New build. Full carbon 29er weight weenie Super Commuter.

[Samd]

Lycra trolling level: Expert.

Great story Kepler!

 

[Kabbage]

Love the bike Kepler, a couple of questions;

What rating is the motor? (I assume it's 250 or 350W right?) but what power are you actually pumping through it? You are running it at 75V, 15A max, so around 1000w max?

I have the 500W BPM motor, which is a little bigger, from memory - but I really like how small yours looks. I am running at 48V 25A - could this result in similar overall performance on your motor? (I assume your higher voltage would allow higher top speed - hence your torque wind?)

are you running it sensorless, or does it have halls?

Also, where did you get the motor from (local in Melbourne?)

 

[Kepler]

Thanks Kabbage,

The motor is rated at 36v 250W. I am running it at a max 750W so around 10 or 11A. Most of my riding is done at around 450W and switch to 750W if I want to maintain speed up a hill or feel like a bit of high speed cuising. So far the motor only gets warm but never hot so I think it could handle a fair bit of operation at 750W.

With a 700c wheel and 75v it will wind out close to 50 kph which is plenty fast enough for this bike especially with a 72 deg head angle.

Motor is sensored and I bought it off Ben Moore who is on this forum and Melbourne based. He sells them $130 which considering you don't need to pay freight, I think is a fair price.

 

[Kabbage]

Thanks Kepler, appreciate your responses mate....

I got my BPM from BenMoore also, turns out he lives around the corner near my kids school. Easy. And $130 is a bargain, really.

Of course all of this makes me think of more questions; sorry.

Spokes? Customs? Where did you get yours from. I have had some great spokes from JRH, but I also see that Gloworm in Sydney is now doing custom spokes (no Sapim, but DT Swiss at least).

Also, what did you do for your rear cluster? I assume this motor still takes freehub (is it freehub or freewheel, I always get them mixed up? the one without the spline). How did you match your hub up with your shifter? This has always proved to be a PITA for me, first I got a 8-speed cluster from ebikes.ca, but was advised (by FT) to try locking out the rear and going to a 3-speed using front only - works much better for me.

 

[Kepler]

Usually just get the spokes, rims, and nipples from Ben. He also has 7, 8, and 9 speed crew on clusters. Spokes and nipples are good quality a rarely break any even on the Fighter. Only using 14# too. If I need custom lengths, I usually go to Cycle Science in Glen Waverley.

I like having a full range of gears but it takes a bit of mucking around to get it all to work smoothly and reliably. Important thing is to match the gear count with the correct shifter. Using a nine speed shifter on an 8 speed cluster works, but always ends up with few gears that dont select perfectly. Also if using an 8 Speed, dont use a 9 / 10 speed chain. Get a 7 / 8 speed chain. Its a bit wider and will shift better on an 8 speed cluster.

 

[Kepler]

Having the CA3, I thought I might try a torque sensing bottom bracket rather then a speed PAS. Was a bit of a gamble as I couldn't modify the fame or drill any holes if needed. Luckily the bottom bracket housing has a 4mm drain hole in it which was just big enough to slide the torque sensor wire through. Also needed to lift the controller by 3mm so the torque sensor wire could run underneath it. Picked up a 5 bolt spider to suit the square taper bottom bracket and ratted a 52 tooth chain ring from my road bike.

So far so good.. Everything fits and lines up so now it just leaves wiring, programming, and testing. Looking forward to how this goes as it has been something I really have wanted to try. Will also be interesting to see how much better it is compared to a speed PAS and whether it really is worth all the extra cost and effort.

 

[Whiplash]

Hmm very interested in this as well, I think it would be great for trail riding to keep your hands firmly planted on the bars all the time instead of reaching for the throttle all the time. Would be much more seamless as well!

 

[Kepler]

Managed to get a run out of the bike yesterday with the torque sensor in operation. Took a bit of time to work out the settings but managed to work most of it out. I need to modify the CA3 so that i can run 18S with the torque sensor. The CA internal voltage reg doesn't have enough capacity to handle the extra current draw of the torque sensor at the higher voltages. Got around this for now by just running 12S. Working through some hacks on CA3 thread to get back onto 18S though.

So to the riding experience. Firstly, very different to running an RPM base PAS which basically works like a throttle on off switch. If pedalling is sensed, it sends full throttle to the controller. This works OK on low powered setups and can even work on medium power setups (up to say 2kW) but you need to be very careful and aware that the bike might give you full full throttle at times when you dont really want it. I also find that this type of PAS is not conducive to getting some exercise or improving economy as even a bit of ghost pedalling will give you full throttle. I did get around this though by using the 3 speed switch and setting the current limit nice and low when using the PAS.

The torque sensor is completely different. Assist is proportional to how much pressure you are putting on the cranks regardless of cadence. So if pushing really hard in a tall gear, you will get max assistance from the motor. However, if pedalling lightly, the assistance will be very low or even non existent. This promotes pedalling effort by rewarding you with assist if you are willing to increase your pedalling input and in turn equates to improved economy and range. I still have the throttle button and can push this any time for a boost if feel the need for it.

Of course all this is very tune able and you can set the assist to human torque ratio to what ever you like. You can also offset the torque input so that rather the assist starting from zero torque upwards, it starts from say 10 Nm upwards giving you a window that you can pedal in without any assist at all.

Other features I really like are that you can now see how many human Watts are being applied and how much assist is being applied together with totalised stats as you go.

So to negatives. The fact that the CA3 requires modification to run above 48V with the torque sensor is a pain. To be fair though, high voltage and pedal assist usually dont go together.
A square taper bottom bracket with plastic screw in end caps doesn't scream quality and strength. Again probably fine for the target market but a strong off-road rider I think would soon find the mechanical limits of this device.

Anyway, I will keep on testing and tuning today. As far as pedal assist goes, there is no doubt that this set up is worth the time and effort over a basic RPM PAS.

 

[full-throttle]

Nicely done Kepler!

Your bike is becoming more and more of a pedelec. Or s-pedelec I should say

 

[-dg]

If the pedal assist is proprotional to the force on the pedals does it vary depending on pedal position? That is, mid stroke with the pedals horizontal there is a lot of force, but when the pedals are vertical there is little torque. If the CA simply amplifies the applied torque it seems like it would sort of surge and relax as the pedal force varied. Or does it try to integrate or smooth the sensed torque to produce a steady throttle signal?

 

[pendragon8000]

Nice one Kepler, pity about v limit.
Have u thought about rpm x torque = power? Seems like you can have one or the other? If you pedal fast in low/slow gear there will be less torque, so that would call for button pushing?
Edit
Btw the CA v3 has a 12v pin somewhere if that has enough current for torque pas...
Sorry 10v not 12.

The CA internal voltage reg doesn't have enough capacity to handle the extra current draw of the torque sensor at the higher voltages.

I see. That is the 10v pin. Bummer

 

[Kepler]

If the pedal assist is proprotional to the force on the pedals does it vary depending on pedal position? That is, mid stroke with the pedals horizontal there is a lot of force, but when the pedals are vertical there is little torque. If the CA simply amplifies the applied torque it seems like it would sort of surge and relax as the pedal force varied. Or does it try to integrate or smooth the sensed torque to produce a steady throttle signal?

The CA averages the torque over each crank revolution to smooth this out. It does take a bit of tuning to get it spot on though.

 

[Kepler]

Nice one Kepler, pity about v limit.
Have u thought about rpm x torque = power? Seems like you can have one or the other? If you pedal fast in low/slow gear there will be less torque, so that would call for button pushing?
Edit
Btw the CA v3 has a 12v pin somewhere if that has enough current for torque pas...

I thought the same thing in relation to needing more assist with higher cadence and as such needing to take both RPM and torque into account. However, now that I have riden this type of setup, its quite obvious that torque is the only input you need. Basically the assist is all about reducing effort. If you can spin the cranks at a high rpm but under low load, then you aren't working hard anyway and dont need much assist.

I am not sure if setting to RPM mode on the CA works with the torque sensor and thought it was only for when you had a magnetic ring PAS installed. Might be wrong though, it might give proportional assist with RPM.I will give it a try today.

In relation to voltage taps in the CA, it has a 10V for the torque sensor and a 5V for hall throttle etc. Problem is that the torque sensor puts a high load on the CA. This is compounded by running higher battery voltages which in turn down rates voltage reg.

 

[-dg]

If the pedal assist is proprotional to the force on the pedals does it vary depending on pedal position? That is, mid stroke with the pedals horizontal there is a lot of force, but when the pedals are vertical there is little torque. If the CA simply amplifies the applied torque it seems like it would sort of surge and relax as the pedal force varied. Or does it try to integrate or smooth the sensed torque to produce a steady throttle signal?

The CA averages the torque over each crank revolution to smooth this out. It does take a bit of tuning to get it spot on though.

Is this tuning part of the supplied CA firmware, or is it something you tune to your particular cadence? Also, it seems that if it knew position in addition to torque it could do this more easily/precisely. Does it use both, or is the choice of sensor either/or but not both?

 

[Kepler]

I am not sure if setting to RPM mode on the CA works with the torque sensor and thought it was only for when you had a magnetic ring PAS installed. Might be wrong though, it might give proportional assist with RPM.I will give it a try today.

Gave this a test. It will run in RPM mode but doesn't give you proportional assist based on rpm. It just operates like a standard magnetic ring PAS. One thing though, it was responsive and would start and shut down power without that annoying run on delay a magnetic ring PAS tends to give you.

 

[Kepler]

If the pedal assist is proprotional to the force on the pedals does it vary depending on pedal position? That is, mid stroke with the pedals horizontal there is a lot of force, but when the pedals are vertical there is little torque. If the CA simply amplifies the applied torque it seems like it would sort of surge and relax as the pedal force varied. Or does it try to integrate or smooth the sensed torque to produce a steady throttle signal?

The CA averages the torque over each crank revolution to smooth this out. It does take a bit of tuning to get it spot on though.

Is this tuning part of the supplied CA firmware, or is it something you tune to your particular cadence? Also, it seems that if it knew position in addition to torque it could do this more easily/precisely. Does it use both, or is the choice of sensor either/or but not both?

Tuning is all built into the CA firmware. It even has a pre selected Thun bottom bracket option that pre sets quite a few of the parameters for you. I found in hindsight most of the presets we very close to optimum anyway.

Not quites sure what you mean about knowing position and torque but the thun torque sensor has an 8 pole postion sensor built in and uses this to calculate cadence. With torque applied averaged over each revolution, power delivery is quite smooth even when you stand hard on the pedals in a high gear. This feels great when riding the bike and gives you the felling of super legs as the high human effort is quickly rewarded with max assistance and in no time you are accelerating like a pro rider.

Pushing really hard on the pedals, I can match my 750W assist for about 15 Seconds. 1500W out is Pro rider territory and having the seamless delivery of the torque sensor has me kidding myself its all me :lol:

 

[-dg]

Tuning is all built into the CA firmware. It even has a pre selected Thun bottom bracket option that pre sets quite a few of the parameters for you. I found in hindsight most of the presets we very close to optimum anyway.

Not quites sure what you mean about knowing position and torque but the thun torque sensor has an 8 pole postion sensor built in and uses this to calculate cadence. With torque applied averaged over each revolution, power delivery is quite smooth even when you stand hard on the pedals in a high gear. This feels great when riding the bike and gives you the felling of super legs as the high human effort is quickly rewarded with max assistance and in no time you are accelerating like a pro rider.

Pushing really hard on the pedals, I can match my 750W assist for about 15 Seconds. 1500W out is Pro rider territory and having the seamless delivery of the torque sensor has me kidding myself its all me :lol:

Thanks for this information, that is exactly what I was hoping for and goes a long way to justifying the expense of the Thun BB. I have one of the Aerovironment Charger bikes which is frustrating because a lot of the bike part is kinda janky, but the pedal torque sensing control is awesome, it feels like riding a tandem with Lance Armstrong (you know ... legs totally enhanced).

How well do you think this would work on cargo bike with a BPM or MAC? Could I get away with no throttle and just have a couple buttons for high and low levels of assist?

Does the Thun BB look reasonably reliable mechanically, ie similar to other square taper BBs?

 

[Kepler]

It would work very well on cargo bike with a BPM or MAC and you could certainly get away without a throttle. If you use it with a CA3, you can use a 3 way switch to set the amount of assist that suits. You can also set 3 profiles on the CA3 that allows to swap between on he fly. So many options.

 

[Nusse]

I would like to build something similar to your bike. 40 km/h ( which probably requries ~500W without pedal) would be enough for me.
Do you know the maximum speed with 12S?

 

[Kepler]

I have the torque version on this bike which is 201RPM version. Does around 35kph on 12S on a 700c wheel. Not too bad and for most of the time, quite acceptable. I believe you can get the 260RPM version of the SWXH which should have you at 40kph. 500W will get you 40kph on this type of bike no problems.

The high torque and 18S kind of gives you the best of both worlds and allow you to wind out to 50kph when you want to. I have my current limit set at 750W which is what you need to maintain 50kph.

 

[Kepler]

Minor motor issue has crept in. Running a fair bit of 750W through the motor and 70V. The motor electrically is doing really well and doesn't get too warm. Also the gears hare coping fine with this level of power and as still quiet.

However, the sprag clutch or one way clutch as locked up so it no longer free wheels. Surprisingly the wheel still spins down quite freely; certainly better then the big DD hub motors I have used.

Still, something I need to fix so it looks like a job for today will be to manufacture a tool to open up one of these motors. Should be a good exercise just to inspect the windings and gears after the first 500km of operation

 

[pendragon8000]

it looks like a job for today will be to manufacture a tool to open up one of these motors.

like a gear puller. i made a ghetto one from a scisor jack. im sure yours will be allot nicer than mine.

 

[headwind]

Hi Kepler,
Thanks for all the info you've posted in this thread, it has been very helpful. Hope your clutch repair goes well.

Can you suggest which LiPo batteries to use and where to get them from? My goals are stealth mounted (something like battery bottle or your seat bag setup), 12S and around 4Ah. The reason for small capacity is the amount I pedal means I run at 10 Whr/km and I'd like to swap between 2 batteries (so that I have a charged spare battery ready to swap in).

Thanks,
Simon

 

[Kepler]

Thanks Simon.

I tend to use Turnigy batteries from Hobby King as I think they give you good bang for you buck.

Keep in mind if 4ah is what you are after, go with 5 ah and leave 20% for safety and battery longevity.

 

[headwind]

Cool, thanks for the info.