Motor discussion. Are 6374's worth it?

I live downtown so it’s mostly flat but a few hills around, some big. Typically I’m not going that way, though

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I think you should consider swapping the dual 5065 to 6354. 6354s are actually lighter, capable of slightly more current than 5065s, and fit more easily narrower trucks (which should be lighter and less likely to bend)

I’ve run single 5065, single 6355 and dual 5055, the latter is obviously the most fun, I don’t go fast, limited to 35km/h, but the little ones handle it all, they get hot but not uncomfortable, can hold them in my hand all day long

To this day haven’t found a hill they could’t climb with 40A each and 34:14 gearing and 80mm wheels, I think 20% was the steepest so far

Two(three) buts:

1: I’m severely limited on battery amps, 30A, so the motors stay most of the time far away from the 40A limit

2: If I geared them for greater top speed I can see them getting too hot on bug hills

3: they are lighter than a dual 6355, and since my goal was to go crazy on weight reduction they are perfect

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You should keep in mind that what the motors are “rated for” is really just a load of bullshit. Try running a 6374 motor at 3kw and tell me how long it lasts before the magnets are overheated or the phases short out due to molten enamel. I think most 6374 are really rated for 2kw at peak. and thats optimistic. Look at lets say industrial motors that are rated for at least 1kw, the size is the thing you should take note of.

@Andy87 when calculating that peak power output you can not use 4.2V per cell, it will always drop to at least 3.9 (for example with 30q or vtc6 at 15A drain per cell, for 20 it goes even lower)

I find the single 6374 with 1:5 reduction still lacking in torque on 225mm wheels, which is kinda crazy since on wet pavement I am struggling to not do a burnout on low speed, but on good dry asphalt I would want more acceleration :). With a regular longboard its probably insane.

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Just complementing, power doesn’t matter, what matter is current

There is a point you run into saturation in the core and any more current is turned to heat without increasing torque

@Deckoz have you trying lowering the motor current in small increments to see if there is any loss in performance and if the temperature drops? If you really are hitting these high currents for any significant amount of time I bet the motors are saturating, but since you ride at high speed and the battery current is way lower than the motors it could be just a high average current and the only way as you said is bigger motors

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here’s some info from a different thread:

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This, sustaining 30mph+ is what does it. My amperage usage quadruples from 28-29mph @ 2.6-2.9 motor amps, into the 15-25+ motor amps and higher at 32-35mph. It’s gotta do with some scientific wind breaking power around 30mph, same dilemma cyclist deal with breaking 30mph.

That mixed with 100 degree days and 170F+ pavement 1.25" away makes all the issues. I can run in winter/spring/autumn on 65 degree days with 6374 just fine. I think it’s a mix of internal and external saturation from ambient temps, more copper would just mean it’s still saturated likely, just with a lower equalibrium temp. If the bigger motors we’re just big enough to lower the temps by 15-20 degrees to hover around 145-155 it would keep the bell magnets far enough away from the 170F point where you start to see demagnetization.

Edit: as you can see 15-25A in the higher duty cycles is really only 700-1000 watts. Ie I can saturate a motor with only 700ish watts. This tells me I need more copper.

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Yeah, makes sense

If the problem is saturation, that by your description and motor current it isn’t, you would need more iron, not copper, the saturation occurs when the magnetic flux going through the laminations is higher than the material can handle

But for your case more copper and iron is the solution. cooper for lower losse per volume and iron for more thermal mass to smooth out the high power bursts, and also a bigger motor has more surface area to cool down

Some 3D printed fans maybe? Don’t know if you have space for that

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The math makes sense for that appeared scaling. I’ll send ya some links when I’m off work here.

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100% THIS! Your average 6374 is nowhere near a 3kw motor. All these outrunners were originally designed to run on RC planes, with massive amounts of air pushed into them. And even then, they were never meant to be 3kw sustained. And high heat will permanently destroy the neodymium magnets in these cheap hobby motors far before wires melt.

It is true that an inadequate pack defeats high power motors. Hell, you can have enough parallel cells, but if you build it with single strip nickel, you also fail. But that doesn’t mean the motors are overkill - it means you haven’t built your pack right.

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Most people here only think they need 12/13s and the biggest motors they can find because someone else said they did in another thread. HYPE.

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:wink::grin:

I basically did this with my first autox Datsun too. Everyone said I should go performance n/a on the stock motor. Okay. Week later I’m pulling a twin turbo w/5speed out of a wrecked Sylvia. Lol

*note. I made @psychotiller build me a 12s for my first esk8 build with 6374x2 :roll_eyes: so I’m that guy lol

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Power does matter, because through power, voltage and current are able to convert to one another. I can take a 10kw motor (and by changing the KV) run it 10000V at 1 amp, or 1 V at 10000 amps. The higher wattage motor will always win because it can always run at a higher current given the same kv.

Or in the case of battery pack build, with 100 18650s I could build a 1s100p pack or a 100s1p pack - same wattage, but very different voltage/amp characteristics.

I currently have 2 builds that both have the same battery system, electronics, wheels and gearing. Both are street boards with similar decks. One is running dual Alien HEV 6374/200kv and the other dual Alien HEV 6355/190kv Both sets of motors tested at 170-175kv so not much difference there. I have ridden both for some time now and while the 6374s have more torque and are better for climbing hills a low speeds, they have noticeably more drag when coasting/free wheeling than the 6355s so when riding on flat ground, I have to stay on the throttle more with the 6374s and I get better range with the 6355s The 6374’s are also more noisy running BLDC unsensored. Bottom line, I much prefer the 6355s for all around street riding.

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I thought you gain mechanical advantage over a smaller motor even if the power is the same.

I went from dual 6355 to dual 6374 with the same battery 10s3p and VescX and I did feel a noticeable increase in torque. I do weigh almost double what the average rider weighs though.

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The way i mount my motors i can literally have dual motors of any size. While i am running dual 6374 at the moment, what larger options are out there? I suppose i should just google 8084 and see what comes up? I’m running 10s at the moment, so i guess find anything with 190kv?

I suspect this is the case. It shows up in other hobbies as well. In 3d printing, there’s a huge camp of people that think they need name-brand, hardened linear-rails at $100 a foot on all axes, when in reality some cheapo $3 plastic roller wheels are more than good enough for the application.

A 100 kg rider riding up a 20% grade hill, on a 12s board geared to 40 kmh will theoretically draw roughly 50A. 6374’s are typically “rated” at 70-80A. 5045’s @200 Kv are “rated” to roughly 30A.

Some of us are heavier, climbing steeper hills, or riding at speeds where aerodynamic drag is even more taxing than hill-climbing, but most of us are probably fine running dual 5045’s (or a single 6374, which should be more torquey than dual 5045’s).

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You should see me on my R2, the rear motors and Trucks get so hot you can’t touch them but on the other hand I can ride my dual 6374 board and my motors barely get warm unless im riding consistently over 30mph, I’m adding more copper and iron to my set up but instead of bigger motors I’m going with more motors. Quad 6374 should feel pretty great. I’m going on a trip next week but when I get back my project will see some real progress

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How about 12090

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