Need help with my big wheel scooter project

[azrael78]

Hello everyone, I am planning to build escooter with 16 inch moped wheels, would mount 36v 500w hub motor on the rear wheel and the battery is 36v 10Ah.
My questions are:

1. Can I get max speed 30km/h on flat and 15km/h on 15-20% hill with this motor and this battery?

2. If not, can I put 36v 800w or 1000w controller to get more speed?

3. What performance could I expect from outrunner 6384 120KV with 36v battery? Gear ratio 1:5

The scooter would look something like this:
https://urbandrivestyle.com/collect...ter/products/uni-boost-x-raw-electric-scooter

Wheels I plan to use:

Hub motor:
https://www.aliexpress.com/item/32843078460.html?spm=a2g0s.8937460.0.0.28c42e0eHM59Df


Thansk in advance for your answers.

 

[SlowCo]

If you choose that motor then get the 36V500W version. And buy a 48V 1000W controller and a 48V battery that has at least 25A continuous rating. That way it will do around 50km/h and have serious acceleration. Good luck and update this thread with your build progress.

 

[azrael78]

48v battery is not an option because of money, 36v battery is a gift from my boss who rides el. longboard and he replaced it with bigger battery. I know the 48v is standard and I am not a speed freak, 30km/h would be awesome if it's possible with what I got.
Also any thought on 3684 120KV alternative?

 

[SlowCo]

If you want to do it on a budget then a mid motor could be an option. If you want to use a RC motor that spins around 4800rpm (120kV @ 40V) on a fully charged battery then you'll need to built a multi stage gearing to get to the right rpm for those wheels to go 30+ km/h. It can be done but I don't know how handy you are?

An alternative could be a MY1018 brushed and geared motor and controller combo used as mid drive. If one of those wheels you have is a rear wheel with the possibility to mount a sprocket then it is easy to get the gearing with just a single speed bicycle chain and a front sprocket of a MTB.

https://nl.aliexpress.com/item/3266...chweb0_0,searchweb201602_6,searchweb201603_53
(please search for the best combo incl. shipping and taxes to your own country)

 

[azrael78]

I am in possesion of MY1020 brushed motor 36V 1000W but it's my last option because it's noisy, bulky and and mounting is lot of work.
Do you think that RC 6384 120KV motor could push 30+90kg of weight? That could be cheaper than a hub. Shipping for hubs is a killer from China to Serbia...

 

[SlowCo]

I am in possesion of MY1020 brushed motor 36V 1000W but it's my last option because it's noisy, bulky and and mounting is lot of work.
Do you think that RC 6384 120KV motor could push 30+90kg of weight? That could be cheaper than a hub. Shipping for hubs is a killer from China to Serbia...

And you think mounting a RC motor (4800rpm!) isn't noisy and a lot of work (multi stage reduction!)? have you calculated the gear reduction that the RC motor would need for around 30km/h on your wheel/tire?

 

[azrael78]

I used this calculator:
http://www.recumbents.com/wisil/e-bent/rc_drive/rc_drive_calculator.asp

These are results:

It would have just one gear reduction, like on eboard, aprox 1:6 (I can change sprocket later to get right ratio)
Mounting of a outrunner is easier (whell, in my head anyway )

This is in theory, I dont know could 6384 motor push 120kg (me plus scooter).

 

[SlowCo]

Your moped rim diameter is probably 16" but including those tires the total diameter is at least 20" or more. Then you need to calculate how many amps are needed to provide that speed by that motor.

 

[Amaxophobie]

The 6384 is definitely capable of delivering you desired speed BUT you will have to watch the motor temperatur on longer uphill climbs. I built a scooter with a 6374 170kv and a longboard with a 6384 170kv and both were geared to around 45-50km/h with good acceleration. They are small but very powerfull if used correctly!
The problem is the low voltage of your battery which you say is fixed. These RC motors (50mm - 63mm) work best if their rpm gets close to 7000-8000rpm. All their torque comes from high rpm and big gearing ratios. Your motor will most likely get very hot if you plan to use it on hills a lot.

Is the 120kv also fixed?

I think a major problem will be the gearing as SlowCo already mentioned. Two stage is too complicated for a simple scooter and for a direct drive with 120kv you need a very big chain ring.

A hubmotor would be the easiest and quietest solution. Especially in this power range you can find them very cheap.

 

[azrael78]

Thank you Amaxophobie for the explanation, very helpful!

Do you think 3V 500W hub motor on 16 inch wheel can go 30km/h or more on flat, and 15km/h on medium climb?

Also, for 6384 120KV, I would put 11T sprocket on motor and 65, 74, or 80T (there is a lot of choise on aliexpress and local shops) on rear wheel to get desired max speed.
About 120KV, should I go for more or less KV ?

 

[Amaxophobie]

Do you think 3V 500W hub motor on 16 inch wheel can go 30km/h or more on flat, and 15km/h on medium climb?

Of course if paired with the right controller. If i were in your place I would either buy a hub kit with controller (cheap) OR the hub seperate and a VESC (full programmable controller for about ~100 USD). You can set all the parameters like power and torque here and have an app to show your speed and battery status on your smartphone while driving.

About 120KV, should I go for more or less KV ?

This is quite hard to answer...
Efficiency wise I would recommend higher kv to get to around 7000rpm. That would mean 7000rpm/36V =~200 kv. But because your wheels are very big you need a very very high gearing of around 15:1.
And even on the 120kv you would need around 9:1 ratio. that would result in a 100t chain ring.

For the gearing issue less kv is better but will run inefficient. I don't recommend it!

On my first self built electric scooterthat I mentioned earlier I knew nothing about the behaviour of these RC 63mm motors. So I started with a 90kv 6374 and geared it around 3:1 with a battery voltage of 40V. The acceleration was good and the top speed around 45km/h. But the motor became very hot even on the flat only from accelerating. Then after lots of reading I odered the same motor only with 170kv and changed the gearing to 6:1. And now the motor stayed cool, acceleration got a lot better and top speed went up to 50km/h.

If you compare the rpms it gets clearer:
40V * 90kv = 3600rpm
40V * 170kv = 6800rpm

To sum it up: Small RC motors need high rpm and high gearing if you want to use them on EVs. Since you have a big wheel this will be hard to fulfill. Kick-scooters and longboards come with small wheels thats why using RC motors on them is simple.

 

[azrael78]

Thank you again for help, it's clearer now, this could prolong the project by couple months, Higher KV 6384 is twice the price on aliexpress, or maybe at some point upgrade existing battery from 36V to 48V ( new BMS of course), it's cheaper then new DIY 48V battery.