Dual hub motor (F&R) full suspension MTB

Has anyone had success building a dual hub motor (250-500W each) bike? I'd like to build something for my 45 minute offroad (singletrack) commute to town(about 6 miles). The trail has some steep sections that can be muddy and slick which would limit how much power could be sent through a single wheel. I'd like to keep it light so I'm willing to spend the money for A123 batteries. I've got a Jamis XLT 2.0 full suspension dual disk bike that I'd like to use as the platform, ideally keeping the disk brakes. I've seen hub motors using disks, but don't know their source or compatibility. Any helpful information would be greatly appreciated.

Thanks,

Don in Athens, Georgia, USA

I suggest sticking with a single rear wheel motor..

Keep the front wheel light, with disk ..

A rear wheel 409 in a 20" or a 24" , 3 speed and disk brake( if using disk brakes, the rim size is not a factor, but the 24" retains some ground clearence )

40 amp controller and A123's at 66v !!! :wink:

Thanks for the quick reply and advice! Do you recommend the smaller wheel for gearing reasons? How about a gear motor? Would that offer increased torque for hills? Also, when you say 3 speed, does that mean the 3 front chainrings w/o rear gears? I'd like to keep the 26" rear wheel if possible for ground clearance. It looks like your avatar is a similar setup. Do you have any larger pics of your setup?

Thanks a lot for your help,

Don

In my avatar, is a Norco Chaos 2005 model, originally had 26" front and back...

But i am using a 20" rear and 24" front at the moment, ( looks like 24"'s in the picture.. but it's a perspective thing ) ..

And yes. the smaller diameter rims gives the motor more leverage/gearing vs a larger wheel.

3 speed rear freewheel, and 3 front chainrings is all you need..

The Norco looks like a similar setup as my Jamis. Do you have any problem with bottoming out on the pedals with the 20/24 setup? Ground clearance will be an issue for me on my ride. Are there any motors out there that could provide adequate torque while keeping the 26ers and the disk brake?

Don

I ride 90 % road, so with ground clearance i never have any problems, but on more serious off-road it might be an issue.. using a longer rear shock if the frame allows for it will help lift the cranks up..

Without seeing your terrain it's hard to judge, but it's really not that bad, the 20/24 works really well ! :wink:

A longer shock could work...Who makes your disk brake hub motor?

The motor is a crystalyte dual-speed 406 / 409.

I made the disk brake fit with some elbo-grease and alot of beer and bad words..

The motors come with either flat motor covers for a front wheel.. a threaded collar motor cover for a freewheel on a rear motor.. and they are available with 2 x threaded motor covers for rear/disk brake. :wink:

The trail has some steep sections that can be muddy and slick which would limit how much power could be sent through a single wheel.

Click to expand...

You want to match the amount of power each wheel has to the amount of weight on it. Some really steep trails tend to put at least 75% of the weight on the rear wheel (and by shifting your body you can make that more like 90%) which means that you might not get much out of having a front motor.

On the other hand, maybe you will have most of your power to the rear if you pedal (rearwheeldrive) and use two hubmotors as well.

But keep in mind that you will save a lot of weight if you go with only one hubmotor.

maybe this would be a better solution for offroad than a hub-drive..

it would also be lighter than a hub-motor (and of course a lot lighter than 2 hubmotors)

because its using the gears of the bike it -depending of the possible gearings on your bike - can give you power when going up a 30% steep (or even steeper) hill or assist you at the same bike when going 50km/h onroad..

you can use 26" wheels and have also good groundclearance..
http://www.bike-elektro-antrieb.ch/


try this with an bike with a heavy hubmotor in the frontwheel


no problem with groundclearance


a closer look

hmm.. also when not using there motor..
this maybe very useful: so you have 3 freewheels:
1 in the rear-wheel
1 in the pedals
1 at the motor
--> so the pedals do not spin when the motor is running !

the only bad think (in my opinion) on this setup is:
its louder than a hub-driven bike

maybe it would be possible (infact i have already seen such a bike somewhere here at endless-sphere)
to use a hub-motor instead of that motor in the pictures..

you need a cadenz of around 60-90rpm on the pedals

a torquy hubmotor that runs 30km/h in a 26" wheel spins ~240rpm at 30km/h

so: to reach 90rpm only a 2,6gearing is needed..
thats easy duable..

(with the original motor on the pics above, motor to padels is something like 6:1)

so it should be possible to make a more quiet solution... (and stronger as well)


maybe somebody knows which bike i mean..
there were some pics here in the forum..
the motor was mounted like the geard one in the pics from my last picture..
a hub-motor, but it was spinning the pedals by chain so you could use all gears of the bike

Dom ( From australia ! ) had this setup.. he made me the coolest motor cover for a crystalyte with threads to lock a freewheel into it for bottom bracket drive...

have not seen that guy for a long time.. he did great work !!!!

http://www.youtube.com/watch?v=Uv_ydS-fOA0

motor freewheel, really? My german is not that good, and automatic translation is poor at best...

If this is true, awesome because they're using an MY1018 and have 3 motor cog sizes to fit it.

I'm working on one. I would be pretty much finished by now if all the correct parts had arrived when they were supposed to. (don't ask)

Started with an old Wal-mart Mongoose 150 full suspension bike I bought for about $130 5-6 years ago.
Using 2 BD36 Wilderness Energy hub motors, the rear with a single fixed sprocket bolted on, with freewheel on the pedals.
(I'd rather have gone with a rear freewheel, but that would have required a lot more machining than I wanted to do..... Or spending the 3.5 times the money for two matched crystalite motors)

I did kind of 'bailin' wire and duct tape' it together and ride around the neighborhood a couple of times. It worked just fine (even though I didn't have any torque arms mounted yet) doing some light cross country and a few miles around the paved walking paths, and up a couple of steep hills.

Hope to have it finished in another week or two, do some tougher road/off-road tests and post a full write-up & photos here.

It isn't something I'd try to build if I didn't have a decent workshop though.
And Lithium batteries.... Thing would probably weigh over 240 pounds (and that's before I sit my 240 pounds on it.) with the 40AH worth of batteries if they were SLA.
Plus I have no idea how I could find the room and securely mount that much lead.

@Mathurin:
the motor has a freewheel
the pedals have a freewheel included
and the rear-tire has a freewheel..

so:
you can drive the bike without motor-assistance
and you can assist with motor without pedals turning...

@Ypedal: yeah.. thats the bike i meant !
thx...
sounds much nicer than this geared-motor from the swiss team

would be cool to mount a Nano with only 2.1kg and of small size in that way to the bike..


the most beautiful version of bike-motorisation (its absolut invisible) is the gruber assist...
but here again: noice..
and: not that powerfull (only 200Watt input, ~100-120Watt assistance power --> 200Watt assistance would be perfect)
but for looks: there is no cooler motor for bikes..
if you haven´t seen, watch the videos:
http://www.gruberassist.com/


here with mounted motor !!! as said: absolut perfect hidden !
motorweight (including gearing, freewheel): only 750g + weight of controller there is a sum of ~900g

absolut cool: light e-bikes including motor and battery of only 12-14kg weight in sum are so possible !

Wow, the things people can invent and build... That Gruber is just an amazing concept.

Let me know when they figure out how to boost the power to a reliable 1000 watts or so

hmm..
in my eyes it would be enough when they could increase the 100Watt output to maybe 200Watt

as said: its a "Assistant" and not a motor-cycle
with 1000Watt motor a 1000g light battery would be maybe too small

for me there are 3 concepts of e-bikes:

1.) the once with 1000Watt power and more
(why should i add 200watt pedaling, when the motor allone does 5times more ?!?)
they have often BIG batteries (48V - 84V, 10Ah, ... heavy)
(but: 1000Watt input-power of a hub-motor... in praxis this are maybe only 300Watt on a steep hill output-power to the wheel, just to considere !)

these bikes are so heavy, that you don´t wana drive them without motor at all -> motor has to run always -> even bigger battery is needed

2.) the once with hub-motor and ~500Watt power
they are more like bikes...
nevertheless - with hub-motors and batteries - mostly over 20kg of weight
often you don´t wana drive that kind of bike offroad or without motorassistance
(any bike without motor would drive a lot better on human-power than these still heavy bikes with motor turned off)
some of them even have no freewheel (they call that recuparation-break... haha)
--> motor running most time -> big batteries needed

3.) is the design of the gruber bike... only 200Watt inputpower (that are ~100Watt on the wheel)
this is a true assistance..
a hill were i have to pedal with 200Watt on my one would no get a lot easier at same speed with motor assistance, i have only to pedal with 100Watt...
the bike still remains very light because motor+batteries together do not weight more than 2kg !!!

this bike is light as possible -> you can drive it like a bike, not feeling bad influence because of missing freewheel or heavy weight
nevertheless: on steep section or for a further boost in flat when accelerating you can have some extra power

1000Watt would be far too much in my eyes, would destroy the concept of having a light bike with an electric motor you don´t see...even dangerouse (paddels turn when motor is running)

too sum it up:
1* bike for going to work all day, long distance, relativly flat -> and you want to be fast and pedal nearly nothing --> 1000Watt-hubmotor-categorie
2* bike for going shoping, not that fast, flat --> 250-500Watt hub-motor categorie
3* bike for having fun offroad, for enjoying BIKING as it self, light weight, agil feeling, driven most time without motor, motor only for difficult (steep) sections --> a assistance with not more than 250Watt to the wheel that is as light as possible

for me Nr. 3 would be the nicest..
downside of the Gruber assistance:
1.) price (freaking expensive !!!)
2.) to load (noise) in my opinion

when you leave the battery at home, the motor+controller adds only 900g to the bike (on the most center position in the bike)

i bet, you would not realy feel that compared to the same bike without motor...
900g --> thats like a full bike-bottle, not more !

when i go offroading i drive distances of maybe 5-7miles... not more (i do not drive 30miles offroad, do you ?)
so when considere, that each hill i drive up, i also have to drive down and there are also some few flat sections,
the assist-mode would only be used for maye 1-3miles
so you see: the battery realy can be small on that concept
(a 10s1p A123 Fepo4 with only 720g would be enough for 20min of 200Watt --> would be a perfect match on my offroad-driving)

Kraeuterbutter said:

when i go offroading i drive distances of maybe 5-7miles... not more (i do not drive 30miles offroad, do you ?)

Click to expand...

That's the minimum I'm hoping to get out of this current build.

5-7miles or 30miles ?

do you want to drive all time with motor ?
because: with 2 hub-motors (5-10kg) and a big battery driving without motor would be not fun at all

Ypedal said:

Dom ( From australia ! ) had this setup.. he made me the coolest motor cover for a crystalyte with threads to lock a freewheel into it for bottom bracket drive...

have not seen that guy for a long time.. he did great work !!!!

http://www.youtube.com/watch?v=Uv_ydS-fOA0

Click to expand...

I thought that was a great bike, I think it's the same one as here:
http://www.youtube.com/watch?v=RzDDXHTkUm4
I always wanted to get more information on that (like was the motor mounting bracket a commercial item and if so where do you get it, what exactly is the drive arrangement, battery controller etc). If you're out there Dom, post some of the details, please. I hope your broken leg(s) are better.
If anyone else knows the details please let us know.

30 miles. At least one motor on all the time, except when cruising downhill anyway. I have no Idea if this is achievable, especially with the terrain that I am planning to travel, but it is what I'm hoping for.

This is more of an 'expedition' transport than it is a fun bike. I'm an old guy with bad knees, and an E-bike is about the only way I can go where I 'need' to go without resorting to a noisy old Internal Combustion machine.

it should be doable...
needs for sure a lot of (pricey and heavy) battteries

Kraeuterbutter said:

it should be doable...
needs for sure a lot of (pricey and heavy) battteries

Click to expand...

I have 40 AH of Lithium, split into two 20AH packs for better weight distribution.

Not sure what the weight is; somewhere between 30 & 45 lbs, I guess. But I can pick up the whole bike and carry it if I have to... (Dang pedals poke me in the most uncomfortable places though )

hehe.. how much is that in normal metric ? (kg ?)
30lbs (~13,6kg) to 45lbs (~20,5kg)

what weight is that ? the weight of the batteries allone ?