dual motor build

[shredator]

hello, Ive been lurking around this forum for quite a while now, but havent had anything to post about till now. I am currently riding a 5305 in a 700c front wheel with 72v of SLA's. Having the motor in front, and the battery pack on the rear rack on a relatively lightweight, flexy, steel road bike is a bit scary. So I decided to switch to a sturdier frame and rear wheel drive. But then I thought since I already have the front hub motor, why not use both?

so heres what ive got:
5305 in a 700c (29") front wheel, 5305 in a 26" rear wheel, crystalyte 72V, 40A controller, 12 irfb4110's, kelly 72v, 150A regen controller, thumb throttle, drain brain, 72v lead acid pack, One unlucky beach cruiser.

Right now I am thinking of putting the modded crystalyte controller on the rear wheel and using the regen controller for the front. I am not sure how to handle the throttles though. Id like to hear peoples thoughts. Im also not sure how to hook up the regen contol. Does anyone make brake levers with pots in them?

Im shooting for a range of ~20 miles at ~35 mph and Id like to be able to reach a top speed of ~50mph. I know that this thing is going to need a pretty big battery pack, and Id like to get some suggestions about what to use for that. Ill probably put off the battery pack purchase for as long as I can, in hope that prices will come down a bit.

Thanks, Great forum you all have here.

 

[ngocthach1130]

You should get match wheel and matched motor for dual motor set up. Because at high speed the bigger wheel in front will want to go faster and the smaller wheel in the back can't spin fast enough like the front and act like a brake. Then the power of the front 5 series motor will rip the fork out of the frame and you come face to face with gravity, friction, impact force, reaction time, etc...

 

[Doctorbass]

hello, Ive been lurking around this forum for quite a while now, but havent had anything to post about till now. I am currently riding a 5305 in a 700c front wheel with 72v of SLA's. Having the motor in front, and the battery pack on the rear rack on a relatively lightweight, flexy, steel road bike is a bit scary. So I decided to switch to a sturdier frame and rear wheel drive. But then I thought since I already have the front hub motor, why not use both?

so heres what ive got:
5305 in a 700c (29") front wheel, 5305 in a 26" rear wheel, crystalyte 72V, 40A controller, 12 irfb4110's, kelly 72v, 150A regen controller, thumb throttle, drain brain, 72v lead acid pack, One unlucky beach cruiser.

Right now I am thinking of putting the modded crystalyte controller on the rear wheel and using the regen controller for the front. I am not sure how to handle the throttles though. Id like to hear peoples thoughts. Im also not sure how to hook up the regen contol. Does anyone make brake levers with pots in them?

Im shooting for a range of ~20 miles at ~35 mph and Id like to be able to reach a top speed of ~50mph. I know that this thing is going to need a pretty big battery pack, and Id like to get some suggestions about what to use for that. Ill probably put off the battery pack purchase for as long as I can, in hope that prices will come down a bit.

Thanks, Great forum you all have here.

2x 5305

Are you crazy!?? :wink:

Only one like mine is enough... I say Enough but if you go offroad.. that's something different!

but.. 20 miles at 35mph!!!

ok let's do some math!

at 35mph you'll need 1500W of continuous power

doing 20 miles that's (20/35)x1500 =857Wh from 100% to 0 % so let say 1000Wh to avoid overdischarging the cells and preserve great life cycles..

well that's good.. but not using SLAs !!!, think about it 1kWh of SLA is 50lbs +2x25lbs for the motors + the bike 35lbs
that's 135lbs just for the ebike!!

50mph is possible but you will need 105-110V on a 26" wheel and a 5305 and the 4110 will not like that.

I reach 40mph with 84V (drop to 75V) on a 26" wheel and a 5305

But if you use only one motor and the 700C, it will be possible at 90V and at least 50A of continuous current


I agree, that you could rip the front folk with a 5305... they call it brute... you should take it in consideration!! and also i agree that both motor MUST have the same wheel size.. because the difference of speed of those will make energy loss because the 700c will always try to push the 26" wheel and make it innificient...or just be 25 more pound to transport...

Doc

 

[steveo]

I'm having enough problems finding room for my high voltage setup .. ah required even more batteries .. which is alot of weight .. + another motor & controller .. i think you should try things out with just the 5305 .. that should be more of a torque monster then my 5304 .... and my 5304 has unbelievable torque in a 20" rim ... wheelie popping even at 66v ..

just my 2 cents

-steveo

 

[Link]

LOL, yeah. We saw the video of you doing wheelies in your kitchen. Nice.

Anway: You could easily tie the throttles together. Connect it to one controller normally, and run an extra green (signal) wire to the other one.

ROFL, the simulator at ebikes.ca says 80lbs of thrust for a single 5305 in a 26" running on 72V @ 50A. Twins and a higher amperage system and you could be pulling nearly 1G . I want videos of this monster. :wink:

 

[fechter]

You'd run into limitations with traction. As the rear motor tries to make you do a wheelie (which it will), it will reduce weight on the front wheel, causing it to loose traction. You'll never be able to deliver much power through the front until you stop accelerating.

One rear motor should really be enough, as it can handle more power than you can probably supply with the batteries and controller. Besides, we don't want to see anybody get killed.

 

[Drunkskunk]

Welcome to the group!
Sounds like fun to me.

You realy need a small motorbike frame to handle the stress. 3.5 horsepower is roughly equil to 100cc motorbike motors. and you're running 3.8 HP X 2 with this setup, (72V at 40A = 2880 watts, = 3.84 Horsepower) so you're putting more stress on the frame than a 200cc motorbike.

SLA can't handle the power you're asking it to do now, they are going to have short lives with one motor. SLA can't handle 2. you'll need at a minimum some of those cheap ducttape Lithium Ion batteries from Ebay.

For wheel size, you need them to be the same, or you're just wasting power and putting added stress on the frame.

Regen is over rated for for Ebikes, since most of the power is used to overcome wind resistance, and there isn't that much energy stored in rolling inertia on a bike. If you can recapture even 5% of your total energy, you're doing amazing.
But if you want it, go for it. Just skip the idea of doing it from the front wheel. thats asking for a snapped fork. Its also slower to react than a brake, and harder to modualte, so you're asking for a locked front wheel at some point. put it on the rear and it should work fine. better than most other ebikes since this thing will be heavy. But with the weight and complexity of the system needed to make it work, it might be cheaper and easier to go with a battery 5% larger and get the same range.

Overall sounds like a cool project. Got pics of your current bike?

 

[shredator]

Thanks for all the replies!

the bigger wheel in front will want to go faster and the smaller wheel in the back can't spin fast enough like the front and act like a brake.

Since this will only happen at maximum speed, and I dont really plan on riding at max speed all the time, Im not really worried about this.

Are you crazy!??

All work and no play makes shredator build electric bikes :wink:

50mph is possible but you will need 105-110V on a 26" wheel and a 5305 and the 4110 will not like that.

What is the highest voltage/top speed that I can run reliably with the equipment that I listed? I think Ill be happy with over 40mph.

they call it brute...

I realize the danger of the motors ripping out. I am planning on getting some steel plate and making reinforcements at the dropouts. Another thing that I am worried about is the axles of the hubs themselves. Has anyone ever sheared an axle?

well that's good.. but not using SLAs !!!

SLA can't handle the power you're asking it to do now

Yeah, sorry, I should have said that im not planning on using SLAs on the finished product. Ill use the SLA pack i have for set up and troubleshooting. Id like to get input about which type of lipo/lifepo4/whatever pack would be the most suitable for the bike. Im not opposed to building my own pack.

wheelie popping even at 66v ..

pulling nearly 1G

Thats the Idea... Maybe burnouts too.

You'd run into limitations with traction. As the rear motor tries to make you do a wheelie (which it will), it will reduce weight on the front wheel, causing it to loose traction. You'll never be able to deliver much power through the front until you stop accelerating.

I realize this, But I think that it will still be worthwhile to have the front wheel drive. When braking, you get maximum effectiveness and control by using both front and rear brakes together, not only the front. Why would the same not be true when trying to get maximum effectiveness and control when accelerating?
This brings up my concern about the throttles. Part of me wants to keep them separate, so I can modulate them like I do my brakes. What do folks think, better to combine them?

Regen is over rated for for Ebikes, since most of the power is used to overcome wind resistance, and there isn't that much energy stored in rolling inertia on a bike. If you can recapture even 5% of your total energy, you're doing amazing.
But if you want it, go for it. Just skip the idea of doing it from the front wheel. thats asking for a snapped fork. Its also slower to react than a brake, and harder to modualte, so you're asking for a locked front wheel at some point. put it on the rear and it should work fine. better than most other ebikes since this thing will be heavy. But with the weight and complexity of the system needed to make it work, it might be cheaper and easier to go with a battery 5% larger and get the same range.

Thank you for this. I already have the regen controller, so I think ill go for it anyway. Perhaps ill put the Kelly controller on the rear wheel though.

I appreciate the Input

 

[Link]

50mph is possible but you will need 105-110V on a 26" wheel and a 5305 and the 4110 will not like that.

What is the highest voltage/top speed that I can run reliably with the equipment that I listed? I think Ill be happy with over 40mph.

Actually, I'm not sure. Has anyone here EVER managed to fry an X5 with too many volts? A single X5 will probably do 40mph.

Yeah, sorry, I should have said that im not planning on using SLAs on the finished product. Ill use the SLA pack i have for set up and troubleshooting. Id like to get input about which type of lipo/lifepo4/whatever pack would be the most suitable for the bike. Im not opposed to building my own pack.

I think A123s are pretty much your only option. You'd need so much Ping pack to feed those motors it wouldn't be funny. LifeBatts/YESA might work, but, not very many here have much experience with them.

Another thing that I am worried about is the axles of the hubs themselves. Has anyone ever sheared an axle?

I don't think so. Even those who have run 90+ a through them (close to their saturation point) haven't managed to do that.

This brings up my concern about the throttles. Part of me wants to keep them separate, so I can modulate them like I do my brakes. What do folks think, better to combine them?

If you absolutely insist that you use two wheels, then don't combine them. The one in the bigger wheel will be trying to go faster, so it will be doing all the work. If you put them in same sized wheels (please do? it's not much added cost...), it would probably be better to tie them together for simplicities sake. But, it's your call.

 

[Drunkskunk]

I realize this, But I think that it will still be worthwhile to have the front wheel drive. When braking, you get maximum effectiveness and control by using both front and rear brakes together, not only the front. Why would the same not be true when trying to get maximum effectiveness and control when accelerating?
This brings up my concern about the throttles. Part of me wants to keep them separate, so I can modulate them like I do my brakes. What do folks think, better to combine them?

You would never be able to modulate two throttles fast enough to be of any use. you need something to do it automaticly for you. it ain't like brakes, the only time you would need to is when you're losing traction, and any time that happens on a bike, you're not going to be traveling straight and level down the road.

a simple comparitor circuit that senses off the controller's internal current sensors could be used to retard the throttle on a wheel thats about to spin. all you would need to do is tie it in as an overide to the throttle for each wheel. the wheel that has the lowest current demand is the wheel about to spin, and the throttle gets backed off on that wheel before traction is lost. if you want, you could even build in some bias so it keeps the front from spinning but lets the back spin some.

Another option you might add would be a selector switch for front, rear, or both motors. rear wheel drive for burnouts, front wheel for slow manuvering, both for Charging off like a new mistress with your credit card.


On batteries, there realy are only 2 choices for doing it right. A123s, or Lifebatts.

 

[Doctorbass]

Actually, my 5305 run 64km/h (40mph) with 86V standby and 74V under full load at 45A on acceleration and increase to 78V at 40mph wich is 0.82kph/V at 1750W of power to sustain that max speed

with 100V THAT IS THE MAX YOU CAN USE it will give you maybe 74kph (46mph)


About G,

I will buy soon a G meter that calculate the power and G using accelerometer and the weight of your vehicule. This is the Beltronics FX-2 at 50$ on ebay

Doc

 

[lazarus2405]

Okay, we've got a number of problems here.

First, and foremost, I promise you that you will not max out a single x5, unless you really need more than 10hp. Using two will only add 25lbs of mostly-dead weight to your setup. If one x5, with the right battery and controller setup, cannot give you the performance you want, then you need to be working with something sturdier than a bike frame.

Talk to ebikes.ca and ask the easiest way to convert a front wheel to a rear. You may be able to just replace the axle, or trade them your stator for a rear stator. You may be able to save a lot of money, as opposed to buying a whole new motor. Unless you already have it...

I think Ill be happy with over 40mph.

Then stick with one motor.

Actually, I'm not sure. Has anyone here EVER managed to fry an X5 with too many volts? A single X5 will probably do 40mph.

As far as I know, no one, ever, has fried the windings, overheated the magnets, trashed the axle, or otherwise damaged more than the Hall sensors or bearings of an x5. A couple folks have 150v controllers, but I don't know what they've tried. lowell's run 112v with much success, on a 4110 unit with a 100a limit. He, after extended periods of running in the 7kw range, reported that the motor was warm, but not hot.

An x5 will easily do 40. Easily. A 5305, though, will take 100v to do so. Stupid slow windings.

ou'd run into limitations with traction. As the rear motor tries to make you do a wheelie (which it will), it will reduce weight on the front wheel, causing it to loose traction. You'll never be able to deliver much power through the front until you stop accelerating.

Read this again. You'll spin your front wheel while your rear tries to throw you off the bike. If you can get the weight distribution forward enough, then maybe.

I think A123s are pretty much your only option.

Not at all. E-Molis! I love those things... they'll do 10-12C continuous, 15+ burst, so even a 500wh pack would suffice. And they're cheaper than a123s.

Im also not sure how to hook up the regen contol.

The Kelly can use a Hall effect throttle for regen. Mount it on the other handlebar, backwards, so that it turns the opposite way of your main throttle. It'll be variable, and should be pretty intuitive.

 

[shredator]

The Kelly can use a Hall effect throttle for regen. Mount it on the other handlebar, backwards, so that it turns the opposite way of your main throttle. It'll be variable, and should be pretty intuitive.

I like the sound of this. Where can I find a hall effect throttle? How do I tell what type of throttle I have already? what are the different types of throttles?

a simple comparitor circuit that senses off the controller's internal current sensors could be used to retard the throttle on a wheel thats about to spin. all you would need to do is tie it in as an overide to the throttle for each wheel. the wheel that has the lowest current demand is the wheel about to spin, and the throttle gets backed off on that wheel before traction is lost. if you want, you could even build in some bias so it keeps the front from spinning but lets the back spin some.

This sounds really cool to me. Is this something that someone has done already? if so, could someone link me a diagram or schematic?

Thanks to everyone for suggesting batteries. Has anyone used Thunder Sky cells? or are they just too big and heavy?
I have read that heat makes li-ion cells age more quickly. Does this happen to lifepo4 cells? if so does anyone think that it is worthwhile to build the pack with some kind of provision for air circulation?

The project obviously isnt about maximum functionality or just being able to reaching X mph. Its about ridiculous acceleration, building something unique, learning and having fun by pushing the limits.

Thanks

 

[Doctorbass]

An x5 will easily do 40. Easily. A 5305, though, will take 100v to do so. Stupid slow windings.

.

Actually real number are 78V for 40mph at 1400W. I use that setup everyday now.

I personally find that this winding is not so stupid. let me explain why:

-it have the most torque than any other ebike hub motor on the planet.. what help it to get decent speed is that it keep the torque at higher speed.. not the other 5302-03... but the 04 is a trade off.

there is a BIG difference if you operate it at 36V... all other 02-03 and 04 will perform a better speed...

but as you reach the 30mph+ threshold they begin to have the similar mph/V.

And at 100V, i'm sure the 04 have very close speed than the 05.

At low speed this motor have as far the most impressive acceleration you can get! :wink:

Put volts on a 05 and you will see it completly differently :wink:

Doc