Pedal Assist on Hub motors

Hey all,

I have jumped into the ebike game without thinking too much.
I have a specialized alibi and a mongoose artery. They both are road hybrids.
I purchased two BMC hub motors (one front and one rear) and 36v 10ah battery packs, without thinking all the way through.
Now to the question,
I do not like throttle switches of any kind and want to make a pure and simple pedal assist bike. something like a poor mans copenhagen wheel.
If it was upto me i wouldn't even have a display but i think thats a necessity.
Can you please help me on how to achive these pure pedelac bikes as to what controllers to buy ( have not got the controllers yet), and do i need torque sensors or candence sensors.
plus i have heard that the torque sensors are quite pricey, do they work with all controllers, are there cheaper ones.
thanks

Charred.

Welcome to the forum.

Cadence based PAS isn't worth most people's time, in my opinion. But there are some people who actually like it, and whom it works very well for. There are also people who think Justin Bieber is a talented artist. To each their own.

Torque sensors are expensive, but they give you a closer direct feedback for PAS. pedal harder, and the motor gives you more power. the result is a motor output that closer matches your pedaling input, making acceleration and hill climbing more intuitive.

you can set up a cadence PAS for roughly the same cost as a throttle based controller. >$100 from many suppliers. I know you say you don't want a throttle, but try riding with both first. reality surprises people.

A torque based system will run you ~$400 to set up with your motor. a CR48-20 controller, a Cycle Analyst V3, and a TDCM torque sensor is all you need, over the parts you have.

Some cadence sensor implementations are quite crude. I just got a new controller which tries to take the bike to max speed as soon as it detects any pedal motion. Makes the bike not able to be pedaled unless the PAS is disconnected, because you can't go slow. To be fair, it was advertised as intended for throttle control, and each level on the LCD corresponds to a max speed for the throttle, but none of that came thru in the English description on aliexpress. So I will scrap it.

Have no complaints about the "torque simulation" controllers. What they really do is do a smoother job of limiting motor power in the lower PAS levels. I've not tried to see how they handle lower spin rates.

Chargedin said:

Hey all,

I have jumped into the ebike game without thinking too much.
I have a specialized alibi and a mongoose artery. They both are road hybrids.
I purchased two BMC hub motors (one front and one rear) and 36v 10ah battery packs, without thinking all the way through.
Now to the question,
I do not like throttle switches of any kind and want to make a pure and simple pedal assist bike. something like a poor mans copenhagen wheel.
If it was upto me i wouldn't even have a display but i think thats a necessity.
Can you please help me on how to achive these pure pedelac bikes as to what controllers to buy ( have not got the controllers yet), and do i need torque sensors or candence sensors.
plus i have heard that the torque sensors are quite pricey, do they work with all controllers, are there cheaper ones.
thanks

Charred.

Click to expand...

You left out some details, like where you are at(profile please)and the discharge rate of your batteries.
I guessing the batteries can only maintain 20 to 25 Amps, so that will be the limiting factor on your systems(well short of what those expensive motors would take).
Since your systems will be low power, you can use a simple square wave controller w/ 3-speed limiting and still have a good PAS experience. With low power, there is less a tendency for the motor to "lurch"(run up to speed)and w/ a relatively low top speed(depends on your motor speed, something else you didn't tell us), 3 speed ranges are enough to cover your likely road speeds.
I like these controllers;
http://www.elifebike.com/peng/iview.asp?KeyID=dtpic-2014-3K-SPSC.5TSNR
They are inexpensive, quiet and almost as smooth as the "torque imitation" sine wave units, but less trouble to get set up. They can also be easily shunt modified to 25 Amps if your battery will handle it.
You will still need a throttle for rare times you will want to go but can't get your feet on the pedals or you didn't down-shift to a low enough gear, so buy a thumb style and put it on the left.

Thanks a ton for the replies, motomech doc and drunkskunk.
So ya, i've been thinking TDCM a with a CA V3. Seems it will do the job.
You see i am from india and i have to be very sure of what i want since things are quiet tough to find here, so everything is going to be an import.
Cycling is still at its worst in this country, frowned upon really.
I have tried throttle hub bikes, but they didnt do it for me.
i really like to take in the countryside when i ride. throttle is just and intrusion in that experience.
Lets see what i get.
Mid drives like the bbshd, do they offer a better pas experience?

Chargedin said:

Mid drives like the bbshd, do they offer a better pas experience?

Click to expand...

That depends on what you're looking for. BBSHD doesn't sense torque, but pedal RPM. So you get the preset level of assist whether you're pedaling hard or barely making an effort.

Chargedin said:

Thanks a ton for the replies, motomech doc and drunkskunk.
So ya, i've been thinking TDCM a with a CA V3. Seems it will do the job.
You see i am from india and i have to be very sure of what i want since things are quiet tough to find here, so everything is going to be an import.
Cycling is still at its worst in this country, frowned upon really.
I have tried throttle hub bikes, but they didnt do it for me.
i really like to take in the countryside when i ride. throttle is just and intrusion in that experience.
Lets see what i get.
Mid drives like the bbshd, do they offer a better pas experience?

Click to expand...

Perhaps something is being lost in the translation, but it is difficult to understand your reasoning.

I have tried throttle hub bikes, but they didnt do it for me.
i really like to take in the countryside when i ride. throttle is just and intrusion in that experience.....
Mid drives like the bbshd, do they offer a better pas experience?

Click to expand...

As Chalo has explained(twice) hub motors and a mid-drive motor are motors, they really don't have anything to do with how the PAS system relates to the rider. And if you now decide to go w/ mid-drives, what do you intend to do w/ your BMC's?
Pricey paper-weights?
And a throttle is a device that you have the option to use or not use, it does not intrude on how the PAS works in any way.
Given a long enough straight, even the simplest PAS can work very well. One sets the speed range on the controller a couple of miles per hour below your desired speed and one adds to that w/ one's legs.
It seem to me that your biggest roadblock to installing PAS might be your attitude. You seem to be dis-counting a hub motor/simple PAS system w/out even trying one, although, at this point and all the money you have already spent, all you would have to spend is an additional $50 US or so to find out.
Good luck

Thanks for the replies,
You are right, i mean it could be my attitude,
I am wary of a simple pas setup but i will go ahead and install one and see how it goes.
regarding the mid drive, i was just curious.
i do have two semi kits with me ,so, i can try one on first and see how it goes.
I will keep you guys posted. thanks a ton.

Looks like more of Justin's stuff is supporting detailed levels of PAS.

https://www.youtube.com/watch?v=IU4qWSXtJUU

[youtube]IU4qWSXtJUU[/youtube]

I just use the common LCD3 and S12S controller with 5 levels of PAS. I don't have a recommended website URL for this stuff though.
I used for a fair while various thumb and twist throttles but without a doubt the most delightful ebike secret I have discovered over the years is just dry pedaling (due to higher power) with just PAS as my throttle, I find it a considerably more comfortable ride, I could never go back to any other way.
If I feel like actually putting more work into my ride I just lower my PAS power setting, but lately I been feeling lazy and let the motor do all the work. If I had weird forced choice between being forced to have a handlebar throttle on or not have a bike seat it might be a difficult choice for me, which is a pretty weird thing to say.

TheBeastie said:

I just use the common LCD3 and S12S controller with 5 levels of PAS. I don't have a recommended website URL for this stuff though.
I used for a fair while various thumb and twist throttles but without a doubt the most delightful ebike secret I have discovered over the years is just dry pedaling (due to higher power) with just PAS as my throttle, I find it a considerably more comfortable ride, I could never go back to any other way.

Click to expand...

Same here. I have both. Throttle is there basically as a back-up, if my PAS cuts out somewhere far from home, or something else dramatic happens structurally.
Last summer my whole crank broke off and dropped on the road 30 miles from home. Throttle was very nice thing to have then.
Modern simulating 5-speed PAS works well with heavy velomobile and 500W DD. Thing is so heavy, that there is not much jerkiness, it"s smooth.
Older PAS-system i had four years ago was horrible. It was basically on-off all the way. Full throttle or no throttle. It was dangerous, if you stood still waiting the lights to turn green lots of people around you and your foot accidentally pushed the pedal a bit. Bike rocketed forward suddenly with full power.
This new PAS is much, much better.

I find that I enjoy the simplest PAS systems because they give a kind of magic-carpet feel when they take off with just a gentle push. (This quality would probably be obnoxious in a high powered bike.) While torque sensing PAS systems are more precise about power matching, they have a time lag to respond to changes that I find distracting.

What I would find most agreeable would be a motion sensing PAS with throttle override, but one that has a PAS disable switch that didn't disable the throttle. I don't want PAS when negotiating foot traffic or obstacles, but I still might want the motor available at those times. Then when the way is clear, engage PAS and fly away without having to hold the throttle open.

Like a Bafang mid-drive with Luna Hot Rod programming: throttle is enabled in PAS 0 so you just toggle from 0 to whatever PAS level is comfortable with the thumb button.