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Are 50mm OR 63mm Motors Better on V4.12 VESC?


#1

FACT or FICTION: Smaller motors are better than bigger motors when using a VESC

Smaller meaning 50mm Diameter Brushless Outrunners
Bigger meaning 63mm Diameter Brushless Outrunners
Better meaning Less heat? More Reliable?


Lightweight single. 6355 vs 5065?
Did I just fry my Raptor?
#2

When the VESC is is set up with a balanced system it is extremely reliable. Of course like any other ESC if you pair it with a huge motor that has a higher current rating than the VESC will handle you will be in dangerous territory and have a temperamental failure prone system.

Honestly the VESC’s biggest weakness is poor business practices and cheap manufacturing.


Choosing the right motor kv for the VESC
#3

@chaka is right, running a well balanced system is necessary for stability.

10S. 190kv-200kv. Is the ideal esk8 setup for keeping vesc cool & happy.

Also need to be carefully not to have your reduction ratio’s too low. Most people work that out eventually. That will over work the entire drive train and stress the vesc. Especially on the small motors that naturally draw more current as they are much easier to overload.


#4

Especially on the small motors that naturally draw more current as they are much easier to overload.

This is actually false. If you take two single drives with the same settings and try to climb a steep hill the smaller of the two motors will make it to the top while the larger motor will overheat the VESC.


#5

Big statement mate, maybe back it up with some evidence. Are you still running 2:1 ratios & riding at 50mph? Those systems will never work well hill climbing.

From my own practical experience smaller (50mm) hobby grade motors heat up much more under load and have less torque per watt.

Larger hobby grade motors heat up less & deliver more torque for the same wattage. Because larger stator diameters offer a mechanical advantage over the smaller stators. Yes they can handle more current if needed but will heat up less.

For a stable system you need all the elements to be in harmony. You have a track record for pushing the speed limits of eboards beyond a safe & practical level and hence your data is likely skewed based on your inefficient drivetrain designs. I have said it before & ill say it again, speeds over 45Km/h are not practical or safe & definitely stress your electronics.

You are one of the more experienced guys on here & yet you still have not to contributed video test results/data onto the forums so the community can educate themselves further. Maybe now is a good time to prove your claims. You are the resident VESC expert right? why not publish your VESC settings &/or write some tutorials for the community?

NOTE: It is also worth noting that not all motors are equal. Some big motors are just not that good & Some small motors are good, take a look at boosted boards for instance, small powerful motors that don’t get very hot… The next generation of custom made motors we are designing will set a new standard of what is possible with esk8.


#6

Big statement mate

Not really, this is common knowledge among rc airplane enthusiasts or anyone who has done a little research into ESC and motor combinations.


#7

But we are not building/riding on toy planes, RC plane motors are required to do a completely different task, they are also 1:1 direct drive & most esk8 motors we use are geared, with reduction of 2.5 or more.

RC planes run on a much lower voltage at higher rpm with higher KV motors, not to mention the prop size variable, wing span & wing span area variables, power to weight ratios etc… smaller motors are obviously better when trying to minimise flight weight & maximise thrust whilst keeping constant current draw within the specs of the battery.

The constant current & sustained loads endured by an RC plane during flight would seem to be very different from Esk8 load profiles.

Can you please educate us how RC plane setups compare with ESK8 Drivetrains? I am more than willing to learn.

I would say that RC planes are more similar to a hub motor on an ESK8 - However, It is still arguable that the load profile & current draw from a prop & motor during flight is vastly different than what an esk8 motor has to deal with during normal riding conditions. ESK8 don’t have a minimum stalling speed and are not always running at minimum constant current draw as required for flight & total weight is not a critical factor.

All i ask is that you provide some evidence… If smaller motors are magically better for esk8 it should be easy to prove. a watt meter, thermometer, video camera & a hill is all you need.


#8

I think smaller motors are going to win on efficiency In a dual format.
In my head it makes sense.

Fact?


#9

Is it a coincidence that Evolve uses 50mm motors for their GT? I’d bet it was due to their R&D team finding out that 50mm’s work better for what they’re trying to achieve. Would love to hear the science behind it all.


#10

my guess is they are cheaper and still work - so why should they go for bigger motors?
Probably a purely economic decision.


#11

You don’t get to be a big a company in this market with that kind of mentality. The people who go “eh it’s cheaper and works” don’t usually last long in the business. Given that everything else about their GT was well engineered, I’m sure they made a thought out decision about the motors as well.


#12

I think 50mm is fine, especially if you are a lightweight rider and rarely go up hills, you just need to make sure you have appropriate current limits set (e.g. MAX 50A Battery Current or Less per VESC) & a make sure your gearing ratios are appropriate.

However for the money, I would prefer a larger stator, larger copper mass, can handle higher current when needed & can dissipate heat quicker. Larger diameter stators have a mechanical advantage over the smaller ones.


#13

Care to explain why that should be? The other way around would also not be a wise business decision: using something more expensive that works equally well.
What I am trying to say is: both motors perform probably equally well for our use cases so there is no point to use the bigger and heavier one (especially when you have a dual setup that splits the load). I don’t think they did scientific studies to find out which one is actually better and will never do such a thing as long as both options work.


#14

Can’t really comment on which works better with a VESC. But it’s fun watching chaka and onloop argue.


#15

I hear you, and if it were the case that product A works just as well as product B but was cheaper, I’d totally agree that they would use product A. However, my guess is that 50mm do work better than other motor sizes due to the R&D put into making their GT series boards. And not just because they’re cheaper. However, I have no basis or proof for my hypothesis, and will be keeping my eye on this thread for the scientific reasoning to follow :slight_smile:


#16

Yes, I suppose it might be entertaining, but my purpose is not to create an argument, it’s merely a request for evidence to support claims.

If it is proven that 50mm are better for some reason we can all make better cheaper eboards. 50mm are much cheaper to manufacture than 63mm


#17

A single 63mm motor is great with a high end hobby ESC but the VESC V4.XX cannot provide enough throughput to thoroughly enjoy the output of these larger motors.

If you pair a single 6365mm motor with a VESC on 16/36 tooth on 90mm abecs and try to climb a long somewhat steep hill at full throttle the VESC will overheat fairly quickly and you will come to a stop. If you do the same with a 5065 motor you will be able to climb at a continuous rate without the VESC overheating. With gearing this tall on a single drive we are only talking about 5 to 10% grade to get these results.

This is all fairly basic stuff. It is common knowledge that your esc should be capable of handling more current than the motor will pull at max throttle if you want your hardware to last.


#18

I understand what you mean.
However it would surprise me if they actually did some R&D on the motor. My guess is they just buy the stuff in bulk from a Chinese manufacturer and basically have no say in the process besides color or so. I mean why should they spend huge amounts of their resources on something that apparently already works pretty well (SK3s for example have already proven to be up to the task) when there is so much space for improvements that will actually get them customers (just think of their fancy remote with display or apparently super efficient ESC that increases the range they can get out of a 10S3P battery). But I guess we will never know what actually happens behind the scenes, so I could definitely be wrong with this.

PS: That was actually a kind of pleasant argument we had there. Glad something like this can still happen on the internet.


#19

I don’t think the RC plane loads are not comparible to an esk8, unless they use varible pitch props so the load can vary at similar rpm’s, I am not sure if they use variable pitch props.

Just getting into e sk8’s, and brushless motors. Lots of variables to consider. Say both the small and bigger motor have similar specs, (other than the larger motor will have more starting torque and power output) I would say bigger is better if given the same load and the same rpm. Though a smaller motor could have an advantage at certain loads in certain circumstances if geared differently.


#20

In your example it will however matter what that rate actually is you are talking about. Full throttle on a 6365 probably means something different than on a 5065. So if I can get the same climbing rate on a 6365 by lowering the throttle will the VESC stay cool? Full throttle is a weird comparison as it does not tell us anything about the relative speeds. To be a fair argument both motors should result in the same absolute climbing rate.