Commuter Booster - <1kg Friction Drive

[pankaj_india]

that was hell lot of information man ..thanks

 

[adrian_sm]

Minor Update: ESC Mounting & Mudguards

Found some spots that I like for the ESC mounting. Bit different for the two bikes, mainly due to trying to optimise the wire routing, and make it neat.
- The 100A ESC on the mountain bike is mounted directly on the front of the clamp.
- The 85S ESC which has slightly shorter phase wires, needs to sit a bit lower, and is mounted on the side of the seat tube, using a couple of cheap DMR clamps.

I also managed to install a mudguard on the rear. It extends back from the seat stays. So it will save me from the spray, but not the motor. I still need to find a good way to protect the ESC. I found a little electronics enclosure that will do the job, but still trying to work out the perfect cable routing.

Finally, after catching up with full-throttle to steal a twist throttle off him, I get talking about the modified turnigy watt meter again as a souped up throttle interface. It is so close to doing what I need, that we might just try to get it going.

Here are the pics fo the ESC mounting, and the mudgaurds.

- Adrian

 

[adrian_sm]

Watt Meter Mods

I am so in over my head with assembler code on the watt meter. I spent the time a while back to translate Jonas's notes to english, and start working out what all the commands mean and do. But it is very slow going. Not sure if I have the patience for this one.

On a positive note all the spare IO's have nice easy access on the accessible side of the PCB, which means there is no need to remove the display to hook them up, or to reprogram.

Those little via holes in the middle equate to PA3,PA4,PA5,PA6 & PA7. With 3,4,6&7 being free.


If I was to re-write code, I want to keep the current ATTINY261. If I have to change chips it is just not worth it.
I want a solution that just requires adding a few wires, and reprogramming.

My wish list is now includes:
Things already done by Jonas
- Display: "Commuter Booster" displayed on startup
- INPUT: throttle
- OUTPUT: throttle
- uC: Power limitting
- uC: throttle ramp control

Other:
- INPUT: wheel speed sensor input
- uC: Minimum speed threshold for throttle to be allowed
- Display: Speed
- Display: Distance
- Display: Battery % (based on simple voltage reading, normalised to give SOC estimate for LiPo ie. 60%, 70% 80% etc.)
- Display: Power (display current power consumption when moving, maybe peak power when stopped)

If I restrict the features to this, I wonder if it could fit on the little ATTINY261.
Is there still room to do the other things like, peak amps, min voltage, wh, Ah, wh/km. Happy to leave wheel sizes, limits etc hard coded at the moment.

What do you think umejopa, full-throttle? How hard is this?

- Adrian

 

[adrian_sm]

Ride Stats:

Dist: 15km
Ah: 9.585 Ah
Wh: 175 Wh
Amps peak: 124 Amp
Power Peak: ~2400 Watts

Comments:
- I used the assist a lot for the first half like my normal ebike, then started trying to use it more as an assist, just when needed, like hills, or in fast traffic.
- The dead stop adjustments moved during the ride, allowing the ride to over-engage and slip. Ooops.
- ESC was cool at the end of the ride
- Motor warm to touch, but not hot
- Battery LVC alarm sounded just at the end of the final hill
- I don't really like the twist throttle and gear shifting on the same side of the handlebars.
- The ramp control works well
- It needs power limitting to be a bit more refined



- Adrian

 

[Hillhater]

wow ..Adrian ? ... 124A on which ESC ..???

 

[adrian_sm]

Remember that was only a peak, I was never drawing those sort of amps when ever I looked at my watt meter.

I am running this bike with the TURNIGY K-Force 100A Brushless ESC.

Been good so far.

 

[adrian_sm]

Update: Letting others have a go

I let a few people at work have a go on the bike, and of course something broke. The deadstop that limits the engagement with the tyre bent. It is a Little M4 screw and I currently have a temporary spacer out of plastic under it's head (Don't ask why). This provided no support to the head, and over time it bent sideways. Allowing the drive to over-engage, slip, and stopped free pivotting of the swing arm, just when full-throttle jumped on to have a go.

Thanks to full-throttle who let me make a metal spacers quickly in his nearby lab, so he got a chance to have a quick hoon around the car park. Means I can get home too.

Comments I got from people that rode and those that just looked on:
Q: How quickly will it wear the tyre?
Ans: Really quickly when not adjusted properly. But when set up to not slip, maybe 2-3 times as fast as normal wear due to contact with the road.

Q: Is it water proof yet?
Ans: No, not yet. But that is the plan.

Wow it's light compared to my ebike.
Ans: That's the point

Q: How far will it go on those batteries?
Ans: Same wh/km as your other ebike, if you ride it the same way.

I would still ride it full throttle everywhere, even if you say it is just meant to be an assist.
:lol:

Q: How fast do I need to be peddling before I can hit the throttle?
Ans: Walk speed.

Doesn't seem to give much power at low speed, but once you get up to speed you can really feel it.
That's just the power curve of the motor, peak power is at half the no-load speed.

Did you make that? I thought you bought it from FrictionDrivesAreUs.com
Ans: Yep

Q: So how much?
:lol:

Q: Aren't LiPo's the ones that have a tendency to go up in flames? Where do you charge them?

It is not quiet. I don't know if I would use it on bike paths. But I guess if it was legal, it would be alright.

Other observations:
- ESC was warm to touch. Obviously the low speed accelerations around the parking lot, give it a bit of a harder time
- motor was cool

So what did I learn:
1) I need smarts to stop people going full throttle from a dead stop
2) I need to slow the acceleration ramp rate a bit more
3) Drive adjustment is critical
4) I need lots more kms of testing, to iron out bugs
5) It is embarassing to have things break as soon as you let someone else have a go.
6) I think I'll need to have a power limitted legal set-up if I am going to let others ride it

- Adrian

 

[rj7855]

Remember that was only a peak, I was never drawing those sort of amps when ever I looked at my watt meter.

I am running this bike with the TURNIGY K-Force 100A Brushless ESC.

Been good so far.

@Kepler, you were using the Turnigy Brushless ESC 85A w/ 5A SBEC with the same motor?

@adrian, What is (+-) the amount of movement between the idle and engagement stops?

I may be able to contribute a bit to the project, while I suck at metal working (and therefore probably unable to recreate the mounting hardware) I do have 30 years of experience with electronics and 25 in programming. I have made current sensing in the 100A range before... if I can find that design it would be easy to hook it up to an Atmel microcontroller in order to dynamically adjust throttle power. (it also could safeguard against "full throttlers" by limiting the ramp up of rev. up speed) it should not cost more than $20 to make.

 

[Kepler]

Yes I have used the 85A ESC with this motor. Worked fine but it did get quite hot at times. Also its a pain program. I prefer the 100A K-Force.

 

[rj7855]

Yes I have used the 85A ESC with this motor. Worked fine but it did get quite hot at times. Also its a pain program. I prefer the 100A K-Force.

the problem is the 100A K-Force being on backorder at hobbyking. Did you test that 170KV motor yet, I´m very interested to know if that one would be the better option for me ( lower KV means less top but more torque and I have plenty of hills but no room for speeding on my commuter route )

 

[adrian_sm]

Other comments I remembered on the ride home:
- I can't believe how small the controller is!
- it is all so small
- hey I could put the bike on my bike rack with this setup
- how much power?
- so how does it compare to Kepler's?
- how does it work?
- my hub motor alone weighs 7kg

@ rj7855

You don't need more torque with these drives, actually you probably want to limit the torque if anything. The main advantage of the lower kv motor i see is it allows you to safely use a higher voltage battery. Going from 5s to 6s will give you an extra 20% capacity. Which I could have really used on my ride home, I used the full capacity of the battery again.

 

[Kepler]

Been experimenting with the a_sm pivot arm design.

In general, so far I quite like the concept. Having the luxury of laser cut parts and a lathe at my disposal, I have made a few design changes but kept the concept basically unaltered. Main reason for the changes are that l felt the 10mm plate didn't have enough meat to support the 10mm pivot shaft under load and also the 10mm plate is quite difficult to work with. I know that Adrian has not had any issues with the pivot shaft supported by the 10mm pivot plate so it does obviously work. However, I felt more comfortable with 20mm of aluminium supporting the pivot shaft. In an effort not to make the pivot arm to bulky, I decided to laminate 2 x 4mm plates and machine a 12mm boss to support the pivot shaft.

Here's what I came up with.

 

[adrian_sm]

Oooo, evolution. Looks nice and solid Kepler.

 

[Kepler]

Yes I have used the 85A ESC with this motor. Worked fine but it did get quite hot at times. Also its a pain program. I prefer the 100A K-Force.

the problem is the 100A K-Force being on backorder at hobbyking. Did you test that 170KV motor yet, I´m very interested to know if that one would be the better option for me ( lower KV means less top but more torque and I have plenty of hills but no room for speeding on my commuter route )

170 kv motor still hasn't arrived Hopefully have it this week. I will report on how it goes on this thread (if Adrian doesn't mind) as this is the happening friction drive thread

I didn't realize the 100A was out of stock. I bought 10 of them recently (sorry about that).

The K-force is just a re badged Hobbywing Plantanum Pro. http://www.hobbywing.com/english/ArticleShow.asp?ArticleID=442 Maybe have a look for one of these.

 

[full-throttle]

Impressive work Adrian!

Thanks for letting me test ride the drive today, thought I may share my thoughts with the other readers:

When the drive is not engaged the bike feels very light, the whole package is not much heavier than 2 full drink bottles.
The assistance at low speed is not as immediate as with hub drives and the initial engagement might take a little to get used to.
Once at speed the drive is stunning! I simply run out of room, it was still pulling hard.
The noise is a bit of an issue, mostly to the 'spectators' - if you use it you will get noticed.
The strong poins are: low weight, low cost and ease of installation - the whole drive can be put on / taken off faster than it would take to fix a puncture on a wheel with a hub motor.

Ideally it would suit a fair-weather rider looking for some assistance at speed, especially if this person has only one bike (thanks to quick conversion between assisted and normal), inner-city or limited space perhaps.
Another use would be is to carry it on a long rides as some sort of emergency assistance to lesser fit companion

 

[adrian_sm]

Thanks full-throttle. Yeah this no assist from a stand still is an interesting one.

I didn't realise how much I like it it with my hub motor.
- Means I don't have to change down as many gears when stopping
- get away quicker at lights, so don't hold up traffic
- basically you get the assist at all speeds, right from the get go, you don't feel like you have to change your riding style to suit the electronics.

But these friction drives just aren't suited to it. Maybe with halls, and current limiting it could do it.
But it is a totally different riding experience with the friction drive. It really does encourage you to pedal, it's weird. I think as the throttle interface, and smarts advance they will be more seamless.

I still need to tweak the initial engagement, this is all controlled using a little throttle ramp controller at the moment which I haven't had time to optimise. But Kepler's system is a lot more advanced, and would have less down sides than my method.

Noise is the other biggest issue. When the drive is pumping out the power, you can definetely hear it. Quite a contrast to the relative silence of a direct drive hub motor.
I am really keen to see how much quieter it is when I restrict power. I was doing this on the ride home by easing up on the throttle, and it make a big difference to noise levels. Maybe if I restrict it to 1000w, or 750w, or even... ... 200w it will be a bit stealthier. Time will tell.

Now off to get my head around assembler code for the attiny...

 

[jbond]

I didn't realise how much I like it with my hub motor.

Finding the thread fascinating and not wanting to hijack it, but. I wonder how stealthy, light, simple and usable a hub motor setup could be made. Use the lightest Bafang with one of Lyen's 6FET controllers and something like a 24 or 36v A123 or Lipo, 5AHr pack. Overall weight is going to be more than your setup, but not a whole lot more. The bit I'd like to see is some of the RC-style controller effort put into this to offer a current limited "Economy" mode and perhaps Kepler's work on a simple button control. Current limiting can be done with a CA, but if you don't need all the other CA stuff, it should be possible to do the current limiting with a pretty simple circuit.

 

[full-throttle]

Good question jbond,

Even with the smallest motor (Ananda 85 or Bafang Jewel) and the smallest controller (lsdzs micro) the whole system would be heavier and not being able to completely disengage nor taken off easily. The controller on Adrian's drive is size of a matchbox! There's also additional expence and work inwolved with buildimg a wheel. There are advantages as you said.

BTW simple power limiting has been done - I've made 5 boards last year that are still being used AFAIK

 

[adrian_sm]

Very good debate. Once you start limiting the friction drives to legal power levels, one of the really small free wheeling hubs in the front is a really compelling alternative. The major advantage i see is being less failure modes for the average consumer. The friction drives really need to be set up right for them to work nicely. And if this is being done by a novice it is quite likely they will get it wrong. No such issue for a hub motor, just need to make sure the fork can take the loads.

 

[hillzofvalp]

I didn't realise how much I like it with my hub motor.

Use the lightest Bafang with one of Lyen's 6FET controllers and something like a 24 or 36v A123 or Lipo, 5AHr pack. Overall weight is going to be more than your setup, but not a whole lot more.

I would really like a minimal build and first thought of the friction drive. Though after seeing Adrians progress I decided that it wouldn't fill the bill for my audible noise needs.

I plan on trying this with my new Aluminum cannondale build. Going for 48-72V though with 18650s, but maybe just 36V with 26650s. Goal is to run it with one chain ring, one downtube shifter, and a bafang or something. Hoping for sub 30 pounds. Will keep everyone updated, but I sure wish I could make that HV 160 work well with a hub motor. Regarding the fixation of torque arms--- can I do this on a carbon fork?

 

[rj7855]

Noise is the other biggest issue. When the drive is pumping out the power, you can definetely hear it. Quite a contrast to the relative silence of a direct drive hub motor.
I am really keen to see how much quieter it is when I restrict power. I was doing this on the ride home by easing up on the throttle, and it make a big difference to noise levels. Maybe if I restrict it to 1000w, or 750w, or even... ... 200w it will be a bit stealthier. Time will tell.

Much of the noise produced is directly released to the way the motor is being controlled ( sensorless, square wave commutation & pwm ) while we using RC ESC´s there will be not much that can be done about it but with a custom ESC it would be possible to greatly enhance the acoustic properties of the setup. As I´m waiting for the arrival of all ordered electronic parts of my current-limiting controller I have started the design of V2, an ESC with build in controller. The aim of this ESC is to counter the shortcomings of the RC ESC´s, mainly motor startup and drive noise. In the mean time you could try to see if changing the PWM frequency of your ESC makes any difference; The sound could improve on another PWM frequency if the currently selected freq. is close to the resonating frequency of the motor or friction drive mount.

 

[adrian_sm]

Regarding the fixation of torque arms--- can I do this on a carbon fork?

Carbon forks would scare me. What is the actual drop out where the axle rests made of?

 

[adrian_sm]

Much of the noise produced is directly released to the way the motor is being controlled ( sensorless, square wave commutation & pwm ) while we using RC ESC´s there will be not much that can be done about it but with a custom ESC it would be possible to greatly enhance the acoustic properties of the setup. As I´m waiting for the arrival of all ordered electronic parts of my current-limiting controller I have started the design of V2, an ESC with build in controller. The aim of this ESC is to counter the shortcomings of the RC ESC´s, mainly motor startup and drive noise. In the mean time you could try to see if changing the PWM frequency of your ESC makes any difference; The sound could improve on another PWM frequency if the currently selected freq. is close to the resonating frequency of the motor or friction drive mount.

What magic games do you plan on playing to reduce the noise? Sine wave? Higher PWM frequency?
And what is the plan for low speed start-up? Halls? Or just a different sensorless algorithm.

I don't think my motor is hitting the resonance in my mount or frame, the volume is fairly consistent across different speeds. Once I dial down the power a bit, the sound will be reduced. But to be honest it isn't that bad, just not stealth like a hub motor.

Thanks for the tips though. I might try the other frequency setting and see what it does.

- Adrian

 

[hillzofvalp]

Dropouts are aluminum. Might stick with rear hub motor.
(wrong thread? whoops)

 

[rj7855]

What magic games do you plan on playing to reduce the noise? Sine wave? Higher PWM frequency?

Both Sinewave using a pwm at 96KHz, I hope to get some Toshiba tb6582fg soon (the only chip I could find that does sine wave on a sensorless motor) if I can't get those chips I will (try to) implement it in a existing controller. (in that case I might even try to change the motor to WYE for low speed and change it during spinup to DELTA

And what is the plan for low speed start-up? Halls? Or just a different sensorless algorithm.

I want to avoid halls (more wires, difficult to allign....ect)... the Toshiba chip can sense EMF from about 3,5 km/h and further planning on dynamically limiting current in low rpm so a user could full throttle but the controller will limit it to a reasonable maximum that depends on rotation speed and current