2WD project

[TWKF]

Okay, so i'm about to order 2 identical 1500w 48v hub motor kits, one for rear, one for the front (obviously) from ebay. This means 2x 1500w 48v controllers, 2x 1500w 48v hub motors, 2x displays, 2x 20ah 48v batterys, and 2x throttles.
Now, in my small and simplistic mind accompanied by my basic soldering skills, i have figured i can use only one throttle for both wheels (just splitting the cables from the throttle really).

However, i'm wondering what would be the best solution;

one throttle - one display - 2x controllers - 2x batterys - 2x hub motors

Or

One throttle - 2x displays - 2x controllers - 2x batterys - 2x hub motors?

(each controller have each their fitting battery, to gain maximal effect without frying anything by pushing the power needed to power 2 wheels through one controller as well as providing longer battery life.)


I want to have just one display showing on my handlebar, as it wouldn't look really good with 2 displays showing the same speed and a load of wires around.

(I am not going to use the pedal assist AT ALL, will probably remove the chain and pedals entirely and replace them with foot-pegs).

Advice is greatly appreciated!!

 

[docnjoj]

Depending on where you live, taking the pedals off the bike may make it illegal as a bicycle. It might automatically be classified as a light motorcycle.
otherDoc

 

[spinningmagnets]

I would highly recommend a geared hub on the front, due to unneccesary weight, and the fact that geared hubs freewheel (DD hubs have some cogging /magnetic drag when un-powered). But, of course, dual direct drives will work. Also recommend dual torque arms on the front. A single strong variety might be adequate for the rear...(depending)

 

[d8veh]

You need to think about your weight distribution. The torque from the back motor unloads the front wheel, so you get a lot of front wheel-spin from a start, which will wear out your front tyre rather quickly. On mine that used geared motors at 64v 30A, so maybe a bit more torque than what you plan, I got a sort of bouncing of the front suspension during take-off. It would probably work better with a front biased weight distribution.

 

[dogman dan]

Re the displays, you need one display for each battery. So you are stuck with two IMO. But no law saying the either display must be located on the handlebars.

Definitely, 1 throttle, two batteries, two controllers. At least for controllers that high power.

Pedals or no pedals, that's an illegal vehicle for the street in most of the USA.

 

[TWKF]

Thanks for replys!

Yes, i am fully aware that what i am attempting is illegal. In my defence i live in a small area with not much police around, and most people haven't really heard about "electric bicycles" yet!
I already have a street legal BH-motion, and i still get weird looks when i buzz my way around town :lol:

You need to think about your weight distribution. The torque from the back motor unloads the front wheel, so you get a lot of front wheel-spin from a start, which will wear out your front tyre rather quickly. On mine that used geared motors at 64v 30A, so maybe a bit more torque than what you plan, I got a sort of bouncing of the front suspension during take-off. It would probably work better with a front biased weight distribution.

Will it work if i position the two controllers and batterys as far ahead on the frame as possible to gai weight at the front? In addition to take off easy of course, and not blast full throttle at once

 

[MadRhino]

What you don't say is why you want 2WD.
Are you planning to ride deep sand, mud or snow ?
Because that is the only good reason.
One single big motor on the rear can give you better power, speed, and handling.

 

[amberwolf]

Or if you can't afford one big motor, and already have two smaller ones.

Or cant' afford the controller to run the big motor, and again have two smaller ones....

 

[TWKF]

What you don't say is why you want 2WD.
Are you planning to ride deep sand, mud or snow ?
Because that is the only good reason.
One single big motor on the rear can give you better power, speed, and handling.

From what i've gathered around this forum, 2WD will give me superior uphill-force compared to a single hub motor, and a small (small, but still there) increase in top speed. I would not be suprised if i got a quicker acceleration aswell! Do you mean to tell me adding a another hub motor with equal power as the other one, will decrease my performance?

If i haven't made myself clear; What i'm attempting to do is building a (illegal) DYI-counterpart to everyday mopeds. I am 16 myself and my friends all have both mopeds and light motorcycles, but they're spending significantly more money (hopefully) than me

What is certain, that even if i go for just one hub motor, i will still outrun an 50cc that haven't been fiddled around with! Can't wait to see their faces

(I am not trying to be cheeky if that is what it sounds like, i'm just a speed-ravaging enthusiast thrilled to learn! )


EDIT:

Is it correct to assume that when i install 2 1500w motors the bike itself has 3000w (4bhk-ish)? Which happens to be the power of a 4stroke moped 8)

 

[cj7hawk]

What you don't say is why you want 2WD.
Are you planning to ride deep sand, mud or snow ?
Because that is the only good reason.
One single big motor on the rear can give you better power, speed, and handling.

From what i've gathered around this forum, 2WD will give me superior uphill-force compared to a single hub motor, and a small (small, but still there) increase in top speed. I would not be suprised if i got a quicker acceleration aswell! Do you mean to tell me adding a another hub motor with equal power as the other one, will decrease my performance?

If i haven't made myself clear; What i'm attempting to do is building a (illegal) DYI-counterpart to everyday mopeds. I am 16 myself and my friends all have both mopeds and light motorcycles, but they're spending significantly more money (hopefully) than me

What is certain, that even if i go for just one hub motor, i will still outrun an 50cc that haven't been fiddled around with! Can't wait to see their faces

(I am not trying to be cheeky if that is what it sounds like, i'm just a speed-ravaging enthusiast thrilled to learn! )


EDIT:

Is it correct to assume that when i install 2 1500w motors the bike itself has 3000w (4bhk-ish)? Which happens to be the power of a 4stroke moped 8)

Ahh, I can understand about those kinds of motivations... I don't think what you're attempting without experience is all that safe and I'll probably read about you in the papers won't I ?

Anyway, I agree with earlier comments - Unless you're going over something soft and want to stop the wheel biting in, I can't see much practical advantage in two motors over one big one, unless the benefits are economical... All you'll achieve is halving your run time for a small increase in power and may introduce handling difficulties around corners as well.

Anyway, you will get a multiplying effect on torque assuming your controllers are synced and respond equally, which they won't, but I'm guessing they will be at least a little close. So power will be about double... and you will be able to sustain it further than overdriving a single 1500w motor, since you'll have better heat distribution, and once you get close ( assuming you get close ) for back-EMF matching the controller voltage, you'll get reasonable efficiency also, but your top speed will also be limited for the same reason.

David.

 

[d8veh]

After building my four 2WD bikes, I came to the conclusion that 2WD gives two advantages over a single motor. The first is traction when you're in snow, mud or wet grass. The second is that you can use two small light motors rather than a single big heavy one. This helps your suspension to work better because you get a better sprung to unsprung weight ratio. If these things aren't important for you, stick to a single motor.

 

[TWKF]

Thanks yet again for replys!

Okay, I've made up my mind:
I'm sticking with one large hub motor instead of two! Howevwr, when winter comes i'll figure out for my self whether i'll order another kit

Anything else i need to be aware of before ordering chinese junk? Torque arms are in the shopping cart! (I have ordered from china loooads of times in the past, but never a motor!)

 

[MadRhino]

What you don't say is why you want 2WD.
Are you planning to ride deep sand, mud or snow ?
Because that is the only good reason.
One single big motor on the rear can give you better power, speed, and handling.

... Do you mean to tell me adding a another hub motor with equal power as the other one, will decrease my performance?

...
(I am not trying to be cheeky if that is what it sounds like, i'm just a speed-ravaging enthusiast thrilled to learn! )

Nope, I am telling you that you can build much more speed and power with one big motor than with two smaller ones.
...
I am also telling you that handling and acceleration will be much better with one single big motor on the rear, enough to compete with a 250cc 2 stroke MX if you have the money and skill to build it good. Yes, money is an issue, as Amberwolf pointed out. Yet, money can be replaced for a big part with extra labour, and patience to find used high end components.

 

[motomech]

..... and my friends all have both mopeds and light motorcycles, but they're spending significantly more money (hopefully) than me

Dude, not even close! I could buy a used Chinese 49cc scooter, put a pipe, big bore kit and carb on it and it would do 45 mph, all for less money than I have spent for batteries and chargers alone.

 

[TWKF]

..... and my friends all have both mopeds and light motorcycles, but they're spending significantly more money (hopefully) than me

Dude, not even close! I could buy a used Chinese 49cc scooter, put a pipe, big bore kit and carb on it and it would do 45 mph, all for less money than I have spent for batteries and chargers alone.

Hahaha, man i don't know where you come from or what are your moped laws
But where i live (Norway) we need a license for mopeds which can cost from around 700 usd to over 1000!! On top of that the prices for registering and insurance are ridiculessly expensive (around 200usd for registration and 800 for insurance, depends on what bike and what insurance company).

Not to mention you'll neee a proper bike aswell, like a yamaha or a suzuki, which will cost you 1000 for a (decentk) used one :S

On top of that you'll have to pay for fuel, and that clocks in at 2-3 usd PER LITER!!!

^mostly the reason why norway has one of the highest ratios for electric car per car in the world

 

[cj7hawk]

..... and my friends all have both mopeds and light motorcycles, but they're spending significantly more money (hopefully) than me

Dude, not even close! I could buy a used Chinese 49cc scooter, put a pipe, big bore kit and carb on it and it would do 45 mph, all for less money than I have spent for batteries and chargers alone.

Hahaha, man i don't know where you come from or what are your moped laws
But where i live (Norway) we need a license for mopeds which can cost from around 700 usd to over 1000!! On top of that the prices for registering and insurance are ridiculessly expensive (around 200usd for registration and 800 for insurance, depends on what bike and what insurance company).

Not to mention you'll neee a proper bike aswell, like a yamaha or a suzuki, which will cost you 1000 for a (decentk) used one :S

On top of that you'll have to pay for fuel, and that clocks in at 2-3 usd PER LITER!!!

^mostly the reason why norway has one of the highest ratios for electric car per car in the world

I have to admit, I was thinking the same - how expensive can a cheap 49cc scooter be... I guess I never factored the other costs into the situation either.

Actually, kind of sad that an electric bike is the cheaper way to go - but have you checked local laws to make sure you can do what you're planning? Not every country allows powerful cycles and most of europe is settled on EPACs which need to be pedaled and don't give any power past 25 kph. I assume you're going with a thumb throttle?

David.