different e-bike setups

[strantor]

Ok, some may have seen my threads about building a controller (build thread: http://www.endless-sphere.com/forums/viewtopic.php?f=7&t=32231). I have been planning on using a go-kart for a test platform. So far all my attention has been focused on the controller design and I haven't given much thought to the go-kart part of it. A more detailed inspection of my go-kart chassis is making me re-think it. Significant modifications will be needed; such as disk brakes, a live axle, and bigger wheels. I have priced all the parts and it is a lot more than I want to pay. You guys' e-bike shenanigans are starting to wear off on me. If I were to build an e-bike with my motor and controller, I think it would be cheaper and result in an actual viable method of transportation for me. I could actually ride it to work.

My motor (motoenergy ME0709 brushed DC) will be run @ 96V, 150A (300A max) , so 14KW (29KW max); a lot higher power than I usually see the ebikes here.

So, I've been looking at some of the different builds on this site and noticed that all the higher powered e-bikes are using chain/sprocket drives to the rear wheel. why is that? I was thinking that if I placed a small contact wheel on the motor shaft and let it ride on top of the tire, it would greatly simplify things. I would not need to worry about all the torque involved with trying to motor the wheel from the shaft and twisting off all the spokes. I could do it with minimal modifications to the bicycle, and the modification would be less obvious; I could conceal the motor in a "basket"-looking apparatus on the back. I would not need to modify the existing chain drive at all. It could easily be taken off and mounted on a different bike. All I am seeing are the good points; so what are the bad points? I know there has to be at least one crushing reason why this idea is crap.

 

[AussieJester]

Well I for one would love to see a ME0709 friction drive on the front wheel!?..even better!... I don't think anyones even attempted this or those power levels
14kw continuous friction drive, I.d like to see that ::sarcasm::

KiM

 

[dogman dan]

Friction drives are said to work good by many. But I've not heard of one in the 17 hp ballpark. When I ran about 4 hp into a front hub, it got pretty tricky to get back on throttle while leaning through a corner.

 

[strantor]

I wouldn't do it on the front wheel, I was referring to the rear wheel.

Ah, ok, so there's a name for that; "friction drive".

I googled that, and found this:

A Friction Drive System usually consists of a motor with a splined shaft that rides upon the tire of your bicycle wheel causing it to spin and propel the bike. ZAP kits and bikes fall under this catagory. While this system is inexpensive, it is not very power efficient since you are loosing a good portion of your energy through friction on the bicycle tire. It is not capable of reaching high cruising speeds, and tends to wear out tires quickly...

As far is the statement that it won't reach cruising speed: at 96V the motor spins 4700RPM & max stall torque is 39nm (28ft lbs). A normal BMX bike has a 26" tire (81.68" circumference). If I had a 2"(dia - 6.28" circumference) contact wheel on my motor shaft, that would be a 1:13 ratio. that would give me a max speed of 27mph and max torque of 364ft lbs. I don't know how much torque I really need, but 364ft lbs sounds a little excessive (kawasaki ninja 250 only has 18ft lbs http://www.bestbeginnermotorcycles.com/kawasaki-ninja-250-review) and I'd like to go faster than 27mph. so let's try a 6" contact wheel; that gives me 83mph max and 121ft lbs stall torque. This is starting to sound like it might be highway capable (if I was comfortable riding a BMX bike @80mph and the cops didn't catch me).

tends to wear out the tires quickly? I can live with that.

Not very efficient? well, my motor is not that efficient to begin with, and I'm not seeking to demonstrate efficiency in an EV design, but efficiency in controller design.

How fast would you guys say is safe to go on a BMX bike? I've gone maybe 40mph down a hill and didn't feel too unsafe; maybe I would start to feel a little scared around 50 or 60mph? might feel a bit "floaty"?

 

[MadRhino]

That kind of power on a friction drive will spin alot on the tire before it start to move, unless your controller has a "soft start" implemented. Then, once it start to move, Your BMX will have very powerfull acceleration. I would try this with a bigger bike, longer wheelbase and larger wheels would help.

You could also build it currie style, similar to what Luke did with his Pinky build with an Agni 05.

 

[Drunkskunk]

If you don't just compleatly tear the tire off at start up, you'll likely spin the tire on the rim at those power levels, tearing the bead or popping the tube. You might get away with using a 16" motorcycle slick tire on a motorcycle rim laced to your hub. because of the diffrent way the two are measured, a 20" Bicycle wheel is the same size as a motorcycle 16" wheel.

But friction drive is realy only good for 1 - 2000 watts max. after that, you're tearing up tires and wasting power that could be better used to GO! Why not build a gear drive? 29K peak is close to 40 HP. thats as much power as an early VW bug, or a WW2 jeep! why waste half of it? Go look at Luke's Pinky project.


A BMX bike is safe to 20mph, tops. After that, you're roadkill on wheels. the brakes are near useless past 30, and the wheelbase is far to short to be stable past 40. Basicly, one bump, pothole, or rogue squirl in the road at 50mph on a BMX, and your Buzzard Buffet. But then you're putting 29kw on a kid's sized bike, you're not wanting to be safe, are you? Screw Safe. Go for it.

 

[strantor]

That kind of power on a friction drive will spin alot on the tire before it start to move, unless your controller has a "soft start" implemented. Then, once it start to move, Your BMX will have very powerfull acceleration. I would try this with a bigger bike, longer wheelbase and larger wheels would help.

You could also build it currie style, similar to what Luke did with his Pinky build with an Agni 05.

you're referring to this one https://endless-sphere.com/forums/viewtopic.php?f=1&t=28176?

by currie style, you mean motor drive sprocket on one side of the wheel, and pedal drive sprocket on the other side?

I had thought about the contact wheel spinning on the tire, but I didn't think it would spin much if I kept a good amount of pressure on it; but I guess that's wrong thinking. If I put one of those solid core tires (with no tube) I could possibly apply more pressure without ruining the tire, but then it would be a rough ride... just thinking out loud.

What kind of bike would you recommend? My thoughts just went straight to BMX because that's what I loved to ride as a kid.

 

[strantor]

If you don't just compleatly tear the tire off at start up, you'll likely spin the tire on the rim at those power levels, tearing the bead or popping the tube. You might get away with using a 16" motorcycle slick tire on a motorcycle rim laced to your hub. because of the diffrent way the two are measured, a 20" Bicycle wheel is the same size as a motorcycle 16" wheel.

But friction drive is realy only good for 1 - 2000 watts max. after that, you're tearing up tires and wasting power that could be better used to GO! Why not build a gear drive? 29K peak is close to 40 HP. thats as much power as an early VW bug, or a WW2 jeep! why waste half of it? Go look at Luke's Pinky project.


A BMX bike is safe to 20mph, tops. After that, you're roadkill on wheels. the brakes are near useless past 30, and the wheelbase is far to short to be stable past 40. Basicly, one bump, pothole, or rogue squirl in the road at 50mph on a BMX, and your Buzzard Buffet. But then you're putting 29kw on a kid's sized bike, you're not wanting to be safe, are you? Screw Safe. Go for it.

lol, safety isn't my #1 concern, but I would like to live through this project.

That's a good point about the spinning the tire on the rim; I hadn't pictured that happening.

I'll start looking to gearing methods, starting with the currie/pinky style already mentioned.

How much safer would a mountain bike be than a BMX? or scratch that, what's your recommendation for a bike?

 

[amberwolf]

One reason to use a chain drive is for gear reduction, to keep motor speeds high and current draw low. When using a roller friction drive, the diameter of the roller itself is what determines motor RPM vs road speed, as it is just like having the friction roller directly on the ground, as far as gearing ratio goes.

Another reason is power transfer. At very high power levels, the roller and the tire will wear from slippage, especially if you lay on the throttle suddenly and hard. Depending on the roller design and pressure of roller onto the tire, I could imagine that a high power burst at high RPM could actually shred the tire.

One further issue with power transfer is that you have a large roller surface, but it's usually all flat-cylindrical. The tire surface is rounded, so there is very little actual contact patch to transfer power. A curved roller has been discussed, but I don't recall the results. It's somewhere in the back pages of the Motor Technology forum section.

 

[amberwolf]

How much safer would a mountain bike be than a BMX? or scratch that, what's your recommendation for a bike?

What kind of bike do you prefer to ride? That's the real question. "safe" on a bike depends greatly on where you ride it, how you ride it, how it's built, what it's made of, etc.

I'd pick a recumbent, because they're more comfortable and often easier to find places to stick a drive, but if you don't like them that's kinda useless.

A fixie with a big triangle for batteries would be a very simple test bed, especially if you use a smaller rear wheel than designed for, so you can stick the motor in the newly-freed space in the rear triangle (and hopefully still clear the cranks).

A longtail like the Surly Big Dummy, or Yuba Mundo, would be good for the same reason, except you don't have to make room in the rear triangle--it's already there.

 

[Drunkskunk]

What kind of bike would you recommend? My thoughts just went straight to BMX because that's what I loved to ride as a kid.

Suzuki Gama, or a small Ninja, or a something like that. Seriously, 40HP. Thats more power than many motorbikes have. you're going to need a solid frame, wheels, and brakes to handle that power. Basicly, 29Kw peak can turn a bike frame into a pretzel at will.

But sticking it on an bmx bike would be Insain fun once.

 

[Hillhater]

If you don't just compleatly tear the tire off at start up, you'll likely spin the tire on the rim at those power levels, tearing the bead or popping the tube. ..

You need to rethink that... it aint going to happen with a friction drive to the tire ! :wink:

but.. This whole idea is wacko !
Too much power for friction drive ( do some research).
Where exactly would you put that motor on a BMX ? ..above the rear wheel ..think about the weight and balance !
do you have an idea how much battery you will need to make that motor work at anything near its capacity ?
where would you fit that much battery on a BMX ??
There is a reason most people use smaller motors on Ebikes, and why people building with that much power are using Motor bike chassis.

 

[AussieJester]

Dirt jumper with 24in wheels equipped with disk brakes and and a good front suspension fork would be my recommendation over a Kids bmx
If you like that sort of bike, downhill mtbs are also a good choice
If you intend going over 40mph, imo. Jm2cw.

KiM

 

[MadRhino]

you're referring to this one https://endless-sphere.com/forums/viewtopic.php?f=1&t=28176?

by currie style, you mean motor drive sprocket on one side of the wheel, and pedal drive sprocket on the other side?...

...What kind of bike would you recommend? My thoughts just went straight to BMX because that's what I loved to ride as a kid.

Yep, Luke built his pinky, currie style.

I recommend a longer wheelbase, and a slacker steer angle. Luke did extend the rear triangle alot, thus making a long wheelbase that is suitable for power and speed. It also made room for motor and batteries.

A slacker steer angle is what makes the bike suitable for riding bumps at high speed. Then, suspension is best if you want a comfortable and safe ride at high speed, no matter the terrain.

 

[dogman dan]

Mabye with a big enough friction wheel on the motor, but I just keep seeing an image in my mind similar to just taking a dremel grinding stone to your tire. Little sandpaper wheel spinning really fast in one spot burning a hole in the tire.

That really is over the top power for friction drive I think.

Put it onto a chain drive, and better wear high top boots tightly laced. See the " you know this bike is dangerous right" vid from the hill climb.

 

[strantor]

What kind of bike do you prefer to ride? That's the real question. "safe" on a bike depends greatly on where you ride it, how you ride it, how it's built, what it's made of, etc.

I'd pick a recumbent, because they're more comfortable and often easier to find places to stick a drive, but if you don't like them that's kinda useless.

A fixie with a big triangle for batteries would be a very simple test bed, especially if you use a smaller rear wheel than designed for, so you can stick the motor in the newly-freed space in the rear triangle (and hopefully still clear the cranks).

A longtail like the Surly Big Dummy, or Yuba Mundo, would be good for the same reason, except you don't have to make room in the rear triangle--it's already there.

I don't think I would enjoy a recumbent. I preferred BMX as a kid because it was nimble and good for going offroad, which I intend to be able to do with this bike. I always disliked the bigger mountain bikes because they felt too large and clumsy. That might be different for me now since I'm bigger.

Suzuki Gama, or a small Ninja, or a something like that. Seriously, 40HP. Thats more power than many motorbikes have. you're going to need a solid frame, wheels, and brakes to handle that power. Basicly, 29Kw peak can turn a bike frame into a pretzel at will.

But sticking it on an bmx bike would be Insain fun once.

Ok, I see your point. I'm thankful to have your input. I will look into motorbike frams and see if I can find one for cheap. I'm thinking enduro-type; something light & nimble, good for street and offroad.

This whole idea is wacko !
Too much power for friction drive ( do some research).
Where exactly would you put that motor on a BMX ? ..above the rear wheel ..think about the weight and balance !
do you have an idea how much battery you will need to make that motor work at anything near its capacity ?
where would you fit that much battery on a BMX ??
There is a reason most people use smaller motors on Ebikes, and why people building with that much power are using Motor bike chassis.

Well as far as the batteries, what I was envisioning was pretty similar to luke's pinky bike. I had not given much thought to weight distribution, but now I am thanks to you.

I recommend a longer wheelbase, and a slacker steer angle. Luke did extend the rear triangle alot, thus making a long wheelbase that is suitable for power and speed. It also made room for motor and batteries.

A slacker steer angle is what makes the bike suitable for riding bumps at high speed. Then, suspension is best if you want a comfortable and safe ride at high speed, no matter the terrain.

Ok, I'm seeing a pattern here between what you and amberwolfrecommened; long wheelbase. and the suspension and slacker angle. I'm thinking modifying a bicycle to meet all these criteria pretty much entails building a motorcycle, so I'm looking at small motorbike now.

Mabye with a big enough friction wheel on the motor, but I just keep seeing an image in my mind similar to just taking a dremel grinding stone to your tire. Little sandpaper wheel spinning really fast in one spot burning a hole in the tire.

That really is over the top power for friction drive I think.

Put it onto a chain drive, and better wear high top boots tightly laced. See the " you know this bike is dangerous right" vid from the hill climb.

yeah, friction drive is off the table. no longer considering it.

 

[RallySTX]

I had a friction drive ICE on my ten speed bike back in the early eighties. The roller wares fast, the tire takes a beating, and the weight was horrible. You have been given good advice by others here. I would only add that the use of power assist on a bike demands decent brakes, and top notch tires. Truthfully, all aspects of the build are deserving of your best efforts. Remember, you are essentially supercharging a vehicle not designed for it. Unless you use a motorcycle or top shelf mountain bike base, nearly none of the stock stuff will work. I wish you well with your build, whatever it turns out to be.
Brian L.