E-scooter: help with mounting rear wheel sproket

[Armon]

Hi Everyone,

I've a little project that's been brewing for a while.

I plan to convert an Oxelo Town 7 suspension scooter.
So far, I have the electronics and the rear bracket worked out. There are couple of options for motor/batteries depending on the drivetrain.
Motor will be most likely be turnigy 6364, but it depends on the final drivetrain configuration

The drivetrain itself however is giving me some trouble, specifically mounting a pulley/sprocket to the rear wheel.

I would prefer not to replace the rear wheel.
Here's what it looks like:
http://www.decathlon.co.uk/media/813/8138384/zoom_67252331687c46c8b05123ccb09e81e6.jpg

I keep saying sproket/pulley because I'm open to both options. I would much prefer to have a belt drive as it's quieter, however the pulleys that I have found are far too chunky and in my opinion difficult to attach to the wheel.
There is also a question of a freewheel. I've looked around but coudn't find an acceptable solution.

The gear ration i'm after is 5.5+ (7-8 would be ideal)

What would you recommend?
I'm from UK and i'm looking for places where to source the sprockets and mounting tools. Any suggestions?

 

[Armon]

After a lot more search I have finally found suitable sprockets.

Rear wheel: 80t 160mm
Motor: 9t-10t
Pitch: 6mm
this will give up to 8.8 gear ratio. It should work quite well.

I've sketched up the rear wheel and the sprocket:
The wheel is 200mm wide.

and the side view:

Any suggestions on how to best fix it to the wheel?

I also can't seem to find explanations on how the front sprockets are attached to the smooth shaft of the motor.
I've found suitable small sprockets, one with smooth 8mm bore and the other with a flat spot. But without additional hardware I can't seem to see how it will be held in place.

Any advice on this?

 

[made_in_the_alps_legacy]

For the D shaped motor sprocket :When i was in a similar situation as urs, i could use a 'retaining ring' sent with the motor and equiped with a set screw ( see in my signature for further details...)

 

[Armon]

Thanks!

you mention in one of the posts the ratio of 11:65. Was that enough?

Am I going overboard with 80:9? (actually found a better sprocket today with 72t. The shape might be easier to mount)
My calculations put this at 30km/h top speed which I think is little too much.

 

[made_in_the_alps_legacy]

Well... the higher the reduction ratio is, the higher the motor ''kV" can be and motors get cheaper and lighter with higher kV,
... so if you ask me, reduction ratio are never High enough this being said, 80:9 would be quite exceptionnal

I could cross check your speed evaluation but can't find here which motor kV and voltage you plan to work with

 

[torqueboards]

I keep testing higher KV but to be honest 200KV or less is perfect. Any higher the torque sucks for uphills. Maybe if you are 100% flat ground riding it will be fine but higher KV for going mostly uphill is horrible. The alternative is to using higher voltage.

 

[Armon]

I keep testing higher KV but to be honest 200KV or less is perfect. Any higher the torque sucks for uphills. Maybe if you are 100% flat ground riding it will be fine but higher KV for going mostly uphill is horrible. The alternative is to using higher voltage.

I am currently looking at 260KV Turnigy Aerodrive motor.
It takes 10s to run.

Do you have any recommendations on the motor side? I see some turnigy 160kv motors, but the weight is too much! almost 1.3kg!

I like Turnigy 6354 primariy because of it's size: it's only 54mm long, it wont stick out from the back of the scooter as much and the weight is only 483g.

The scooter is already 4.7kg. I haven't done the full calculations yet, but i hope to keep it under 7kg total.

 

[torqueboards]

You can still use a 6S or 8S with the 6354 260KV motor.

The 50mm SK3 280kv and NTM 5065 270kv from HK. Tacon Bigfoot from HobbyPartz works great too.

50mm's IMO are better with 2 motors otherwise a single 63mm is good for added torque.

Single 50mm should be fine with 8S voltage. 6S it's a bit slow uphill.

 

[made_in_the_alps_legacy]

I am currently looking at 260KV Turnigy Aerodrive motor.
It takes 10s to run.

with a 200mm Wheel, 9:80 ratio, 260kV motor, I find a 28km/h theoretical top speed if your system runs at 25V (6s) - Note: my e-scooter runs at 12s and goes twice faster

 

[Armon]

with a 200mm Wheel, 9:80 ratio, 260kV motor, I find a 28km/h theoretical top speed if your system runs at 25V (6s) - Note: my e-scooter runs at 12s and goes twice faster

My main concern with gear ratios is that the motor will not have enough power to accelerate.
Does your start from stop? How do you break?

It feels that 15-18mph is a good speed.
I have found a 72t large sprocket that is much better fit, so I think I'll be going with that, plus there is a choice of 9-12t on the small gear.

Do you have any advice on the freewheel?
I've found this:
http://www.ebay.co.uk/itm/Branded-HFL0822-Needle-Roller-Clutch-Type-One-Way-Bearing-8x12x22mm-/141133692630?pt=UK_BOI_Industrial_Supply_Material_Handling_ET&hash=item20dc393ed6

it would fit the motor directly, but I can't find the right sprockets for 12mm shafts.

I guess the bigger question is: how hard is the scooter to ride without the freewheel? Is it fine to leave it out at this stage?

 

[made_in_the_alps_legacy]

Does your start from stop?

yes

How do you break?

with disc brakes

how hard is the scooter to ride without the freewheel? Is it fine to leave it out at this stage?

it coasts fine even without freewheel, but the Rolling resistance is noticable if you plan to keep kicking

 

[Armon]

great, then I won't bother with the freewheel for the first build.
This means that I have sources for all the parts and can start planning the motor mounting bracket.

I'll order the 72t rear sprocket today. If it fits well, will get the rest of the equipment.

 

[made_in_the_alps_legacy]

yes, I think your evaluation is good enought to start building.
I forgot to ask you how will u control the speed controller ?
(I use a servo tester but there are elegant alternatives around here)

 

[Armon]

Preliminary equipment shortlist:

Motor: NTM Prop Drive 50-60 270KV / 2400W
Reason: 30V working voltage. this will allow me to have 2 4s packs in parallel. they fit nicely on the scooter underside.

Batteries: Turnigy 5000mAh 4S 20C Lipo Pack
Reason: perfect size to fit under the scooter body. 20c constant discharge (30c peak) should be more than enough for normal ride. Based on what I've read from other projects, I expect 20-30A average draw on a flat. (One person reported 12A draw on a flat). Is this reasonable?
I will need 2 packs in series to get required 30V.

Rear Sprocket:Mini Moto 72 Tooth Rear Chain 6mm pitch
Reason: small middle hole. it should be much easier to mount to the wheel.

Motor Sprocket: 9 TOOTH 6mm SPROCKET
Reason: this should give me a solid 1:8 ratio. the bore is 8x6mm and flanges will prevent slippage.

TODO:
ESC
Watt Meter
Safety equipment: fuses, failsaves, etc.
air filled tyre?

 

[Armon]

yes, I think your evaluation is good enought to start building.
I forgot to ask you how will u control the speed controller ?
(I use a servo tester but there are elegant alternatives around here)

I was thinking of using Arduino to generate PWM signal. Simply because I can manufacture my own throttle handle and hook it up.
If I find an ESC that has telemetry output that could be parsed in Arduino, it would be even better.

Oxelo presented an interesting electric scooter where you have no throttle at all. you just use it as normal and the electronics will try to keep whatever the speed you're on. In the future, i'll like to experiment with that.

Do you have any recommendations on ESC? the are so many options. I am after telemetry output and an option to hook up hal sensors for the motor.

P.S. I used to fly nitro helies and while i'm familiar with the radio side of things, esc and motors are relatively new to me.
Just had a look at hobbyking website and was very disappointed to find the options for 8s+ are very limited.. most ESC are for 3-4s

 

[made_in_the_alps_legacy]

that's good if you are skilled to make your own throttle...
Regarding ESC, there is a lot to say...
most of us are riding e-board, and we give our preference to ESC which have progressive brakes ( "car ESC" )
but for an e-scooter, you might skip the need of a brake and lean toward plane/heli/boat ESC,

HV ESC on the hobbyking site

edit : forgot to mention the VESC, open source ESC being developped in the "Stand-up E-scooters and E-skateboards" section of endless sphere

 

[Armon]

that's good if you are skilled to make your own throttle...
Regarding ESC, there is a lot to say...
most of us are riding e-board, and we give our preference to ESC which have progressive brakes ( "car ESC" )
but for an e-scooter, you might skip the need of a brake and lean toward plane/heli/boat ESC,

HV ESC on the hobbyking site

edit : forgot to mention the VESC, open source ESC being developped in the "Stand-up E-scooters and E-skateboards" section of endless sphere

Wow, the VESC feature list looks impressive! Depending on the cost, I would be most interested in getting one.

Failing that, this off-the-shelf esc looks nice:
http://www.hobbyking.com/hobbyking/store/__4691__TURNIGY_Sentilon100A_HV_5_12S_BESC_Ver4_.html
(not sure what BESC means)

none of those have BEC inbuilt which was very disappointing at first as I really need it if I go Arduino route, but i then found out that you can get a separate SBEC device for just a couple of quid so not really an issue

 

[made_in_the_alps_legacy]

Failing that, this off-the-shelf esc looks nice:
http://www.hobbyking.com/hobbyking/store/__4691__TURNIGY_Sentilon100A_HV_5_12S_BESC_Ver4_.html
(not sure what BESC means)

Looks really similar to the one I have on my e-scooter, mine is 120A w. 3 caps. (I burnt the 70A version, I guess the 100A version is just fine)
The VESC is available for sale but I think it still requires some knowhow at the moment

 

[Armon]

Looks really similar to the one I have on my e-scooter, mine is 120A w. 3 caps. (I burnt the 70A version, I guess the 100A version is just fine)
The VESC is available for sale but I think it still requires some knowhow at the moment

Guess you have one similar to this?:
http://www.hobbyking.com/hobbyking/store/__64656__AeroStar_Advance_120A_ESC_Opto.html

the price difference is not as much as I first thought. I might go for this, specially since you said the 70A can be burnt. I'd rather pay few quid extra now and not worry about it in the future.

And it has data logging. Don't know how useful it really is on a scooter, but telemetry was great to have on helicopters.

 

[Armon]

BoM so far:

Motor - NTM Prop Drive 50-60 270KV / 2400W £23.39
Battery -Turnigy 5000mAh 4S 20C Lipo Pack 2x £21.77
ESC - AeroStar Advance 120A £63.02
UBEC - Turnigy 5A SBEC £3.99
ServoTester - Turnigy Servo Tester £3.95
Rear Sprocket - 72t 6mm Sprocket £3.99
Front Sprocket - 9t 6mm sprocket £5.99
Chain - 6mm chain £6.49

Total £154.36

I really hope these battery packs are up to it.

 

[made_in_the_alps_legacy]

Guess you have one similar to this?:
http://www.hobbyking.com/hobbyking/store/__64656__AeroStar_Advance_120A_ESC_Opto.html

Nope, I don't buy from HK, I have this one :

looks similar to this turnigy 120A k-force

 

[Armon]

I've just ordered the motor, batteries and few bits and pieces from hobbyking.
went with NTM 260kv motor.

The UK warehouse doesn't have any suitable ESC, so that will be part of a separate order.

I'm little concerned about using aero ESC in this application because of lack of airflow over the esc and sometimes manual (feet, physical brake) rapid breaking/accelerating .
Have you experienced any problems related to that? Do you find they run hot? Did you add a heatsink or any airflow ducts?

 

[made_in_the_alps_legacy]

Have you experienced any problems related to that? Do you find they run hot? Did you add a heatsink or any airflow ducts?

The 70A ESC I had burned up, but the 120A one is running cool ( 12s x 120A is more than 6kW )
I haven't added any heat sink, I just fixed it outside the e-scooter frame so it can enjoy so fresh air
(bear in mind those ESC cannot be used for electromagnetic braking like a car ESC)

 

[Armon]

I'm aware about the EM brake. I was a little worried that it may get damaged when for example going downhill and the motor starts generating. There is no freewheel. That kind of scenario is non-existent in aircrafts.

If i remember correctly, you do run a freewheel, right?

 

[made_in_the_alps_legacy]

No I am not running freewheel, friend of mine has one, of course you don't have the drag from the motor then,
I think I wrote before it make sens to have one if you want to keep kicking your scooter, I never noticed significant heat built up during long downhill without freewheel tbh.