Commuter Booster - <1kg Friction Drive

[Kepler]

Drive activation via a button to a high throttle setting gives a surge of power and I found this often made you over shoot how fast you wanted to travel. You then needed to release the button and loose your assist or keep on going like a bat out of hell (like you ride ) Our concept is to pick up at the speed you were going, then add to the speed with a few extra clicks if you need too. This way you can maintain the speed you want to actually travel at rather then being forced to ride at the drive's max speed.

With a low powered profile like was set, unfortunately the extra button pushing doesn't have much impact on a moderate hill as you are already at the current limit. However on the high powered profile where the current limit is set at 1400W, the extra button pushes give you the turbo boost you are looking for You also have a throttle advance profile that allows you set how large a throttle increase each button push gives you. The interface was set at its medium setting. The high setting kicks the speed up much more quickly however you cant set your desired speed as accurately.

Bottom line is that its tunable to individual likes. I think the high power, high advance profile will suit your riding style nicely

 

[Hillhater]

This was all on 6S, 24V nominal so around 30 to 35A. I doubt if more voltage will help out much. The ESC (K force100) hardly gets warm. I think bottom line the motor is good for 500W continuous and that it. Keep in mind, it only weighs 414g so theres not a lot of copper in it.

It just seems odd that a motor rated for 40A continuous (60A burst) @ 30v (1200 -1800W ) , should get hot at only half that power ?
I guess in RC use it get a lot more cooling ..together with the higher rpm /voltage.
at the end of the day, its a lot to expect from a small motor ! :wink: ... I will stick with the 6374 !

 

[Kepler]

Unusual for Hobby City to over rate their motors
I am sure it would handle a bit more in the slipstream of a prop, but I think I will stick with my "half the rated power for ebike use" rule of thumb.

 

[adrian_sm]

I am with Kepler for derating the motor. We are using this in a totally different way than it was intended.

The ratings are for running at high RPM in a remote controlled aircraft, close to the peak efficiency of the motor. Meaning it creates little waste heat.
When we put it on a bike, and go up a hill, it runs at much lower rpms and lower efficiencies, thus creating more waste heat for the same nominal power going in, and this is what kills the motor.

 

[ferias77]

Hi,

I am reading this topic since a few days and I am very intereted in it ! I am currently using a mini front Golden motor on my ebike, but I can't mount my disc brakes (the motor is too big), so I am looking for a new solution... And the commuter booster seems to have many advantages.

My purpose is to have an e-bike :
- as light as possible. I thought it was good with my mini Golden motor, but it will be much better with the commuter booster !
- able to reach at least 30 km/h without pedaling on the flat, like my mini Golden motor. The possibility to reach 40 km/h would be the top !
- able to ride 15 km on the flat at 30 km/h without pedaling : I use it as a moped to go to work.
- with the same batteries as my current ebike : I use 2 batteries 5S1P 4900 mah (Hobbycity) serial (10S1P). I would like use it in 5S2P with the commuter booster.

What motor would you advise to me : Turnigy 50-65D 270kv or HXT63-74 200 kv? The 63mm motor would be more reliable, but is 500g heavier...

Thanks for your help.
Eric

 

[adrian_sm]

Hi Eric. Glad you dropped by.

- If you have the room, go for the 6374. You won't notice the different in weight, but it will give you a lot of piece of mind.
- your batteries will be perfect for cruising at about 43kph on the flat at full throttle
- 15km @ 30kph will be fine for you battery capacity, but will be pushing it for full throttle 40+kph the whole way. You would probably want ~15Ah or 5s3p for for that. I typically have been using between 7 and 11Ah for my 15km commute.

The main problem stopping me from selling this is not the mechanical side, but on the electronics side. Mainly to limit power to more appropriate levels for managing heat, minimising the required tire engagement, and reducing wear on tires.

I have it working very reliably with both a hall throttle and push button throttle, but it is not idiot proof yet. I have been riding it to and from work for the last week (a 15km commute through rolling hills) and both esc and motor are warm but not hot. So I am pretty happy with the setup now.

- Adrian

 

[adrian_sm]

I am starting to get a few people asking for when the Commuter Booster will be available. I really didn't want to charge people money for something that hasn't been thoroughly tested. As outlined above the main issue is the electronics side trying to limit power. This is primarily to protect the motor at low speed, hill climbs, and to minimise tire wear and reduce the maximum engagement required with the tire to improve efficiency. If people don't mind dealing with some of these quirks, or better yet helping to find solutions, then I might be able to make a few of these and let them loose on the world. There are a couple of electroncis solutions currently being developed, but nothing rock solid yet.

It would be a raw kit, with all the custom bits required to turn a pile of hobbyking type parts into an amazing ebike kit.

What is included:
- Main clamp pivot block, with all associated fastners and adjust screws
- the Swing arm, with associated fixing grub screws
- the counter balance spring
- friction tape (belt sander material)

What isn't:
- motor, ESC, batteries, charger, LVC, wiring, connectors, electrical enclosures, servo tester, throttle, battery bag, .....
- see this more comprehesive list if you want more details

You will still have to:
- swing a soldering iron to sort out some wiring,
- drill a small hole in the axle clamp that comes with the motor,
- glue some grip tape on the motor
- bolt it all together

Then you will be armed with a tiny, light weight drive that will give you a totally new ebike experience.

So who is up for some Commuter Booster Alpha testing?

 

[aaronski]

I'm up for some alpha testing. I have a Infineon sensorless controller that can easily limit the amps to anything I'd like.

 

[ferias77]

Thanks for your answer Adrian ! Il will look all this information.

So who is up for some Commuter Booster Alpha testing?

I'm up for alpha testing !!! Tell me if it is possible.

 

[p scott]

Im up for the challenge.. the 6374 has been back ordered on HK for a while now ...is there an alternative?.
P

 

[rearengine]

Adrien! They say if you have to ask the price , you can't afford it The Price ???

 

[adrian_sm]

I need to review how much time it takes me to make these up, but likely to be in the $150-200 range. Since I am still doing a lot of the work myself in small batches it is time consuming. And frankly I can't be bothered making too many of these right now.

If these ever get past Alpha testing, manufacturing costs will drop, but I'll end up putting some margin on top to make it worth my while.

BTW for those able to help me solve some of the other issues, I am willing to trade my mechanical bits, for electronics bits.

Things I am interested in are:
- throttle solutions for road bars
- electronics to limit power using standard RC ESCs
- electronics to stop drive engagement at low speed
- adjustable assist levels, selectable while riding.
- electronics to control ramp speed of throttle ie. restricts how quickly the motor accelerates/decelerates, when the user applies full throttle, of lets go of the throttle.
- something that does all of the above.
- maybe PAS integration
- anything that will make the drive more user friendly, and keeps the package small and weight light.

I am open to both open source and closed sourced solutions.

Keplers interface will possibly do all of this and more, but it would be good for people to have alternatives.

- Adrian

 

[rj7855]

Who is up for some Commuter Booster Alpha testing?

Count me in ! then I can finaly getting to work on my current limiting solution

 

[adrian_sm]

Well it looks like there are half a dozen brave souls willing to take on helping me iron out the bugs of the Commuter Booster.

To make things as smooth as possible, I will update a few things for the Alpha testers benefit:
- installation template: To ensure it will fit your bike
- shopping list: to make sure you get all the other bits and pieces to complete the build
- user manual: this will include final assembly, installation, tuning, operation, optional extras instructions
- required tools & skills: a short list of what skills and tools you will need
- FAQ: For stuff I can think of that might baffle you.

So please PM me (if you haven't already) with:
- your name & address
- your seat tube diameter/s
- the mounting hole pattern if you plan to use a motor other than the recommended HXT63-74 200kV

Guess I should start a new thread soon for the alpha testing.

Stay tuned

- Adrian

 

[adrian_sm]

Update: Modified Watt Meter

Finally some success in using the watt meter to be the brains for my Commuter Booster. Wooo hooooooooooo ! ! !

I now have it:
- accepting a button or hall throttle
- outputting the correct PWM for the ESC
- controlling ramp speed for both acceleration and deceleration
- overriding the throttle when a current limit is exceeded

This required leaving the shunt in the wattmeter (rather than using the remote shunt mod) and a bit of code tweaking.

Bad news:
The throttle override is too slow. I think the code is using a current reading that is only updated ever 400ms, which is a lot slower than the rate at which the throttle is updated. Since I have enforced relatively slow throttle response, I can probably get away without a proper PID control, but I at least need to supply the feedback loop with the instantaneous current reading.

Next step mod the code to take a shunt reading immediately before applying the throttle override logic.

I will be really happy if I can get this too work.

- Adrian

 

[adrian_sm]

Update: Installation Template

Here is the updated installation template.
Make sure when you print it is printed without scaling.

1) Cut out both templates.
2) See if the first one fits between seat tube, seat stays and tire.
3) Wrap the second one around your seat tube to check what size it is.

[EDIT] Original attachment deleted, as out of date. Replaced with updated version.

 

[damonjackson_spl]

I'll print and check my voodoo dambala 29er in the morning!!

 

[adrian_sm]

Voodoo dambala 29er. :? Looks like a pretty small rear triangle, especially with 29er wheels.

Hope it fits.

 

[damonjackson_spl]

Voodoo dambala 29er. :? Looks like a pretty small rear triangle, especially with 29er wheels.

Hope it fits.

It has sliding rear dropouts for single speed setup. I slide them back and see if it fits!! If it fails I'll try the van moof

 

[p scott]

Update: Installation Template

3) Wrap the second one around your seat tube to check what size it is.

Adrian: Most steel bikes have a seat tube with an inside diameter of 27.2 mm and an outside diameter of 28.6 mm (1 1/8").

Good news..the template fits both of my road bikes!

 

[adrian_sm]

Update: Modified Watt Meter
Next step mod the code to take a shunt reading immediately before applying the throttle override logic.

I just updated the code by added the following in the READ_GAS_RAMP section, just before the "LDS R22,Amp_100_L "

	LDI R25,0b10001011	; <NEW> Shunt
	OUT ADMUX,R25		; <NEW> Set ADMUX to read shunt
	RCALL ADC_READ		; <NEW> Dummy read mux clear
	RCALL ADC_READ		; <NEW> Real read of ADC
	STS Amp_100_H,R25	; <NEW> Data value high and low bytes 
	STS	Amp_100_L,R24	; <NEW> Get latest shunt reading

I basically takes a live reading of the shunt, just before the throttle override decision is made. And...... it appears to work. 8)

It is dark and raining out so haven't taken it for a ride, but burning rubber on the shed floor, and applying the brakes both resulted in about 35 Amps max, when the limit was set for 30Amps. There may have still been a bit of pulse to the power output, but really hard to tell with such a inconsistent load test.

Will have to take it out for a real spin, but looks promising so far. This should be able to limit the power for me, which will help make the 50mm motor viable, and help make the whole system more efficient.

- Adrian

 

[adrian_sm]

Adrian: Most steel bikes have a seat tube with an inside diameter of 27.2 mm and an outside diameter of 28.6 mm (1 1/8").

Ooops. I'll fix that tomorrow, and update the template. Thanks for that.

Good news..the template fits both of my road bikes!

Awesome, you can stick with the more robust 6374 motor then. The template is for the bare minimum, if you have a bit of extra room, that means you can engage the motor with your tire a bit more for extra traction with a high power setup, or if you plan on riding in the wet.

- Adrian

 

[damonjackson_spl]

Voodoo dambala 29er. :? Looks like a pretty small rear triangle, especially with 29er wheels.

Hope it fits.

It has sliding rear dropouts for single speed setup. I slide them back and see if it fits!! If it fails I'll try the van moof

ok good news, have plenty of room for the bigger motor!!

will take digi verniers tonight to give seattube O.D!!

 

[hillzofvalp]

How do you guys feel about mounting an outrunner underneath the bottom bracket, with pivot arms coming off the bb axle? Am I visualizing a worthy concept that needs attention? Or have we touched on this already...? The motor would have to be a smaller variant to clear the crank arms.

 

[adrian_sm]

I have definitely considered it before. But it is very exposed down there, especially in wet weather.
You also have less width to play with as the chainring is pretty close. Mounting features also change a fair amount between bikes.