MAD Storm…The attempt to create the Most Powerful Direct Drive_LoL

How-Tos & Esk8 mechanics
#38

No you are not alone :rofl:

#39

Clever simulator :yum:
I would actually go with custom Kv motor and ask for 60-75Kv based on the wheels you are going to use.

85mm wheels are nice but the clearance will be a problem

#40

I wanted, but the price would be more than double

When using a direct drive, from a motor perspective the Kv hardly matters, unless it is too low that you don’t get the speed you want, what changes is that you will need a higher motor current on the ESC to produce the same torque, since I will have plenty of cooling for it will probably not overheat

The clearance may be an issue, my pulleys have the same clearance as the motor will have and they are fine, surely the motor is much longer

#41

True that that the motor will give you the same output with higher current but that works jus tin theory. In the reality you will get a pretty inefficient motor, that will sucks a lot of current and drain your battery. In my experience, Kv in direct drive matters more than gear drive since you can not compensate with the ratio. I have use 130Kv motors as direct drive and of course they work but not even close in comparison with efficiency and performance of the lower Kv one. You will most of the time stop and accelerate. The too things where they will suck, braking and torque.
You can find custom Kv motors for 50-60 each btw.

Concerning the clearance I do not know which diameter you set for the the current wheel pulley but you want to add a sleeve around the thin aluminium can of the brushless motor so a 69mm diameter is the minimum you will get with a 63mm motor to have a decent protection. That is the MAD Storm and the wheels there are 90mm… 85 is possible but you will scratch it really really easy.

#42

It may be, I never tested the same motor in different Kv’s, if it’s not exactly the same motor with the same cooper mass it can’t be compared

I say it doesn’t matter because lets say you get a 200 Kv motor with 10 mOhm resistance, if you rewind it for 100 Kv you will need half the amount of current to produce the same torque, but the motor resistance is multiplied by 4, since the cooper loses are I²R, the cooper loses in the motor are the same for both Kv

In my testing with the direct drive simulator, doing my usual routes, the consumption was only 5% than a geared setup

I was planing to run without any sleeve, in my current board the motors already sit a little higher than they will with the direct drive, the can is surely beat up, but nothing broke

#43

I have tried the same motor delta and wye. 75Kv and 130Kv. Resistance was similar but the difference was a lot.

Without sleeve it can work. Maybe epoxy the magnets.

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#44

delta should have 1/3rd the resistance of wye and the kv with delta should be the wye kv multiplied by sqrt(3) or 1.73205…

#45

I know the ratio, just say that real application is what matters and in my experience balance before hand Kv base on the setup works better than just provide more current. Same motor, in the 130Kv version was draining my battery in 13km. In wye I go over 22km no problem. Never drained completely. Of course they both perform on paper, but I empirically experienced significantly different performance.

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#46

Rey, how is the axle (12mm?) installed in the hangar? is it simply pressed in? Does it have a keyway, or similar to prevent rotation?

#47

you might want to check the original thread on the other forum. I have posted so many pictures that everyone can make his own version :blush:
Anyhow hanger is 12mm, hole and grub screw to secure it to the central part of the truck.

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#48

the losses in the controller would be 4 times higher if you double the kv and double the current for the same torque at the same rpm, even though in theory the losses in the motor would stay the same

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#49

that makes sense and would explain the difference I found, Thanks!

#50

also since you could potentially ride faster with the higher kv it may be more tempting to lose efficiency that way as well…

#51

not in my case unfortunately, I couldn’t because I was hitting all the limits set in the VESC for motor and battery. That things was demanding so much current. Most of the losses was for the hills. Probably at constant moderate speed would have been fine. But in the city is was pulling too much to perform less than its 75Kv version.

#52

Yeah, my increase in consumption was probably due to other resistances, 190 Kv direct drive I was running 70A to get a good torque

#53

believe me find motors around 70Kv and you will be happy about it. You will have to put quite some work to modify it. 190Kv direct drive is just not good, even at high current. Brakes must be weak too

#54

If they turn out to be bad I will hand rewind them, I need to practice for a future project

But you are right about brakes, using only regen and shorting the coils, at low speed there were almost no brakes, them I changed to active brakes and it worked perfectly

#55

I also use active braking because that is a known issue of direct drive, but above 5kmh the brakes are good with lower Kv motor. Anyhow good luck and make sure to post pics about it :smile:

#56

I didn’t pay attention of how low speed I could go without active, will test next week

Thanks, sure will, follow any progress here

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#57

I will!

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