Commuter Booster - <1kg Friction Drive

[adrian_sm]

Bench Test #2

6s 5000mAh 20C Turnigy LiPo

[adrian_sm]

Note what happens when you guess the drill size for a tapped hole... a broken tap.

Hi, FWIW, if you mean that you didn't know what size to drill, metric threads are dead easy to remember: it's the diameter - pitch eg M6 1.0 pitch tapping size is 6-1= 5.0mm. If you mean you knew that but guessed the drill size, measure the bugger next time

Like the drive

Cheers,
GT

Thanks GT. I was just lazy. Picked up a bit, eye-balled it against the screw, and thought she'll be right....

I might take two seconds next time, and remember "metric threads are dead easy to remember: it's the diameter - pitch". Thanks.

Adrian

[gtadmin]

No worries Adrian. When I did my trade, everything was imperial and you had to refer to charts or a Zeus but not with metric. Another advantage of being metrified

Cheers mate

[Hillhater]

Adrian,
have you tried testing it with a load on ( brake ).
.. curious to see if you have any sync issues

[full-throttle]

Looks great so far! So small and light.

What are the no-load speed and current?

Careful of squashing those butted Al tubes, could always make the clamp wider to distribute the load.

[adrian_sm]

Thanks mate.

I am loving the light weight, only about 1.5kg, including battery, controller, drive everything, added to an already light bike.
You totally forget it is there. So different to the usual ebike that weighs in around 30kgs, and you try and avoid having to pick up.
This one still feels totally like a normal bike.

Haven't looked at no load speeds, as speedo is on the front wheel at the moment. Based on kV and 6s, should be up around 50-55 kph.

No load power was (from memory) about 20w for 2s LiPo, and if I fully engaged the motor by hand, to simulate the full loaded rolling friction, I think it was 50w. But this was with huge amounts of motor engagement into the tyre, and I may have totally got these numbers wrong, as I had had a few beers at this time, and my memory isn't great at the best of times.

And this was really quick and dirty tests, without tuning the amount of engagement, and really should be done at 6s LiPo once I get the friction, geometry, and amount of engagement all tuned.

I think the most important thing to get the no-load losses down is to get the motor to tyre friction better. This means less pressure is required, which means less tyre deflection, which means less rolling friction. Well that is the theory any way, we will see how it goes in practice.

Next challenge will be the throttle, at the moment I just have the servo controller taped to the top tube. Way to dangerous, once I get the drive engaging properly. Bit like setting cruise control in the car, but putting the controls in a really non-intuitive location. So if you need to turn it off in a hurry, you brain just can't react quick enough. I have images of that guy that got stuck in his car without being able to override his cruise controll....

At the moment I am thinking of have a normally open button up at the handle bars, adjust the controller for a soft start, and leave the servo controller some where handy to tune speed. So you have to hold the button down to engage the throttle. This should do for testing, then I can work out a more permenent/user friendly solution.

[adrian_sm]

Careful of squashing those butted Al tubes, could always make the clamp wider to distribute the load.

Not too worried. It is clamping on the entire circumference, no point loads, and the seat-tube would support things on the inside if you got crazy. But to be honest it isn't clamped down that tight.

Thanks for the warning though, I'll probably crush it and then you can tell me I told you so.

- Adrian

[full-throttle]

..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

[adrian_sm]

..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

CBM1.jpg

Sounds cool will have to give it a go. Will it work on this turnigy watt meterhardware?

As for road grit. I'll let it run with no protection at first to see how it goes. Then add protection later if needed. Got an idea on how it can be done neatly. Might use the same mounting features as future hall sensors.

[adrian_sm]

Man I should stop posting from my phone. I missed the text on the screen , and that it is identical to my turnigy meter. Awesome work. Too cool.

Update:
Dropped off at Bunnings and picked up some no-name anti-slip tape.
$7 for 5m. That works out as 22 cents for per motor. I can live with that.

IMG_1286.JPG (87.08 KiB) Viewed 1046 times

[adrian_sm]

What are the no-load speed and current?

Just did a quick test at 6s, with anti-slip tape on the motor.

The amount of engagement into the tyre makes a huge difference. On the second try with a smaller amount of engagement was up around 150W. Then I applied the brake and saw about 1000W with no slip.
Lots more tuning to do.

I also weighed all the parts for a complete drive system.
789g - 6s 5000mAh LiPo
743g - Commuter Booster Drive
131g - 85 Amp ESC + Servo Tester
107g - Little frame bag to hold the battery

Total weight for the whole system 1771g, or 3.9 pounds.

Not bad for something putting out a 1000 watts.

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It all manages to fit in the little frame bag too.

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- Adrian

[adrian_sm]

Adrian,
have you tried testing it with a load on ( brake ).
.. curious to see if you have any sync issues

Sorry missed this, before.

No real data on sync issues yet.


My only onroad tests so far were before the grip tape, so when I hit the throttle too hard the motor would tend to slip, rather than lose sync.

I have the grip tape on now, seemed to work well in the shed when applying the brake. But I had the wheel going pretty quick, then applied the brake. I believe it will be more of an issue at low rpms, when you suddenly hit the throttle. The road test should defeintely show this up, but unfortunately family and work keep interupting testing.

[adrian_sm]

Just had full-throttle drop by my desk at work, and tried a throttle interface he has built. Very nice work.

This would allow the use of a hall or pot throttle, or he said you can use up/down buttons.
You can see his creation at the bottom of screen in this little video of one of his bench tests a while ago.


But the big problem is on a road bike there is no nice place to put a typical throttle. I was toying with the idea of using momentary buttons somehow/somewhere, and noticed that my Shimano control levers have little button moldings in the grip region. Full-throttle said these are for the Shimano Flight Deck bike computers.

A quick goodle search later, and here is a picture from a shimano manual, that shows the location of one of the buttons, and the hardware you can buy.

Shimano Flight Deck Buttons.PNG (18.19 KiB) Viewed 791 times

This looks promising. I might be able to install a couple of buttons discretely in existing hardware, in a pretty damn good ergonomic location. Great for me, not so good for anyone without these control levers.

Question is what the button logic would be. Maybe use these to increase/decrease speed, and a momentary switch that must be held down to go.


Good food for thought, but must get the mechanicals sorted first.

[etard]

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. 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.

[Hillhater]

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.

[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. 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

CBM1.jpg

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.