E-pocketbike - C6374-200 motor

Hi there,
after my succesfull built of my longboard ( http://endless-sphere.com/forums/viewtopic.php?f=35&t=56568) it's time for a second project : an electric pocketbike.

Some data :
pocketbike :
motorsprocket = 11T , ordered from this seller today : http://www.electricscooterparts.com/sprockets25chain.html
wheelsprocket = 68T (#25 chain)
motor : C6374-200 kv motor
lipo: 6s 5000mAh
ESC : Hobbywing 120A (untill 12s)
BEC : 3.5A

ESC will be controlled by a general servotester.
Bike has proper working disc brakes

Some very early pictures :

That's a lovely project,
looking forward to see your progresses, especially how you are going to deal with the servotester,
any top speed evaluation yet ?

The pocketbike has a standard throttle in the handle bar, that operates a Bowden cable that shifts up and down, during throttle changes.
So I have to make a translation from this movement to the rotation of the potentiometer of the servotester. I already have some ideas, however let’s see if it’s feasable.
Regarding top end speed; when calculating with 6 cells lipo of 3.5V average and a motorsprocket of 11T and a wheelsprocket of 68T, with a motor kv of 200, and 5% total losses this leads to 35km/h (22mph), which is ok for me I think.
On the other hand, 12s lipo would also be possible with this ESC (I have more 6s packs), which would increase the speed drastically to about 70km/h (43mph) which I think is a little to fast for this little monster …

But first let’s see if the motor can handle the forces, since they are a lot higher than a typical “small wheel longboard” ….

666yeti666 said:

The pocketbike has a standard throttle in the handle bar, that operates a Bowden cable that shifts up and down, during throttle changes.
So I have to make a translation from this movement to the rotation of the potentiometer of the servotester. I already have some ideas, however let’s see if it’s feasable.
Regarding top end speed; when calculating with 6 cells lipo of 3.5V average and a motorsprocket of 11T and a wheelsprocket of 68T, with a motor kv of 200, and 5% total losses this leads to 35km/h (22mph), which is ok for me I think.
On the other hand, 12s lipo would also be possible with this ESC (I have more 6s packs), which would increase the speed drastically to about 70km/h (43mph) which I think is a little to fast for this little monster …

But first let’s see if the motor can handle the forces, since they are a lot higher than a typical “small wheel longboard” ….

Click to expand...

na 43mph if fine but will be to slow to accelerate with your motor choice and will get to hot to quick.. mine is geared for just under 50mph ( tops out at around 46-47mph ) and its a real hoot to ride.. ( it is a different motor ) i think for it to have good acceleration you may have to gear it down a bit more even when running it on 6s

aha, that's good info.
The gear ratio is currently 1: 6.18 so indeed is not too high, maybe 1:10 would be better, but then I would need a wheelsprocket of 110T since my motorsprocket is quite fixed with 11T (this is mainly due to availability of motorsprockets) and I doubt if that's available. I will check for that. Of course then the topspeed would drop, but that can be compensated by a higher lipo count.

Can you tell me more about your application and what your gear ratio is at ?
Does it run on 6s lipo ? What are your max currents during acceleration ?

thx
Sebastien

666yeti666 said:

aha, that's good info.
The gear ratio is currently 1: 6.18 so indeed is not too high, maybe 1:10 would be better, but then I would need a wheelsprocket of 110T since my motorsprocket is quite fixed with 11T (this is mainly due to availability of motorsprockets) and I doubt if that's available. I will check for that. Of course then the topspeed would drop, but that can be compensated by a higher lipo count.

Can you tell me more about your application and what your gear ratio is at ?
Does it run on 6s lipo ? What are your max currents during acceleration ?

thx
Sebastien

Click to expand...

Its a competitive race bike for indoor minimoto tracks. current limit is 160A on 12s , and I think ( from memory )the motor sprocket is 13t and rear is 55i'sh
the motor has a kv of around 120

a race bike, oh well that's nice of course, but ehm, with 13T and 55T you'd even had a lower gear ratio 1 : 4.23.
But of course your motor has a much lower kV and as such more torque. What was the weight of the brushless motor ? Mine is about 750gram.

Don't you have a link to your built ?
thx
Sebastien

666yeti666 said:

a race bike, oh well that's nice of course, but ehm, with 13T and 55T you'd even had a lower gear ratio 1 : 4.23.
But of course your motor has a much lower kV and as such more torque. What was the weight of the brushless motor ? Mine is about 750gram.

Don't you have a link to your built ?
thx
Sebastien

Click to expand...

motor weigth is around 1kg . I did not document the build , sorry.
here is a link to a thread http://endless-sphere.com/forums/viewtopic.php?f=12&t=32042&start=125 and there is some vid about half way down the page.

The motor is soooo smalll for the bike

gwhy! said:

666yeti666 said:

a race bike, oh well that's nice of course, but ehm, with 13T and 55T you'd even had a lower gear ratio 1 : 4.23.
But of course your motor has a much lower kV and as such more torque. What was the weight of the brushless motor ? Mine is about 750gram.

Don't you have a link to your built ?
thx
Sebastien

Click to expand...

motor weigth is around 1kg . I did not document the build , sorry.
here is a link to a thread http://endless-sphere.com/forums/viewtopic.php?f=12&t=32042&start=125 and there is some vid about half way down the page.

Click to expand...

ok thx,
your other project is a serious built , wow, respect !!

@cwah:
well, this is the motor I had available, so let's see if it works out at all.
On the other hand it's no 'racing-project' . Would be nice if my kids could drive it safely as well ...

The motor is soooo small for the bike

Click to expand...

Experiments are fun, but if you want to be able to sell this motor later, keep a close eye on the temperatures. I would have personally recommended an 80-84 @ 170-Kv, or an 80-100 @ 130-Kv. Several builders (incl. Thud) have re-terminated the 80-84 to Wye, which converts the motor from Delta, and cuts the Kv in half for a result of about 80...and also makes life easier on the ESC.

ok, thanks for the tip.
So what you are saying is basically: lower kv, higher torque.

At this moment I could compensate it by choosing another, higher teeth count wheelsprocket, let's see what's available.
I know a guy who can also rewind motors, but the cost is not in proportion to the cost of the motor.

Rewinding is clearly an option, but simply re-terminating the Delta/Wye connection of the phases is pretty quick and easy. Thud wrote the pictoral on re-termination, and also re-winding these motors, in order to get specific characteristics.

By lowering the Kv, you can use higher voltage to get the same motor RPMs. Sometimes this can allow you to use easier-to-source sprockets (instead of custom units), and at other times it can allow you to use higher voltage, but...lower amps. Amps are where the majority of the heat comes from. Another source of excessive heat is loading the motor at half it's max RPM, and bogging the motor down.

Even if a 63mm motor will "work", the extra copper mass of the larger motor will allow the motor to run cooler (and hopefully last longer), plus it can then absorb bigger temporary heat spikes without damage.

Start out with too much reduction while using the highest volts you can fit. Swap-in lower final reduction sprockets to gradually raise the top speed while you monitor the motor temps. Keep the max temps at 200F/93C or less.

The problem with just re-terminating from delta to wye is that the wye termination will actually run hotter if all other things are equal. its a great way to get the kv down but it will run hotter. power is power no matter how you come to get that power i.e higher volts or higher current.

Any update on this project? I'm working on just like that at the moment and would like to see if its working

Hi All, indeed the project is still ongoing, however not a lot of progress.
The thing I managed to make is the mechanical construction around the motormount. I took some aluminum plate (used 2mm for the bottom one) and bended it to make it strong. Also added some extra plates to further enhance it so it is a strong kind of box part.

However now that I’ve put it onto the bike it seems still some bending is possible with respect to its mount. Due to the fact that the motorgear is quite small I can imagine it can skip teeth under pressure, when driving off, so have to think about a mechanical enhancement to the frame ...
There is 2 guidance wheels (not mounted on the pictures ) that pull the chain more horizontal, so could help a bit as well to prevent skipping.

Furthermore I received the mechanical/electrical throttle handle as well as the interface to the motorcontroller from this guy : http://alienpowersystem.com/ (delivers fast but the downside : delivery cost to mainland is very high …)

Autumn has really started here in our little country (the Netherlands) , so potentially less distractions from my other hobby ; flying RC helicopters ….

So far the updates uptill now
regards
Sebastien
















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Completely forgot to mention that i purchased the motor gear of 11teeth and the rear gear of 88teeth....
Regards
Sebastien

any progress?

unfortunately no progress ...

Regarding the colorcode for the wuring of the electric throttle, it is as follows :

Red = +5v
Green = signal
Blue = negative
Yellow = positive battery for battery level