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[SKATEway]POST 2

Hello every one!

So the challenge of this week was to finalize the choice about batteries and motors. And we did it. First we did again the motors calibration we need for our system. Last week we did simple calculations. Taking all parameters, we conclude that we need two 450w 48v motors. Plus, we choose a hub motor to the gain space. We had to be aware about the function of the engine. We made sure it is a two direction motor with the good controller. I contacted the seller and he confirmed this fact.

Here motor + controller : https://www.aliexpress.com/store/product/8-inch-450W-48V-brushless-non-gear-hub-motor-electric-scooter-electric-motor/1461770_32476560207.html

For batteries, again for gain space, we found batteries kit to build by ourself. One more avantage, its less expensive. LifePO4 48V 15Ah (http://evcomponents.com/diy-battery-kits/48v15ah-headway-lfp-battery-kit.html).

For the next week, finish the list of composents (accelerometer, board, led …). Begin the PCB of our system with Expedition PCB that I installed this weekend.

Have a great week!

Charles

SKATEway, week 2

Hi,

Last week, Charles and I thought we were more or less done with defining our project. It turns out we were not. We based our specifications on existing projects, however no other project is exactly like ours, and we may not have access to the same parts. We thus had to come back to our pen and paper to set a new course of actions: we now need to compute the torque we want for our engine, which will give us its power, which in turn will lead us to the batteries we need. Because of this change of course, we had to modify our PSSC.

A precious discovery we (that is, Alexis) made, is the hub type of engine. With this, we could fit the engine inside of the wheel, which would yield tremendous saving of space on the central piece of the SKATEway. It could be the solution to a rather tricky issue we ran into: since we want the part on which the feet rest to pivot like a waveboard would, we need to link the feet-resting part to the central part with a cylinder and a spring or device of some sort that allows the feet-pod to get back to its original position. However, if the engines were to take all the space under the central pod and the batteries under the feet-pod, we would not know how to realize such a device. With a hub engine, we could have a cylinder with a spring inside running under the central pod from one foot-pod to the other. We do not know yet if we will be able to find a fitting hub engine, but we sure do hope so.

So far, Charles and I have been quite out of pace with the other groups progressing much quicker than us, so we also need to improve our teamwork: a project is not only about the product, but also about the team behind it.

I may post our PSSC another time, but for now, our main objective is to be done with the torque, engine and batteries by tomorrow evening. Quite a challenge to be honest.

Alban

ps: some little sketches of the board.

pps: do check out our hackster.io page.

sketch1sketch2

[SKATEway]POST 1

Hello,

Once week after the beginning. Here is where we are.

This week has been used to fix the system’s calibration. In the last post, I determined some values, but I based them on existing projects. I made calculs by myself for more accuracy from existing data such as acceleration (a = 2 m/s²),  total weight (100 Kg), spoke of the wheel (r = 0.11 m), rotation per minute (63 ras/s) . To extract resulting data such as couple (C), motors power (P), 48V batteries intensity (I).

C = a * m * r = 22 Nm

P = C * w = 690 W

I = P/U = 15A

The coming week, will be used to identify exactly what components we would use. The main challenge would be about motors and batteries. For motors, hub or not? A hub is space gain but the power delivered by the engine is less than a classic motor. The space is also a problem for batteries. We have to find the most flat as possible. We have to choose betwen several kind of batteries (lithium, lithium-ion, lithium iron posphate, lead …) We need to determine the need. We must not oversize our system because the battery is the most expensive item of the project. If a simple lithium battery is enought, we won’t pick the last lithium iron posphate generation battery.

Ps : A picture to visualize our SKATEway (made by my mate Alban)

rose_1v1

Charles

SKATEway, week 1

Hi,

This first week of ROSE has been quite a busy one, albeit not nearly productive enough. With my partner in crime, Charles, we defined our project: the SKATEway. It is basically an electrical skateboard designed for an urban area, such as Paris. Imagine Segway making a longboard. Finding a shape that would be easy enough to make was quite a challenge, and we clearly struggled with it. So much so that the presentation we gave in front of the class and Alexis and Sam was a rather painful experience. However, it is said that we learn from our mistakes, and we sure did. Thanks to our teachers help, we were able to get an idea which we refined during the week-end, and now, we do have our specs for the project:

  • Dimensions: 23 x 68 cm (depth will be determined by the engines and batteries)
  • Wheels’ diameter: 21 cm
  • Batteries: 2 x 48V LiFePo
  • Engines: 2 x 350W
  • Weight: < 15 kg
  • Speed: > 17 km/h (we would like to reach 25 km/h at least)
  • Slope: 20-30% (depending on the size of the batteries)
  • Autonomy: ~1 h

Thanks to those specs, we were able to define our PSSCs (Project Specific Success Criteria), which will guide our entire work for the semester.

I’m really excited by this project and will keep this logbook updated with our future advancements.

Alban

ps: here is a modest 3D model of our project.

rose_1v1

[SKATEway]POST 0

Hi,

I am Charles, and am working with my mate Alban on SKATEway, a new kind of skateboard.

This first week were used to think about the project and main specifications.

Its a skate board with three sections. One middle section fixed and two side sections mobile (like snake board), which can rotate. Two twenty centimeters wheels  on both sides of the middle section.

The skate should be used in urban environment. It would be very handy and with small size.

The skate is driven with the bodyweight. Tilt the body forward and backward to manage the speed. Tilt the side sections with the ankle to manage the direction, move to the right, to the left. (accelerometer sensor)

The main complexity is the machinery. How to build this, what kind of materials. What kind of engine power and batteries. It has to be resistant and support up to 100Kg

We can estimate a weight about 15Kg. supllied with two 350W motor for each wheel. Equipped with two batteries of 48V Lifepo4. Autonomy of One hour minimum planned. Max speed about 20Km/h

The estimate price is about 900€. We could reduce the price further with new knowledges.

New functions are comming to make it much more fun!!