Have you done a Rear Hub and Mid-Drive Hybrid drive system ?

[ScooterMan101]

If you have run both a rear hub and a mid-drive on a bike what are your experiences.

I live in a place that has Mountains that are often very steep and long .
I also go long enough distances on the flat areas to want to and right now do use a rear hub motor .
However I have smoked a Mac rear hub going up the Mountains and have tried to take a rear DD hub that had 1k watts going through it up another Mountain Road. It did not make it up to the top , I could feel it almost coming to a stop and it was very hot so I turned around .
I have a bike that will able to hold more than one battery and can pull a trailer as well when needed( that I can also put more batteries on ) .
My first question is ... since I would prefer to use a rear hub motor on the flats , and then switch on the mid-drive when I get to the steep roads ... Would the freewheel in the mid-drive motor get worn out if I don't peddle ?
I do plan to use both the mid-drive motor and rear hub motor when going up the steep Mountain Roads .
Any other considerations you can think of ?

 

[neptronix]

A few problems.

- 1kw DD, unless it's in a 20" wheel, isn't enough to do any serious hill climbing in the first place, a RH212 ( more like 1.5kw-2kw cont ) might be another story due to it's extra poles and diameter. Try it on the ebike simulator and see if this motor could take care of your needs alone.

- Hub motor to cassette/freewheel interfaces are typically not designed for more than human power, and you're probably going to be pushing 5x that into the motor's shell.. the side cover shearing is likely over time. It would be way better to run a front motor in combination. Or use a wimpy 500w mid drive.

- DD will continuously have a small amount of drag and you'll find yourself using it in combination with the mid drive when climbing to overcome this.

- Consider two mid sized geared hubs; 14lbs in total and a total monster at hill climbing. The only problem is that front suspension forks aren't strong enough to handle 1kw longterm, so this isn't advisable unless you have a non-suspension fork.



- An alternate for this that is safe on a front suspension fork would be a rear 1-1.5kw DD hub and front ~500w geared hub motor.

 

[hillslayer@]

Works fantastic l have 2 bikes with 1500 watt hubs one with a Bbso2 and one with a BBSHD up hills at 48 volts better than a 60 volt hub . Run the biggest chainring you can fit on the mid -drive and I run a five speed freewheel. The breaking side covers is a myth as far as I can tell no one here has actually broken one.

 

[neptronix]

I've broken two side covers with leg power ( and i don't even stand when i pedal ), and seen others do the same, so that's why i'm very cautious about side covers.

 

[hillslayer@]

I've broken two side covers with leg power ( and i don't even stand when i pedal ), and seen others do the same, so that's why i'm very cautious about side covers.

What brand hub motor? I have been running full power on my mid -drive hub combos on hill climbs and can't see anything deformed or cracked.

 

[neptronix]

Some models are gonna be stronger than others. What hub motors are you using?
Do you pedal much and very hard?

I sheared the freewheel off a MAC motor and some older MXUS geared motor with leg power.
I've heard of a RH212 ( DD ) freewheel being sheared off on pedal power. But that design was particularly weak and got revised.

 

[hillslayer@]

CSC hub on a 29 er mountain bike plus a Bbso2 is my main bike pedal assist up hill all the time. The true test will be this summer on my fat tire cruiser, the freewheel mount sits 3\4 of an inch away from the cover, that's a no name Chinese motor with a BBSHD.

 

[hillslayer@]

Looks like leaf motors might have weak side covers also

 

[ScooterMan101]

" - An alternate for this that is safe on a front suspension fork would be a rear 1-1.5kw DD hub and front ~500w geared hub motor.
Neptronix I will consider this , as I already have two rear hub motors , the one that I would use for the steep mountain roads it the Volimart 1500 rear dd that I bought a few years ago on e-Bay that is still sitting new in the box , controller up to 48/52 volt . Although some of them I have read have a controller that runs the motor backwards.
One bike does have a front steel fork. So for that bike I could probably buy a 750 watt front hub ?
With 1-2 torque arms.
Other bike has Thru-Axle , All my Front Suspension forks are Thru-Axle. so on that it sounds like a rear DD and a Mid-Drive would be best. I already have a used BBS02 and BBSHD .

I would love to be able to afford to buy my systems from Grin. I consider them the Best. I have several small parts from them and a couple of Cycle Analyst's . But any complete system from
them is just not doable on my low pension . I do have a number of rear hubs and the 02 and HD . to work with . sounds like now I just need a front 750 watt geared front hub kit. up to 52 volt ( 58.8 Hot off the charger pack ) , From the lowest price , US warehouse shipped company .

 

[ScooterMan101]

CSC hub on a 29 er mountain bike plus a Bbso2 is my main bike pedal assist up hill all the time. The true test will be this summer on my fat tire cruiser, the freewheel mount sits 3\4 of an inch away from the cover, that's a no name Chinese motor with a BBSHD.

I was planing on using my Volimart 1500 dd on the rear and one of the Befangs on the mid section, But was thinking about a 30-32 or 34 tooth chainring as I would only use the mid-drive and rear hub when going up steep and long roads .
I don't put in much watts through my legs, I ghost peddle or spin in a easy gear while using a throttle 95% of my rides.
Where I live I would be using the Rear Hub 80% to 90% of the time. The mid drive or a front would only be for the other 10-20 % to prevent the rear from smoking .
Just wondering what kind of ware the mid drive freewheel would get as for long trips I use the throttle most of the time .

 

[ScooterMan101]

Neptronix ,
If I lived anywhere you I would let you play around with all the Ideas I come up with.

Now it is getting to the point where trying to get a motor / controller / cycle analyst / pas / throttle from different companies to work is just too confusing for me .
I ruined a brand new $ 200 Lyen 12 fet controller that I bought from him a couple of years back because I did not get the Halls and or Phase wires correctly connected , even though it ran on the bike stand just fine , it did not heat up on the bike stand , but on the test ride it and the motor got hot and stopped working the Motor mfg said the motor most likely is ok , I opened it up and it looks good .
However. Lyen won't talk with me now , he probably thought that would happen and kept trying to talk me into running it hall sensor less . I am guessing that has happened to him/his customers many times.

 

[hillslayer@]

I was planing on using my Volimart 1500 dd on the rear and one of the Befangs on the mid section, But was thinking about a 30-32 or 34 tooth chainring as I would only use the mid-drive and rear hub when going up steep and long roads .
I don't put in much watts through my legs, I ghost peddle or spin in a easy gear while using a throttle 95% of my rides.
Where I live I would be using the Rear Hub 80% to 90% of the time. The mid drive or a front would only be for the other 10-20 % to prevent the rear from smoking .
Just wondering what kind of ware the mid drive freewheel would get as for long trips I use the throttle most of the time .

Reasons for a big chainring are it allows you to stay on cogs closer to the motor and when climbing hills with a DD hub you want to keep your speed up as that is what DD hubs run most efficiently at. By not running huge amps threw either motor you can climb at a good speed forever almost.

 

[neptronix]

I agree that the market for DIY kind of sucks.
I had an incredible hard time finding both programmable 2kw+ controllers that weren't crap... and matching accessories so that i didn't have wiring nightmare.

Ended up with a spintend VESC

10 years i would have just bought an infineon from em3ev..

 

[ScooterMan101]

Reasons for a big chainring are it allows you to stay on cogs closer to the motor and when climbing hills with a DD hub you want to keep your speed up as that is what DD hubs run most efficiently at. By not running huge amps threw either motor you can climb at a good speed forever almost.

What size chainrings and what tooth count rear cogs do you use when going up long , and short but steep hills ?
Yea I plan to use both motors in lower to mid range power , together when going up the steep hills.

With my BBS02 a 36 tooth front and 32 rear could not make it up some hills I tried to go up.

 

[hillslayer@]

I am running a 60t chainring and a 14 to 28 5 speed freewheel on pavement mostly, the 24t cog will climb 15 % grades at 18 to 20 mph . If you plan on doing steep off-road you may want something in the 40 t to 50t range. With a 36 t chainring you would almost never shift out of the 14t cog. But if you have some really steep hills it wouldn't matter to much because the hub powers you along 30 mph plus on everything else.

 

[Chalo]

I have used a BBS02 and a large powerful front hub on the same bike, but not at the same time. I used different size and style rear wheels for both motor systems.

If you have really fierce hills to deal with, I see one of two ways to go. Either get a big heavy direct drive hub motor and run it on multi-kilowatts (heavy but fast), or use a BBS02 or BBSHD feeding a NuVinci, Enviolo, 3x3Nine, Rohloff, or other e-bike rated internal gear hub. Use relatively big sprockets on both ends, with good chainline, so you can diminish the thrashing you'll lay on the chain drive. The latter approach can be lighter, lower powered, gentler on your battery, and generally more versatile-- but at the cost of being harder on your bike and more expensive both to buy and to maintain.

Or as Nep suggests, use two modest hub motors in both wheels. Double the torque without overcooking anything and without putting 20 pounds of hub in one spot.

 

[neptronix]

Yeah honestly i find that balanced weight is so much better when it comes to handling the bike, working on it, or leaning it up against something.

When a hub gets down to about 10lbs, i stop feeling wagging on the rear end from the weight. Put on a 14lbs hub and you start to feel it.

But a DD plus mid drive is probably north of 20lbs worth of motor if we're talking about cheap ones..
..you may as well graduate to a leafbike 1.5kw or RH212 at that point and skip the mid drive.... it will be a lot lighter.

With a mid drive and a front 5lbs geared hub motor being intermittently pushed to 2x it's power.. the weight will be reasonable and fairly even. It would probably require a fork swap if you have a thru axle only fork though.

This is the route i plan to go.. 4lbs lightest.bike mid drive at 1300w cont, 5lbs bafang g370 at 600w peak..
..because it's awesome to do >35mph on 9lbs of motor!

 

[scianiac]

I think if you do any of the numbers two motors always ends up being less efficient, more dead weight, more complex, more weird edge case issues. Like you can easily get a hub or mid drive with plenty of power to do anything you want, anywhere from mild assist to fold the frame in half with a bike that is so fast it's dangerous. The hills or weight you are towing only determine how big the motor needs to be. If you need two motors you just have picked two undersized motors.

 

[hillslayer@]

If you already have the hub just bolt it on the bike with the mid -drive none of these guys have this setup, once you ride it if you don't like it super easy to go back. I have already pointed out why this is superior to a single motor if you climb steep hills l see no reason to build something that costs more and have to monitor the temperature.

 

[Chalo]

I think if you do any of the numbers two motors always ends up being less efficient, more dead weight, more complex, more weird edge case issues.

My current two hub motor bike divides up the heat load and the dropout traction torque, while letting me use very ordinary cheap and plentiful motors at low stress levels. But I still get twice the climbing power and acceleration compared to one or the other motor.

 

[neptronix]

I think if you do any of the numbers two motors always ends up being less efficient, more dead weight, more complex, more weird edge case issues. Like you can easily get a hub or mid drive with plenty of power to do anything you want, anywhere from mild assist to fold the frame in half with a bike that is so fast it's dangerous. The hills or weight you are towing only determine how big the motor needs to be. If you need two motors you just have picked two undersized motors.

Not always, two DD hubs means better efficiency at climbing and steady state.. already proven a long time ago. And you see the ability to do this if you look at how past the loaded speed, efficiency increases.

Each motor in this case with DDs gets ~2% more efficient by splitting the load.



We get a massive efficiency advantage when climbing hills by splitting the load also... we can chug up a continuous 10% grade for 28 miles and the battery runs out just before the motor starts getting into the danger zone.



The most striking part about 2x DD hubs is the massive increase in efficiency from a stall, which is their weak point.

Can be the same case with certain geared hubs that are exceptionally efficient, exceptionally efficient ones tend to have efficient gears.. so the extra friction is not a big deal, and the ability to scale big hills without the pair of motors getting stressed is awesome.

Two geared hubs that have more friction than usual will be worse ( except when climbing hills ).

 

[scianiac]

You guys missed my point, I mean one motor of either type twice as large would be more efficient than a hub and a mid. Similarly I think one hub twice as large would in general be more efficient but than one but that would be closer just due to how poorly hub motor shed heat, more surface area with two motors even with more end turn losses, more dead weight in the motor and controller, etc, etc.

I think OP was mostly looking for efficiency and using one at a time would be the most inefficient, both at the same time would be better and one larger motor would be the most efficient. I think people get caught up in the rhetoric about hub vs mid efficiency when it's relatively small for most use cases when compared to a correctly sized motor that is correctly setup and utilized.

 

[neptronix]

Yeah, a 50mm wide DD can hit 90-92% peak efficiency instead of 88% peak efficiency, so two motors are less better than one.. but.. a single big motor won't fit into a regular bike's 135mm dropouts, which might be an issue.

If that's not an issue.. the grin 45mm wide rear motor might be the ticket.. 13.5lbs, and with a small enough wheel, you can handle a 8% continuous grade for 17 miles. On the flat, you'll see 89% efficiency on this motor, which significantly exceeds the flat-ground efficiency of a typical mid drive.. because a mid drive like a BBSHD is only ~84% efficient



I would prefer this drivetrain except that my legs don't like super wide pedals.. and honestly, a fatbike isn't for everyone.

...now you could say... what about these 4kw CYC mid drives.. they compete... but... the problem we still have is an insufficient drivetrain strength on a bicycle to support that much power.. it will be a regular thing to be replacing drivetrain parts.. it also has a bizarrely wide Q factor so the pedal width is far from biomechanically optimal for pedaling... and it may have unpedalable RPM.. i forget...

There is really no best choice, just compromises..

 

[ScooterMan101]

You guys missed my point, I mean one motor of either type twice as large would be more efficient than a hub and a mid. Similarly I think one hub twice as large would in general be more efficient but than one but that would be closer just due to how poorly hub motor shed heat, more surface area with two motors even with more end turn losses, more dead weight in the motor and controller, etc, etc.

I think OP was mostly looking for efficiency and using one at a time would be the most inefficient, both at the same time would be better and one larger motor would be the most efficient. I think people get caught up in the rhetoric about hub vs mid efficiency when it's relatively small for most use cases when compared to a correctly sized motor that is correctly setup and utilized.

What I am looking for more than a few points of efficiency is a way to save wear and tear on a mid-drive.
After using both rear hub motors and a Befang BBS02 and a BBSHD mid-drive I want to
get the most amount of years of life of my/a
BBS02 and BBSHD , as well as the most years and miles out of my drive train. I only ( Need ) , the mid-drives for going up the steep hills and mountains around where I live. So on one or two of my Bikes I would like to use a rear hub motor that is used most of the time.
The main objective is Use the Rear Hub on the Flats, and only use the mid-drive when going up very steep and or long and steep roads. thereby extending the life of the mid-drive and my chain and chainring and cassette.
Now in the last two days, because of a suggestion by Neptronix , I have been considering using a 500 watt front motor on one of the bikes because it has a steel rigid front fork . But after many hours of research over the last two days , I am finding it is hard to find a 500w geared front hub that both has 6 bolt holes for my fork that can only use a disc brake , and is low cost . The cost of those that I so far have found is nearly the cost of a BBS02 from China .
In the Case of a Befang front 500 watt 48 volt motor it is over $400-$ 450 I would just get another BBS02 for even under that amount.
So unless I can get a front I 500w geared hub laced into a wheel with all the wireing preferably HiGo connectors , controller and display for $ 200 apx. , I will just have to get another base model BBS02 or ToSeven dm02.
With a Befang BBS02 , can put it on any bike that I have, the front hub would only work on one bike .

 

[ScooterMan101]

On a diferent note , Is a Befang BBS02B 500 watt motor the same as a BBS02B 750 Watt motor ?
Just different settings for higher amps ? or is there different hard components inside the motor ?