A light electric stand up scooter

[ferias77]

Hi,

I am starting to build a light electric stand up scooter to complete my electric bike that I can't carry with me.

The purposes are :
- Range : 15 to 20 km
- as simple and as light as possible : 5 kg for the electric scooter + 1.5 kg for lipo batteries (2 x 5S 5000 mAh in a backpack). I use these batteries on my electric bike.
- Topspeed : around 30 km/h.
- able to go up a 8% slope

I took the formula which permits to calculate the required power for a classic bike :


m = 80 kg
V = 30 km/h
g = 9.81 m/s²
p = 0.08

=> Power = 217W on the flat and 740 W for a 8% slope

The motor will be this : http://www.hobbyking.com/hobbyking/stor ... oduct=7870


The scooter : http://www.decathlon.fr/trottinette-pla ... 52915.html


The diameter of the wheels is 125mm.

I am hesistating for the transmission... It will be made with a chain or with a commuter booster.

- with a 6mm chain : http://www.conrad.fr/chaine_a_rouleaux_ ... 121328_FAS
10 teeth for the small gearwheel : http://www.conrad.fr/pignon_pour_chaine ... 243_216008
25 teeth for the big gearwheel : http://www.conrad.fr/pignon_pour_chaine ... 216011_FAS
No load speed : 170 kv x 20V x 10 / 25 x pi x 125 mm = 32 km/h => 32 x 85% = 27 km/h for the top speed of the scooter on the flat.
I would like to have a free wheel on the back wheel. I am looking for this freewheel, but I don't find... I see only one solution, it would be a bmx free wheel : http://gear.ridemonkey.com/mtb/acs-bmx-freewheel
But it will be difficult to adapt...



- with a commuter booster : the no load speed would be 170 kv x 20V x pi x 63 mm = 40 km/h => 40 x 85% = 34 km/h for the top speed of the scooter on the flat.
But I don't know if a commuter booster would be efficient with a non inflatable wheel...




What do you think about it?

Eric

[adrian_sm]

I would be confident of the chain drive many have tried it before you and it has worked.

The friction drive on a hard tire will be limited by the small contact area between motor and tire. if you apply too much power it will just shear the tire material. The other thing is the way you have mounted your swing arm would only allow the drive to work driving the scooter backwards. For the swing arm design to work it must swing in the opposite direction if that makes sense.

I am keen to see it work, but would probably try on a larger model scooter if possible. With bigger diameter wheels (for a safer ride at speed) and pneumatic tires ( for better drive engagement and to provide some suspension). It would also be good to see the batteries mounted on the scooter if possible.

I don't know amlot about kick scooters but aren't there already lower powered electric scooters sold by the manufacturers. Maybe it would be possible to just upgrade one of those instead?

- Adrian

[def215]

ill have to agree with adrian on this one. i have a spindle drive rc power electric scooter and the spindle drive is really harsh on the hard tires. everytime im done riding, theres a film rubber dust all over the rear end of my scooter because it likes to shred up tires, and thats only around 2 miles of riding. i think friction drive is good if you want to keep things nice and simple, but i still believe chain drive will be the better drive system for all weather riding.

this is what mines looks like, well at least the drive system:

im on 6in. hardtires with a .650 inch drive spindle and it absolutely hauls. it puts my gas powered scooter to shame

i like the CAD renderings.

[ferias77]

Thanks for your replies.

Adrian, my purpose is the scooter to be as light as possible. So I don't want a 38 kg scooter like this :
http://cgi.ebay.fr/E-SCOOTER-500W-TROTI ... 1120056986

At the moment, I am riding the scooter without motor, and the non inflatable wheels and the lack of suspension is absolutely not a problem.

def215, I am not sure to understand how your transmission works. It is a friction drive with a roller? Do you have other pictures?

I will try to find posts about electric scooters with a chain, but my first search hadn't be very fruitful. The biggest problem is the free wheel...

Eric

[adrian_sm]

38kg? Damn that weighs more than my full suspension hub motor ebike.
I was think more like the razor electric scotters like this one, that weigh in at ~15kg, and that is with lead batteries.
http://www.ebay.com.au/itm/Razor-E125-Electric-Scooter-Free-Shipping-/300519899316?pt=AU_Scooters&hash=item45f861c0b4#ht_2991wt_907

Do you really need it to freewheel? I don't think any of the others I have seen freewheel.

They just look like a straight belt or chain drive.
http://scootersupport.com/razorparts.htm




The motor I use for my friction drive only take between 35-60w to spin them noload full speed on 5s, equivalent to road speeds of 45-60kph.
I imagine if you are propelling the scooter via human power it will be well below the full speed you have it geared for when under electric power, so you would only be pushing against a fraction of that ~50w back EMF.

Just a thought.

- Adrian

[nyx]

Hello Eric,

I think you are french as you now Conrad and Decathlon ? I am french and i have a very similare project.

I wanted an light electric scooter for using it in the subway and using it as an non-e-scooter.
Then i chose the oxelo Town 5 for many reasons :
- it is cheap
- it as 200mm wheels which is nicer for driving and for installing a motor
- it as an hollow Rheum which should be great for installing all electrics parts.

My goals, making it electring with the same Dimensions and max 8-9Kg (it weights 5.5Kg currently), just enough power to maintain the speed once launched with the foot (about 20-30kph).
I thought to the commuter booster for the transmition as it is easier to make, no chain, but i gave up this idea as it is not an inflatable wheel.

Finally i choose a #25 chain, a 68 Tooth Rear Sprocket, and a 15 Tooth Freewheeling Sprocket which will allow me to use the scooter without the motor slow down it.
I allready installed the Rear sprocket on the wheel, it was pretty esay, i am now installing the motor in the Rheum, this weekend i could realise the first test with the motor

Here is the motor i selected :
http://www.hobbyking.com/hobbyking/stor ... duct=14740
It as a 450KV and can reach 1000W, and it feets almost perfectly in my scooter. I shouldn't use the 1000W, i will use a 4S 5000mAh for testing, and i have 3S 2200 too, if 3S provides enough power i will put 3S batteries as with an 4s it will consume more Amps.

I just hope that my calcs for the transmistion are good, i will now once the motor installed. I think i will add an fan for cooling the motor.

May be would you pictures ? as we have an very similar project i think we can share ideas

See you

Thibaud

[adrian_sm]

Thibaud,

Sounds like you are build a nice little ride there. Looking forward to seeing it up and running.

But that motor looks very small for your application. I have run the 5065-270kv motor on my bike, and managed to burn it up doing about 35kph up a hill. This was before I put any current limitting in place. I doubt your smaller motor is going to survive, unless you gear it for much lower speeds, or put some current limitting in place.

My calcs have your no-load speed on 4s at ~60kph. Which is too high. I think you will need to go for a lower kv motor, or have greater reduction in your drive train.

BTW what 15tooth freewheel did you use, I am sure Eric will be interested. Links would be useful.

Cheers, Adrian

[nyx]

Thanks for your message Adrian,
i first plan to use 3s and i think i calculated 42Km/h with noload and 100% efficiency. I already had the motor so thats why i will try it. The problem is that i can't find a motor with similar size and less KV which is a problem. and i don't see how to increase the readuction...

here i bought my oneway sprocket and the chain :
http://www.electricscooterparts.com/sprockets.html

it's made with an one way bearing

[def215]

def215, I am not sure to understand how your transmission works. It is a friction drive with a roller? Do you have other pictures?

I will try to find posts about electric scooters with a chain, but my first search hadn't be very fruitful. The biggest problem is the free wheel...

Eric

yes its friction drive. here is a picture of the drive train:

this isnt a recent picture of it, but here it is next to another scooter:

this one was originally a gas powered one like my other one but i just couldnt find a motor for it,so it became an electric. i still havent weighed it yet but i know its way lighter than the gas one, and the gas one weighs about 25 lbs.

[adrian_sm]

The problem is that i can't find a motor with similar size and less KV which is a problem. and i don't see how to increase the readuction...

I hear you. Any chance of fitting a larger 50mm or 63mm diameter motor?
Then you can get lower kv's

[sk8norcal]

Hello Eric,

I think you are french as you now Conrad and Decathlon ? I am french and i have a very similare project.

I wanted an light electric scooter for using it in the subway and using it as an non-e-scooter.
Then i chose the oxelo Town 5 for many reasons :
- it is cheap
- it as 200mm wheels which is nicer for driving and for installing a motor
- it as an hollow Rheum which should be great for installing all electrics parts.

that scooter looks nice! been looking for something like this.. a suspended xootr..
you have the full suspension version ??

http://www.playgroundonline.com/product ... 10597.aspx

[nyx]

Hi All,


Adrian, thank for you help. Today or tomorow i will make pictures, like that you will see my setup. I could use a motor with a larger diameter, but not longer, i think i exist si why not, i will test with this one, i have an "tester" which i plug bettwen battery and ESC, so i can check in real time the Amps.

@sk8norcal : I have exactly the scooter you show but without suspension, in france we can find both, but with suspension the price is double and its weights 7Kg against 5Kg without suspension...

[nyx]

Hi guys,

back from my first driving test. This morning i manage to finish my motor instalation so i just made tests on a car park.
well i'am pretty pleased, i was scared to burn my motor without beeing able to drive as Adrian prevent me.

for the fisrt test i launch myself with the foot, without with the motor, then i start the motor. and it runed !
After this i made several test, one by starting only with the motor, its not impressive but i justed wanted enough power to maintain the speed.
During all the test i keeped an eye on the power tester, at the max i reached 50A and about 700W with 4S batteries. but the throttle was not a the max, so as you said Adrian, a full throttle,i think the motor will burn.
I will try with 3S batteries, it could be enough and i would be really happy

Here are few pictures, sorry for the quality, i don't have my camera with me

[ferias77]

Adrian, I thought I needed a freewheel in order not to send current to the battery. I don't know if the RC controlers can bear it...

Nyx, thanks for the photographs and the link for the freewheel. A friend who build an electric kmx gave me this freewheel, but I would have prefered a freewheel with only 10 teeth, with 15 teeth on the motor, the gearwheel of the back wheel will be too big...
Well done your scooter. The way you put the motor is very original. Do you have an idea of the top speed you reached during your tests?

PS : Yes, I live in France, in Bordeaux.

[nyx]

Hi ferias77,

installing the motor like this is interesting, it's discreet and the scooter doesn't need more room than without the motor. But its hard to find a motor which fits.
I made an second test this afternoon, its hard to say but I think i was between 20 and 30kph.
The motor was pretty hot, as it is Intended for a plane with lot of wind, the motor hasn't any "auto" refreshing, so I think i will add an 40mm fan, and i'll try to make littles blades on the motor to increase the wind in it.
Tomorrow i'll test 3s batteries, i think it should be better as i have enough power. if I can use full throttle I'll have to put definitively an Power tester on the Handlebars. Doen't any one know one which the display could be exported (I don't wan't to have too long wire for batteries) ???

Thibaud

PS : I am from Lyon

[adrian_sm]

First up. That is an awesome build. It is so compact, I love it. But I don't think that motor will last. Even with a little fan attached to it, it will struggle. You will need to either go for a bigger motor, or limit the current going to it, which will also obviously limit the power you can get from it.

Here is a link to a mod I did to a watt meter, that allows you to have it mounted up on you handlebars, without running the battery wires the whole way. Hope it helps.
viewtopic.php?f=28&t=22187&start=270#p350307

I have also modified the watt meter to actually act as a servo tester, and limit the throttle when the current gets to high. It works fine without the remote shunt mod above, but never worked with the remote shunt due to electrical noise issues.

Here is a link to Jonas' mods that I based it on:
viewtopic.php?f=28&t=22187&start=165#p337690

Hope that helps.

- Adrian

[nyx]

Thanks for the links Adrians,
I don't know if i'll make a such mod, i think i will place the wattmeter at the half height of the handlebar, by this way once the scooter Folded the wattmeter will be more protected. I am stell thinking about it.

Yesterday i made new tests with my 3s 2200Battery. Even with this low capacity the power was really good, in fact as good as the 4s 5000, that because i didn't use full power on the 4S.
so its decided, i will use an 3S 6000mAh, as you said Adrian, i will have less power than with an 4s battery, but with an 3s i am allready at the max capacity of the motor, so more power from the battery should only by usefull for burning the motor
then i made an test in real condition : going from my garage to my home, its about 1Km. 4 road to cross. At each acceleration, i helped the motor with the foot. Finally it perfectly fits with what i needed : an light electric scooter with a small motor just enough to maintain the speed.
the speed was good, on flat i think i am about 20-25Kph. and finally the motor was not hot. on flat at constant speed it pulls between 100 and 200Watts.

now i have to pass all the wire in the scooter, make Hoods for protecting the battery, the motor and the chain. And Finally make an system to Tighten the chain.
i'll make new pictures.

and then, i'll can go to work with my scooter by taking the subway

[swbluto]

First up. That is an awesome build. It is so compact, I love it. But I don't think that motor will last. Even with a little fan attached to it, it will struggle. You will need to either go for a bigger motor, or limit the current going to it, which will also obviously limit the power you can get from it.

I regularly run the same motor at 25 mph and I climb hills with it, and it's not burning up anytime soon. The hottest it gets is to 150 degrees which is far away from its temperature limit (Which is something like 300-400 degrees).

[adrian_sm]

Here is the motor i selected :
http://www.hobbyking.com/hobbyking/stor ... duct=14740
It as a 450KV and can reach 1000W

I regularly run the same motor at 25 mph and I climb hills with it, and it's not burning up anytime soon. The hottest it gets is to 150 degrees which is far away from its temperature limit (Which is something like 300-400 degrees).

Really you use that little guy at 25mph, and hills. No current limits?
I assume those temps are in farenheit.

[nyx]

Adrian, i Think it is possible with an big reduction and 5 or 6S batteries the motor can reach 1000W without pulling more than 50A which is his max. On my side i will check the Timing of my ESC because i am not sure of it.

To complete yesterday i pulled about 450mAh for 1Km then with the 6000mAh battery, i should reach 10Km which is more than hopped.
Question to expert : My #25 chain is too long, do you think that i can cut one link and continue tu use the master link?

Thibaud

[swbluto]

Here is the motor i selected :
http://www.hobbyking.com/hobbyking/stor ... duct=14740
It as a 450KV and can reach 1000W

I regularly run the same motor at 25 mph and I climb hills with it, and it's not burning up anytime soon. The hottest it gets is to 150 degrees which is far away from its temperature limit (Which is something like 300-400 degrees).

Really you use that little guy at 25mph, and hills. No current limits?
I assume those temps are in farenheit.

LOL. Ok, I admit I was looking at the original post where he talked about the 3250 W 63-74 Outrunner. Yeah, that little guy might have heating problems with continuous power requirements above 500W or so (Like climbing a long 7% hill), though I wouldn't doubt it could easily sustain 15 mph on flat land.

[nyx]

LOL, i read 25 Kph, but 25mph effectivily would be incredible for this motor

[ferias77]

Looking at all the motors available to Hobbyking, I found this :
http://www.hobbyking.com/hobbyking/stor ... oduct=4651
2 times lighter than the 63-74 170 with a Kv of only 206 ! But 43 A max... I don't know if it would fit.

I regularly run the same motor at 25 mph and I climb hills with it, and it's not burning up anytime soon. The hottest it gets is to 150 degrees which is far away from its temperature limit (Which is something like 300-400 degrees).

swbluto, with what vehicle and what voltage do you use de 63-74 motor? Is it the 170 Kv? Do you use a freewheel? I think I won't use any freewheel for the first design, but I would like to be sure not to burn the ESC when the motor is not running...

Eric

[nyx]

Hi Eric,
I saw this motor too, its looks not bad, but a bit too long for my scooter. I think 43A is not a problem if you have a big reduction and enough Volts.
Concerning the ESC if you use airplane/heli ESC you won't have problem as it is designed for it. I often saw planes flying with me motor cuted but with the Helix turning because of the wind, do you see what i mean?

The only reason i took a freewheel is to use the scooter without the motor slowing down me. But i would prefer an 10tooth freewheel, if anyone knows if it exsist, I take !

[swbluto]

Looking at all the motors available to Hobbyking, I found this :
http://www.hobbyking.com/hobbyking/stor ... oduct=4651
2 times lighter than the 63-74 170 with a Kv of only 206 ! But 43 A max... I don't know if it would fit.

I regularly run the same motor at 25 mph and I climb hills with it, and it's not burning up anytime soon. The hottest it gets is to 150 degrees which is far away from its temperature limit (Which is something like 300-400 degrees).

swbluto, with what vehicle and what voltage do you use de 63-74 motor? Is it the 170 Kv? Do you use a freewheel? I think I won't use any freewheel for the first design, but I would like to be sure not to burn the ESC when the motor is not running...

Eric

Quick specs:

29 volt LiFePO4 battery; 8 inch pneumatic wheels; 63-64 230 kV motor; and 15/80 gear reduction ratio. It's a belt drive without a freewheel. Be sure to turn off the "brake feature" in the ESC.