Convert a double-motorized wheel electrical bike

Many E-bike fans sent us such an enquiry: May I convert a double (F&R) motorized wheel to my bicycle? Recently we have done such a test to convert F&R double hub motor to the bicycle.

The whole conception of double hub motor conversion as follows:

Which problems should we think about before we get ready to convert double hub motor to the bicycle?
a).Whether 1 battery can supply 2 hub motors?
b).Whether 1 throttle can operate the F&R hub motors well at the same time?
c).Whether one pair of brake handles can control the F&R hub motors?

As we all know, every hub motor with one single HALL working system, there is no doubt we have to use two controllers while convert the F&R hub motor to the bicycle.
So, the next problem lies in how to maintain the simultaneousness of the running and the braking for the F&R hub motor.

So, the solution to the above problem as below:
Material Preparation:
48V/20AH pingbattery *1
48V/1KW hub motor *2
48V/1KW controller *2
Brake handle *1 (L&R)
Throttle *1
Bicycle(GIANT ATX690) *1

1) How to fulfill both controllers connect with one battery?
We split one pair of Anderson pole into two pairs (Side B) first, and then connect side A to the original battery output Anderson pole.


2) How to fulfill both controllers connect with one throttle?
Similarly we split the black connector of the throttle signal cable into two.


3) How to fulfill both controllers connect with one pair of brake handles?
We split the white connector of brake handle cable into two.


4) The overall look when double hub motor conversion completed.



Finally, we get a conclusion as below:
* We drive at a fast start, and the top speed can reach 62KM/H on the street road.
* We have to install both same type hub motor to ensure the F&R motorized wheel drive at the same running circle. However, another new problem following, it’s too hard to be controlled the bicycle at the turning because of the same speed of both wheels. So next, we should make a great breakthrough to realize the conversion of double hub motor.
* Honestly, we don’t suggest you to try double hub motor. It’s too hard to be controlled 
* Thanks in advance for your attention. Time permitted, I’ll constantly upload some more pictures &videos later.

[youtube]http://youtu.be/Sq5_KJdA2MM[/youtube]

Now I want to add a little equipment to limit the speed of the rear motor when I turn right/left.
A hall sensor will tell the rear motor controller to limit the electric current just like this:

You realize you may have caused a few heart attacks here with this. Now this is 2 of your $1,049 kits? There's too many people here that WANT something like this for you to say "Don't actually build one."

(Hey, this IS the way to use a post to advertise your product, I must say.)

Dauntless said:

You realize you may have caused a few heart attacks here with this. Now this is 2 of your $1,049 kits? There's too many people here that WANT something like this for you to say "Don't actually build one."

(Hey, this IS the way to use a post to advertise your product, I must say.)

Click to expand...

It’s really too hard to be controlled. I really don't suggest do just like this.
This is not a solution, just a testing. Take it easy
There are so many cheaper and easyer way to get faster speed.

Perhaps you would like to look at these threads (among many others):
http://www.endless-sphere.com/forums/viewtopic.php?f=6&t=24094
http://endless-sphere.com/forums/viewtopic.php?f=2&t=33429
http://www.endless-sphere.com/forums/viewtopic.php?f=3&t=43434

amberwolf said:

Perhaps you would like to look at these threads (among many others):
http://www.endless-sphere.com/forums/viewtopic.php?f=6&t=24094
http://endless-sphere.com/forums/viewtopic.php?f=2&t=33429
http://www.endless-sphere.com/forums/viewtopic.php?f=3&t=43434

Click to expand...

So many great works
I find that when I driving it, it is hard to turn left or turn right, because two wheels are the same speed.
As we all know, when a bike turns left or turn right, the front wheel should be faster than the rear wheel.
If we only use one throttle controlling two wheels, how to fix this problem?

Let off the throttle during the turn?

I'm wondering if using geared hub motors that have a freewheel clutch might fix the turning problem. I think it might, in that this would then allow the wheels to turn at different speeds more easily.

Neat bit of development, any way. I've often wondered if it would be worth doing a twin hub motor bike like this, and I'm only aware of one other, and that uses two small geared hub motors that reportedly work OK.

I'd like to suggest that ES member "kingfish" is one of the builders that have the most hands-on experience building and using a two-motor system. He rode on a very long road-trip with one. There's always more than one way to end up with a two-motor system, so a comparison may prove to be useful.

teklektiks 2WD Yuba Mundo
http://endless-sphere.com/forums/viewtopic.php?f=6&t=36959

kingfish's 2WD FAQ
http://www.endless-sphere.com/forums/viewtopic.php?f=2&t=33429

I have two 2WD bikes: Bothe use Q100 250w motors. One has 201 rpm motors and the other 328 rpm. The faster one does about 50kph. I haven't experienced any steering problems with either of them. In fact they both steer exellently.

My second build was a single rear motor in that identical Giant bike. It handled like a piece of crap. After my 3rd build with the battery in the triangle, I realized how wrong it is to have the battery on a rear rack. I changed the battery in the Giant and it is a HUGE improvement.

steelzhu said:

Dauntless said:

You realize you may have caused a few heart attacks here with this. Now this is 2 of your $1,049 kits? There's too many people here that WANT something like this for you to say "Don't actually build one."

(Hey, this IS the way to use a post to advertise your product, I must say.)

Click to expand...

It’s really too hard to be controlled. I really don't suggest do just like this.
This is not a solution, just a testing. Take it easy
There are so many cheaper and easyer way to get faster speed.

Click to expand...

steelzhu said:

I find that when I driving it, it is hard to turn left or turn right, because two wheels are the same speed.
As we all know, when a bike turns left or turn right, the front wheel should be faster than the rear wheel.
If we only use one throttle controlling two wheels, how to fix this problem?

Click to expand...

The throttle does not lock the motor/wheel to a specific speed (think about holding the throttle fixed and going from the flat to downhill - the bike speeds up) - your front and rear wheels are free to run at different speeds - and in this case we are talking about a miniscule speed difference. I think you have some other handling problem...

d8veh said:

I have two 2WD bikes: Bothe use Q100 250w motors. One has 201 rpm motors and the other 328 rpm. The faster one does about 50kph. I haven't experienced any steering problems with either of them. In fact they both steer exellently.

Click to expand...

+1 ... I ride 2WD with no hint of a turning issue 0-40mph.

amberwolf said:

Let off the throttle during the turn?

Click to expand...

I do just like this now But as you know, two 1000w hub motors and 20ah cell is very heavy.
So I want a better choice. Maybe I can cut off rear wheel hub motor when I turn with a switch?

Gordo said:

My second build was a single rear motor in that identical Giant bike. It handled like a piece of crap. After my 3rd build with the battery in the triangle, I realized how wrong it is to have the battery on a rear rack. I changed the battery in the Giant and it is a HUGE improvement.

steelzhu said:

Dauntless said:

You realize you may have caused a few heart attacks here with this. Now this is 2 of your $1,049 kits? There's too many people here that WANT something like this for you to say "Don't actually build one."

(Hey, this IS the way to use a post to advertise your product, I must say.)

Click to expand...

It’s really too hard to be controlled. I really don't suggest do just like this.
This is not a solution, just a testing. Take it easy
There are so many cheaper and easyer way to get faster speed.

Click to expand...

Click to expand...

Your are right

[youtube]xP6fAPJa7cE[/youtube]

d8veh said:

I have two 2WD bikes: Bothe use Q100 250w motors. One has 201 rpm motors and the other 328 rpm. The faster one does about 50kph. I haven't experienced any steering problems with either of them. In fact they both steer exellently.

Click to expand...

350W hubmotor*2 = 50kph -- This is really a good chievement!
Normally the speed of 330 rpm hubmotor will be less than 40KM/H without riding.

steelzhu said:

d8veh said:

I have two 2WD bikes: Bothe use Q100 250w motors. One has 201 rpm motors and the other 328 rpm. The faster one does about 50kph. I haven't experienced any steering problems with either of them. In fact they both steer exellently.

Click to expand...

350W hubmotor*2 = 50kph -- This is really a good chievement!
Normally the speed of 330 rpm hubmotor will be less than 40KM/H without riding.

Click to expand...

328 rpm is at 36v. I run with 12S lipos that are actually 48v, so actual max no-load speed is 437 rpm equivalent to 32.6 mph or 52.1 kph. The motors work hard when hill-climbing. They can manage a 10% hill OK, but everything - especially the controllers - gets hot on steeper hills, but great for normal roads, where it's difficult to go slow. The whole setup is vey light at about 22kg.

teklektik said:

The throttle does not lock the motor/wheel to a specific speed (think about holding the throttle fixed and going from the flat to downhill - the bike speeds up) - your front and rear wheels are free to run at different speeds - and in this case we are talking about a miniscule speed difference. I think you have some other handling problem...

Click to expand...

On most ebike controllers the throttle does try to hold the motor at a constant speed, as the majority of controllers use a speed demand throttle. Certainly the speed will vary with terrain, but if the throttle is held at a constant position the controller will try hard to maintain motor speed, but increasing current to the motor if the speed is below the command speed and decreasing it if it's above the command speed. Whether that is the effect here is debatable, but nevertheless I believe that having direct drive hubs arranged like this may well cause some odd torque related effects.

d8veh said:

I have two 2WD bikes: Bothe use Q100 250w motors. One has 201 rpm motors and the other 328 rpm. The faster one does about 50kph. I haven't experienced any steering problems with either of them. In fact they both steer exellently.

Click to expand...

My guess is that this supports the theory I put forward earlier that using geared motors with freewheel clutches may be a factor in the good handling of your 2WD bikes.

Jeremy Harris said:

On most ebike controllers the throttle does try to hold the motor at a constant speed, as the majority of controllers use a speed demand throttle. Certainly the speed will vary with terrain, but if the throttle is held at a constant position the controller will try hard to maintain motor speed, but increasing current to the motor if the speed is below the command speed and decreasing it if it's above the command speed. Whether that is the effect here is debatable, but nevertheless I believe that having direct drive hubs arranged like this may well cause some odd torque related effects.

Click to expand...

The point of the remark about the terrain was simply to note that that the bike speed is not bound exclusively to the throttle but is affected by load. In this case the slower wheel will see a reduced load due to the other motor - in spite of any speed-throttle effect, the slower wheel will speed up due to the reduced load as if going down hill. I do not know the wheel speed differences due to turning but they must be fractions of a percent - arguably far below the control accuracy of the controllers.

Jeremy Harris said:

d8veh said:

My guess is that this supports the theory I put forward earlier that using geared motors with freewheel clutches may be a factor in the good handling of your 2WD bikes.

Click to expand...

Click to expand...

Gear motors will not disengage the freewheel unless the load is removed making operation under acceleration or hill-climbing essentially identical to that of DD. In these situations the tiny effects of speed differences between the wheels are certainly overwhelmed by the loads and power otherwise in play and which will tend to keep the freewheels solidly engaged. Turning on inclines has never caused my motors to disengage.

I suspect the effects of fork geometry and front drive with a heavy DD motor are having a far more material effect on steering...

My points were primarily that with direct drive hubs you can have a different torque, including a braking torque, applied to the front and rear wheels, depending on their relative speeds. In the case of the geared motors with free wheels there is a decoupling that takes place so this effect is lessened or removed altogether. As soon as one wheel exceeds the throttle demand speed then the free wheel clutch will disengage and motor torque (in either direction) is removed from that wheel.

Whether this has a noticeable effect I'm not sure, but I do know that when I had a 400 series Crystalyte on the front of my old recumbent there were some marked handling issues when trying to turn with power applied. Having said that, the weight of the Crystalyte motor also upset the handling to a lesser degree even without power applied, so the problems the OP has experienced may be just an artefact of the wheel weight and frame geometry.

I would suggest three quick tests all run at the same speed: first two runs with the rear and then the front motor phase connections unplugged, then a final run with both motors under power (same speed on this run as the first two).

Ignoring frame geometry for the moment:

1. If both 'unplugged' tests very substantially alleviate turning difficulties, then this is likely a 2WD issue as originally described.
2. If steering with the front wheel unpowered is poor, then front motor weight (or diameter/mass) is likely contributing to the problem.
3. If steering with only the front wheel powered is worse than (2), then FWD is likely contributing to the problem.

I suspect (1) is very unlikely and that both (2) and (3) will prove to be true.

teklektik said:

I would suggest three quick tests all run at the same speed: first two runs with the rear and then the front motor phase connections unplugged, then a final run with both motors under power (same speed on this run as the first two).

Ignoring frame geometry for the moment:

1. If both 'unplugged' tests very substantially alleviate turning difficulties, then this is likely a 2WD issue as originally described.
2. If steering with the front wheel unpowered is poor, then front motor weight (or diameter/mass) is likely contributing to the problem.
3. If steering with only the front wheel powered is worse than (2), then FWD is likely contributing to the problem.

I suspect (1) is very unlikely and that both (2) and (3) will prove to be true.

Click to expand...

Unfortunately these are direct drive hub motors, so riding with one motor unplugged will create a torque difference, because of cogging and drag from the disconnected motor.

I don't disagree with your suggestion as to the likely cause.

Jeremy Harris said:

Unfortunately these are direct drive hub motors, so riding with one motor unplugged will create a torque difference, because of cogging and drag from the disconnected motor.

I don't disagree with your suggestion as to the likely cause.

Click to expand...

I had considered this and felt that it seemed unlikely that the drag effect in the two unplugged cases would both identically mimic the reported 2WD difficulty which is based on a claim of torque imbalance in a single direction - there would be cleary discernable differences in the failure modes. However, I take your point, the presence of the effect to any degree will sully the results.

I realize we were essentially on the same page - the test was intended to sway the OP

steelzhu said:

As we all know, when a bike turns left or turn right, the front wheel should be faster than the rear wheel.

Click to expand...

I didn't know this and after thinking about it for a while now, still can't visualize why this is true. Can someone help out here and offer up a quick explanation or link? Thanks!

d8veh said:

steelzhu said:

d8veh said:

I have two 2WD bikes: Bothe use Q100 250w motors. One has 201 rpm motors and the other 328 rpm. The faster one does about 50kph. I haven't experienced any steering problems with either of them. In fact they both steer exellently.

Click to expand...

350W hubmotor*2 = 50kph -- This is really a good chievement!
Normally the speed of 330 rpm hubmotor will be less than 40KM/H without riding.

Click to expand...

328 rpm is at 36v. I run with 12S lipos that are actually 48v, so actual max no-load speed is 437 rpm equivalent to 32.6 mph or 52.1 kph. The motors work hard when hill-climbing. They can manage a 10% hill OK, but everything - especially the controllers - gets hot on steeper hills, but great for normal roads, where it's difficult to go slow. The whole setup is vey light at about 22kg.

Click to expand...

If the controller is too hot in 48v. Maybe you can get a 48v controller.