E-Freeboard

[Ace6.3]

Hi All,
I'm new but I've been lurking this amazing website for quite some time now. I have decided to build an e-freeboard (http://freebord.com/).

As you can imagine is quite hard to motorize the caster wheels. So my idea is to put electric motors on 2 outer wheels on different sides of the board and control them with a remote. I could use them either all the time (with some fancy control for inverting direction), or just to gain speed.
Since I currently have low funds I wanted to only put 1 motor and basically use it as an alternative to pushing when I'm leaning on that side. Then add the other motor and an maybe a gyroscope (to choose which one to turn on) when I have more money.

Here are the specs:

Deck+Trucks: Freeboard Bamboo Deck+ G3 Trucks
ESC: VESC
Battery: Zippy 6S1P 5000mAh (I want to be able to cover at least 15km, so this might be upgraded)
Mounts: Enertion Mounts
Remote: Wii Nunchuck

I still have to decide which motor and wheels to use:
Motor: Should I go with a HobbyKing motor (I was looking at the SK3 - 6374-149kv) or with the Enertion R-Spec2.0 190kv. Aside from weight their specs are quite similar. Has anyone had experiences with both of them? Since I won't be constantly using it differences in unpowered drag might really make the difference.

Wheels: I'd like to mount Freeboard's Da-Blue which seems to be the best wheels for sliding. However these are 80mm wheels. Do you guys think I should opt for something bigger like an 85 mm?

 

[psychotiller]

I'm not sure how much time you've put in on the freeboard, but it sounds dangerous motorizing the out side wheels. Especially when only two of then make contact with the ground at any given time...a company is already producing a motorized version of that board with the casters as the drive wheels.

 

[Chalo]

I would think that powered casters would tend to lead their pivots rather than trailing as usual. Seems like a recipe for problems.

 

[Ace6.3]

Thank you guys for your replies and observations.

I have actually never ridden a freeboard, but on the other hand I have quite some knowledge on electric motors. This probably explains my design choice. While driven casters might actually be the best solution from a mechanical, they require brush motors that are poorly reliable in industrial environment, not to say on the road. Also, I don't really like the idea of how the weight increase might slower the caster wheels. Indeed to host the motor, pulleys, brushes,... the casters should go from a about 200 grams(~7 ounces) to almost a kilogram (~2 pounds).

From a mechanical point of view a freeboard, with only two outer wheels on ground, is not too different from a bike with training (caster) wheels. If the outer wheels weren't constraining the casters the board would be moving in random directions, just like a cart when you push it away. Obviously, it is mandatory to avoid throttle when sliding or, anyhow, when the central and (driven) outer wheels are not aligned (the board is moving sideway).

I should get my freeboard in a couple days and test all this out. Please let me know if this still doesn't convince you. It's better to realize about problems now then after having spent several hundreds on components!

Thank you

 

[LEVer]

http://www.leiftech.com

 

[psychotiller]

Catching an edge on a snowboard on ice hurts a little sometimes. On the pavement on a freeboard it's a whole different ball game. I used to sell them and could spin 900s in our showroom. It was fun, but sometimes painful.
Take your time. Have fun!

 

[sk8norcal]

I should get my freeboard in a couple days and test all this out. Please let me know if this still doesn't convince you. It's better to realize about problems now then after having spent several hundreds on components!

I used to ride with a couple of their team riders,
They are amazing to watch, making it look easy.

I never got used to mine (1st gen with no hooks), gave up on it.


Leiftech's powered caster wheels seems to work pretty good.

I think powering the sidewheels might work too.....

 

[psychotiller]

I should get my freeboard in a couple days and test all this out. Please let me know if this still doesn't convince you. It's better to realize about problems now then after having spent several hundreds on components!

I used to ride with a couple of their team riders,
They are amazing to watch, making it look easy.

I never got used to mine (1st gen with no hooks), gave up on it.


Leiftech's powered caster wheels seems to work pretty good.

I think powering the sidewheels might work too.....

Asking for trouble powering the sidewheels, but good luck

 

[Ace6.3]

Some updates:

Since some showed doubts regarding the mechanical design, today I presented it to my team. (I'm a control engineering PhD student in a robotic research group, that also includes two doctors in mechanical engineering.) They all said it should work. (But maybe they just want me dead )
So today I proceeded to order motor (Enertion R-Spec 2), mounts, belt & gears (ratio 14:36), ESC (VESC) and an Nyko Kama remote. Sadly, everything except the remote will not be shipped before Nov. 18 since the VESC was in preorder .

I will shortly get battery & charger. In this regard, I can't find many information on which switch to use. Is a normal switch, maybe with a capacitor in parallel, enough or should I get something more specific?

 

[LEVer]

You don't think a spinning wheel up in the air will be a problem when it hits the ground?

 

[Ace6.3]

You don't think a spinning wheel up in the air will be a problem when it hits the ground?

Honestly, no.
1) It isn't problem when I jump on my bike or scooter.
2) Since the setup will be single drive I don't see why I should accelerate while the driven wheel is not touching the ground.
3) If it were a problem, I could cutoff the motor when the load drops suddenly (wheel getting in the air).

Why do you think it would be?

 

[SlowCo]

You don't think a spinning wheel up in the air will be a problem when it hits the ground?

Why do you think it would be?

No problem at all.


Just put up the video of the result for our enjoyment...