Turnigy 6374 192kv, help!

[nielsb]

Hi !

First a small introduction:

My name is Niels and live in the Netherlands.
I'm 29 years old, father of two, and studying administrative law at the UVT.
My interst in electric powerd vehicles started with an electric powerd boat.
8,5 meters long, 140 years old, with 2x 1650ah battery and a 48 volt - 7kw electromotor, on witch I occasinaly
do tours with people in our canal. (in the pic it's me, my father and my two children).

Now it started with an idea to convert my old carbon peugeot race bike into an electric powerd bike with an friction
drive, to reduce weight and make easy changes in the setup. I believe it is called the kepler system(?).

Now I started out, very boldly, by ordering some components:

- 2x 3700mah 5s 18,5v lipo and safety packaging
- a charger and a 12v 28A power supply (LED driver)
- and the most imported one! a Turnigy aerodrive motor, 192kv 2750watt 80A max
http://www.hobbyking.com/hobbyking/store/__18129__Turnigy_Aerodrive_SK3_6374_192kv_Brushless_Outrunner_Motor.html

I still need a servo tester wich I will convert to throttle control, and an ESC.

Now my question is, what would be the best setup for my motor (and lipo pack in series or parallel)
My main difficulty is finding the right (not to expensive) ESC.

I am wondering if I put my 5s lipo's in parralel, creating 7400mah at 18,5 gives me enough to enjoy this motor, also it would give me a cheaper ESC, the 10s/12s ones are very expensive.
If I calculate the right ESC with this setup i get : 2750watt motor / 18,5v = 148 Amp, but I don't understand how I can drain more amps than the 80A Max on my motor??? what am I doing wrong?

Also, what kind of ESC is mostly used? With BEC seems more handy to me, because my servo tester will have power from the ESC rather than OPTO where I will have to provide my servo tester with a spare battery or UBEC.

Now, I'm really new at this, and R/C, so my kwoledge is currently based on reading a lot on this site and R/C sites.
I really hope you can help me out!

Greetings,
Niels

 

[E_mountainboard]

hey Niels,

I have the same motor ( I have two infact that power a 2wd mountainboard. The controller I use is this one ( http://alienpowersystem.com/shop/car-esc/alien-150a-2-12s-car-esc-hv-twin/ )
But you might be better of using one like this since you only need to control one motor: http://alienpowersystem.com/shop/airplane-esc/alien-120a-3-12s-jet-esc-hv/
Or one from hobbyking: http://www.hobbyking.com/hobbyking/store/__600__182__Speed_Controllers-HV_ESC.html
But you need to know that at 18.5v you won't be able to pull 2750 watts, the voltage is just to low for that at best you would get a theoretical peak wattage of about 1450 watts. If you want more power you will need to get a higher voltage. Bec or opto doesn't matter that much because I think you can just connect the power cables of the external bec ( ubec ) in parallel with the ESC's power cables. I would choose your voltage according to your top speed. ( if your wheel has a diameter of about 70cm the motors is 6.3 cm in diameter and turns 192* 18.5v = +/- 3550 turn/ min. Then you can calculate you top speed. 192 * 18.5 = 3552
3552/ (0,70 / 0,063 ) = 320 -> In one minute your wheel turns 320 times.
320 turns/min * 2πr ( wheel circumference) * 60 * 10^-3 ( m/s -> km/ h )
320 * 2 * π * 0,70m * 60 * 10^-3 = +/- 60 km/h
That is a speed that you propably won't reach because of friction wind ressistance etc... It will also be quite a heavy load for your motor you could compare it to starting your car in third gear... ) If you really want to choose your gear ratio I would use gears and not a friction drive. But it is possible, just give it a push to get going.

 

[nielsb]

Thanks for the tips!
I will be looking at HV ESC's, now trying to find a cheaper one, but that is hard for a HV.

Also I will be staying with friction drive, because I'm trying to devolop a system that simply can be transferred to another bike.

But for amperage, I can trust it will not raise above the 80amp max from my motor?

 

[spinningmagnets]

Welcome, nielsb. Look over this thread in the link below about friction drives. The drives that use the motor shell as the driving roller are smaller, lighter, and simpler (like Kepler and Adrian). But the drives that use a separate roller have better performance on steep hills (like EVTodd and spinningmagnets).

Holland is pretty flat, so either style will work well for you. Look through this discussion and we can talk more. You will not need an ESC with an amp-rating of more than 80A with a friction-drive.

http://endless-sphere.com/forums/viewtopic.php?f=28&t=14403&p=214997

 

[nieles]

I will be looking at HV ESC's, now trying to find a cheaper one, but that is hard for a HV.

calculate you top speed. 192 * 18.5 = 3552
3552/ (0,70 / 0,063 ) = 320 -> In one minute your wheel turns 320 times.
320 turns/min * 2πr ( wheel circumference) * 60 * 10^-3 ( m/s -> km/ h )
320 * 2 * π * 0,70m * 60 * 10^-3 = +/- 60 km/h

you might not want to go higher than 5-6s with a friction drive(with the motor directly on the wheel)

the power rating of the motor needs to be "matched" to the top speed of you bike. since you are not using gears, you battery voltage is the only thing that can be changed to suit the needs. (its more technical than this, but a little hard to explain without knowing your technical know-how)


PS my name is niels too, and also from the netherlands (Zwolle).

 

[nielsb]

Look through this discussion and we can talk more

Thanks for the thread, a lot of examples! So for my build is a little different. I used materials I had lying around to come up with a proto type. The motor is a 192kv 6374, The ESC is a 100A K-force, the battery a single 3700 mAh 5s LiPo and I used a servo control to accelerate. But unfortunatly, it doesn't work quite well..

I think the motor slips.. But also I have the feeling there is very little power, even if it doesn't slip.
So what do you advise? I can use some belt sander paper for extra friction, I can try to use springs and give the motor more depth in de tire. And maybe I should change some settings of the ESC? They are now all standard.
Below I will put a picture of the ESC's standard settings. Also I made a video of the prototype:

Video:
http://www.youtube.com/watch?v=QOJfJnWEPD8
Pic:

 

[nieles]

try lowering the timing (0deg)
and experiment with the start mode.
the rest of the settings should be fine.

the fact you cant get any power is because of the slipping. try a rubber band from the end of the wooden plank to the axle of the wheel.

you could also try lowering the pressure in the tire.

 

[nielsb]

Hi Niels,

I tried the using a rubber tire tube, but it has just slipped off very easely, I can't seem to fixate it to the outer shell without glue. I tried tying the motor-platform to the axle of my bike on either sides. You can see in the pic the blue copper wire. It seems to work, at least inside the house The weather (as you would know) is very wet at the moment.

Could you explain to me the Timing Mode what it's link is to degrees? And what the influence is on the motor functioning?

 

[nieles]

with advanced motor timing, (more than 0 deg) the kv of the motor will be higher. as a result, you can draw more power from the motor, but it will also create more heat (hotter motor)

instead of the copper wires, you should try a rubber band. and maybe put a hinge in the wooden plank, so it can move up/down as needed.

 

[E_mountainboard]

http://www.benl.ebay.be/itm/Anti-Slip-Tape-with-Reflective-Strip-Non-Slip-High-Grip-/310492474242?pt=UK_Flooring&hash=item484acb2b82&_uhb=1
Maybe the anti slip tape might help you with your problem.

 

[EVTodd]

You have that motor really far back on the tire. When it spins it's trying to work it's way off and away from the tire. If you have it forward of the center (vertical) line of the tire it will try to bite into the tire as it spins.