mikewait

I'm running a Tekin Rx8 2050kv and Esc in my Losi 2.0 buggy,
right now i have 2 venom 2s lipo's i believe they are maybe around 5000 mah or something i'm not to sure they don't say on them
im using them in series which makes 4s.

i have the stock 45 spur, 16 pinion setup and running without a body the motor gets to hot, i cannot touch it for more than 3 seconds which is i think too hot.

Basically my gearing, Kv and battery setup is wrong.
How do i get longer run times? And not as much heat? and more performance.

I'm probably going to pick up a 5s and 6s 5000mah 40c lipo.
I'm also willing to change kv for my motor, maybe with something lower...

What kv would be best for my setup to get longer runtimes and amazing power (better than what i have right now?)
without as much heat?

So what kv should i swap to? 1900 kv? 1700 kv? 1350kv? I'm not on a tight budget so im willing to change motors and batteries etc.

guver

My Feedback: (325)

You have the right idea, that is to gear down mechanically or "electronically" with a lower kv motor. There's nothing wrong with paralling the batteries either to use 2S on your existing motor and gearing it up if you have to. It's going to be worse of course with a 5S and 6S.

Our speeds and set-ups may be very different , but for comparison my 6S set-ups use a 1500 kv and a 1900 kv motor, I'm going to a 1100 kv motor.

mikewait

ok thanks, i was just confirming that lower kv is less heat... usually
except what would the difference be between a 4s 2050kv and a 6s 1350 kv both gear how needed.
Which would have more speed, more torque, longer run times and less heat?

I'm just trying to see if it is worth it to change kv and up the cells in my lipos?

guver

My Feedback: (325)

The power and speed would be very similar , but the 6S is just carrying more battery (if the cell size is the same) and would have longer runtime because the current is less if both loads are similar. I think it is worth it to max out the voltage.

rccrazer

been there myself gearing is your biggest problem. if your motor or esc gets over 200 degrees farenhieht then your magnets will loose there magnetism. that means that your effancey will go down as well as your speed. your esc will possibly meltdown if it gets hotter than 200 degrees farenhight. not good.

more kv means that there is more speed. but less kv means you get more torque. so its kinda a trade off.

yourefficiency comes from your battery and esc. the more power it takes to run the motor and esc makes it take more power from the battery. everything will run from that. so if you can change your esc to a lower amp esc then go for it. but keep the motor inside its kv range. that will most likey bring up your power and run times.

so gearing to keep things under 200 degrees, and amps to get things running! trust me been there done that several times.

Slo-V Flyer

You have it wrong about the ESC. The using a lower rated ESC does not CONTROL and properly limit the amps, it is rated for certain amps to SAFELY pass through that the motor will pull. You need to understand that the MOTOR is the one that's drawing current depending on the load, the ESC has to be able to handle that current, and the battery is supplying the current (so the battery should always be rated for over what the motor Amp rating is to be on the safe side).

Using a 60A ESC for a 100A motor in a 1/8th scale truck WILL toast your ESC when you get to the limits of the ESC, which will show up as a very hot ESC and most likely burn up and smoke. Using the ESC to "limit" the amp the motor sees is very bad way to go about things.

With that said, your target should be to keep the ESC temperatures well below 160*F if possible, and the same for the motor. Running a motor hot just means wasted energy as heat and overall potential danger, and the motor and anything else down the power chain should be upgraded.

Also, excessive voltage with wrong gearing can cause bad heat issues for the motor and ESC (and batteries maybe) if the motor is just not suitable for the job.

However as mentioned several times, yes first always check gearing. If the truck is just too underpowered once you get the motor geared and running right, then yah, go up in size, otherwise you're set.

mikewait

Correct me if i'm wrong,

4s 2050kv- geared however needed
-Geared to reach roughly 50 mph
-uses more amps
-less run time
-equal power


6s 1350kv - geared however needed
-Less heat than 2050kv
-More run time since less amp draw.
-same speed and torque as 2050

Is this accurate? Because it seems to me that most people i know are running low kv and high voltage, because the run time gain and equal performance. As long as it is geared properly you shouldn't have a problem temp wise?

Which setup would heat up more?
is the information above correct?

Slo-V Flyer

The 1350 Kv motor will be making quite a bit more low end torque due to it's lower Kv, and will run more efficient and cooler over all, geared for the same speed, using your above 2 examples.

guver

My Feedback: (325)

If the motors are the same size then they will make about the same power because ultimately you have geared them both for the same top speed. The runtime of the 6S system is going to be more if you are using the same size/capacity cells since you are carrying around a bigger battery (2 extra cells)

mikewait

Alright thank you guys! You were all very helpful and helped me find a answer to all my questions!
Next week i'm going to pick up a 1350kv motor and 2 6s lipos and probably going to sell my 2050 once i get the new setup working

Thanks!

rccrazer

ever so welcome my great friend. PLUR!

bkfamily1

My Feedback: (1)

Pardon my interruption, but this topic of changing the number of cells and voltage and the effects on power and such is of great interest to me.

when you say "if the motors are the same size" what are you referring to? what is the "size" of an electric brushless motor?

when you say "about the same power" what do you mean by "power?" the torque delivered to the spur and hence the acceleration?

I think I understand that going to more cells (4S to 6S) while at the same time going down in kv means you preserve top speed (lower kv but more volts) and get more acceleration due to more torque from the lower kv motor. Is that correct?

what happens to the amps drawn by the motor? are they less because at higher voltage you need less amps for the same power?

rccrazer

kv mean turns per volt. so say you have a 2200 kv motor running on two 2s lipos in aseriesconnectionthat makes 14.8 volts. so then you take 2200 multipled by 14.8 and that gives you 32560 turns for however long it will run.

typicly the more kv you have the more top end speed you will have but you will have lesstorqueoff the line. lower kv motors aren't as fast but have tons of torque

does this help you at all?

Slo-V Flyer

bkfamily1

My Feedback: (1)

Thanks!

mikewait

What gearing would you guys recommend to start off with if i'm running 1350kv and 6s 40c?
I will probably need more torque than top speed because the track i race at is very technical and involves quick acceleration to quickly pop over triples. What gearing would be a good stating point?

Slo-V Flyer

If it's a technical track, I'd first see if you can get a rough idea of the motor Kv and voltage they run over there. Chances are that will help you right there with the motor and battery part, and gearing can be worked out from a few guesses/advice.

In any case, if it's a tight track then 6s might be a tad on the fast side, or just too much power. You may want to simply run 4s and gear up a little. But I'll let others pitch in as far as actual gearing.