear wheel would be equally offset by the torque from the front motor, (with equally sized chainrings).

Rear hub bearings will suffer more stress.
Though, compared to the weight of the bike, rider , batteries etc. I would think this to be a minimal factor!

So the "fail waiting to happen" would be the chain, or rear cluster. Both easily replaceable, and cheap ...

I wouldn't like having to shift through the derailer range either, that is too many gears for the need of a powered bike and too weak for any interesting power to last.

You don't have to shift through anything ...
You could pick whatever ratio suits your present needs, and keep it there ...


Even though the "legal" eBike speed is, (USA), a Federally recommended 20mph ... 30mph seems more ... eBikey ...
Personally, I would recommend a, wide spaced, 7 speed 11-34T rear cluster.
Effectively producing a 3:1 torque increase at the bottom end.

30 mph capable eBikes.
(Up to 10 mph) - With a common 500w, (output), motor, that would give you the torque of a 1500w, (output), motor!
Errr ... except at about 30%, of no load speed, the 1500w motor might be, barely, 30% efficient, meaning that the 1500w output motor might require 5000w input to produce the same torque as the 500w, using 600-650w input.
With judicious shifting, this efficiency advantage continues, but at a reducing rate, as speed increases, equalizing somewhere in the mid 20's mph.

So ...
Looks like a nice little toy-project to me!

I planned on doing similar, but using an eZip gear reduction brush motor.
Noisier! ... but cheap and simple!

Note: 30mph from a 500w motor?
Estimated power requirements for propelling a Mountain style bike, with upright seated rider is near 700-750w.
Lowered seat with crouching rider lowers this estimate into the 500w range.

See -Aerodynamic Factors

Wind resistance is the major factor, above 20 mph!
Funny enough ... even the addition of a rounded front basket, makes for a noticeable speed increase!
... I don't believe pink tassels on the handle bar ends help! ... err ... actually, they might.

 

[bzhwindtalker]

Having a mid drive is also a great thing when you are doing some offroad stuff, jumps ext...
1. Variable gearing let you adapt your pace to the terrain while staying efficient
2. A mid drive gets the weight out of the rear wheel, and does not frock up the suspension as much as a wheel hub
3. Having the weight centered on the frame helps to prevent wheelies and gives you better balance in jumps
4. Using a mid drive means you can use standard wheel sets that can be brought locally for super cheap, Decatlon in France sells very nice 26' disc mtb wheels 40€, when a strong rear hub motor wheel build can cost $$$...

 

[MadRhino]

@DrkAngel

All those numbers are fine, but most lack a 0 at the end to make any Ebike interesting to me.
When you start feeding 10 times human power, which I consider only the beginning of interesting performance, a bicycle drive train is not very long to show its limits.

 

[deardancer3]

Great thread

I hope the OP is getting the data that he is looking for.... this is turning into a nice non defensive comparison of the two drive techniques.

there are people here letting all see the personal side of what it takes and what you get for your investment for chain drive. no free lunch... dont use a kmart bike/components for chain drive.. you need to know how to set one up correctly. there might be some fabrication.. some research might in order. the payback is there if you need it-- a versatile and high performing ebike.

but dont fool yourself... if you are a desk jockey that does not know how to run a perfect chain line.. if you dont know how to tell what quality reliable components are and are willing to buy them... if you are not willing to take the time to get it perfect, be honest, and really consider if a hub motor would be more your style, or pay someone to do this for you.

But if you need the performance, if you enjoy the versatility, if you can and will get it right and take care of it... i think it is the way to go.

all good ebikes will get used a lot and are heavier and faster than a non electric bike, so pay attention to wheels tires and brakes.. frequently

my two watts worth.