Kraton Germans go for higher KV?

[milehighspeed]

The higher the KV the higher AMP load the motor can take and the less hot it gets.

mmm....the higher the KV the more hot it gets. As @Jerry-rigged notes, i have never seen anything that says the manufactures are changing the construction of the motor in some way to dissipate that heat better or utilize components that can handle it more as they up the KV. The charts tell you the motor is going to draw more (which will result in greater heat) but i don't think they are telling you it will take more. In RC you don't "KV up" to reduce heat...you "KV down". Think i just made up some terms there

 

[RC-Dude]

Heat is a side effect. Nobody tries to generate heat.

Take a 600 gramm motor. One with a higher KV and the same motor with lower KV. All the same just a different number of windings. Go to Hobbyking or any site that has the same motor with different windings. The higher the KV, the more Amp it can take. That is an apples to apples comparison. Same weight, different windings.

Now look at a Hobbywing SL 4985 1650kV compared with the stock 6s Arrma motor 2050KV. The 1650KV with the lower KV can take more heat. But it is an apples to oranges comparison. Totally different weights. 587 gram (4985) compared to (4274 2200kv) 418gram. The 1650kv motor has alot more surface area to get rid of heat. But take the same 418 gram motor and give it 1650kv. It will probably fry on your first run in a Kraton.

 

[jkflow]

Didn't read through all of it, but some observations.
Max6 is 8S capable and the 1650kV motor generates A LOT less heat on 6S. That is the main reason I took that road.
Temps are typically an issue in the US while in Germany its not that frequent.

Edit: Heat generation in a motor is based on efficiency. Lower kV gives a higher efficiency in return i.e. less heat by design.

 

[milehighspeed]

The higher the KV, the more Amp it can take. That is an apples to apples comparison.

Maybe im just not interpreting your use of the word “take” correctly and what your noting. Yes it will draw more amps.

Just trying to be clear that everything else equal (gearing, car, tires etc…), apples to apples as you say; a lower kv motor (even of similar size and build) is going to run cooler not hotter. Slower….yes, but cooler.

 

[RC-Dude]

That is right. Less KV will be cooler if you use a small pinion.
What I am saying is that the motor with the higher KV can handle more Amps all else beeing equal. . If you would try to run the same motor (less windings) with lower KV at the same amps by using a bigger pinion it would get hotter a lot faster.

You can take the motor with less KV and it will be cooler. But you might not reach the speed you want. So having a bigger motor with KV a bit higher, it will handle the external heat (weather) better and can handle the higher amps drawn.

So if you want to really reduce weight (for whatever reason) and want a small motor you should go for higher KV and a smaller pinion for it to handle the heat better.

But too high a KV with too big a pinion will draw too much Amps and get hot.

 

[jkflow]

Don't confuse kV rating with Amp draw. Has nothing to do with anything.
They both take in equal amount of voltage and amps, power is equal. You just get more torque out of the lower kV and you can gear up higher to compensate for the speed while the heat generation is still less. In both cases, at same speed, they still draw 'Ex: 100A'
This is all about efficiency.

Higher torque gives you lower heat loss when accelerating. You just lose out on top end speed, where the higher kV wins.

 

[Hammer Down]

 

[ARRMA King]

Because you guys are stuck with esc voltage cell count limits (3-8s) the only way you can realistically increase efficiency of the system is to volt up & kv down for the same rpm target (lowers amp load).

This is why I run higher voltages to increase efficiency/cooler running and not exactly eek out balls out top speed like everybody thinks they have to do

I think the Germans for the most part always want to strive for max efficiency, where electrical input is converted to 90%+ motor output. We see this themed in all their engineering.

Yes a higher KV motor can handle amp and heat spikes better due to thicker lower resistance wire. In my time of killing motors I have found it’s the copper that fails first before you need to really worry about magnetic de-gaussing.

I will say in my field testing of setups lower kv is cooler running but due to the nature of high copper resistance, inductance and hysteresis effects, it almost has a built in punch control softener, where as a higher kv when geared appropriately will always have that add’l power everywhere at your fingertips.

Have a plan for your setup priorities and plan accordingly to suit.

 

[RC-Dude]

Most magnets in brushless motors can handle over 220 deg Celcius. The glue that hold the magnets and copper varnish are the problem.

Best is to look at what others are using if the topic is too confusing. Up on voltage is always a good one if KV is lowered at the same time.

 

[MeHurricane]

My guess is that we are all lemmings and use what we see as the best stuff. Maybe in Germany the bashers that they look up to are running 2200kv motors. Imagine If Rich Duperbash and RcDude81 started to use 2200kv motors with success we'd have more people jumping on the bandwagon. Light is good from a less breakage standpoint. I seem to remember seeing RcDude81 using a 1650KV in his Xmaxx and I thought it was a lot of truck for that.

Looking to get a 2200kv for one of my Typhon's to experiment with but probably won't put it in a heavier rig unless the experiment works well.

Hurricane

 

[ARRMA-GET’M]

Don't think it's representative. Same physics over here.

The Max 8 combo is 189 EUR.
The Max 6 combo is 239 EUR.
Seems a lot of sellers push the Max 8 combo.

Or maybe we just go on the Autobahn without speed limits if we want speed while you guys put it in your rc cars.

I’ve got a turbo build in my garage I only drive rarely and as fast and powerful as it is, I get the same exact thrill out of speed running lol… but nooo I don’t FEEL my stomach drop when I race the rc car but I do get the racing heart beat and adrenaline from it and the gratification of speed and mph goal

The higher the KV the higher AMP load the motor can take and the less hot it gets. Look at charts of brushless motors of any manufacturer. Same weight motor with higher KV can handle more heat and Amps. If the KV is too high you'll have trouble finding a small pinion and tires are likely to burst if they can't handle the speed.

The bigger the Motor the better it can handle heat. Just more mass where the head can dissipate. That is why you don't need a fan on the Max6 combo. The motor does not get hot if driven with "normal" pinions.

Geee idk about that… more power equals more heat period. Heat will always be a byproduct of energy even if it’s a gas engine or the human body. Lower kv = less battery consumption and vise verse. Motors don’t
“Handle” amperage, they only consume voltage. Amperage is a measurement of resistance against the flow of voltage. Any motor can “create” heat by putting resistance on the motor like a bigger pinion or anything that can hinder the motor from rotating. There’s more ways to talk about the comparisons of low-high kv motors if this is interesting to anyone?

 

[BashingBrian]

What about the new Max8, that has an even higher kv (2250) motor than the previous version

 

[Double Apex]

I was wondering that too. Why do HW (and I think CC also) only have >2000kv motors for 1/8 scale cars. Do we know something they don’t or is it the other way around.

 

[Jerry-rigged]

I was wondering that too. Why do HW (and I think CC also) only have >2000kv motors for 1/8 scale Basher cars. Do we know something they don’t or is it the other way around.

Fixed it For you...

Both HW and Castle make short stack, <2000kv motors for racers. But bashers always want more power, so they also build bigger, higher KV motors.

Heat is a side effect. Nobody tries to generate heat.

Take a 600 gramm motor. One with a higher KV and the same motor with lower KV. All the same just a different number of windings. Go to Hobbyking or any site that has the same motor with different windings. The higher the KV, the more Amp it can take. That is an apples to apples comparison. Same weight, different windings.

Now look at a Hobbywing SL 4985 1650kV compared with the stock 6s Arrma motor 2050KV. The 1650KV with the lower KV can take more heat. But it is an apples to oranges comparison. Totally different weights. 587 gram (4985) compared to (4274 2200kv) 418gram. The 1650kv motor has alot more surface area to get rid of heat. But take the same 418 gram motor and give it 1650kv. It will probably fry on your first run in a Kraton.

KV does not equal Power.

Power in electric motors is made with watts, - Amps*Volts, and it is the AMPS that makes the heat.

1650kv does not tell you how much POWER the motor makes, only the speed it wants to run. 1650kv motor will be slower than a 2200kv motor, it will be build with more windings, which increases internal resistance, which decreases the max amps the motor can draw. Less amps = less power = less heat.

As a side note, I have a 1/16MT in my garage. The RTR version came with a 380-size, 2838 2000kv motor that ran on 4s. By your logic, that motor would light up like a light bulb and burn down the truck. But it didn't. But, 4s vs the 2s motor I run in mine makes a bigger difference than motor size, so still not an apple to apple comparison.

 

[ARRMA-GET’M]

Fixed it For you...

Both HW and Castle make short stack, <2000kv motors for racers. But bashers always want more power, so they also build bigger, higher KV motors.

View attachment 219574

KV does not equal Power.

Power in electric motors is made with watts, - Amps*Volts, and it is the AMPS that makes the heat.

1650kv does not tell you how much POWER the motor makes, only the speed it wants to run. 1650kv motor will be slower than a 2200kv motor, it will be build with more windings, which increases internal resistance, which decreases the max amps the motor can draw. Less amps = less power = less heat.

As a side note, I have a 1/16MT in my garage. The RTR version came with a 380-size, 2838 2000kv motor that ran on 4s. By your logic, that motor would light up like a light bulb and burn down the truck. But it didn't. But, 4s vs the 2s motor I run in mine makes a bigger difference than motor size, so still not an apple to apple comparison.

Yes all that you’ve stated is true and accurate. Others I think still have more in depth questions about the topic..

 

[ARRMA-GET’M]

What about the new Max8, that has an even higher kv (2250) motor than the previous version

What about the new Max8, that has an even higher kv (2250) motor than the previous version

Higher KV is accomplished by using less copper wounds inside the motor can, if you were to unwind that copper coil from inside the motor can and measure it’s length in a straight line, it’ll be a shorter wire than what the length would be of a lower KV like an 800kv motor. Copper wire stores energy and it slows down the current as in…
(The speed that electricity passes through it). So higher kv= less copper used and less copper = a shorter distance that electricity has to pass through and the faster it can drain energy from the battery so the more rotational cycles per second and that’s essentially the kv concept. NOTE: even though lower kv motors don’t spin “FASTER” they have more “TORQUE” because they use more copper windings which draws energy from the battery at a much slower rate. So when to put stress or heavy load on a lower kv motor, for example (800kv) the battery does not experience “voltage drop” like it would with a power hungery high kv motor, so the power levels of the battery remain very consistent and stable which helps keep the motors rpm at a steady pace and not drop or slow down like it would if the battery voltage was to drop.

I was wondering that too. Why do HW (and I think CC also) only have >2000kv motors for 1/8 scale cars. Do we know something they don’t or is it the other way around.

My bad, can you be more specific about 1/8 as in on road or off road? Because manufacturers want things to last and also be affordable, they won’t always put the most power motor/esc into a RTR kit or advertise their combos in anything more what is typical. Another sales tactic that’s essential to the future of the business is… they want to attract younger generations into the rc hobby because it’s a
“long term customer” they also want parents to buy these toys for their kids so it’s got to be user friendly, safe, durable and most importantly not complicated at all. They know that a REAL rc enthusiast doesn’t need their help finding their way around to build a Frankenstein Kraton/typhon drag car lol. Once you in, your hooked.. and that’s what they want to do.

 

[RC-Dude]

A heavier motor can handle more amperage as it can get rid of the heat better, it has more magnet weight inside and more coil weight. It does not have to work as hard to get the same wattage as a lighter motor. If you take a 1650 kv Hobbywing on 6s and adjust your speed via pinion to 80 km/h and compare it to the stock motor 2050kv on 6s with speed adjusted to 80 km/h via pinion, you'll find the stock motor needs a fan, the 1650KV does not. Typical Kraton or Mojave setup. Why? Because the 1650 kv motor is a lot heavier, can handle more power without getting so hot.

If you take two motors , same weight (400 gram) but different KV and adjust the speed in both identical trucks via pinion to 80 km/h you will find that the motor with the higher KV, running at the same speed (80km(h) will not be as hot.

So in summer you want the 50% heavier motor as it can dissipate heat better.

The problem with high running KV motors is when it will run fine on a 18T pinion but will get too hot on a 19T pinion. On a heavier low KV motor the difference in heat between one tooth is not as drastic.

So comparing motors in RC cars makes more sense when you adjust to the same end speed via pinion. (Or spur and tire diameter). Because that will draw similar amperage. The heavier motor will stay cooler.

Now compare a 500 gram motor at 2000KV at 100km/h in a Kraton with a 1000 gram motor at 2000KV in a Kraton. The heavy motor will stay cool, the lighter motor may get damaged. (Now that is theoretical as you will have trouble finding a 1000 gram motor with 2000KV.) So that is where the compromise comes in with a Hobbywing 1650 KV ca.600 gram motor compared to the 2050KV stock 6s ca.400 gram motor. The 1650KV motor needs a bigger pinion to reach the same speed as a stock Kraton. Adjusted to the same stock 6s Kraton speed (via pinion) it will stay cooler.

This all makes sense when comparing an unsensored motor with another unsensored motor. With the same type of winding.

 

[Double Apex]

My bad, can you be more specific about 1/8 as in on road or off road? Because manufacturers want things to last and also be affordable, they won’t always put the most power motor/esc into a RTR kit or advertise their combos in anything more what is typical. Another sales tactic that’s essential to the future of the business is… they want to attract younger generations into the rc hobby because it’s a
“long term customer” they also want parents to buy these toys for their kids so it’s got to be user friendly, safe, durable and most importantly not complicated at all. They know that a REAL rc enthusiast doesn’t need their help finding their way around to build a Frankenstein Kraton/typhon drag car lol. Once you in, your hooked.. and that’s what they want to do.

I ment for off-road. Until recently HW had only one “basher” (non sensoren) off-road combo for 1/8 according to their own product sheets: the max8 and 2200kv motor. Because a lot of people judged is as too light (runs hot) and went for the Max 6/4985 combo which is technically a 1/6 scale combo.
I would expect HW to fill the gap and come up with a 42xxx 1800 kv -ish motor. Instead the new HW systems have even higher KV’s.

 

[Yonic]

If you take two motors , same weight (400 gram) but different KV and adjust the speed in both identical trucks via pinion to 80 km/h you will find that the motor with the higher KV, running at the same speed (80km(h) will not be as hot.

Interesting. But why is that? Won’t they be the same?

 

[ARRMA-GET’M]

I ment for off-road. Until recently HW had only one “basher” (non sensoren) off-road combo for 1/8 according to their own product sheets: the max8 and 2200kv motor. Because a lot of people judged is as too light (runs hot) and went for the Max 6/4985 combo which is technically a 1/6 scale combo.
I would expect HW to fill the gap and come up with a 42xxx 1800 kv -ish motor. Instead the new HW systems have even higher KV’s.

Interesting. But why is that? Won’t they be the same?

I’m not on board with “Rc Dude’s” previous comment I’ll have to pass on that one.