need help selecting motor and esc

Started by chintal, January 19, 2014, 12:09:31 PM

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chintal

i have a 1:10 4wd off road electric rc car
but it's stock motor is brushed and has nicd 2.5 amps battery
so want to upgrade it to brushless system
i already have a 3s 10000mah(10amp)lipo  battery
please suggest the best parts for this javascript:void(0)
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iamahuman

A 10Ah 3s lipo wold be too big and heavy for a 1:10 vehicle.

If it's got a brushed power system in it, the drivetrain is probably good enough for brushed power only. If you go brushless, you need to use a very mild motor.

What is the size of the motor? If the mounting holes match up, you can use a brushless motor. If not, you'll need to make your own mount.
"Chuck Norris once overcharged a lipo. Thank him for the Sun."

SSC LCG Slash 4x4.
JQ THE eCar.

chintal

Its got all metal parts and drivetrain is good enough for a brushless motor
Plz suggest a combination
If a 10amps would be too big plz also suggest appropriate battery
Ty
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iamahuman

Which car is it?

What is the size of the motor?
"Chuck Norris once overcharged a lipo. Thank him for the Sun."

SSC LCG Slash 4x4.
JQ THE eCar.

chintal

http://henglong-toys.com/P.Show.asp?nhl=229
this is the car i bought
all details as per the site
roduct Details:
1:10 Scale Electric Powered 4WD off road R/C Truck
Factory Assembled - READY TO RUN
Chassis: 2mm Thick Aluminum Chassis
Drive Type: Shaft Driven
Drive: Full Time 4 Wheel Drive
Motor: Type-550 w/Heat Sink
Electronic Speed Control 320A Stepless
Transmission: Single-Speed
Gearboxes: Sealed Front and Rear
Shocks: Aluminum Alloy Bodied
Front/Rear Differentials: Planetary Gear Type
LCD 3-Channel Transmitter with Steering and Throttle Trim
Body: Fully Trimmed and Painted Body
Battery: 7.2V 1800mAh Ni-CD
Australian Standard Charger
Ball Bearing
Suspension: Hydraulic Pressure Aluminum Alloy
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1firefly2

Dear Chintal,

If you have a brushed 550 motor, then go for brushless 540 size (~ 36 mm x 50 mm).

Given that you have 3S Lipo(your pack's mah is too high/ heavy), please take a look at the following motor:
http://www.hobbyking.com/hobbyking/store/__27860__Turnigy_Trackstar_1_10_10T_3900KV_Brushless.html

Now for ESC to drive this motor, following will suffice:
http://www.hobbyking.com/hobbyking/store/__14634__Turnigy_TrackStar_1_10th_Scale_60A_Car_ESC_Version_2.html

I have not seen that vehicle so cannot comment on other upgrades but if you wanna try, then its good to experiment.

Try to get a 2S Lipo to be on "safe side" though. This seems good enough:
http://www.joyrisinghobby.com/Pages/ProductDetail.aspx?pro=159


Regards,

chintal

all parts in the car are metal expect for the arms they are of plastic but tough one
will that do or do i need to upgrade to metal arms
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chintal

and how long will it run with a 5amps 3s battery
and with a 2.2 amps 3s battery
and 3.3 amps 3s battery
what diffrence does it make if i use a 3s or a 2s ?
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1firefly2

Right now, I think there is no need to replace the arms with metal ones.

In similar conditions, same vehicle running in similar way requires similar power.
So a 5000 mah 3S Lipo will give almost twice as much run time as a 2500 mah 3S Lipo (pack weight difference may be considered for exact ratio)
Similarly, You may calculate ratios between 2200 & 3300 mah batteries.

3S vs 2S...well if you use 3S 'judiciously' with lower gearing, then you will get more run time / less heat for same capacity of Lipo pack. Otherwise 3S means more rpm, heat & serious wear and tear in the drive train.

Now if you want to replace a 5000 mah 3S battery with a 2S one for similar run time, we have to roughly calculate the mah of the 2S Lipo required to do so.

Let us see:

Your vehicle at a 'W' weight takes 'F' amount of force from 'T' amount of torque from the motor to move at an average speed 'S' against friction & air drag etc for given weight and shape of the vehicle. To this, the motor has to 'work' against the surface friction, drive line friction, air drag etc.

For a given vehicle, this work done per unit time, power 'P' is same for same conditions.

Case 1 - 5000 mah 3S Lipo:

Power required = P (as above)

Power = Volt x Amps,
P = 11.1 x I1

Case 2 - 'Y' mah 2S Lipo:

Power required = P

P = 7.4 x I2

So,
I1 / I2 = 7.4 / 11.1 (Notice I1 < I2 so less heat!)

But I1 is current drawn per unit time from 5000 mah capacity of 3S Lipo
Hence, the ratio I1 / I2 gives us the ratio of mah1 / mah2 i.e 5000 mah / Y mah :)

Therefore, 5000 / Y = 7.4 / 11.1
or, Y = (5000 x 11.1) / 7.4 = 7500 mah or 7.5 A Lipo pack!!

In this way you can choose 3S / 2S or can identify mah to match your run time as per your requirement.

Please correct me if I am wrong somewhere & sorry for this long boring post as I am quite bored here in office  :(

chintal

Thanks for all this didnt get the gear part
Cz nt into cars mostly into multicopter's
Wt would be a smaller gear and wt would be a bigger gear plz explain wid a examle
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GhostRider

Quote from: chintal on January 22, 2014, 05:46:38 PMThanks for all this didnt get the gear part
Cz nt into cars mostly into multicopter's
Wt would be a smaller gear and wt would be a bigger gear plz explain wid a examle
If you add more power i.e: higher mah battery then it would require lower pinion gear.

It all depends on which brushless motor you choose post which you can decide on 2S/3S

As far as I have seen your 1/10 scale, go in for velinon 550 motor, it might be expensive but one of the best...which will support upto 3S lipo

1firefly2



There are two preliminary gears in drive train:
1. Drive gear (Pinion)
2. Driven gear (Spur)
Pinion is mounted on motor shaft which drives Spur that transfers power to drive line.
If motor's rotational speed is N1, Pinion teeth count is T1 & Spur teeth count is T2, then:
N1 / N2 = T2 / T1, where N2 is speed of Spur gear.
This is gear ratio.

If one increase T1 & or decrease T2, then we say higher gearing (Top speed of vehicle increases but acceleration decreases).
If one decrease T1 & or increase T2, then we say lower gearing (Top speed of vehicle decreases but acceleration increases).

Now the speed of motor and so the vehicle is directly proportional to voltage.
So if you use 3S in place of 2S, the speed will increase and so will the heat and wear tear.
To increase run time, gearing has to be lowered as mentioned above while raising voltage translating into same speed as before.

chintal

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1firefly2


chintal

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chintal

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chintal

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