30mph Amp Mt

[Ramsey3704]

Hello everyone,

I am new to the world of RC, but have owned a DJI Mavic Pro for a few years. Picked up an Amp Mt by reccomendation of the LHS for myself a more importantly my 6yr old daughter. Looking to get just a bit more out of it for when she progresses a bit and to keep up with the Arrma Big Rock I am getting once they start shipping the V3 at the end of the month. She has had a toy grade truck for a few years so has some basic skills.

I already ordered:

2s Lipo 5200mah with voltage alarm and charging bag.
Battery connector adapters (until I decide on battery connector then will resolder)

HTRC c240 Duo charger

Future Parts:

Hot Racing Metal Spur gear
20kg Ks 3518 servo

Rpm servo saver eliminator

Surpass Hobby f540 v2 brushless motor ESC combo. Thinking 3300kv over the 4370kv. Probably with a 15-17t pinion.

DumboRc x6 TX and RX


Trying to keep it fairly budget as it’s a kids truck so breaking this will happen!

 

[TrackJunkie]

I just recently got the 3300kv f540 and am hoping to get it running tonight. I will post my results. One thing to watch out for on those is that the output shaft is shorter. You have to split the difference between the pinion being too far in to fully engage the spur gear and the pinion set screw not being fully on the shaft. I went with more gear engagement and only have maybe a little more than half the set screw catching the end of the shaft. We will see how that works...

 

[Ramsey3704]

I just recently got the 3300kv f540 and am hoping to get it running tonight. I will post my results. One thing to watch out for on those is that the output shaft is shorter. You have to split the difference between the pinion being too far in to fully engage the spur gear and the pinion set screw not being fully on the shaft. I went with more gear engagement and only have maybe a little more than half the set screw catching the end of the shaft. We will see how that works...

Good to know. Thank you.

 

[Steve g]

Good to know. Thank you.

I just recently got the 3300kv f540 and am hoping to get it running tonight. I will post my results. One thing to watch out for on those is that the output shaft is shorter. You have to split the difference between the pinion being too far in to fully engage the spur gear and the pinion set screw not being fully on the shaft. I went with more gear engagement and only have maybe a little more than half the set screw catching the end of the shaft. We will see how that works...

Did you try spinning the pinion gear around? Would have to put it on the motor when its out of the truck

 

[TrackJunkie]

So I took the motor out and reversed the pinion like suggested above and it worked well. You have to slide it as far in on the flat as it will go, but it’s just good enough. I got it running with the new motor on the old nickel metal battery. So far I love it . it’s significantly quicker without being ridiculous wheelie over backwards powerful. With the redcat racing esc there is no chugging to speak of. I will do some gps speed runs tomorrow

 

[TrackJunkie]

Did some gps tests tonight. Compared to the stock set up the top speed on the stock battery increased from about 17 to 20 with much better acceleration. Putting in a 2s lipo Made it much punchier and prone to wheelie, but only brought the top speed up to 21-22. After a good eight minutes of Full throttle bashing mixed evenly between asphalt and fairly thick grass the motor was on the hotter end. I could hold my finger on for two seconds, but it got a little uncomfortable. Maybe go a tooth down if you plan to be off road alot, But I think the stock gearing Is about right for my use.

 

[Sleds]

I filed my pinion down so that the set screw is fully on the shaft and it's working well. I also went with a 21 tooth pinion and that's good for around 30 mph with the 3300 motor. They're actually a fun little car, my son and I set ours up for the local track and they do pretty good around it.

 

[TrackJunkie]

Is that on 2s or 3s? I was expecting near 30 but only got 22. I calculated the theoretical top speed (voltage Times kv rating divided by gear reduction Times tire circumference) and got 25 mph, so my 22 seemed reasonable, but it seems like everyone else gets 30 with any brushless set up. I wasent going for big top speed anyway, but i was surprised.

 

[Sleds]

Is that on 2s or 3s? I was expecting near 30 but only got 22. I calculated the theoretical top speed (voltage Times kv rating divided by gear reduction Times tire circumference) and got 25 mph, so my 22 seemed reasonable, but it seems like everyone else gets 30 with any brushless set up. I wasent going for big top speed anyway, but i was surprised.

That's on 2s. On 3s my car is an animal, doing about 30mph when you punch it it flips over. If you put some weight in the front it might be controllable, but just the car by itself it's not drivable on 3s. But that's with a 5000mah 50*C 3s, not sure if it would be different with a smaller 3s with a lower C rating.

 

[Sleds]

On my sons, we have a 2650kv motor and I've got his set up with a 25 tooth pinion and his top speed is almost the same as mine. But I've got his tuned so he can run for a half hour straight on the track with a 5000mah 50*C 2s and his motor is just warm to the touch. His is a sensored Cheetah motor and is very smooth and the power is more linear.