PatrickGSR94

So I've been thinking for awhile now that I want to convert my heavy, upright steel utility bike into an e-bike, because I use it to haul a heavy trailer full of stuff around town. Our town has lots of hills, and going anywhere on that bike with the trailer is very slow, and seems like it takes forever. A grocery store trip takes nearly a solid hour of riding just to get there and back home again.

So my LBS held a Trek factory demo in my area this past weekend, and I got to try out their Powerfly full suspension e-assist bike with a Bosch mid-drive unit. The bike weighs 50 pounds, and it had Chupacabra 27.5 x 2.8" tires on it. At first I thought it might be a little hard to handle. But then I got going on it. WOW such fun! I rode it on some new MUP paths nearby, and then took it down some hard-pack gravel roads. It was a very smooth and easy ride. I could pedal as hard as I wanted to, or not. I could easily cruise along flat ground at 16-17 MPH. When I got to a large interstate overpass, I bumped the assist up a notch and sailed over the hill like it wasn't even there!

I've had the e-assist bug for awhile now, but now I've REALLY got the bug badly! I've been leaning towards a BionX rear wheel hub motor setup, mainly because of its built-in torque sensing capability, and because I've heard of Bafang 8FUN users having issues with plastic gears and stuff failing after a couple thousand miles or so.

Any thoughts or suggestions on a 26" wheel hub motor that can take an 8-speed cassette, AND be able to use disc brakes?

2old

IMO, you can't do better than BionX especially with their three year warranty. The only consideration would be the length of the hills. Generally, if you can maintain a speed of 8-10 mph, the hub motor won't overheat.

PatrickGSR94

You mean, if I can maintain 8-10 mph assisted? I'm sure that wouldn't be a problem. Around here it's rolling hills, nothing really long. But it's hill after hill after hill, seems like.

PatrickGSR94

Any other recommendations as a "first" e-bike setup that wouldn't break the bank as much as BionX? I know there's a lot of cheap Chinese junk on the market. Not sure I want to mess with all that.

2old

There's plenty of good Chinese junk too. Seems like a hub conversion would work for you. I have ridden a $240, 1000w
kit for a year without incident, but it depends on how DIY you want to be. You're pretty close to ebikekit in PA, a pretty good vendor with an excellent individual, Dan, who is available to answer questions.

Johnny Mullet

Check out a Sondors E-bike. My buddy has one and put many, many miles on it trouble free.

slomoshun

Geared hubs:
CR’s 350 watt Hill Topper Electric Bike Kit, Electric Bike Batteries: Electric-Bike-Kit.com
Leed’s 500 watt The 500 Series Electric Bike Kit by Leed Bicycle Solutions

Mid-drive:
8Fun/Bafang Bafang 8FUN BBS02 kit Controller Upgrade - California Ebike

350htrr

Here is what my 350 watt BionX does for my riding assistance, in the first post... https://www.bikeforums.net/electric-b...r-numbers.html

Dunbar

You should test an e-bike without a torque sensor before converting your bike to one of those systems. Torque sensing makes an e-bike feel more like a standard bike (but on steroids.)

PatrickGSR94

Yeah I don't think I want to build something without the torque sensing stuff. The 8FUN kit uses a cadence sensor and brake lever switch to cut the motor off, which still doesn't sound as smooth and seamless as one with torque sensing. 8FUN's plastic gears and other internals also give me pause as to its reliability.

What is a FWD electric wheel like? Seems like that would be weird being "pulled" around.

2old

My first conversion was a front hub and it's still fun. The beauty is that you have two wheel drive and the weight is nicely balanced with a downtube mounted battery. FYI, mine has only an RPM sensor, but I don't mind. Strangest thing is riding offroad, if the front wheel comes off the ground, it kind of "spits" when it alits.

NoPhart

IMHO stick to the mid-drives. BBS## are not Chinese junk by any stretch of the word. Gears are wonderful and "quiet." Leveraging the motor output via mid-drive is the way to go.

Best to ride the different style of E-bikes to truly understand the differences in feel. One thing is for sure in the electric bike industry, high price doesn't always mean high quality. Much of what is out there is way over priced for what it is...

Doc_Wui

I've never had the pleasure of riding an e-bike with torque sensing pedals. The multi-level pedal assist (PAS) on my BBS02 mid drive is fine and smooth enough for me.

I also have ebikes with the simple 3-level PAS and agree that they are fairly crude at lower speed. Until you get to a preset speed, your cadence doesn't seem to matter.

Still, a Bionx is $2499, while my cheapest hub motor with battery was under $500, and it still feels like I have power steering in the pedals. I'm happy with what I have.

By the way, plastic gears are really nylon. The tales of melted gears are from people who are pretty hard on their rides or from newbies who lug their motors up hills. If one understands how to use gears on a bike, and treats his motor like the tiny appliance it really is, all motors should be good. By the way, Bafang sold 830K motors in 2015, which included their mid drives and hub motors. All use nylon gears.

2old

Only kits that I know of with torque sensors are the BionX and Lectric Cycles' BBS kits (although I'm sure there are more, with more to come). I've ridden lots of OEM bikes with torque sensors and their main advantage (FOR ME) is when ascending tortuous terrain; as long as you keep pressure on the pedals the motor produces power, whereas on a system with RPM sensor if you stop pedaling, you stop.

NoPhart

I've never completely understood exactly "how" the torque sensors sense pressure on the pedals. Can anyone tell me the details on that?

On the BBS## BaFang mid-drives the throttle is always there to override and apply power. That's nice. They normally use a single magnet on one spoke that tiggers a sensor on the rear chainstay each time it comes around. It works with the timeout setting in the controller, so if the magnet doesn't come around within the time setting programmed it assumes you no longer want power. The throttle will over ride that shutoff.

It seems to me that with a multiple magnetic and sensor at the crank (like I see out there for sale) would act very much like a torque sensor, in that, the sensor will be getting triggered more fequently (every inch or so of movement).

Is that all a torque sensor is, more frequent trigger points? Or is there some other electronic mechanism that is at work? If so, what is it?

350htrr

As far as I know it's a sensor on the rear axel, It senses the amount of "twist" that the pedal pressure makes it twist and sends that signal to the controller and the controlled decides how much power to use for that level of assistance the rider picked and that level of input from the rider pedaling and a certain % is added to the pedaling effort... just my understanding of it.

Doc_Wui

Yes, electronics can sense pressure on a pedal, but what can it do with it on a mid drive, if the rider has already stuck the darn bike in the highest gears, and is trying to climb up a hill. Me, I'd want to program the controller to throw that rider off the bike with a shock to the hidden electrodes in the seat, but then I'd have to pay for the seat device, plus a sensor to detect the gearing. Guess I would settle for a "Please downshift" message on the LCD.

I just received a controller that advertises "torque sensing simulation". I guess it promises better feedback in low pedal pedal assist. Will try it out soon.

NoPhart

What kind of sensor can measure twist or even pressure? That is what I don't understand.

I couldn't really tell any real difference in models with a "stated" torque sensor and others myself. Some seem to apply power slower than others, but it didn't seem to be related to the pressure on the pedals. If I just pedal at a constant pressure, they all seem to get up to the speed/power setting that is programmed. The stated non-torque sensor models just seem to get there quicker.

350htrr

Then it just sends less power because there isn't much torque on the rear axel, gear down and the torque increases and so does the amount of assistance...

350htrr

Then I suspect it's the programing of the controller that is not optimal, On mine I can change it to instant on and feel the assistance right away, or instant on but it dials up slower and so smoothly that you would swear it's all you. Yet you cant do the same when you turn it off, so it wasn't really all you.

NoPhart

I suspect it is really the software that makes the biggest difference in feel, not the torque sensor itself.

I just found this which is probably as detailed as I'm going to find about this topic:

https://www.electricbike.com/torque-sensors/

It seems personal preferrence and software settings are once again the biggest issues between models. I'm guessing a poorly programmed torque sensor is no better than a poorly programmed cadence sensor and a properly programmed torque sensor has a slight advantage over a properly programmed cadence sensor. And once again, throttle overrides them all and you get exactly what "you" want when you want it...

350htrr

That electric bike torque-sensor article is 100% correct IMO explaining the different type of sensors and the advantages of a real properly set up torque sensing system like the BionX is exactly the reason why I bought the BionX, You can't even compare, a cadence sensing set up, or even the other power sensing set ups, or even a throttle set up to it... Not even in the same game, or same ballpark, I say...

chas58

I'm a mechanical/materials engineer, and we do this all the time. Its basically a "strain gauge" that measures the distortion in the material

If you really want to know how this works, you can read:
https://en.wikipedia.org/wiki/Strain_gauge
As the object is deformed, the foil is deformed, causing its electrical resistance to change.

That is how you measure the deformation, and can calculate the torque from that.

chas58

Any hub or mid drive motor by Bafang
A Cute Q100 motor for light weight 350-500 watt hub motor.

Anything sold by emv3e or lunacycles (see my post on vendors).

Do you want a system that is as strong as a good biker or a lot stronger than you. Do you want to help by peddling, or just sit back and let the motor do 80%-100% or more of the work? Are hills an issue (something steep enough where a fit biker would struggle to go over 10mph)?

How fast do you want to go (cost goes up exponentially (literally)
How far do you want to go
Is weigh an issue (do prioritize weigh over power, or vice versa?)

chas58

Actually, its on the pedal arm, or the bottom bracket (although I have seen them on the pedals or even on the shoes).