Typhon Low kV, high gearing vs high kV, low gearing?

[Ari33]

I was offered HW XR8plus for a price I couldnt refuse and decided just to go for it. I will need a sensored motor for it and have been looking at the HW 4274SD motors.
The two options are 1800kV and 2200kV bit the 1800kV is a fair bit cheaper...

Low kV high gearing vs high kV low gearing..

If both were geared for the exact same top speed, how would the feel and performance compare between them?

 

[DoNoHarm]

I’ve always wondered this. Always! Some people say the lower kv motor will run cooler.

 

[NastyNate]

That is what I have understood. Lower kv motor = higher torque, but slower speeds... I think... The "can" is a factor as well from what I have researched as well. Apparently bigger is better with cooling. The 4092 1730kv seems to be a sweet spot. That's the combo I'm thinking about purchasing for my kraton. I'm green af so I'm sure others will chime in. Guys if I'm wrong tell me I'm struggling to figure this out as well.

 

[DoNoHarm]

That is what I have understood. Lower kv motor = higher torque, but slower speeds... I think... The "can" is a factor as well from what I have researched as well. Apparently bigger is better with cooling. The 4092 1730kv seems to be a sweet spot. That's the combo I'm thinking about purchasing for my kraton. I'm green af so I'm sure others will chime in. Guys if I'm wrong tell me I'm struggling to figure this out as well.

Forgot there’s always this response as well lol. No offense by the way- but we know. Obviously a bigger fan is going to be cooler. That’s all correct. The question is, if everything is the same except kv, but they’re each geared for the same speed, what is better.

 

[LibertyMKiii]

This also is depending on what that speed is. If your goal is 70 mph the answer is different than if the goal is 110 mph.

On a 70 mph setup the higher kv is likely to be the better choice.

As you already figured out the gear ratio removes torque. The lower kv adds torque.

Also peak power is said to occur at different rpms.

I have wanted to experiment on this, but it's expensive. To add another factor you have delta and wye winds, which output torque differently as well as different amperage draw.

-Liberty

 

[slick2500]

I think in theory if both were geared for the same speed being the same size can only difference being the kv, that both motors would perform equally.

 

[3d-rc.myshopify.com]

Given you want the same outcome. Are you looking for acceleration or off the line punch. Lower kv will give you the kick with a cooler running motor. Higher kv will get you you there a tad slower but run hotter. Unless 30mph is what you are looking for then they both would feel the same.

 

[Branson_Basher]

Try a Google search "gear down volt up" for some more reading on the subject. I first heard that term used in a video by Holmes Hobbies but I didn't find it when I did a quick search for it.

As best as I remember it goes like this...
For a given voltage there is a motor size that runs most efficiently (I've seen charts that list it online). Gear your vehicle (this is final gearing, including tire size) to run at the speed you want.

Most likely you won't hit the magic number dead on but get it as close as you can and the motor will be efficient.

Sorry for not posting the charts, etc. but I went through this process a few years ago and trying to do research on my phone sucks...

Clear as mud?

 

[Cr3pitus]

It's actually somewhat of a misconception throughout the RC community that kv and motor torque are 1:1 correlated. As kv increases the torque constant changes and the current increases so torque stays relatively constant. A motor can easily be high torque high kv, as torque is much more a result of physical properties of the motor like stator size and air gap, but the problem really is more that current goes up Rapidly as kv increases and you end up with either a current demand higher than you want or higher than your battery can dish out. I think it's more useful to pick a motor size not kv for desired torque, and pick kv based on craft weight.

So in my opinion, assuming all else equal about the motors besides the winding, and proper gearing for both, the biggest difference is going to be different spikes in current draw under acceleration and braking. In terms of how they feel to drive, it's going to depend on the speed you like to drive at whether one feels better than the other. I think personally on cars this size and up you get a little more area under the bell curve range of "proper gearing" with a lower kv.

 

[JvG]

As @Cr3pitus stated weight is a factor here:
My Tamiya has a 4400kV, Rustler 3500kV, Kraton 2050kV, Baja 780kV and offcourse the cans get bigger.
But still the op's question isn't answered.
2 identical cars, same weight, geared for same speed, with high and low kV motors. What is the difference?
Is it power (low) versus speed (high)?

 

[Ari33]

As @Cr3pitus stated weight is a factor here:
My Tamiya has a 4400kV, Rustler 3500kV, Kraton 2050kV, Baja 780kV and offcourse the cans get bigger.
But still the op's question isn't answered.
2 identical cars, same weight, geared for same speed, with high and low kV motors. What is the difference?
Is it power (low) versus speed (high)?

Thanks everyone...

I have experienced the difference on quadcopters but just wanted to know if it compared directly with surface RC.... particularly in cogging at low rpm's but I guess with being sensored its not a real factor.. at least in my case.

My quadcopter experience...
Same frame, same escs (with ample amp headroom)
Motors- 2140kV vs 2300kV

Props. 2140kV- 5550 (5.5" size and 50deg pitch)
2300kV- 5040 (5" size and 40deg pitch)

This provided similar-ish overall performance but the 2140kV combo was more consistent over more of the flight period while the 2300kV combo had a much larger performance drop off over the flight.

The 2140kV combo was extremely snappy at low rpms (higher torque) I could do 80mph vertical dives towards the deck, flick the autolevel switch and instantly break props.. "crack!".

The 2300kV combo was less snappy at low rpms but I could hit 100mph in the vertical dives but the props were also less likely to break when I levelled it instantly.

The 2300kV was like a lower torque/ higher bhp peaky race engine that was much faster at the beginning of the flight +10 -15mph but towards the end of the flight was slower by about the same margin due to sag.

The 2140kV was like a higher torque lower bhp offroad/rally engine that didnt perform quite so well initially but didnt drop off in performance half as much towards the end of the flight.

I'm thinking/hoping that this application would be pretty similar. I drive mostly on the loose and there is already shitloads more torque than I can use so Im thinking the higher kV might suit me better... as well as offering a power curve that doesn't flatten off at high rpm's. IF... the lipo can provide it that peak amperage.

If I go with the 2200kV my Esc and Lipo's will be pushed far harder. I'll probably upgrade to TG graphenes and gear it to suit the escs temps rather than target a fixed mph target. 60-70mph should be plenty and the XR8 plus should be able to handle that with our cooler scottish climate...

Does that all sound about right?

Go with the 2200kV then yeah?

 

[LibertyMKiii]

If peak speeds desired are around 60-70 then I'd stick with the 2200kv

This is assuming its not full of heavy aluminum upgrades and big heavy tires.

 

[Ari33]

If peak speeds desired are around 60-70 then I'd stick with the 2200kv

This is assuming its not full of heavy aluminum upgrades and big heavy tires.

It has stock wheels and tyre sizes, I do have the front and rear HR alloy hubs, steering mech and links but nothing else. That extra weight is also offset by running 4000mAh 6s packs so it weighs slightly less than a stock 6s typhon on 5000 mAh 6s Lipos.

Thanks for the confirmation Liberty, its very reassuring coming from yourself. Congrats on the premium membership too btw.. You fully deserve it.

I'f we crowdfunded a motor for you, would you be interested in doing a full comparison between these two setups for us?

I'd be more than happy to put a few dollars towards this happening.. would be great to understand it better and add to the collective knowledge on here.

 

[Cr3pitus]

Thanks everyone...

I have experienced the difference on quadcopters but just wanted to know if it compared directly with surface RC.... particularly in cogging at low rpm's but I guess with being sensored its not a real factor.. at least in my case.

My quadcopter experience...
Same frame, same escs (with ample amp headroom)
Motors- 2140kV vs 2300kV

Props. 2140kV- 5550 (5.5" size and 50deg pitch)
2300kV- 5040 (5" size and 40deg pitch)

This provided similar-ish overall performance but the 2140kV combo was more consistent over more of the flight period while the 2300kV combo had a much larger performance drop off over the flight.

The 2140kV combo was extremely snappy at low rpms (higher torque) I could do 80mph vertical dives towards the deck, flick the autolevel switch and instantly break props.. "crack!".

The 2300kV combo was less snappy at low rpms but I could hit 100mph in the vertical dives but the props were also less likely to break when I levelled it instantly.

The 2300kV was like a lower torque/ higher bhp peaky race engine that was much faster at the beginning of the flight +10 -15mph but towards the end of the flight was slower by about the same margin due to sag.

The 2140kV was like a higher torque lower bhp offroad/rally engine that didnt perform quite so well initially but didnt drop off in performance half as much towards the end of the flight.

I'm thinking/hoping that this application would be pretty similar. I drive mostly on the loose and there is already shitloads more torque than I can use so Im thinking the higher kV might suit me better... as well as offering a power curve that doesn't flatten off at high rpm's. IF... the lipo can provide it that peak amperage.

If I go with the 2200kV my Esc and Lipo's will be pushed far harder. I'll probably upgrade to TG graphenes and gear it to suit the escs temps rather than target a fixed mph target. 60-70mph should be plenty and the XR8 plus should be able to handle that with our cooler scottish climate...

Does that all sound about right?

Go with the 2200kV then yeah?

Quads are historically the RC of my greatest experience as well. I used to race quite a bit on a 6s lightweight build but I got tired of dealing with the wetness of the pnw USA making it difficult to fly year round.

If it's always cold where you are I doubt there'd be any problem going with the 2200kv motor, but in theory it would run a tad warmer than the 1800kv motor most likely. The Typhon is relatively shall and light so it's not like you're trying to drive a 20lb truggy on a higher kv setup. It's relatively safe and accurate to consider below 2000kv a dedicated 6s and up setup, 2000-2300kv a 4-6s setup, and above that a dedicated 4s setup. If you're going to ever run 4s you definitely want the 2200 unless you wanna go slow.

 

[LibertyMKiii]

It has stock wheels and tyre sizes, I do have the front and rear HR alloy hubs, steering mech and links but nothing else. That extra weight is also offset by running 4000mAh 6s packs so it weighs slightly less than a stock 6s typhon on 5000 mAh 6s Lipos.

Thanks for the confirmation Liberty, its very reassuring coming from yourself. Congrats on the premium membership too btw.. You fully deserve it.

I'f we crowdfunded a motor for you, would you be interested in doing a full comparison between these two setups for us?

I'd be more than happy to put a few dollars towards this happening.. would be great to understand it better and add to the collective knowledge on here.

That would be great!
I don't believe I am "there yet" with either of my speed cars, but I would like to compare a variety of KVs.
The car would have to be extremely consistent and controllable (which mine are not yet).

I would want to do full scientific methodology with 3+ identical runs each. Tons of data gathering between runs with the Castle data logs as well as manual measurements with the IR temp gun etc.

My current thoughts are to use a TP4070 simply because it is sort-of the go to for speed runners. (and I have one of the highlighted already)
I would potentially test the following KV ratings all on 6s:

-Liberty

 

[olds97_lss]

For me personally, I have 2 6S trucks with 2200kv castle motors in them and 1 6S truck with the blx2050 motor in it. Different esc's across the board:
ERBEv2 - 2200kv traxxas/castle non-sensored with HPI F360C esc (MMv1)
Savage Flux HP - 2200kv castle sensored with MMX esc
Outcast 6S - 2050kv BLX Arrma with BLX185 esc

The one thing I notice most is the 2200kv's on 6S really howl when at WOT and they tend to run quite a bit hotter (20F+ more than the blx2050kv). I run the same tires on all 3 trucks (wrapped 3.8" trenchers), but my outcast is the fastest top speed of the 3, yet it's motor seems to handle the stress better.

I just recently got a blx2050kv to try in my ERBEv2. I'll stick with the same esc I have in it for now and I'm intending on gearing it 2T higher (18T vs 16T) on the pinion to make up for the loss of motor RPM's. Will see how it does, but likely won't get a good feel for it until next spring as it's cooled off here. I will likely run it some this winter, but it will be cold/snow bashing which I never did with the outcast.

I don't know why... but never wanted to run the outcast in the winter. Now that the ERBEv2 is a v2 and running on 6S vs 4S, I'm not sure how well it will hold up when it's plowing through snow and it's 30F outside. I don't usually bother running when it's colder than that as I don't care to stand out in the cold.

 

[Ari33]

That would be great!
I don't believe I am "there yet" with either of my speed cars, but I would like to compare a variety of KVs.
The car would have to be extremely consistent and controllable (which mine are not yet).

I would want to do full scientific methodology with 3+ identical runs each. Tons of data gathering between runs with the Castle data logs as well as manual measurements with the IR temp gun etc.

My current thoughts are to use a TP4070 simply because it is sort-of the go to for speed runners. (and I have one of the highlighted already)
I would potentially test the following KV ratings all on 6s:

View attachment 53476

-Liberty

That would be awesome. You are the perfect candidate for the job with that degree of dedication to producing some real meaningful data. Its would be a great choice of hardware too as it would receive a lot of interest from the speedrunning community.

Im thinking that it mightalso be interesting to be able to add sensored into the mix ...IF.... you already had a sensored tp power motor? Not a huge deal if you don't though.. What do you have currently?

If you set up a patreon or similar, start a thread on the subject here... and also spread the word to your other forum hangout locations, I'm pretty sure we could collectively get quite a few subscribers willing to help make it happen.. win win for everyone..

 

[LibertyMKiii]

That would be awesome. You are the perfect candidate for the job with that degree of dedication to producing some real meaningful data. Its would be a great choice of hardware too as it would receive a lot of interest from the speedrunning community.

Im thinking that it mightalso be interesting to be able to add sensored into the mix ...IF.... you already had a sensored tp power motor? Not a huge deal if you don't though.. What do you have currently?

If you set up a patreon or similar, start a thread on the subject here... and also spread the word to your other forum hangout locations, I'm pretty sure we could collectively get quite a few subscribers willing to help make it happen.. win win for everyone..

Currently I have the non-sensored TP4070 5D wind (1700kv), which is planned to be used on 8s at some point.
I will keep that in mind, the idea of using Patron and looking for supporters. Hopefully by the end of the year my car will be ready. I have to create a final body from the mold and 3D print my rear tail/wing combo.

There is either lots of secrets or it may simply be unknowns, when it comes to motor selection. I hope such an experiment can clear up confusion and misconceptions. As it stands I can easily tell someone a recipe to make their Arrma 6s go 100-120mph. Also how to take a bone stock electronics Kraton v4 to 96mph. Beyond that is theory and guesses, which I hope to have answers for in 2020.

-Liberty

 

[LibertyMKiii]

The one thing I notice most is the 2200kv's on 6S really howl when at WOT and they tend to run quite a bit hotter (20F+ more than the blx2050kv). I run the same tires on all 3 trucks (wrapped 3.8" trenchers), but my outcast is the fastest top speed of the 3, yet it's motor seems to handle the stress better.

@Ari33 I have seen enough posts about Arrma 6s cars with 2200kv motors getting hot, that I can agree that it MIGHT get too hot. As you said running the 4000 mAh LiPos hopefully help keep the weight down enough.
Ambient temps and driving style will ultimately be the deciding factor. 150 to 200kv although seemingly little can make quite a difference in heat and rpms.

 

[DoNoHarm]

For me personally, I have 2 6S trucks with 2200kv castle motors in them and 1 6S truck with the blx2050 motor in it. Different esc's across the board:
ERBEv2 - 2200kv traxxas/castle non-sensored with HPI F360C esc (MMv1)
Savage Flux HP - 2200kv castle sensored with MMX esc
Outcast 6S - 2050kv BLX Arrma with BLX185 esc

The one thing I notice most is the 2200kv's on 6S really howl when at WOT and they tend to run quite a bit hotter (20F+ more than the blx2050kv). I run the same tires on all 3 trucks (wrapped 3.8" trenchers), but my outcast is the fastest top speed of the 3, yet it's motor seems to handle the stress better.

I just recently got a blx2050kv to try in my ERBEv2. I'll stick with the same esc I have in it for now and I'm intending on gearing it 2T higher (18T vs 16T) on the pinion to make up for the loss of motor RPM's. Will see how it does, but likely won't get a good feel for it until next spring as it's cooled off here. I will likely run it some this winter, but it will be cold/snow bashing which I never did with the outcast.

I don't know why... but never wanted to run the outcast in the winter. Now that the ERBEv2 is a v2 and running on 6S vs 4S, I'm not sure how well it will hold up when it's plowing through snow and it's 30F outside. I don't usually bother running when it's colder than that as I don't care to stand out in the cold.

Yup! All true! Actually olds, I bet if you took one of those castle escs and threw them into the arrma paired with the arrma motor, it’d give it even more top end rip. I know I sound like a broken record with “my e revo 2.0” but when I swapped from the stock esc to an mxl 6s mm2, the motor actually gained a lot more on the top end, AND ran hotter too (both of my motor deaths were after I put in that esc) For all cars I’ve owned that didn’t have mamba monsters stock, when I swapped one in, it’d be like a supercharger. The motor would have extra howl at the top end (you described it perfectly) it’s in the escs programming. Downside is hotter motor, upside is more go! I thought I was the only one. I tried it in so many cars and the results were constant!! I know you said your arrma goes faster and handles the stress better, but that may be because of something else that’s not related. I believe there’s extra rip potential there.