Smaller Pulley = less heat + same range?

How-Tos & Esk8 mechanics
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#26

And 25% more voltage, leaving power consumption the same. In a perfect world with 100% efficient motors.

Reality is your current drop will be less than 25%, but your voltage requirement will still be 25% more.

#27

25% less motor current so 43-44% less motor heat, so a bit less battery current as well, as the battery wattage will be roughly equal to the useful work plus the wasted heat, when switching from 16t to 12t.

#28

If u don’t account for iron losses.

if u want to run a motor as efficiently as possible (least heat and most range) and you like to accelerate hard or have hills, at top speed you’ll likely be best with more heat from iron losses (eddies) than copper resistance losses.

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#29

You are right about belt slip, i remember way less skipping with a 16T pulley under the same or higher belt tension.

Since i started using a motor mount with less center to center distance (385 instead of 435) the issue also got worse. The issue only occurs under breaking.

I recorded 60° C multiple times as the motor temp with the 12t.

I will test out 20T with a 395mm belt soon and post the result

#30

Side question: what is the use of 100A Motor and 50A Bat? Using a dual VESC wouldn’t it mean 100A (2x 50A) max draw from the Battery?

In other words: what is the benefit of 100A per motor if the Battery max current per side is 50A?

Or is the motor amps setting for both sides combined and the battery amps in VESC per side?

#31
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#32

I’ll go on record here saying you’re going to get shittier range with a smaller pulley going the exact same speed

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#33
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#34

xmatic hasn’t been working great for me since I put my xenith on 5.3, but I think if you’re on 5.1, it’s dead simple to change gear settings and set a max speed limit.

I’d set a top speed of 20mph and go for two exact same rides and then look at the wh/mile. Should be pretty simple to settle this debate.

#35

If green loctite (sorry, traveling so number is nit available) was not a thing I think plenty of us would test just to satisfy boredom. But having removed one set of pulleys out if necessity while setting off my smoke detectors (torch) I would rather not

#36

I’ve never recommended using Loctite on motor pulleys.

Once is enough.

#37

That’s not sufficient – the SOC should start the same and the hills be the same and the wind be the same.

#38

Yep, agree - start from full charge, do the same ride path, and do it on a day with no wind.

#39

and same temp motors and outside.

i gotta get logging and missing everything.

and stay in the same position, and that’s likely going to screw the comparison

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#40

Why not go 1:1 then? more top speed and more efficiency, according to your theory… then you’ll have a direct drive and we all know those are more efficient and put out less heat than geared, right? Why use a gear reduction at all if it just makes the board slower and less efficient? Perhaps its time everyone re-thinks their drivetrain to take advantage of the efficiency benefits of getting rid of gear reduction, if its true that reducing the gear reduction ratio improves efficiency.

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#41

Ok I have done a first test ride. However I can’t tell if the range is better or worse. For this I’ll need to do another test drive as suggested.

However I can already say:

  • temperature measured with a infrared thermometer after a mix of steep climbs, carving and straight speeding:

12t @20° C ambient temperature = 49-50° C
20t @25° C = 50-54° C

12t breaking = belt slip
20t breaking under similiarly loose belt tension = no belt slip

12t also causes higher rolliing resistance than 20t by a lot. Therefore pushing the board is a easier with 20t.

At the same limits for bat and motors 20t reauired full throttle to get up a steep climb while speed was dropping. 12t still allowed for slight acceleration up the same hill with full throttle.

Sidenote: when carving at 15-20km/h it was harder to maintain a consistent speed with 20t compared to 12t.

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#42

If bigger pulleys significantly reduces rolling resistance, maybe we should all be running massive motor pulleys and low kv motors?

#44

One more thing: could it be possible pulley size has an effect on handling when carving?

I feel like there was more reluctance to get into a smooth carving motion.

My theory: in each corner a lot of friction is generated between rubber and road by lateral forces. When you get into a corner speed decreases under constant throttle input. The rear wheels now have more leverage towards the motors because of the bigger pulley.

Therefore I imagine the motor rpm drops further and speed decreases more than with a smaller pulley and changing the feel of the board in corners.

Does this make sense?

#45

I ran two idlers but the belt was wayyy to tight for efficiency. I think 14t is a good middle ground.

#46

I don’t think so, because the reason rolling resistance is reduced is the same reason why it takes more energy to climb a hill. It’d balance out with the increased energy going the other way to accelerate with a worse ratio.

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