Big Rock My big rock build

[Wes13]

Got the last parts from jenny's this week to start my build so here it is.
I had allready changed servo for a 25kg one from amazon, added some proline body protectors and mounted an old vorteks wing i found for cheap.
Now i'm changing motor & esc after i switched those to a granite mega.
Firma 130 & surpass 3670 2850kv motor.
Got a 5 pack of pinions aswell from 17t to 21t, the 21t should be able to get it to 100km/h or 62mph we will see.
Got some rocket fans aswell to try keep the temps down.

 

[Izzy]

Can't wait to see Finish

 

[DRBNGR]

Yo

Got the last parts from jenny's this week to start my build so here it is.
I had allready changed servo for a 25kg one from amazon, added some proline body protectors and mounted an old vorteks wing i found for cheap.
Now i'm changing motor & esc after i switched those to a granite mega.
Firma 130 & surpass 3670 2850kv motor.
Got a 5 pack of pinions aswell from 17t to 21t, the 21t should be able to get it to 100km/h or 62mph we will see.
Got some rocket fans aswell to try keep the temps down.
View attachment 168472

You're going 4S?

 

[Wes13]

Yo

You're going 4S?

No, not for now.
Reason i went with the 4s esc is to try keep it cool when i'm running a bigger pinion.
That is the theory anyway will see soon when i do some test runs...

 

[DRBNGR]

Isn't the 2850kv motor a bit low then?

 

[Wes13]

Isn't the 2850kv motor a bit low then?

Thats why i have pinions from 17 to 21.
17t should give about the same speed as the stock 3200kv motor with 15t pinion...

 

[DRBNGR]

As i am struggling with choosing the right motor for my BR. Why did you go for the 3670 2850kv and did not take the 3660 3200kv? Is there any positive effect that i don't have on my radar?

 

[Wes13]

As i am struggling with choosing the right motor for my BR. Why did you go for the 3670 2850kv and did not take the 3660 3200kv? Is there any positive effect that i don't have on my radar?

The motor is longer so has more torque.
It should run cooler in general then the stock motor

 

[DRBNGR]

Is that fact? This is the information i have been missing on my search! The longer the motor the higher the torque?
But more teeth on the pinion lower the torque again right? So doesn't that neutralise?

 

[Wes13]

Is that fact? This is the information i have been missing on my search! The longer the motor the higher the torque?
But more teeth on the pinion lower the torque again right? So doesn't that neutralise?

Yes but in return you get more speed.
Thats why i got 5 pinions with the motor to search for the sweet spot.
You should download the "rc car gearcalc" app, it tells you exactly what speeds to expect with what motor and pinion

 

[DRBNGR]

Are you more the speedrun type of driver or more the jump and backflip guy?

 

[Wes13]

Are you more the speedrun type of driver or more the jump and backflip guy?

Both

 

[TheDude]

SPEKTRUM™ 2200Kv BRUSHLESS MOTOR /SPEKTRUM™ FIRMA™ 130A SMART ESC /INTERCO SUPER SWAMPER TSL BOGGER TIRES/ off of my busted axial ryft thing does double backflips off speed bump with a 26 tooth pinion but i need better cooling to use that size gear can still backflip off my porch with 15 tooth i haven't put the 26 t back on because it was getting warm gotta put more fans to cool enough to run a full battery pack without getting right to the edge of to hot

 

[DRBNGR]

Both

Damn i was hoping that this makes the difference. Ok, i will try your setup too.

 

[Jessica Hyde RCPD]

Damn i was hoping that this makes the difference. Ok, i will try your setup too.

I can tell you, that the xx70 series motor is the way to go in a Big Rock. This gives you higher torque when using the same size pinion as stock and allows more gearing options for doing different things. So, you really just need to change from basher tires to street tires after you change the gear. Then vice versus. The 20t pinion is a good spot to start with stock setup. My last video shows you a very good setup. I added HR pivotballs to stock links. I have not drove it yet. 4s with the 6s BLX system is fun. I also recommend Acer Racing Ceramic Hybrid bearing for the center drive shaft. It holds up and helps.

 

[Wes13]

Got to 82km/h (51mph) on 17t pinion.
Runs very cool aswell.
Gonna try bigger pinion soon

 

[basher27]

View attachment 169977
Got to 82km/h (51mph) on 17t pinion.
Runs very cool aswell.
Gonna try bigger pinion soon

I have also have a big rock and just bought the same esc and trying to find a good motor to pair with it. It sounds like both of us are trying to achieve the same goal running a 4s system on 3s to run larger gears and keep everything cool. Have you been pleased with the proformace of your setup after using it for awhile? Is the motor a 4s capable motor? Lastly has the driveline of the car held up? ex. slipper clutch, drive shafts, diffs ect? Can you attach a link to purchase the motor? Thanks.

 

[Wes13]

Didn't have lots of time lately so not been running much.
Still on the 17t pinion.
4s should be possible for this motor but it will probably overheat, 3s is great.
No issues yet, but as i said haven't been running alot...
https://m.banggood.com/Surpass-Hobb...ds=search&act_poa=POA6079025&cur_warehouse=CN
I got the 2850kv motor

 

[basher27]

Thanks for the response. How are you liking the rocket fan? Is there a noticeable difference? Does it take any mods to install or plug and play?

 

[Wes13]

The motor fan is plug n play, but can only be tightened by 2 screws on the stock heatsink.
You do need to plug the motor fan in the esc and the esc fan in the reciever because the cable is not long enough.
If you don't change the esc fan, you will need to run a longer cable.
For the esc fan you can run a 30mm rocket fan and keep the esc cover but you will have to trim the inside of the cover to make it fit like i did. You can also just leave the cover off