4000kv amp mt gearing running 3s lipo 50c

ecxampbasher88

New Member
Messages
1
i have upgraded to all metal gears and im about to start running it on 3s lipo 50c and i dont want to burn out the motor its a 4000kv system 4 pole 70A Onyx system does anyone have a gearing setup for pinion and spur that would be suggested that i can pick up
 

KyleRC

Well-Known Member
Messages
307
I have blown 4000kv motors on 3s before where the magnets come off the rotor. The smallest pinion i could fit with a 540 size can (without modding the trans case) was an 18tooth. It might be easier to buy a lower kv motor or run that one on 2s and gear it up if you want 3s LiPo speed. IMHO 3s 4000kv is just too much for a light 2wd .

you could try running an oversized spur but you Won’t be able to use the gear cover
 

Steve g

Well-Known Member
Messages
288
Location
Massachusetts
I used to run a 3900kv on 3s, with 2.8 badlands. I used a 16t pinion with the stock spur. Had to shave some of the transmission case to make it work. It would get hot fast off road, like the previous post mentioned its not a good idea to run such a high kv on 3s. Now I run a 3300kv 6 pole on 3s on 1 truck, and a 3100kv 4 pole on another. Those motors are much better for 3s.
 

Aggie72

Member
Messages
13
I used to run a 3900kv on 3s, with 2.8 badlands. I used a 16t pinion with the stock spur. Had to shave some of the transmission case to make it work. It would get hot fast off road, like the previous post mentioned its not a good idea to run such a high kv on 3s. Now I run a 3300kv 6 pole on 3s on 1 truck, and a 3100kv 4 pole on another. Those motors are much better for 3s.

Whats your gearing on the 3100kv? Spur and pinion?
 

Breenus

Member
Messages
8
I've been running my Amp MT on the hpi branded flux 4000kv for the past year or two. The motor does get hotter than I like, though, and even when moving at pretty high speed it does a wheelie when I get on the accelerator. I actually have to be really careful not to do flips, I definitely will be putting some weight up front, too. Since it has too much speed and power I'm going to check my gears, I have a couple spur gears sitting around and one of them might help all of these issues.

Stock gears were fine, but I bought Team Associated metal replacements and decided to use them, well most of them, there is still at least 1 plastic in there somewhere because looking through parts the Associated bag still has the big plastic gear, so I must have left the stock in there on purpose. I may find that it's a better ratio than the one sent with the Team Associated kit.

The motor came with heatsink and fan but no three wire connector to fit my ESC(also hpi branded), I may try connecting the two wire fan to the three wire ESC if I can dig up the proper piece of electrical converter/connector. Even without the fan that heatsink would help, so I'm going to take the little fan off and just put the heatsink on if nothing else. I routinely take my laptops apart to clean and reapply thermal paste, I should be able to come up with a good way to attach the heatsink securely in place and then would be able to put some Arctic Silver on it 😉

I destroyed the left front wheel caster block and the right rear suspension arm came loose twice on the day so I've ordered aluminum replacements for wheels, suspension, and steering. While I have it that far apart I might as well take the gearbox apart, too.

I'm using a Traxxis 25C 3S LiPo rated at 5000mAh, it's incredibly fun and crazy fast. I don't think I've ever had it at top speed but it has to be over 50mph. Trying to get to see what top speed looks like is what led to the recent destruction lol. I should have just had fun instead of testing my little Frankenstein's monster.

I thought I was saving money by buying the ECX Amp, but I've easily put $500 into it since buying. I probably get more out of it doing it myself, overall, but $650 would have bought a very nice short course truck.
 

Breenus

Member
Messages
8
Ok so the aluminum replacements for the broken wheel hub are coming today and I already have all the other Hot Racing aluminum parts installed. I realized the fan with two wires can be connected to the three wire esc cable so I wired that up. The motor was hot enough to be a little worrying so I'm happy to have that working too. I can't wait to get these last part on and run the truck again!
 
Messages
7
Whats your gearing on the 3100kv? Spur and pinion?
I recently installed a 3100kv motor / 60A ESC in my Ruckus. I've found it great fun on 3S with the stock spur and pinion (87/18, I think). I've got a 19 and 20 tooth pinion on the way but tbh, it runs well as it is.
 
Last edited:

Aggie72

Member
Messages
13
I recently installed a 3100kv motor / 60A ESC in my Ruckus. I've found it great fun on 3S with the stock spur and pinion (87/18, I think). I've got a 19 and 20 tooth pinion on the way but tbh, it runs well as it is.
Thanks for replying. I'm running 19/87 on a hobbywing 3200kv. Running 2s. Temps are 110s give or take on street and 2s. About a 10 minute run. Full throttle consistently. I'm gonna test 3s this weekend. I have a circuit 2wd converted to buggy. Just wondering what you used and Temps!!
 

Steve g

Well-Known Member
Messages
288
Location
Massachusetts
Sorry for the late reply. 18 or 17 pinion 87 spur on the 3100. 16/87 on the 3300 now. Was 18, but gets hot after 1 pack.
 
Messages
7
Thanks for replying. I'm running 19/87 on a hobbywing 3200kv. Running 2s. Temps are 110s give or take on street and 2s. About a 10 minute run. Full throttle consistently. I'm gonna test 3s this weekend. I have a circuit 2wd converted to buggy. Just wondering what you used and Temps!!
The motor and ESC is just a cheapo, Surpass Hobby off AliEx (combo cost around £30). I normally by run my Ruckus off road on 3S and tbh, haven't taken the temps. It gets pretty warm if you've been gunning it but not to point it can't be touched, so I've not bothered.
 

Aggie72

Member
Messages
13
19/87 on a 3s runs pretty good. Checked the temps on grass after 15 minute hard run. About 159. Not bad. Fast as jack but a wheely king. Need to adjust punch. Gonna try a 20!
 

Djones48

Active Member
Messages
44
So what is the kv reading behind motors? If I want to upgrade the motor/esc for my amp I see brushless motors with a high kv for under $100 and that is with an integrated esc built in. Then I see others with a lower kv for way more, like $275. Is it the quality of the motor or are there other factors to consider?
 

Lephturn

Well-Known Member
Messages
154
If is voltage x RPM roughly, but as I understand it higher KV means the Power is higher in the rpm range of the motor. Heavier vehicles with more torque requirements need lower kv while lighter vehicles with less torque needed low in the rev range can run a higher kv and go faster. You can always gear up the higher torque motor for more speed but you need to your heat. It’s about more than kv rating - there are motors with the same kv rating with much different lengths and overall volume. I don’t have a good handle on it yet. I think lighter vehicles can go faster with higher kv motors. It’s not As simple as more or less kv is better. The Amp is quite light so I think you have more choices butIm not certain. So far I think around 3000 or 3300 kv in a 540 size is probably good, but I will let you know.

I was planning to put the Racerstar 540 3,300 kv in my Volcano but I’m thinking it might run really well in the Amp on 3S. Probably way overpowered.
 

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