Direct drives repurposed as outrunners lol.
Or just the next step in size. 68mm with 16/18 magnet pairs?
Lower KV will have higher winding resistance though. Might not come ahead by much from an efficiency standpoint.
Not sure what point you are trying to make. 
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Why is this an issue? Isn’t that like perfect?
16s and 90Kv puts you in a great spot to gear things for the usual 65 motor amps. And even then I runy maytech 190kv up to 90amps without much issues
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If you want speed you still have to have a low gear ratio. 90kv 155mm pnuematics and the same gear ratio as I have now (16:58 aka 3.63) would leave you with a 30mph top speed. The lower your gear ratio (2:1 compared to 5:1) the more heat your motor created which leads to overheating faster.
And that’s on 20s
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I’m not 100% convinced of that. Higher speed means more airflow which is good, but also means more eddy current and switching losses, which is not good.
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Just from my testing, 24/58 produced much more heat then my current 16/58 ratio
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How well do you think 16s would run on 1:4 190kv and 200mm pnuematics?
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Short gearing is a high ratio which means large mechanical advantage (5:1)
Tall gearing is a low ratio which means small mechanical advantage (2:1)
Just for reference.
Also I’m not convinced that just gearing yourself low will create more heat. Pretty sure if you assume the same speed and incline. Heat is not a function of amps. It’s a function of efficiency and power. So if I have a 1kw motor and 95% efficiency then I produce 10w of heat. Period.
(I’m ignoring iron losses here because they are dispositionally small)
The primary affect on efficiency is torque load.
And the curve looks as follows
Now look at the green line. This tells you that as a rule of thumb. The efficiency of a motor is a function of finding the right mix of torque and speed. Say You wanna hit the max efficiency and produce minimum heat. Then you’d want to gear your motor such that You operate to the left of those torque values. (To the right would be “over loaded” as Live pushed past maximum efficiency)
Now what that gearing looks like for 90kv motor at 16s. I don’t know yet.
But I’m just making a point that it’s not simply “Amps make motor hot, Ooga Ooga” 
There’s a sweet spot for a motor where the max efficiency load is less than what we want. Ideally we set things up. so that the torque/speed combo is right at cruising speed. Say 25mph.
Tldr takeaway is here :
Now say we’re talking 90kv vs 180kv (cause it’s an easy ratio) I’m pretty sure that if this graph is a 180kv. And sa your gearing is on that sweet spot. Then a 90kv would move the peak to the right (more efficient at higher torque) by 2x. And You could effectively halve your ratio (say from 1:4 to 1:2) and maintain the same efficiency.
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This graph is somewhat misleading since it doesn’t take into account any current limits and just uses the back EMF as limitations
You can see the efficiency map doesn’t look anything like that
You can use the graphs I made here as a reference to play with gearing, just take two torque and rpm points that are comparable with a different gear ratio
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FTFY.
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I’m trying to say that with a 12s pack it would draw around 40% more amps to deliver the same total power
Lol thanks. I didn’t have a calculator on me.
Numbers are hard. My theoretical degree in theoretical electrical engineering didn’t prepare me for arithmetic.
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Holy God that’s sexy
But unfortunately I’m going to have to flag you as we don’t allow that sort of smutty porn on here.
Your graphs are much nicer yes. Though mine doesn’t tell the complete picture. Yours really round it off. Though I stand by my point of motor heat is not simply a function of torque.
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Are you sure? Because direct drives sure love heating up. Or do we run our motors so far from the peak efficiency value that it doesn’t even matter?
Edit: I see now in Pedro’s graphs that it’s true that higher voltage could give less efficiency, but that’s at very low amps. For our use case it really looks like higher voltage and less current = better. Also crazy how it looks like higher speed has more of an effect than lower current. damn
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Pretty sure. Keep in mind that while your direct drives may have roughly half the kv. You are comparing 1:1 gearing to something like 3:1 or 4:1. So your max efficiency torque is 2x but your comparative torque load is 3x or 4x
I’ll say that I’m not expert in this. I do silicone not power.
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Its hard to predict by graphs alone thought.
the faster you spin the motor the more cooling you have, the faster you board goes the more cooling you have, but also the faster it spins the more core losses it has. You can melt a 190 Kv motor by just spinning it no load on the bench at high voltages
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I just ordered some Maytech 6374 140KV motors for my 16s build. The calculator says my loaded top speed will be 42mph which is plenty on channel trucks.
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How big do you guys want your batteries, how are you gonna fit a 20s8p somewhere, that and i dont wanna die when im working on my board xD
im just jealous, i also want an 18s board 
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100S1P so I can ultra-fast charge with only 5A and have tiny wires everywhere (and the world’s biggest BMS)
Might get electrocuted if it starts raining though
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