Would This Outrunner be suitable for an E-Bike

[RayLiu]

Hello everyone, this is my first post in this forum, and I'm building my first electric bike. For this electric bike I will be using a 24 volt 14Ah lead acid battery pack, a 125 amp hobbyking esc and I would like to use a direct friction drive with this motor: http://www.hobbyking.com/hobbyking/store/__22036__NTM_Prop_Drive_50_60_270KV_2400W.html
I'm wondering if this motor when used with a 24 volt system would be able to get me up to at least 40km without pedalling. I'm also wondering if the lack of a skirt bearing in this motor would hinder anything.

 

[rich43]

You would probably need some sort of gearbox to reduce the rpm to maybe 250.

 

[Miles]

You would probably need some sort of gearbox to reduce the rpm to maybe 250.

The proposal is to drive the tyre with the motor can (friction drive).

 

[Dauntless]

Before I get started, does anyone have fricition drive experience with that 8mm shaft? Need to know if it can hold up. A skirt bearing for friction drive is an excellent idea.

I don't think you understood what Rich was trying to convey. Let's see if I can make it clear from the ground up. The diameter of the motor is 1.985", x pi that'll be 6.184", etc. Two revolutions mean almost 12.4". 30 revolutions is 31 feet. But one (1) volt will spin the motor 270 revolutions in one minute, the surface of the can covers 279 feet. Just over 3.17 miles an hour.

Let's assume you're using a 26" wheel, which I assume Rich meant was supposed to spin 250 rpm. One revolution is 81.68", almost 7 feet. That motor will spin more than 13 times for the wheel to spin once. Rich wants you to go just under 20mph, 776 revolutions being a mile then 1/3rd of that times 60 minutes is 20 miles.

Theoretically if you push that can right on the tire and run 3s, 11.1v, on the lipo, you'll get 3,000 rpm.that's just over 1,500 feet in a minute before you figure on losing something under load. 4s would be over 2,000 feet in a minute, more than 20 miles an hour and almost 40kph.

But this motor is most efficient at 6-8s, over 35mph and over 45mph, respectively. Too fast for just a bicycle.

A nice torque converter with a 2:1 reduction, or just a 1" diameter pinch roller on the end of the shaft, would bring the 8s speed down and make the motor more comfortable going uphill. Probably it would make life easier for your controller.

Specifically for your 24v battery we're taking 6500rpm in significant digits, let's call that 38mph/61kph, you need 3:2 reduction. Maybe a 1.33"/33mm capstan actually touching the tire. A motor that small around, maybe a 3240, will be physically insubstantial and I don't think you want to use such. This motor would only be good idea if the housing is not pressed on the tire, running 4s battery might be risky.

Just one theory.

 

[RayLiu]

Before I get started, does anyone have fricition drive experience with that 8mm shaft? Need to know if it can hold up. A skirt bearing for friction drive is an excellent idea.

I don't think you understood what Rich was trying to convey. Let's see if I can make it clear from the ground up. The diameter of the motor is 1.985", x pi that'll be 6.184", etc. Two revolutions mean almost 12.4". 30 revolutions is 31 feet. But one (1) volt will spin the motor 270 revolutions in one minute, the surface of the can covers 279 feet. Just over 3.17 miles an hour.

Let's assume you're using a 26" wheel, which I assume Rich meant was supposed to spin 250 rpm. One revolution is 81.68", almost 7 feet. That motor will spin more than 13 times for the wheel to spin once. Rich wants you to go just under 20mph, 776 revolutions being a mile then 1/3rd of that times 60 minutes is 20 miles.

Theoretically if you push that can right on the tire and run 3s, 11.1v, on the lipo, you'll get 3,000 rpm.that's just over 1,500 feet in a minute before you figure on losing something under load. 4s would be over 2,000 feet in a minute, more than 20 miles an hour and almost 40kph.

But this motor is most efficient at 6-8s, over 35mph and over 45mph, respectively. Too fast for just a bicycle.

A nice torque converter with a 2:1 reduction, or just a 1" diameter pinch roller on the end of the shaft, would bring the 8s speed down and make the motor more comfortable going uphill. Probably it would make life easier for your controller.

Specifically for your 24v battery we're taking 6500rpm in significant digits, let's call that 38mph/61kph, you need 3:2 reduction. Maybe a 1.33"/33mm capstan actually touching the tire. A motor that small around, maybe a 3240, will be physically insubstantial and I don't think you want to use such. This motor would only be good idea if the housing is not pressed on the tire, running 4s battery might be risky.

Just one theory.

I'm not really worried that much about the torque the motor can provide because in the area I live in, there is not a single hill, the entire area is flat. And as for the concern of the amp draw being too much for the ESC, I will be using this ESC:http://hobbyking.com/hobbyking/store/__19440__Birdie_125A_Brushless_Boat_ESC_NO_BEC_.html
with a watercooling loop that uses a 120mm radiator such as those found in computer watercooling systems. I will also be using a high powered fan to cool the outrunner as it is running, the pump for the esc and the fan to cool the outrunner will run on a seperate 12 volt battery. I believe this setup will be able to handle all the amps. As for my speed being too high, faster is always better .

 

[yawstick]

I'm still pretty much a noob here and very little experience with friction drive though I did try in on my trike build. I would suggest you keep it simple and forget the water cooled ESC and the motors are a bit like a squirrel cage fan and pump quite a bit of air through themselves on their own. If you design for the 20 mph speed you are not going to be pulling 100 amps very often anyway and probably never with a friction drive. I'm using this motor... http://www.hobbypartz.com/96m608-bigfoot160-5335-245kv.html which is close to the one you suggested but it can run on 44 volts as well if you want to add more volatge down the road at least you have a motor that can use it. If you use less... no harm done. A six cell controller is only about 60 bucks and normally has the battery eliminator to power a servo tester or something. http://www.hobbypartz.com/07e10-proton-100a.html
I'm using this controller http://www.hobbypartz.com/07e26-proton-100a-hv.html It's designed for 12s and it seems to be ok so far.
I had in mind a simple reduction drive if I had continued with the friction drive. Gets the motor away from the dirt and grime from the tire and takes the load off the motor bearings. I may mock it up tonight and post some pics to see if there is interest in it.

 

[Hillhater]

I'm not really worried that much about the torque the motor can provide because in the area I live in, there is not a single hill, the entire area is flat. And as for the concern of the amp draw being too much for the ESC, I will be using this ESC:http://hobbyking.com/hobbyking/store/__19440__Birdie_125A_Brushless_Boat_ESC_NO_BEC_.html
with a watercooling loop that uses a 120mm radiator such as those found in computer watercooling systems. I will also be using a high powered fan to cool the outrunner as it is running, the pump for the esc and the fan to cool the outrunner will run on a seperate 12 volt battery. I believe this setup will be able to handle all the amps. As for my speed being too high, faster is always better .

One piece of advice...... carry a spare ESC with you.

 

[spinningmagnets]

Welcome rayliu. I have a friction drive, and it has been performing very well for me. Here's a thread that I want you to look over, and hopefully it will give you some ideas. http://endless-sphere.com/forums/viewtopic.php?f=28&t=14403

Kepler and Adrian are well known for making a drive that uses the motor-shell as the roller. This method is the smallest and lightest a friction drive can be.

EVTodd and I have both built drives that have the roller separate from the motor. This of course makes the drive larger, heavier, more complex, but...it has a couple of performance benefits that appealed to me. I only wanted to go 20-MPH, and one configuration of my drive performed well on fairly flat land using a 1.25-inch roller on 24V...and for hills, I went to a one-inch roller using 37V.

Regardless of the drive configuration type, the 63mm diameter motors have proven to be the best size. They can be found in Kv's from 149-to-295.