Commuter Booster - <1kg Friction Drive

[adrian_sm]

That is a great idea, for a booster all you would really want are maybe three different throttle positions: off, hi speed, lo speed. Adrian, you are designing a brilliant drive, and super stealth.

Thanks. I like the idea of a button throttle in theory, but will depend on how it works in practice. On my other bikes 95% of the time I an either full throttle, or nothing. But I think I won't quite grasp how much I appreciate that other 5% until it isn't there.

You could probably tell a cop it powers a light on your handlebars and he wouldn't think twice IMHO. That would help you get by the ridiculous watt limit you guys have there.

Very nice idea. :lol: Infact the ESCI have has a 5.5V 5Amp output, that I was planning on using for my lights. Perfect excuse.

[EDIT] Fixed typo.

 

[adrian_sm]

I am sure you know that you can convert your Turnigy servo tester into a throttle interface ( for pot or hall) very easily.
Details are on the forum.

Yeah, I did realise, but thanks anyway. In fact that is why I picked the $6 servo controller I did. The problem is really finding a nice place to mount a throttle on a road bike handle bars. All my current ideas end up being more complex than the entire motor drive system. Some sort of trigger throttle would probably be my ideal. But bloody hard to make it ergonomic and universal enough for all handle bar types.

Maybe just a combo of the buttons, for high/low/off, and keep the servo controller pot to adjust things on the fly.
Or full-throttle was keen on doing this with a uController, instead of a physical potentiometer in the servo-controller.

I think Kepler has something along these lines in the pipeline that I am sure will surface shortly. If I procrastinate long enough he will have hopefully solved all my throttle woes.

I am sure it will be much more clear once I have some road time on the bike.

- Adrian

 

[Hillhater]

Yes i agree, there is no easy solution readily available ..yet !
So, have you tried a low speed start or acceleration under load yet ?
( sync failure under load has halted me until i find a better ESC ..or spring for the Castle ! )

 

[adrian_sm]

Nope, not since I put the grip tape on. Too busy with work and kids. Might get a chance in the dark tonight once kids are in bed.

But this drive was never designed for low speed starts. The controllers aren't designed for it, and the motor has crap efficiency so will dump all the power into killing the motor rather than going forward. This is probably why Kepler's new smarts will stop someone from hitting the throttle unless you are over a threshold speed.

The other option I will probably try at some stage is a little 6-fet bike controller, either sensorless or sensored. I have a sensored one on my main bike that has been great, and from the look of some recent testing it might be up to the job on a little outrunner like this.

- Adrian

 

[Kepler]

I think Kepler has something along these lines in the pipeline that I am sure will surface shortly. If I procrastinate long enough he will have hopefully solved all my throttle woes.

I am sure it will be much more clear once I have some road time on the bike.

- Adrian

One of things I identified a while back was how useless standard twist and thumb throttles were for many bikes in relation to fitment. Good news is we have already included a button throttle in the design. Hardware is sorted. We are just working on the logic at the moment. We are looking to cover a single button arrangement and dual button attangment.

Preliminary logic with a single button arrangment logic is as follows:

Throttle will be completely off if the button isn't pressed
Press and hold => motor ramps smoothly to 40% throttle
Release and quickly press and hold again => motor ramps up a further 10%
Repeat the quick realease and press to continue increasing throttle by 10% increments until full throttle is reached.
Release the button for more then 2 seconds and the throttle goes back to zero.

A two botton throttle works in a similar way except the second button gives you a 10% decrease in throttle.
Any of the 2 buttons would hold throttle
Releasing any of the 2 buttons for more then 2 seconds would return the throttle to zero.

I think the single button arrangment will be quite adequate for a friction drive. Will be doing some testing in the next few weeks.

If anyone has any other suggestions in relation to a different logic for a button throttle, I am very keen for the feedback

 

[gtadmin]

Releasing any of the 2 buttons for more then 2 seconds would return the throttle to zero.

Wouldn't that be both buttons?

 

[full-throttle]

That's a nice and simple approach. As long as the brakes can overpower the motor in emergency type situations. 2 seconds could be an awful long time if a car/kid/dog runs in front of the rider unexpectedly (happens all the time) A brake sensor would solve that. How would you make an universal one though??

The other thing: buttons can be uncomfortable to hold down for extended periods of time. Some are not even designed for such things (the spring weakens)

Have you considered a PAS (pedal assist sensor)? One that provides a 0-5V (or 1-4V) proportional to the cadence.

 

[umejopa]

..and being made of plastic won't even damage the paint, right?

Your friction drive is a very elegant and simple alternative. What are you going to do against the road grit ingress?

BTW feel free to borrow the throttle interface, it works with both pot and hall throttles AND the code now runs on the Turnigy meter which is extremely easy to hook up to throttle, making it an inexpensive monitor at the same time. Here's a teaser

Good work to make throttel inteface of a watt meter What uP is in it ? Have take my apart now
Can I borrow some code from you full-throttle ??

We get snow now so I hade to muth slip on drive :| Have to try to put some griptape on my motor now.
//Jonas

 

[spinningmagnets]

Beautiful work! I like it.

I have lots of extra capacitors and you can have two if you like (the shipping to me, cost more than the capacitors!). You may encounter some heavy PWM-mode when accelerating with a load. I believe I have the same ESC (Turnigy 85A), but I have not ridden it yet (throttle to arrive soon, can't wait!).

It would be a shame to fry a $40 ESC for lack of $3 worth of caps! The worst part is having to wait another 2 weeks for a second ESC to arrive...

 

[Kepler]

Releasing any of the 2 buttons for more then 2 seconds would return the throttle to zero.

Wouldn't that be both buttons?

Yes I mean both. Off cause you are only pressing one button at a time.

 

[Kepler]

That's a nice and simple approach. As long as the brakes can overpower the motor in emergency type situations. 2 seconds could be an awful long time if a car/kid/dog runs in front of the rider unexpectedly (happens all the time) A brake sensor would solve that. How would you make an universal one though??

The other thing: buttons can be uncomfortable to hold down for extended periods of time. Some are not even designed for such things (the spring weakens)

Have you considered a PAS (pedal assist sensor)? One that provides a 0-5V (or 1-4V) proportional to the cadence.

Friction drives are not to hard to overpower with your brakes in an emergency however, we have brake sensor inputs built in. Hard to make them univeral though. Just using a hall sensor input for this.

As these drives are typically hill assists rather then full time assist, the switch is only being used for a short period of time. I have used a simple button setup before and actually found it quite compfortable as you arn't chasing a postion to hold it in. Also looking at using a pressure sensitive strip rather then a button.

Lots of options to test. PAS is already to go also to meet our stupid Australian requirements in the near future.

2 Seconds may prove to be too long for de activation. This off cause will be optimized during testing.

Should have the code by the end of the week so looking forward to some more testing.

 

[adrian_sm]

Okay time for a major update. I took the bike on the ride to work this morning for it's first major shake down.

Good news:
- it worked
- ~50kph on the flat
- ~40 kph up hill, with pedalling
- totaly disengages when not in use, and feels like a normal bike
- able to tune engagement to avoid slipping

Bad news:
- I think I cooked the motor

Here is the summary

First ride with anti-slip tape on motor.
15km ride to work, through usual mix of rolling hills, and gentle slops.
Needed to adjust the drive engagement, as slipped first time I tried to go up a decent hill.
Strangely this actually twisted around the seat post slightly, which I hadn't expected.
Using the servo controller as a throttle was .. hmmm.... lets say, less than ideal.

So what did I learn from the first shake down:


1) Throttle
- feel like I want a torque control rather than speed control.
- issue is that if you go faster than the set motor speed, the drive disengages. Then when speed drops the motor doesn't re-engage.
- with a torque based throttle, it would keep increasing the motor speed to keep drive in contact.
- so this implies some current sensing control loop

2) Softer Deadstops
- both limit stops need to be softer.
- full engage stop can hit hard if you increase throttle quickly, soft start may help. Currenlty this is a hard stop
- full disengage stop can hit hard if you suddenly release the throttle, as the wheel spits the motor back out. Current stop is a rubber tube with ~2mm wall thickness over the head of an M4 scap head screw.

3) Drive Engagement / Pick-Up
- slowly increasing the throttle may not engage the drive properly
- could improve the spring balance, and reduce main pivot friction with non-journal bearing, to imporve pickup
- could uControl initial throttle to ensure enough torque to lift motor in to tyre
- could nominally have light contact with tyre

4) Power Limiting
- I cooked the motor
- need some way to protect the motor from over temperature events.

Here is what happened.
- I was about 10kms into the ride, only occasionally using the drive.
- Was starting to get a feel for when/how to use the drive, so started want to find out what it could do.
- First test was flat road/no pedaling speed. ~48kph
- then sat at the lights for a bit 1minute or so.
- Up hill test, pedalling @ 40kph, ~1km
- Round corner, another up hill, engage drive, little bit later suddenly drive kicks itself out, no power.
- pull over to side of road, lift wheel, apply throttle, motor stuttering back and forward
- ESC warm not hot
- motor hot to touch, IR temp sensor says 75C on pivot arm that has good face contact with stator.
- I did have a temperature/LVC alarm hooked up, but it wasn't getting an accurate measurement of the motor, as the sensor had lifted off the aluminium swing arm that mounts the stator.
- Looked at the watt meter stats. ~ 100wh, ~ 125 Amp Peak, ~ 2600 Watts peak. Ouch that's a bit more than I was expecting.
- no time to trouble shoot so, just rode to work.
- joined up with a couple of cyclist from work at the final hill climb to work, and easily kept up with them as the drive is totally disengaged. I would have really struggled with my Giant dual suspension hub motor ebike.

Just had a look at the motor and it looks like the windings might be toatsted, and shorting.
It is difficult to turn over by hand now, in a walking through mud type of way.
ESC looks fine.


Well that was fun. :lol:

- Adrian

 

[adrian_sm]

If anyone has any other suggestions in relation to a different logic for a button throttle, I am very keen for the feedback

You are light-years ahead of me, as I only have about 20 minutes of friction drive experience, but here is my 2 cents worth of ideas.

1) Torque Throttle (not button logic related specifically, but hey this is my thread, I'll do what I want)
- throttle could be torque control, rather than speed control
- this will help maintain drive engagement, I think might feel more natural, and more inline with power limit functions.

2) Two button design
- hold both buttons to increase speed/torque
- hold one to lock speed/torque
- release both disengages drive

3) One button design
- hold button to increase speed/torque
- momentary release and hold again to lock speed/torque
- release button to disengage drive

and finally ...

4) Temp Sensor based throttle Override
- ability to limit throttle based on temp sensor input to stop motor overheating.
- will need secondary feedback to user that system is in temp reduced power mode, ie. beeper.

- Adrian

 

[Kepler]

That reads like a journal of the trials and tribulations of the last 6 months of my life. What can I say except "been their"

Well, proof of concept has been established so that’s the main thing. $40 bucks is a small price to pay.

That little motor was never going to survive that sort of load. I would even say 1000W is big ask for that little motor.

See if you can squeeze that 63-74 in. Its worth the extra weight, believe me. Got any 5S packs?

I now use a 63-74 on my road bike (MK2 drive) and it still has the original servo tester interface. I limit it 90% throttle using a resistor across the Currie thumb throttle. That softens up the response a bit and still gives me close to 40kph on a 5S pack. Peaks at about 1500W. Very easy to live with.

 

[adrian_sm]

That reads like a journal of the trials and tribulations of the last 6 months of my life. What can I say except "been their"

I meant to says thanks for all your efforts. I wouldn't be where I am now, without all the hard work you have done. Cheers.

Well, proof of concept has been established so that’s the main thing. $40 bucks is a small price to pay.

That little motor was never going to survive that sort of load.

I was fully expecting to break something on the ride. I would have put money on it being the ESC first. But 6s, on a tiny motor, with no current limit was more than the little guy could handle. Imagine that. :lol: $40 well spent.

I have the same motor with dodgy bearings sitting on a shelf at home, but not much point fixing it up and repeating the same experiment. Need to go easier on it some how, or go for a bigger motor.

So:
- 5s
- less than 100% throttle
- bigger motor
- forced air cooling
- temp based throttle limits
-


Hmmm options options.

Got any 5S packs?

Nope only :
- 2x 2s 1300mah
- 2x 3s 1300mah
- 2x 6s 5000mah

I now use a 63-74 on my road bike (MK2 drive) and it still has the original servo tester interface. I limit it 90% throttle using a resistor across the Currie thumb throttle. That softens up the response a bit and still gives me close to 40kph on a 5S pack. Peaks at about 1500W. Very easy to live with.

40kph, 5s, 63-74 sounds pretty good to me. Will need to modify my mount system a bit, but I needed to put my learnings from this one into a new design anyway. That will make my drive tip over to a weight of ~1.2kg, I'll have to change the title of the thread. :lol:

I would prefer a system that is more robust anyway. So unless I find a elegent way of protecting the little motor, I might just go for the bigger motor that can shed the waste heat a bit better while I play around with the design. Then I can optimise it later.

- Adrian

 

[adrian_sm]

BTW feel free to borrow the throttle interface, it works with both pot and hall throttles AND the code now runs on the Turnigy meter which is extremely easy to hook up to throttle, making it an inexpensive monitor at the same time.

Good work to make throttel inteface of a watt meter What uP is in it ? Have take my apart now
Can I borrow some code from you full-throttle ??

//Jonas

Jonas, I doubt you will get the code from full-throttle, he has spent a bit of time on this and has some plans I think, but you can find the schematics, here, and write your own.

Good luck,
Adrian

 

[adrian_sm]

Beautiful work! I like it.

I have lots of extra capacitors and you can have two if you like (the shipping to me, cost more than the capacitors!). You may encounter some heavy PWM-mode when accelerating with a load. I believe I have the same ESC (Turnigy 85A), but I have not ridden it yet (throttle to arrive soon, can't wait!).

It would be a shame to fry a $40 ESC for lack of $3 worth of caps! The worst part is having to wait another 2 weeks for a second ESC to arrive...

Thanks for the offer, I appreciate it. But I can probably scrounge up some caps myself locally.

For now I am never engaging the dive at low speed for now. Maybe once I stop melting motors I will.

What throttle are you planning on using?

 

[drifter]

Adrian, I think you get some of that heat from the friction of the roller (motor) on the tyre, even more so if there is some slipping. I noticed this with my first drive but didn't do enough rides to collect any data. Kepler would have plenty of knowledge regarding this so I might be wrong.

 

[Kepler]

That reads like a journal of the trials and tribulations of the last 6 months of my life. What can I say except "been their"

I meant to says thanks for all your efforts. I wouldn't be where I am now, without all the hard work you have done. Cheers.

Well, proof of concept has been established so that’s the main thing. $40 bucks is a small price to pay.

That little motor was never going to survive that sort of load.

I was fully expecting to break something on the ride. I would have put money on it being the ESC first. But 6s, on a tiny motor, with no current limit was more than the little guy could handle. Imagine that. :lol: $40 well spent.

I have the same motor with dodgy bearings sitting on a shelf at home, but not much point fixing it up and repeating the same experiment. Need to go easier on it some how, or go for a bigger motor.

So:
- 5s
- less than 100% throttle
- bigger motor
- forced air cooling
- temp based throttle limits
-


Hmmm options options.

Got any 5S packs?

Nope only :
- 2x 2s 1300mah
- 2x 3s 1300mah
- 2x 6s 5000mah

I now use a 63-74 on my road bike (MK2 drive) and it still has the original servo tester interface. I limit it 90% throttle using a resistor across the Currie thumb throttle. That softens up the response a bit and still gives me close to 40kph on a 5S pack. Peaks at about 1500W. Very easy to live with.

40kph, 5s, 63-74 sounds pretty good to me. Will need to modify my mount system a bit, but I needed to put my learnings from this one into a new design anyway. That will make my drive tip over to a weight of ~1.2kg, I'll have to change the title of the thread. :lol:

I would prefer a system that is more robust anyway. So unless I find a elegent way of protecting the little motor, I might just go for the bigger motor that can shed the waste heat a bit better while I play around with the design. Then I can optimise it later.

- Adrian

If you dont want to add weight, the Hyperion 4045 240kv on 6S could be an option if you can still get them. Still only good for around 1200W in an ebike config though in my opinion. I agonised with the weight thing and the larger diameter but for the sake of an extra 400 grams, just couldn't go past the 63-74. I have bought 20 of them now and never had a failure yet.

 

[Kepler]

Adrian, I think you get some of that heat from the friction of the roller (motor) on the tyre, even more so if there is some slipping. I noticed this with my first drive but didn't do enough rides to collect any data. Kepler would have plenty of knowledge regarding this so I might be wrong.

I doubt if heat from friction was a problem. This type of setput hardy slips anyway. I am sure 2000 plus watts was the problem

 

[adrian_sm]

Adrian, I think you get some of that heat from the friction of the roller (motor) on the tyre, even more so if there is some slipping. I noticed this with my first drive but didn't do enough rides to collect any data. Kepler would have plenty of knowledge regarding this so I might be wrong.

I doubt if heat from friction was a problem. This type of setput hardy slips anyway. I am sure 2000 plus watts was the problem

I agree. If your drive is slipping, you have stuffed up. Bugger all heat from tyre contact. I was just pumping too much current through the coils, leading to too much waste heat, leading to toasty coils. I just rebuilt the motor I'll upload pics in a sec.

 

[adrian_sm]

If you dont want to add weight, the Hyperion 4045 240kv on 6S could be an option if you can still get them. Still only good for around 1200W in an ebike config though in my opinion.

What's the best way to limit power then. These little ESCs just set a speed, and dump whatever current is required to do it. So if I stick with the same battery voltage what are my options.

I am starting to think a throttle interface that can sense current, and limit the throttle if it gets too high might be a good thing.

I agonised with the weight thing and the larger diameter but for the sake of an extra 400 grams, just couldn't go past the 63-74. I have bought 20 of them now and never had a failure yet.

I have nearly convinced myself to build the next prototype around the 63-74 motor. You are right they are so much better suited. More solid construction, beefier bearings, skirt bearing, bigger mass to take the heat. The biggest down size for me is actually not the weight, but the size. It will limit the number of bikes the drive will fit. A lot of modern frames have very little space between seat tube, seat stays and tyre. The industrial designers got all fancy, and closed it all up. Old school frames with nice horizontal top tubes, have heaps of room.

Are you running these on 6s? Have you taken any steps to stop overheating?

 

[adrian_sm]

Here are some pics of my toasty coils, and the fresh set I just replaced them with.

Last image shows the puny size of the bearings in this motor. I really can't see them lasting very long.

View attachment 2
View attachment 1

 

[umejopa]

BTW feel free to borrow the throttle interface, it works with both pot and hall throttles AND the code now runs on the Turnigy meter which is extremely easy to hook up to throttle, making it an inexpensive monitor at the same time.

Good work to make throttel inteface of a watt meter What uP is in it ? Have take my apart now
Can I borrow some code from you full-throttle ??

//Jonas

Jonas, I doubt you will get the code from full-throttle, he has spent a bit of time on this and has some plans I think, but you can find the schematics, here, and write your own.

Good luck,
Adrian

Thanks Adrian for the link Have some experins with the Altmel uP soo I will test some code on it.

 

[adrian_sm]

I agonised with the weight thing and the larger diameter but for the sake of an extra 400 grams, just couldn't go past the 63-74. I have bought 20 of them now and never had a failure yet.

Are you running these on 6s? Have you taken any steps to stop overheating?

Sorry just re-read your earlier post.

63-74 on 5s, resistor mod to currie throttle, limits things to ~1500W.

So If I limit my throttle somehow to give similar 1500 watt peaks, I should be getting closer to a robust system.

I just realised another solution, I have a Cycle Analyst - Stand Alone. I could use this to take control of the throttle. This will make tuning things a lot easier.
Will have to look in to how hard that is going to be.... Or get my mate full-throttle to write up a bit of code for me, and modify the watt meter to do the same thing, but something tells me de-bugging two systems at once is not a good idea for some reason.