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 Alex's EV Mountain Board Project

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rdubard
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PostSubject: Re: Alex's EV Mountain Board Project    Wed Oct 26, 2011 7:08 pm

Really cool (but perhaps a bit dangerous) project!

Some thoughts: Have you (or anyone you know for that matter) actually tried running 4 of the 2S LiPo packs in series, then two of those setups in parallel? I am concerned that the cells will have to be carefully chosen to have almost identical properties and be all fully balanced charged to match in order to keep them working well. The weakest cell will have to handle the same current as all the others in the series, and the weaker of the parallels will undergo charge from the higher voltage one.

Does the ESC contain a bec already? If so, why use another?

How are you gonna control this? With a TX while standing on the board? Just wondering. I really don't see a problem with that.

Will you drive just one, or both of the wheels on the front (or back)? If so, how? I'm interested in the linkage mechanism.

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Jeff L
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PostSubject: Re: Alex's EV Mountain Board Project    Wed Oct 26, 2011 8:48 pm

FYI, it *WILL* launch out from under you. Take a look at Charles Guan's Straight Razer:

It's built around an 80-100 and is basically a wheelie machine. You could actually get away with a much, much smaller motor and still be insanely fast.

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Cody
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PostSubject: Re: Alex's EV Mountain Board Project    Wed Oct 26, 2011 11:47 pm

Jeff L wrote:
FYI, it *WILL* launch out from under you. Take a look at Charles Guan's Straight Razer:

It's built around an 80-100 and is basically a wheelie machine. You could actually get away with a much, much smaller motor and still be insanely fast.
Alex and I had already talked about wheelies. I used Thomas' scooter as an example instead of Charles.
With the gearing and the longer wheelbase I think it could be a more controllable wheelie
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Jeff L
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PostSubject: Re: Alex's EV Mountain Board Project    Thu Oct 27, 2011 11:13 am

Alex Udanis wrote:
This is sounding more and more dangerous fun. My biggest concern right now is the issue with cogging on start up. I was reading that is a common issue with large un censored brushless motors with large loads.

Yeah, if you don't start off rolling the motor will not have sufficient torque to start and your ESC will die a fiery death (a well-known phenomenon in sensorless brushless scooters). Without hall effect sensors, it won't start from a dead stop.

On the topic of control problems, I'm dead serious: this thing won't stay under you. The motor will cause the board to accelerate too fast for you to successfully stay on, especially given the power you're feeding it. The only way to counter this would be a more complex control system to handle gradual acceleration. Otherwise, your finger will twitch a little on the controls and you'll end up on your booty and the board will end up 50 feet away in whatever direction it was travelling.

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PostSubject: Re: Alex's EV Mountain Board Project    Thu Oct 27, 2011 7:19 pm

[quote="Jeff L"]
Alex Udanis wrote:


On the topic of control problems, I'm dead serious: this thing won't stay under you. The motor will cause the board to accelerate too fast for you to successfully stay on, especially given the power you're feeding it. The only way to counter this would be a more complex control system to handle gradual acceleration. Otherwise, your finger will twitch a little on the controls and you'll end up on your booty and the board will end up 50 feet away in whatever direction it was travelling.

And what experience are you basing this on? This isn't a direst driven scooter, it a much longer mountain board with larger wheels that are geared down. Yes I agree it will have the ability to come out from underneath of someone who isn't taking precaution but with a gradual push off and soft start on the controller I don't think it'll be so much of a problem
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Jeff L
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PostSubject: Re: Alex's EV Mountain Board Project    Thu Oct 27, 2011 9:25 pm

Cody wrote:
Jeff L wrote:

On the topic of control problems, I'm dead serious: this thing won't stay under you. The motor will cause the board to accelerate too fast for you to successfully stay on, especially given the power you're feeding it. The only way to counter this would be a more complex control system to handle gradual acceleration. Otherwise, your finger will twitch a little on the controls and you'll end up on your booty and the board will end up 50 feet away in whatever direction it was travelling.

And what experience are you basing this on? This isn't a direst driven scooter, it a much longer mountain board with larger wheels that are geared down. Yes I agree it will have the ability to come out from underneath of someone who isn't taking precaution but with a gradual push off and soft start on the controller I don't think it'll be so much of a problem

Straight Razer isn't direct driven either, and is actually geared down considerably; I've seen it in person quite close up. For the speed target (and hill climbing performance) Alex is looking at, a motor running at 500-1000 watts would be much safer (and likely cheaper and more compact). The motor he's looking at tops out at 4440 watts (based on maximum power delivery from the ESC and batteries), far more than what's necessary. The vehicle Charles normally uses his giant motors on is a significantly larger scooter which he still has trouble controlling on startup at times, and that's even with handlebars.

At the very least, Alex needs something to safely limit starting acceleration. If you consider the problem more closely, an electric skateboard (or scooter, or any vehicle you ride on standing up) with rider is extremely top-heavy. Ignoring the basic dynamics involved will result in significant physical pain.

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Koolaid64
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PostSubject: Re: Alex's EV Mountain Board Project    Thu Oct 27, 2011 9:33 pm

i have some hi watt scooter motors and some even large motors i can sell to you for cheap. ill get pic when i get home tomorrow if your interested.

-Kyle
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Koolaid64
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PostSubject: Re: Alex's EV Mountain Board Project    Mon Oct 31, 2011 9:25 pm

here is the scooter motor



and the other bigger better badder motor



it wants to be a mag but its just not =P

any way i have no real specs on them, i just know they are high watt motors

if any one should happen to want them for bots to i have four of the big boys and five of the scooter motors. one has a bent shaft though witch is fixable if you know what your doing

Kyle
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