more efficient hub or mid drive

Discussions related to motors other than hub motors.
This includes R/C motors, botttom bracket, roller and geared drives.
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dustyearlobe   100 W

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Re: more efficient hub or mid drive

Post by dustyearlobe » Aug 27 2013 7:35am

Toorbough ULL-Zeveigh wrote:
if it wasn't on video rakesh would have wrote:the motors being delivered by bosch & panasonic to me are very ineffcient.

...it is an absolute insanity to be able to use a bottom bracket system on a bicycle.

http://www.youtube.com/watch?v=Q4PQbbFSbbM#t=532


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& no hitting below the belt.
things where going so well until about 10min in ,,,thanks for that I got a giggle on

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crossbreak   100 MW

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Re: more efficient hub or mid drive

Post by crossbreak » Aug 28 2013 8:54am

"middrive is like a little internal combustion engine"

this guy should cell hoovers :mrgreen: he actually has no idea how things work :roll:

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Re: more efficient hub or mid drive

Post by d8veh » Aug 28 2013 11:45am

I love these threads. Whether you have a crank-drive or hub drive, the motor efficiencies follow a similar curve that depends on their actual speed compared with their maximum no-load speed. How much efficiency you get depends on how you use your bike. A hub-motor spending a lot of time spinning at 2/3 it's maximum RPM can be very efficient. If you have a crank-drive, you can get low efficiency by choosing too high a gear. Then there's everything in between. I have two GNG crank drives and two 500w Bafang hub-drives, all with the same battery and similar 30 amp controllers. I can't see any significant difference in amp-hours used between any of them when I do the same journeys at the same speeds. The journeys are moderately hilly.

Another interesting point: I also have a 2WD off-road bike with twin Q100 250w motors. If I'm on a medium hill with one motor, I can see the amps go down, when I switch on the second motor and keep the speed the same, because I can use less throttle, which pushes the efficiency curve down the speed range, so that both motors are working more efficiently. The more the one motor was struggling, the greater the reduction in current.

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recumpence   100 GW

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Re: more efficient hub or mid drive

Post by recumpence » Aug 28 2013 4:18pm

Also, remember, just because motor efficiency is high, does not guarantee that you will get decent range. For example, the expensive Astro motors I use are up to 94% efficient. However, you need at least two reduction stages to get the power to the rear wheel. That means you lose around 6% to 8% in those stages. So, the actual efficiency is more like 88% or less and that is the absolute peak. Most situations would see even lower numbers.

I like to give actual watt-hours per mile at a given speed stopping at the point I started (to eliminate elevation and wind as variables). This gives real world info.

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pdf   10 kW

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Re: more efficient hub or mid drive

Post by pdf » Aug 28 2013 4:27pm

My experience is similar to others. Both my mid-drive and hub setups get about the same average efficiency for day to day driving, around 18 Wh/mile. The mid-drive can be a Wh/mile lower sometimes. Speed is the biggest thing that effects the efficiency I see. If I spend a lot of time over 20 mph (esp. on moderate hills), the efficiency starts to go down significantly regardless of which bike I am on. The mid-drive has awesome efficiency on hills, but then again I am geared way down so not going very fast either.
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dustyearlobe   100 W

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Re: more efficient hub or mid drive

Post by dustyearlobe » Aug 29 2013 2:43am

ok this is all very good side by side comparisons but lets say for instance you have a hub and a middrive both wanting 45mph speeds the hub motor is going to need some voltage thrown at it say twice what the middrive is going to need so on a same run you would have to half the middrives results then compare so,s to compare result with the same mass battery ,,,not realy facts and figures but simpley whats achievable with a certain amount of batterys

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crossbreak   100 MW

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Re: more efficient hub or mid drive

Post by crossbreak » Aug 29 2013 4:26am

ok this is all very good side by side comparisons but lets say for instance you have a hub and a middrive both wanting 45mph speeds the hub motor is going to need some voltage thrown at it say twice what the middrive is going to need so on a same run you would have to half the middrives results then compare so,s to compare result with the same mass battery ,,,not realy facts and figures but simpley whats achievable with a certain amount of batterys
some full stop would be nice in your "sentence". Cant really read what you wanna say. If you want a true middrive, which lets you pedal at 45mph, you need at least some special setup like the "dual Jackshaft freewheel drive" or Hammerschmidt Freewheel cranks to keep chain load down. At steady 45mph your middrive will be less efficient than the same motor used in a hub.
recumpence wrote: For example, the expensive Astro motors I use are up to 94% efficient. However, you need at least two reduction stages to get the power to the rear wheel. That means you lose around 6% to 8% in those stages.
well said. What about a motor that has 24poles instead of 8, could still have the same efficiency, but would run 2500rpm nominal instead of 7500. Only one 5:1 stage needed. That would be some innovation finally :shock: Of course it has to be slightly larger in dia

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dustyearlobe   100 W

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Re: more efficient hub or mid drive

Post by dustyearlobe » Aug 29 2013 7:03am

why do you see a hub being more efficient than mid drive when you need twice the voltage for a hub than you do in a middrive ....(no pedalling)
some full stop would be nice in your "sentence". Cant really read what you wanna say.
I didn't breath when I was writing it :roll:

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gwhy!   1 MW

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Re: more efficient hub or mid drive

Post by gwhy! » Aug 29 2013 8:16am

A geared mid drive is going to be more efficient on average as the most efficient rpm of the mid drive can be kept in about the same place no matter what the road speed is... you are not going to get the most efficient rpm from a hub motor 100% all the time as this will be determined by road speed. But it will still be a close call unless you have a really bad setup and there are other factors that are effecting the efficiency.

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speedmd   100 MW

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Re: more efficient hub or mid drive

Post by speedmd » Aug 29 2013 8:27am

Agree gwhy

There is a sweet spot running toward half / 3/4 throttle where mine runs super efficient and easy to keep it there with a bunch of close spaced gear ratios. I am thinking of trying it on one of my ten speed close ratio setups for road use. Not being able to do this on a hubby is a major current drain when off pipe and even slight throttle is added.

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crossbreak   100 MW

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Re: more efficient hub or mid drive

Post by crossbreak » Aug 29 2013 11:08am

dustyearlobe wrote:why do you see a hub being more efficient than mid drive when you need twice the voltage for a hub than you do in a middrive
No chain loss. At constant speed on a flat road. During acceleration /hill that is different.

A standardized drive cycle would be nice to compare. Like the city-NEDC. Even better, would be one with hills
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Toorbough ULL-Zeveigh   100 MW

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Re: more efficient hub or mid drive

Post by Toorbough ULL-Zeveigh » Aug 29 2013 11:33am

crossbreak wrote:this guy should cell hoovers :mrgreen: he actually has no idea how things work :roll:
clearly.
after all he's only sold a couple thou copies of his designs & hold just 6 patents.

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gwhy!   1 MW

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Re: more efficient hub or mid drive

Post by gwhy! » Aug 29 2013 11:41am

crossbreak wrote:
dustyearlobe wrote:why do you see a hub being more efficient than mid drive when you need twice the voltage for a hub than you do in a middrive
No chain loss. At constant speed on a flat road. During acceleration /hill that is different.

A standardized drive cycle would be nice to compare. Like the city-NEDC. Even better, would be one with hills
Image
what do this chart mean... is it trying to prove some thing :mrgreen:

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Re: more efficient hub or mid drive

Post by speedmd » Aug 29 2013 12:29pm

Toorbough ULL-Zeveigh wrote:
crossbreak wrote:this guy should cell hoovers :mrgreen: he actually has no idea how things work :roll:
clearly.
after all he's only sold a couple thou copies of his designs & hold just 6 patents.

http://www.linkedin.com/in/rakeshkdhawan

arschklar.
After watching the video link, I have to agree with crossbreak. Except I don't think he can even sell many vacuum cleaners. This guy know squat about bikes. Front hub motor :?: Seriously. The ones that old folks all over are causing them to fall off their meager ebikes. Compares mid drives to ICE bikes. Does he not think that riding in underdeveloped areas is legitimate transportation. Shows they will give patents to anyone that can hire a lawyer. You go for it and follow this guy, right off the cliff. :P He should stick to motor and controller design, and stay out of what constitutes suitable vehicle design. Obviously not qualified to speak on that.
Last edited by speedmd on Sep 01 2013 3:52pm, edited 1 time in total.

d8veh   100 GW

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Re: more efficient hub or mid drive

Post by d8veh » Aug 29 2013 5:01pm

gwhy! wrote:A geared mid drive is going to be more efficient on average as the most efficient rpm of the mid drive can be kept in about the same place no matter what the road speed is... you are not going to get the most efficient rpm from a hub motor 100% all the time as this will be determined by road speed. But it will still be a close call unless you have a really bad setup and there are other factors that are effecting the efficiency.
The crank drives have theoretical advantages, but they're not realised in practice. A side-by-side test will show you that. In practice, you sweep the crank motor through its whole rpm range in each gear as you accelerate through the gears. You don't hold it at optimum rpm. You have access to higher power at any time with a crank drive, so you tend to accelerate faster using the higher power. There's loads of other reasons too. It's all down to how you ride and control the motor, but for normal operation, being sensible about how you use the power/speed, they come out the same. The only ones that seem to get really good efficiency are the low-powered European ones with torque sensors and without throttles, that appear to get very good ranges, but it's an illusion. You have to pedal harder with them. You can't be lazy with them and take a rest from pedalling hard.

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crossbreak   100 MW

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Re: more efficient hub or mid drive

Post by crossbreak » Aug 29 2013 5:11pm

true, d8vid. ´Just the same as with the new turbo gaz engines. They have a flat torque curve, just like phase-amps limited BLDC motors. People tend to use the torque they get and forget to shift.

The solution is not cry and throw away the theoretical gain in efficiency, but in fact use it. I use it, many other do and adore it. The rider must get educated if he isn't. Gas cars do the same (ever seen a Prius display ;) ok, you cannot shift :mrgreen: ) SO I suggest using a phase current limit, to keep the motor within it's good efficiency range and inform the driver when he should shift. And the driver will shift again :shock: That is what I suggest for quite long now. I see this problem with my girlfriend frequently on both car and ebike... ok I dont, she is actually educated now :mrgreen:

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Re: more efficient hub or mid drive

Post by gwhy! » Aug 29 2013 6:16pm

d8veh wrote:
gwhy! wrote:A geared mid drive is going to be more efficient on average as the most efficient rpm of the mid drive can be kept in about the same place no matter what the road speed is... you are not going to get the most efficient rpm from a hub motor 100% all the time as this will be determined by road speed. But it will still be a close call unless you have a really bad setup and there are other factors that are effecting the efficiency.
The crank drives have theoretical advantages, but they're not realised in practice. A side-by-side test will show you that. In practice, you sweep the crank motor through its whole rpm range in each gear as you accelerate through the gears. You don't hold it at optimum rpm. You have access to higher power at any time with a crank drive, so you tend to accelerate faster using the higher power. There's loads of other reasons too. It's all down to how you ride and control the motor, but for normal operation, being sensible about how you use the power/speed, they come out the same. The only ones that seem to get really good efficiency are the low-powered European ones with torque sensors and without throttles, that appear to get very good ranges, but it's an illusion. You have to pedal harder with them. You can't be lazy with them and take a rest from pedalling hard.
Most of what you have said I would agree with , and it would be all down to how you ride and control the motor, but if geared correctly then you will not be using the whole rpm range in each gear in a fully loaded state. If you were going for efficiency then you would hold it at a optimum rpm in the optimum gear for the desired road speed and this is something you can not do with a non-geared system i.e a hub motor.

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Re: more efficient hub or mid drive

Post by d8veh » Sep 01 2013 5:08am

Yes, I agree with everything you say. In theory the crank drive should be more efficient. The comparisons that I've done in practice don't show that, so I'm trying to offer possible reasons why.

I have relatively hilly regular journeys, and I have hub-motors and crank-drives with similar 30 amp speed control controllers. I always pedal with similar effort, using the motors to make the hills easy. The battery consumption is always in the same range regardless of which system I use. It's the best comparison I can do. If I thought crank drive was more efficient, I'd use it all the time, but I don't have anything that says it is other than a lot of theory.

I wish I'd got the Nuvinci harmony now instead of the manual version because that can keep the crank rotation speed constant.

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Re: more efficient hub or mid drive

Post by speedmd » Sep 01 2013 9:51am

If you include some "real" off road steep hilly and loose terrain it will become obvious. Simply no comparison. One works well and the other not much or at all. For mellow road riding/ cow trailing, most likely it will be throttle control variance causing most of the diff.

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Re: more efficient hub or mid drive

Post by Whiplash » Sep 01 2013 10:57am

My sentiments EXACTLY. A hub motor would last about 5 minutes on my local trails, and I mean that literally it would melt before the top of the first climb. My mid mounted MAC has thousands of miles of that same terrain on it and keeps right on going barely getting warm!

Bottom line, if you want to climb REAL trails you need a gear reduced drive either with a LOT of motor or shiftable gears. This is what the mid drive is for. Regular street riding usually the hub is an easier choice.... But a mid drive single speed can be a BEAST if you use the right motor and set it up right! :wink:
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Toorbough ULL-Zeveigh   100 MW

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Re: more efficient hub or mid drive

Post by Toorbough ULL-Zeveigh » Sep 01 2013 2:34pm

Whiplash wrote:My sentiments EXACTLY. A hub motor would last about 5 minutes on my local trails, and I mean that literally it would melt before the top of the first climb.

Bottom line, if you want to climb REAL trails you need a gear reduced drive either with a LOT of motor or shiftable gears. This is what the mid drive is for.

:wink:

i doan unnerstan howe ucan say this when 4 overpriced mid-drives got beat like a rented mule by an el-cheapo hub-motor.
where did your fastastic mid-drive finish in the race?
unless you live by pikes peak i doubt your trails can steeper for longer so no worries there about hub melting.




speedmd wrote:You go for it and follow this guy, right off the cliff. :P
mmm no, he had nothing to do with designing the segway & neither would i own one.
speedmd wrote:Shows they will give patents to anyone that can hire a lawyer.
so tru.
remind me, how many patents do you have again?
speedmd wrote:Accept I don't think he can even sell many vacuum cleaners
well, except he's manufactured & sold more ebikes than you have or likely ever will.
and yes if rakesh ever does decide to design a vacuum cleaner i'll probably give him some more of my money.

(n.b. it's except not accept. :oops:)
you might have difficulty landing that vacuum cleaner salesman job since you're obviously not qualified to speak. :mrgreen:
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Re: more efficient hub or mid drive

Post by gwhy! » Sep 01 2013 2:49pm

Toorbough ULL-Zeveigh wrote:
i doan unnerstan howe ucan say this when 4 overpriced mid-drives got beat like a rented mule by an el-cheapo hub-motor.
where did your fastastic mid-drive finish in the race?
unless you live by pikes peak i doubt your trails can steeper for longer so no worries there about hub melting.
I have not seen Pikes peak in the flesh ( only see vids ) but it looks like a major road that goes uphill, its hardly a hilly trail. I think a well setup mid drive would do the business better than a hub ( but this is another debate and do not really need to be started in this thread :-) ).

The guy in the youtube vid is a BS'er and if he manages to sell thousands of ebikes due to his BS'ing then good luck to him, but people that fall for his BS'ing really needs do more research before taking what he says as gospel or they will end up looking as stupid as him but without as much money..

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speedmd   100 MW

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Re: more efficient hub or mid drive

Post by speedmd » Sep 01 2013 3:01pm

Good one Toorbough ULL Zeveigh, where ever your from.

You know nothing of my long cycle building background and product development experience as well as my patents. If you had half a clue you would STFU for certain. Just because a well set up hub motor bike won a hill climb ROAD race against a bunch of, YES, over priced out classed mid drives proves what exactly. Lets do the same race with equally powered mid drives except take the hiking trails up the pike. You in? Did not think so.

As far as the man crush you have on your fella that compares mid drives to internal combustion engines, you go ahead and promote the front hub motor as he does. :P Simply Clueless. Tell us, do you have a front hub motored bike? If not, Why not. He thinks they are just as good. Let us know how the vacuum works. : :lol:

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Re: more efficient hub or mid drive

Post by Whiplash » Sep 01 2013 10:51pm

Lol! Yes, I agree there! In fact, you bring me a stock hub mounted in wheel running at its rated voltage to my trails, if you can even follow me up more than two without coming to a complete stop, melting it, or getting a huge run at it I'll buy your plane ticket home oh, and here's the real catch, it has yo be able to top out at at least 30+ MPH like mine does. Oh yeah and it can't peak over 1200 watts either! Lol!!! Hell if a hub will do that in the wheel, I'll even announce my defeat here on the sphere in its own thread! Its just not going to happen. Some of my trails are very difficult to walk up and approach 40+* inclines! Most of the time I'm nearly over the front tire trying not to flip backwards! :twisted:

No offence meant here just all in good fun but I just had no choice! Lol!

Here's one of the easier paved roads the trails are steeper yet!
Power is a fascinating thing, the more you have, the more you want, but the real power is having the restraint not to use it all at once...............Um...Yeah..

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Re: more efficient hub or mid drive

Post by crossbreak » Sep 02 2013 6:42pm

there are some nice front hubs, dont get me wrong :D Problem i have is this guy lumps together all available drives, a lot of crap can be bought. Indeed there are crappy middrive and nice sub 2kg front drives. Still it is no honor to sell a lot of crap to the big masses. btw patents are a great way to stop innovation. Also, this guy with the Crystallite Hubmotor just wont since there was no concurrence :lol: very funny talk here, but not scientific at all. Why do people ask what a drive cycle is? Sry i'm too lazy to explain, read wikipedia :lol:

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