Drivetrain Design for Boosted's Electric Skateboard

http://boostedboards.posthaven.com/technical-progress-part-ii-dual-motor-drivetrain

by skdoo • 13 years ago

121 48 13 years ago

boostedboards.posthaven.com

beambot• 13 years ago

On the image showing the brushed vs. brushless... How much of that size difference is due to gearing? A scooter shaft's output is much lower RPM than a skateboard. Your gearing seems to be via belt drive.

Any chance you'll sell just the motors...? ;)

skdoo4• 13 years ago

You're right, there's a gearbox on the brushed motor and not on the brushless one. The gearbox is the part with the shaft sticking out, and the motor is the part with the heatsink fins.

And you can buy the motors already! We are using a slightly modified version of a RC airplane motor. Our first prototypes used motors we bought at a local hobby shop.

samstave• 13 years ago

Can we buy a kit of the motors and drive train and put it together ourselves?

doorhammer• 13 years ago

I think this is still, by far, one of my favorite "last mile" solutions. It's got a pretty slick look, it'll do basically all of the work for me, and I could carry it inside somewhere pretty easily.

Biggest downside I'm wondering about is only being able to use it when it's dry out (not sure there much to be doe about that while staying reasonable).

I'm a fairly avid cyclist, though. I think than between a boosted board and my trusty bike, I'd cover a pretty huge swath of my use cases.

Really interested in this.

oneiric• 13 years ago

I've ridden a long board in the rain. My legs have never been so wet. FAR wetter than biking or walking in the rain.

With this at least you could wear boots because you wouldn't have to kick/push/coast.

ececconi• 13 years ago

I really wish the city I live in has much better bike lanes or sidewalks so I could use this thing to get from point a to point b further than just my suburban neighborhood. I can't wait to see people riding these things in the city.

mike_esspe2• 13 years ago

Can you apply this to folding kick scooter?

Lightweight electric kick scooter could be useful to larger audience as a "last mile" solution.

8ig8• 13 years ago

For more than a year, I commuted to and from work (3 miles each way) on a lightweight electric scooter I bought on Craigslist for $100. It's been a while, but I used to skateboard, surf and snowboard, but having the handlebars of a scooter in an urban environment is huge for me in terms of control and safety. I used to call it the poor-man's Segway.

Edit: Not mine, but these look nice: http://www.goped.com/products/Electric.asp

mike_esspe2• 13 years ago

They are extremely heavy.

My current kick scooter weights 12 lbs and i consider it heavy. I can't imagine handling 35 lbs, my bike is lighter :)

reneherse• 13 years ago

I think that taking this [1] rather insane idea for a "longboard stroller", and replacing the child(!) with one's laptop bag and maybe some kind of fairing would be a pretty sweet solution for those of us not agile enough for regular longboarding.

[1] http://www.blessthisstuff.com/stuff/living/misc-living/longb...

jacquesm4• 13 years ago

A child shaped crumple zone. I already feel pretty squeamish with kids on the bike (2 kids, one adult, one bike).

dmd• 13 years ago

It looks amazing, but I'm having trouble understanding where the power comes from.

The Kickstarter says 20 mph, 6 mile range, 2000 watts, which gives an energy of 600 watt hours.

A Macbook battery is around 60 watt hours, and weighs about 1.5 pounds; 10 of those would weigh 15 pounds - and take up a ton of space. I don't see the volume of even ONE in any of the photos I've seen.

Where's 600 watt hours of battery hiding?

skdoo4• 13 years ago

The battery is just under 100 watt hours. The motor power lets you accelerate uphill, but the range is calculated from riding at a constant speed on flat ground.

jlgreco• 13 years ago

I wonder what sort of grade it can climb, and how far. As a "last mile" vehicle this looks quite promising but for me the "last mile" of my commute is my entire commute (well, two miles), and it is straight up a hill.

Eh, walking is probably good for me...

Jack000• 13 years ago

I think 2000 watts is peak, not nomial power.

staunch• 13 years ago

Any chance these will ever get down to ~$300? I guess what I'm asking is if this is the Tesla Roadster and there's an economy model a few generations down the line? Or will this always be for people more serious about using them for commuting, etc?

skdoo4• 13 years ago

It's possible to get something like an electric Razor scooter for ~$300, but the parts they use to hit that price, like lead-acid batteries, make it a lot less appealing.

Just like a car or motorcycle, right now there's a floor to how cheap it can be and still be great. If that gets lower over time, all the better.

zwieback• 13 years ago

I love this post because it shows some real engineering. The fact they put so much effort into the test equipment shows that there's some serious characterization going on vs. just throwing together parts.

pocketstar• 13 years ago

I really wouldn't call this "real" engineering. As a mechanical engineer it really sounds like they literally threw it together and hoped it fit after they tested the motors "...models were assembled together in the CAD software to check for fit, clearance, and interference." I saw no mention of fatigue analysis or FEA, both are now days required for "real" mechanical engineering. Without that just cross your fingers the motors don't fall off after 1000 miles. Other than that it is pretty comprehensive.

jacquesm4• 13 years ago

Vibration is the real killer for stuff like this. Hard to model for and with potentially catastrophic consequences.

pravda2• 13 years ago

I really wouldn't call this "real" engineering.

Throwing stuff together and seeing if it works is the essence of engineering.

skdoo4• 13 years ago

Our engineering team spends much of its time and effort on failure analysis. FEA is one of many tools we use during the design process, and we left out some details in this post for the sake of brevity and clarity.

tlrobinson• 13 years ago

Real engineering [compared to software development]

ballard2• 13 years ago

Awesome.

A go pro video of going from Filbert and Lyon to Filbert and Van Ness, now that would be rock: http://goo.gl/maps/OlHc7

For those that don't live in the city, it's one of the steepest streets in the western hemisphere.

nl• 13 years ago

http://www.strava.com/segments/948473

The 11% average over 1km isn't too bad, but the start looks pretty steep. Strava shows it at up to 40%. That's not exactly 100% accurate, but I've ridden 25-30% slopes on Strava and they are hard enough that on my road bike I can't stay seated (the front wheel comes off the ground) and if it is the slightest bit wet the rear wheel slips when you stand.

I'd be very impressed if this can make it up there with a person on it.

ballard2• 13 years ago

Great video about boosted

http://youtu.be/U1scP9uZP9Y

kunai• 13 years ago

Obligatory: http://xkcd.com/139/

What are the safety concerns of something like this? A top speed of 20mph will definitely be unstable for general usage, and even 15 seems more like bicycle territory, where you're seated and have an aerodynamic shape.

We might see many people falling off of these in the future...

penrod3• 13 years ago

A longboard turns in the direction you're leaning and so is dynamically stable. In fact (counter)steering is more intuitive than on a bike because you don't have to coordinate lean and handlebar angle.

The main issue with skateboards is 'speed wobble' vibration in the trucks, but a well set-up board generally isn't prone to this.

devenson• 13 years ago

Most wipeouts I've had on my longboard are when the board stops suddenly from debris and you continue moving forward, usually with your feet trailing slightly behind. Its a recipe for injury, and its why this mode of transport is only for those capable of taking a good tumble every now and then. The solution is to not travel faster than you can run, and to always be vigilant for small rocks, twigs, sand, and especially things that will jam under a wheel but continue to slide forward like pinecones.

The length of the longboard mostly prevents speed wobble which is an uncontrollable side to side swaying which tends to increase in amplitude once it starts.

jacquesm4• 13 years ago

I really hope the link between the remote and the board is secured properly, it would be a really nasty prank to overpower the transmitter from some vehicle and to cause it to accelerate or come to a sudden stop. Griefers are not limited to being active online.

nikatwork2• 13 years ago

I'd love to see a mountainboard/pneumatic tyre version of this for us poor souls cursed with terrible road surfaces. I'd also love to see compatibility with Original Skateboards spring trucks.

But anyways fantastic product, I'll definitely be picking one up at some point.

pkorzeniewski• 13 years ago

Interesting, but I'm still waiting for hoverboards.. 2 years to go :)

Yaggo• 13 years ago

I wonder if they ever considered hub motors for better efficiency and quieter operation (no belt), or would it be too big technical challenge to custom-build (basically the wheel and motor would be single integrated unit).

robomartin• 13 years ago

One of the reasons for which motors in scooters and other electric vehicles are large and bulky is that they have to be designed to last a long time in real world environments.

The motors being used for this project are hobby model aircraft motors. These motors put out a lot of power per unit volume but are most definitely not designed for continuous duty at anywhere near to full output. They are also not sealed against the elements and have bearings selected for reasonably balanced loads with relatively low radial loads.

I have piles of these on my workbench ranging from cheap Chinese units to top of the line German designs. I use these on our planes, helicopters, multi-rotors, boats and cars. At the top end you have amazing hand-crafted quality with a prohibitive price (unless you want to pay $8,000 for a skateboard). At the low end they are cheap and they are junk. I've seen everything from magnets coming off, coils burning out, power leads coming off, bearings going bad prematurely and shafts bending.

In short, while the design process is interesting, I think the most fundamental flaw is being ignored: The motors are not designed, nor are they suitable for, this kind of an application.

Drivetrain Design for Boosted's Electric Skateboard

Related Stories