Home Build 100 cc Electric : Electronics EXPERTS needed

[Bcountry]

Good Day all

I am currently in the brainstorming process for building a nice riding Electric Bicycle.

This will be from scratch using of course many off the shelf parts, Gears, Bearings, etc.

However I do not wish to buy a mid drive kit. It will be more fun to build it.

I am a mechanical engineer so I can Handel the gearing and mechanics involved but I lack experience with the electrical side. Also I have full access to a CNC Machine shop so I can machine all my own parts.

I have tremendous experience with gas bikes but they aren't riding the roads here anymore. Time for electric.

Basic Concept thus far:

Ok this is gonna be a complex system but it will preform.
I'm thinking electric motor.
Custom machined mounting that includes containing the motor and the required gear reduction for said motor. Also included in this gearbox...we will call it transmission for now. The Motor is approximately 6 inches wide. This should fit nicely in the frame.

The transmission will also include a Variator which will allow for the motor to spin at a more consistent RPM and provide much more speed range without stressing the electrical system.

The variator in the transmission will connect to another variator mounted to a jackshaft and output to a chaindrive which runs a Spock on the rear wheel which is mounted on the disk brake mount.

#1 The Motor

http://www.hobbyking.com/hobbyking/...Max_100cc_Size_Brushless_Outrunner_Motor.html

Ya I don't need fast but I would like to travel 25 / 30 Mph without straining the motor. And I don't want trouble with hills.

So I need help with a few things here.

The Motor Rpm is rated 167KV.
The Motor Voltage is 45 volts approx.

So 167 x 45 = 7515 thousand RPM ???
Or is it 7515 rpm. I'm confused here.

I need to be able to calculate the motor Rpm under the load it would experience starting off with the bicycle say at 2 mph.

Also I need to figure the torque the motor can output from stall.

This I need to develop the geartrain.

My next big question is how to control the motor speed which seems possible using a servo tester and ESC.

Where the throttle turns the knob on the Servo Tester to control speed.

So I assume the Servo tester will be powered by a separate battery.
I believe the Servo tester outputs signal to the ESC controlling the output pulses to the motor.

In order to not fry the electronics the ESC needs to Handel up to 170 amps. The max of the motor. But the amp handling of the Servo tester need not be so high because only the ESC will have the power supply for the motor running through it.

Somebody please educate me here.
Some links explaining these topics would be great.
Electrical schematics even better.

 

[Trey]

Bcountry- Welcome to the forum! You seem far more experienced and well equipped than most, including myself.
You will surely get some help from the E-Bike folks here, and it sounds like an interesting build. I'll be following along.

Best of luck.

Trey

 

[Mike B]

That is a motor designed to spin a propeller. Yes, it runs real fast. It is also designed to have a lot of air flowing across it (from the propeller)

You will need a lot of reduction (at least 10:1) and a fan to blow air over the motor to cool it.

 

[KCvale]

That little electric motor is designed for model RC aircraft, hence the output to attach a propeller.

Much like a ceiling fan, they are designed to spin very fast with just wind resistance and not worth a darn to drive anything mechanical.

From what I read for that $340 price it has a couple little RC lithium packs, like in RC cars, that won't even get you and your bike around the block before it needs recharge at the power draw you will need for actual real mechanical use if it would ever do it in the first place.

I suggest you look at much larger BLDC motors with a planetary gear box attached to it, and a sprocket friendly output shaft.

E-cyclone sells some I have used with good luck, SickBikeParts.com has a whole kit for $400 less a battery which you will soon find out is the most expensive investment if you want any range.

Here is an example of a fairly inexpensive build.
$400 for the 36V 960W complete kit including the pedal side freewheel dual sprocket chainring and controller, and $320 for 36V 25Ah LI 'bottle battery' with mount and smart charger.

The bike has an internal 3-speed on the rear that both the motor and pedals can use.

When you pedal, the freewheel sprocket on the motor means no pedal drag.
It just spins free.

When the motor spins the chainrings the pedals just freewheel like a ratchet wrench, and you can do both at the same time with motor throttle control.

Dandy for 5 to ~30MPH top speed operation and ~20 mile range depending on how much you help with pedaling and a torque monster, all of these type motors are.

I went a bit extreme on a couple as well.

1.8KW 48V motor and 1KW LI battery pack for both of these 7-speed builds.

Note there is only one drive chain so the disc brake remains.

There is also plenty of room for your custom mounting stuff, seems I have to do that anyway to get things where I want them, but that should give you a pretty good idea of the size and kind of motor and battery you need to propel you and machine around and propel they do, either of that 2 kick the crap out of most any direct drive 66cc 2-stroke gas engine in every way for ~35 miles or so.

 

[Bcountry]

Thank you very much for the replies. I am looking for a dc motor that is around 7 hp. Links to motors that are feasible are appreciated.

I'm figuring about 2000 for my initial budget and as I said gearing isn't a problem. I just need a motor with the proper torque and HP to start.

Please point me in that direction.

 

[Mike B]

http://www.goldenmotor.com/

One of the sponsers here. 5 KW is seven HP, although I would take a good look at their new 3 KW motor with a matching sine wave drive.

 

[Bcountry]

Thank you Mike

Is this your #1 choice for a motor?

It has good specs. As far as rpm being 3000 to 6000.
All most ideal for running a variator belt driven transmission. The variator constantly changes the final gear ratio as the rpm increases. This extends the speed range.

I would believe that the motor. Needs to spin at 3000 rpm to attain the optimal torque.

I believe the variator I have in mind engages around 2000 rpm normally. And runs efficiently to 6 or 7 K rpm. At any rate the operating rpm of the variator is adjusted by changing the weights in it.

I need to run some torque / HP calculations to see how this compares to the China girls.

And most importantly I need to figure battery requirements. The nice thing about the variator is it will provide a more uniform load on the motor which should be easier on the current draw / amount of amps pulled by the motor.

At 3000 watts this motor pulls 3000 watt hours??
But it has a peak of 6000 watt hours ??

Is the average running wattage approximately 3000 watt hours or is it gonna fall between the 3 and 6 K.

I'm looking for baseline watt hours so I can calculate and size the battery I need.

Any links on batteries?

I will run through my calculations later tonight and post them.

Thank you again.
Big Country

 

[Mike B]

You don't need a transmission with an electric, they can produce full torque at zero speed.

Just a fixed reduction to the wheel will be fine. Don't need a clutch either.

 

[Bcountry]

Yes I do believe the 3 KW BLDC motor is gonna be my choice. It should have more than enough power and the cost isn't bad at all. Now I'm looking at what else I need for this system.

Accessories and goodies, what are the best add on parts.

Thank you again so much. I would have wasted a bunch of cash going in the direction I was.

Now I just need to figure out what else is best to put this system together.

Are there other builds using this motor?

More advice is greatly appreciated.

 

[Mike B]

Not that I know of, although I could be on the list -

That 3 KW motor is pretty new, has all their latest tricks and the matching sine drive is even newer.

I'm thinking electric mini-bike, no pedals, no CA reg even.

I've always loved the old school minibikes, had a "lil indian" when I was a kid -

 

[Bcountry]

Well I've done two days of research and I like the golden motors idea.
But there located in China. I think shipping is gonna kill.

Has anyone bought anything from there?
If so how was the experience.

 

[Mike B]

I've bought 3 Magic Pies and 2 batteries (1 Ping and 1 GM)

The shipping cost is high, but it's all air freight and the stuff arrived in good shape real fast.

Amazingly fast like less than a week.

 

[Bcountry]

I've done some preliminary calculations and it seems I will need to gear this motor down to use it like I plan.

I figure on a CVT that runs a 4.7:1 ratio at 2200 rpm.

So I calculate that at 2200 rpm with 4.7/1 ratio and a 10 t driver sprocket with a 40 t on the wheel I end up at about 16 Mph.

I'm thinking I need another 5/1 reduction putting me around 3mph at 2200 rpm.

I don't want to flip the bike when I hit the throttle.

What are some opinions.

9 Nm torque output from the motor could flip me if I'm geared to high.

 

[Mike B]

I would just go 5:1 straight from the motor to the wheel, forget the CVT.

The controller will control the torque from zero to max and the sine wave drive will give you smooth rotation at any speed.

 

[Bcountry]

I'm thinking there is a lot more involved. I have completed all the math required to get an educated answer. I think I'm going to start a new thread. After all this is about the 3kw motor now.

I have a lot of info to post and I believe it will be easiest in a more specific thread.

I appreciate your help Mike. I would also be interested in any info regarding that 5kw build. It would be helpful.

 

[KCvale]

Put manual gears in-line.
Gears change everything regardless of power source.
I agree about avoiding a mechanical CVT, they are power vampires.

 

[culvercityclassic]

KC you ever use this kit: http://www.sickbikeparts.com/catalog/product_info.php?cPath=26&products_id=181

 

[KCvale]

KC you ever use this kit: http://www.sickbikeparts.com/catalog/product_info.php?cPath=26&products_id=181

Yes, a few actually.

The 650-1680W 24-48V BLDC motors with a planetary reduction on the output and freewheel sprocket have given me no problems but serviceable if they ever do.

The Kelly controllers however leave a bit to be desired.
They are programmable from a PC/Tablet/Etc with a special serial -> usb cable and their free Windows software to set limits and I played with it for the first few, but didn't on the last couple.

This specialized is still kicking butt all over...

... but this fat tire has toasted 2 controllers so far.

Make sure you set limits.

Mounting is always a custom job but it's the same JS freewheel system.
You can mine here
http://kcsbikes.com/KCsBuilds.asp?motor=Electric&Drive=All

 

[culvercityclassic]

Thanks KC for the info, not sure what route to go. I do want the power tho and the distance too.