Home Build 100 cc Electric : Electronics EXPERTS needed

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.

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.

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

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.

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.

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.

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.