Powerful Hub Motor with Front Derailleur Only

[HDMW]

Hello :
I rode a human powered HPV FS 20 for a few years until it was creamed by a truck. Now I'm looking at the Azub T-Tris 20 which I plan to electrical assist.
For the moment I'm ignoring the bottom bracket drives as these seem to require a departure from normal bicycling. (i.e. back pedaling to shift gear, motor brakes and perhaps other oddities).

I am interested in powerful assist. I can maintain 20 kph easily on the flat so I will not pay two grand for a machine which cuts power at 25 kph.

So far these seem to be the choices for an eTrike.

1 A hub motor with a rear derailleur. (the 19th C approach).
2 A hub motor and a bottom bracket gearbox such as the Pinion. (cost no object apporoach)
3 The ADCM IGH which might (or might not) work with a frame with vertical dropouts. (the unknown approach)
4 A powerful hub motor and a front derailleur and three chain rings. (low cost and simplicity).

I understand the numder of gears required tend to be inversely proportional to power.
So, could item 4 work?
And could the chain line be a problem?

Best Wishes : Hubert Wagner
France

 

[spinningmagnets]

It's been done, and yes...it works. The original influence was the trend of using wider hubmotors to get more power. The MXUS 3000W is most often seen with a single-speed freewheel (although I have seen some frames squeezing-in a 2-speed freewheel into the tight 135mm drop-out width). Three gears seems to be ideal on a powerful hubmotor (for those who have tried that), as well as already available in well-sorted common (and affordable) components.

Even if you only need two widely-spaced chainrings on the bottom bracket (high ratio to add pedaling while at top speed, and a very low ratio to pedal home if the electric power system fails)...if the ratio is too wide between them, then...the derailleur shifting will function more smoothly and reliably if there is a chainring halfway between the two that you use.

 

[ferret]

I'm ignoring the bottom bracket drives as these seem to require a departure from normal bicycling. (i.e. back pedaling to shift gear, motor brakes and perhaps other oddities).

Hi.
Mid drives does not require departure from normal bicycling.
For front gears only you will still need a rear derailleur, or a tentioner. So ,arguably, a rear gears only setup is simpler that a front only setup.

Avner.

 

[HDMW]

Hello :
I'm encouraged to hear a front derailleur with three chain rings can be used with a 3kw hub drive.
May I presume the same the principle applies with a slighly less powerful hub, say 1,5 kW?

Could there be a problem with the chain line if one had three chain rings?

If this set up works, then why would anyone be tempted to buy a bottom bracket gearbox for €1500 with more than three or four gears? Is this because the manufacturer expects motors are low powered?

Incidentally, I don't want a rear derailleur because they are difficult to clean, need constant adjustment and are prone to damage.
Did the French invent them? If yes, we have something to answer for !

Regards : Hubert Wagner
France

 

[MadRhino]

With a powerful hub build, you don't need any gears. Your speed and acceleration won't let you use them anyway. That is the main performance advantage of hubs over BB drives. By the time you shift your BB drive to 40 mph, the hub is long gone at 60 mph and braking for the next corner already.

 

[HDMW]

Hello :
I'm not interested in throttle only riding. I'd like to be able to pedal with assist, but well over the silly 25kph limit of many hub motors. (I need the exercise).

So, if I'm making 20 kph on the flat, I wish to choose assist to boost that to whatever, with no cutoff. I assume that's why I need some gears; low to start off, medium for flat and high for the down hill.

Otherwise what is the point of paying for electric assist? (There is no hill here I cannot climb without assist - and I'm 75)!

Best Wishes : Hubert Wagner

 

[SlowCo]

What is your desired speed on the flat? If you don't need or want more than 45km/h you might consider a MAC 6T motor kit with PAS in a wide 20" rim. That way you can keep the 3 front chainrings and the rear cassette. You can choose the ideal cadance and have enough assistance to reach the 45km/h.
https://em3ev.com/shop/upgrade-mac-kit-with-4750v-battery-1500w-max/

 

[spinningmagnets]

The so-called "gravel bikes" typically use a high-mounted style of derailleur on the front, in order to avoid getting as much mud as possible from being packed into the front derailleur. That is one benefit to having 3 gears on the front derailleur instead of 3 or more on a typical rear derailleur, since the common style of rear derailleur hangs down where it can easily be hit by rocks, or a simple "wipe out"...

 

[markz]

We need to know your desired speed while on the throttle/pas.
The ebikes that are legal are limited to 32kph, but are expensive.
I would assume you'd want a light setup as well.

Also what is your weight and the weight of your cargo (all in) ?

If you are pedaling along and you want to not use the motor and pedal as well, then a geared motor would suit your needs as there is no drag like on a direct drive motor.

I would assume since you can pedal at 20kph, you'd want to go atleast 30kph or even 35kph at most which is what I like to ride at while on pathways, its a comfortable speed to ride at.

You can go to ebikes.ca and click on the motor simulator and play around with everything. Perhaps use 125W as Human power. I'd say the Bafang CST, eZee/BMC/MAC. Then play around with 36V or 48V for your desired speed.

 

[MadRhino]

Sorry. "Powerful hub motor" is a subjective notion, and we hear watt we are used to. :wink:

 

[ferret]

Incidentally, I don't want a rear derailleur because they are difficult to clean, need constant adjustment and are prone to damage.

As I wrote earlier, even if you only have gears at the front, you will still need a rear derailleur or a similar mechanism to take up the slack in the chain when you shift from a big chainring to a smaller one. You still have a difficult to clean, prone to damage mechanism even if you have only one rear gear.

Avner.

 

[Chalo]

Incidentally, I don't want a rear derailleur because they are difficult to clean, need constant adjustment and are prone to damage.

As I wrote earlier, even if you only have gears at the front, you will still need a rear derailleur or a similar mechanism to take up the slack in the chain when you shift from a big chainring to a smaller one. You still have a difficult to clean, prone to damage mechanism even if you have only one rear gear.

On top of that, rear derailleurs work lots better than front derailleurs. For equal component quality, setup, and maintenance, the rear will always shift better for longer.

 

[tigcross]

TDCM makes a nifty DD hubmotor with 5 speed Internal Gear Hub built-inside of the motor. If your max power is 1500 watts It could handle it (and 1500 watts in a 20" wheel is lots of torque). If you're looking for meaningful pedaling at higher speeds you might also put on a Pattison or Schlumph 2- speed crankset.

On my previous build I used a Rohloff Speedhub as an intermediate transmission, it has the biggest range of any bike transmission at 508% over 14 gears. It had the range to allow for meaningful pealing from 0 to t 60 KPH. looking at the Azub, I think you might be able to shoe-horn an IGH like the Rohloff or shimano 11 speed as an intermediate transmission. However, as sweet as the Rohloff was, I found that I was accelerating and decelerating so much in city traffic that I got pretty tired of running up and down the gears, and on my next build I went to an altogether different system of utilizing the human energy.

One note about construction: if you look at the chainline on the Azub, you will see that it needs a rear derailer to set up the slack (bottom) chain-line. I expect you could put another guide pulley somewhere to compensate for the absent derailer.

Good luck with the build.

 

[HDMW]

Hello List :

There’s quite a lot to think about in your answers. Thank you all for your input.

Here is the data Markz requested.

My height and weight : 172 cm (68 in), 80 kg (176 lb). Most of the time I’d be pulling a two wheel trailer with two weeks of groceries.

Two further questions :

1 Just how bad is the drag of a ungeared hub drive? (I’m thinking, out of power, 10 miles from home on a wet, cold, Novermber night).

2 Can the mid-motors be set up to function in the background without constant control input from the rider?
(So far I understand there is no torque sensor for the Bafang motors).

The TDCM motor is interesting I agree. If the motor can be fitted to the T-Tris, then the TDCM torque sensor could also be fitted. That setup makes a lot of sense to me.

Tigeross said, “However, as sweet as the Rohloff was, I found that I was accelerating and decelerating so much in city traffic that I got pretty tired of running up and down the gears, and on my next build I went to an altogether different system of utilizing the human energy”.

What would that ‘altogether different’ system be?

I’ll follow up Markz’s suggestion to do some work with the simulator at eBikes.

Regards : Hubert Wagner

PS : I like your megawatt bicycle accessory MadRhino

 

[dogman dan]

With three gears up front, you will indeed need a tensioner, essentially identical to a derailleur. Or a derailleur used as a tensioner, locked in place for that single gear.

With enough power, as other said, you won't be using anything but your highest gear unless broken down. You are, overthinking this.

For the vast majority, the needs are easily filled by 1000w. A 500w rated geared rear hub motor, fed with 20-25 amps of 48v. And a 7 speed derailleur gear on the back, that more or less gets left in its highest gear, or perhaps the highest 3 gears.

This type setup tends to be cheapest, is very reliable, and plenty of power unless you tow trailers, or weigh 300 pounds. Derailleur problems pretty much vanish, when you stop shifting, but the low gear is handy if you are limping home at 5 mph, nearly out, or completely out of battery.

Oops, you are towing a trailer. Now we need to know the grade and length of hills you might climb. If its long and steep, then you should go to a direct drive, even though a geared motor will be much better at coasting, or pedaling with no power. Or a mid drive.

The rule of thumb is 300 pounds weight. above 300 pounds for you, the bike the trailer and the groceries, then the grade of your hill better be less than 5% and length less than one mile, or 2k more or less, for using a 500w rated geared motor.

If your weight is more, and your hill is more, then I advise going to a bigger, heavier, direct drive motor, and feeding it 2000w max. (48v 40 amps). The DD will resist, so you just have to be sure your battery will last all the way to home. if you can save back just a tiny bit, you can pedal many miles feeding the motor a tiny trickle of power, which eliminated the motor cogging slowing it down. Obviously doubling the size of the motor, and its power, means doubling the size and cost of the battery.

Chances are, you can easily avoid loading the trailer quite so heavy, perhaps with only one weeks food, once you have the easy ride to the store with assist. Then you can run the 1000w system, with a better coasting geared motor.

To continue overthinking it, a mid drive with a full range of 21 or more gears (derailleur) is indeed the best way to go to tow heavy weight up hills. A well tuned cadence type PAS control can work very well, combined with the riders proper gear selection. It need not be torque sensing. However, nothing sucks quite as bad as a very poorly tuned cadence PAS. ( usually this is too long before it starts up, followed by too much power) Fortunately most current systems do allow the rider to tune the PAS.

Personally, I'll take a simple throttle every time myself. Its not that hard to learn to use a throttle to constantly tune the power you need, and achieve the perfect ride. This perfect ride for me, is the same effort level and cadence, uphill and down. only a throttle responds so instantly and infinitely to do that, IMO. But like I said, tune it right and PAS comes pretty close. But not as perfect as your hand on a throttle can get it.

 

[The fingers]

1 Just how bad is the drag of a ungeared hub drive? (I’m thinking, out of power, 10 miles from home on a wet, cold, Novermber night).

Been there. Done that.
Just think of a stationary exercise bike with the resistance brake dialed up about half way. You won't be cold for long. :wink:
A little juice left can overcome the resistance, but zero power can become a mountain climb after a few miles.

 

[amberwolf]

So far these seem to be the choices for an eTrike.

1 A hub motor with a rear derailleur. (the 19th C approach).
2 A hub motor and a bottom bracket gearbox such as the Pinion. (cost no object apporoach)
3 The ADCM IGH which might (or might not) work with a frame with vertical dropouts. (the unknown approach)
4 A powerful hub motor and a front derailleur and three chain rings. (low cost and simplicity).

There are other options, such as the way I built my SB Cruiser trike: There are 3 chainrings on the front, but it has no derailer; I manually move the chain from one ring to the other, depending on my plans for the ride. The large ring is for if I am able to pedal along with the motor. The small is in case I have a problem with the motor system, and have to pedal regardless of how well my joints are doing.

Then the chain goes back to a 3speed IGH in the frame, with a derailer below it's input sprocket solely to keep the chain tensioned when it's moved from one ring to the other. The IGH is there for it's low gear for the just in case situation above, but it's higher two for pedalling along with the motor. (I can't input much power, and it's not a light trike).

Then there's an output sprocket welded to the IGH's spoke flange, and chain goes from that back to the trike's transfer axle, which goes back to the left wheel's input freewheel. Someday I'll find parts taht will let me make a useful differential and output to both wheels.

THe motors are DD (not geared) hubs in 20" wheels, as I'm after torque for hauling hundreds of pounds of cargo, groceries, and/or dogs, with or without the trailer. But even unloaded, it's pretty hard to pedal above a couple MPH, even on the flats, mostly from the weight but partly from the drag of the DD hubs when unpowered.

I have a second iteration in design stage that will use geared hubs instead, in 26" wheels, because it will be a LOT easier to pedal if I need to.

See the link in my signature for the SB Cruiser for details.

Also, Tigcross's build is in his signature if you want the details of his pedal-energy-recapture system.

 

[tigcross]

What would that ‘altogether different’ system be?

Hi, as Amberwolf said, my build link and website are in my signature. In short: My bike uses a generator drive where most of the time the human energy go into creating electricity to supplement the battery. I don't think it would work very well for your desired goals, and it requires the 500 Watt+ power we can use in Canada.

a couple more observations for you're project:

-The regeneration feature of Direct Drive hub motors would be an asset to you if hauling cargo. Regenerative breaking is very nice for handling heavy loads;

-The downside of Direct Drive is that they definitely are not fun to pedal unpowered, but to be honest many ebikes end up heavy enough with batteries and cargo that they are all difficult to move unpowered;

-if unpowered use is very important then a gearmotor or mid-drive is what you want, but you will lose regenerative breaking;

-have you looked at the Hase delta configuration trikes out of Germany? they are expensive but very well made. They make a model with a Shimano steps motor, or you could easily add your own hubmotor to the front wheel. I also like the Delta trike layout they use as it places the rider higher up and more visible than a tadpole trike.

 

[HDMW]

Hello Tig :
I looked at your project. Most impressive.

I'll follow up your suggestions re Germany.

However, I'm coming to the conclusion the TDCM IGH with a torque sensor in the bottom bracket might suit me. (I don't like the idea of the DD drag when not powered). I note Grin offers controllers up to 40A. These motors seem to be routinely fed more than double their rated capacity. Interesting.

Incidentally, I've just come across this bit on a French project. The announcement is two years old so you may already know about it. I guess this is a fuel cell application.

http://www.telegraph.co.uk/news/worldnews/europe/france/11904005/French-unveil-world-first-hydrogen-powered-electric-bike-emitting-only-pure-water.html

Regards : Hubert

 

[tigcross]

thanks for the link Hubert, I hadn't seen that one. I do think that a fuel cell might suit my bike eventually, that's the great thing about electric drive, whether it's fuel cell or a battery, it's just power.

I'm using one of Grin's 40 amp sine-wave controllers at 72 volts, I usually run at 1500 W max for efficiency reasons, but I've run at the full 2800 W for extended periods with no problem. My hub motor is more of a scooter style, so has more mass for heatsinking.

Good luck on your project,

Tig

 

[amberwolf]

However, I'm coming to the conclusion the TDCM IGH with a torque sensor in the bottom bracket might suit me. (I don't like the idea of the DD drag when not powered).

The motor itself is still a DD. The IGH is only for the pedal drivetrain.
main thread
https://endless-sphere.com/forums/viewtopic.php?f=30&t=63284&hilit=TDCM+IGH
couple of builds
https://endless-sphere.com/forums/viewtopic.php?f=6&t=85652&hilit=TDCM+IGH
https://endless-sphere.com/forums/viewtopic.php?f=4&t=85075&hilit=TDCM+IGH
a search on TDCM IGH will find more discussion about it

I note Grin offers controllers up to 40A. These motors seem to be routinely fed more than double their rated capacity. Interesting.

For short peaks you can do much more than double on many DD motors; continuous use at higher power makes more waste heat which can be a problem to get rid of, moreso the more "layers" there are to the motor, which is why geared hubs don't usually handle "overpowered" use nearly as well as DD hubs.

Since the TDCM motor is a DD, it should also be capable of much higher than rated peaks of power.

 

[HDMW]

Hello List :
Amberwold said, "Since the TDCM motor is a DD, it should also be capable of much higher than rated peaks of power".

I'd not realized the TDCM was DD. In what way is the TDCM with gears different from a geared hub drive?
Will the TECM have the same resistance to moving when power is off like other DDs?

Regards : Hubert

 

[tigcross]

Hi Hubert,
The TDCM is a Direct Drive Motor with a 5 speed internal gear hub inside the hub. So you get five gears, but it is still a DD with Regen. A bit confusing as it does have "gears".
A Gearmotor is a hubmotor that uses a much smaller electric motor with a planetary reduction gear to get more torque from the lower power motor. An added feature of Gearmotors is that they have a freewheeling mechanism built into the planetary reduction. They also offer more torque per watt due to the planetary reduction.

Grin has a good explanation of the difference on their site. http://www.ebikes.ca/learn/hub-motors.html

 

[HDMW]

Hello List :
My earlier remarks aside, I've come to the conclusion a geared rear hub motor and the Pinion 12 sp gearbox might be the best option. A geared motor with a single sprocket seems to be the most appropriate.

My aims are still to use the motor to assist my own efforts and to allow me to reach say 40 kph on the flat. And I want to ditch the rear derailleur. Does this combination sound sensible? Will I be able to use the gears up to 40 kph? Or is this a throttle only situation?

I'm thinking of using this setup on an Azub T-Tris 20 which is made in the Czech Republic.

My regards to the List : Hubert Wagner
France

 

[ScooterMan101]

This is supposed to be a real good chain tensioner ... http://www.jensonusa.com/Paul-Melvin-Chaintensioner-Black?pt_source=googleads&pt_medium=cpc&pt_campaign=shopping_us&pt_keyword=&gclid=EAIaIQobChMI0oqZ9ZD72AIVSmx-Ch0hfwVmEAQYAyABEgLpnvD_BwE

Note: Jenson USA will often price match other places.

https://maxthecyclist.files.wordpress.com/2015/10/md028507.jpg