Need some help designing a electric scooter

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Chiro
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Need some help designing a electric scooter

Hello there,

I am an art school student and am working on a electric scooter design right now and I need a big help.

I need an electric scooter that carries a person (210lb guy), and make 30mph on flat easily and clime on 25% grade hill without stopping.

My first question is that how can I make the scooter possible?

I need to make a performance requirement document first so that I need to know the "power" that requires to carry the 210lb person with that speed. How can I calculate the numbers? What would be the minimum requirement?

And my second question is that which combination of a motor and a battery can make the scooter possible? I know there are many, but if you have any recommendations for the motors or the batteries, I will be appreciated.

As you can tell from my questions (I am aware that the questions are too general, but I have to ask them first to be more specific), I don't know much about physics. I might be too dumb for you guys but please bare with me as I need you guys help badly.

Any input will be appreciated and thanks in advance :)

Chiro

garygid
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Re: Need some help designing a electric scooter

As an art student you can design to reduce aerodynamic drag, rolling friction, and scooter weight.

Then, with those figures, one can figure the power needed.

The energy needed will require knowing how far the scooter must go in each mode (level and climbing).

Oh, one also needs to know the minimum acceptable speed for climbing.

Cheers, Gary
XM-5000Li, wired for cell voltage measuring and logging.

Chiro
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Re: Need some help designing a electric scooter

Hi, garygid

I haven't thought about the aerodynamics and the rolling frictions of the scooter yet. Thanks for mentioning.

The scooter will be designed as a daily commuter and used mainly as a transit connecting vehicle which connects a home to a train station and a train station to a work in San Francisco Bay Area. The idea is very similar to that of community bicycles, but I am doing it with an electric scooter and I would like the scooter to be more of a utility vehicle than a performer.

With the ease of finding parking spaces, I am designing the scooter as a "Moped", so there is 30mph top cap on the performance but no restriction on the power plant or the battery used, so I am widely open to any power configurations.

But at least, I would like the scooter to carry people with 75 percentile weight which is about 210lb with ease.

Regarding the on the hill performance, I haven’t decided yet. Hmmm, do you think 15 mph reasonable? But I don’t have reasoning behind the number, so I have to think it through.

The distance wise, I am thinking about 30miles per-charge. And if it is possible, I would like the scooter to run on Toshiba’s SCib battery

http://gizmodo.com/gadgets/batteries/toshibas-scib-battery-recharges-fast-lives-for-10+years-332312.php

Here is a rough idea of what I am doing.
20081227123809s.jpg

Thanks!

reikiman
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Re: Need some help designing a electric scooter

Interesting design... A few thoughts..

"More is a slippery slope" .. that is, I found it hard over time to stay at 30 miles/hr when the vehicles around me are doing 50-80 miles/hr (depending on road) and especially how the SF Bay Area is constructed to make it easy for car drivers and hard for everyone else. Maybe it's different in San Francisco but down in Silicon Valley mass transit is pretty bad and it has seemed more prudent to not rely on that. If we had BART it might be different.

The main reaction I have to this design is that the cargo pods are outside the center of the vehicle. Supposedly its best, especially on a motorcycle, to carry the bulk of the weight in the center of gravity. Your design has it out at the edge.

A suggestion for the front cargo pod is to mount it such that it bolts to the main frame rather than to the front fork. I'd think stability would be harmed if the front fork had a lot of weight hanging on it.

In terms of aerodynamics ... Have you seen this: http://www.craigvetter.com/pages/470MPG/Last%20Vetter%20Fairing.html

A particular idea you could draw from that is with the front cargo pod in your design, you could build a covering for the front wheel and that should do a lot to improve aerodynamics.

Chiro
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Re: Need some help designing a electric scooter

Hi, reikiman

Thanks for the great critique! I really appreciate your input.

For this project, I am designing a scooter for people who live within a 5 mile radius from Bart or CalTrain stations. The scooter is not meant to be a long distance runner but meant used on cycling paths (there are always cycling paths around Bart) or off main roads to get to Bart or CalTrain stations. And it has to be a moped in order to do that, so that is why it has to be 30 mph top speed.

My idea is not to create something to sell but to create something that people would want to try for a small fee. I have done some researches and realized that most people just won't go green when it comes to choosing "a vehicle". They always choose convenience over greenness.

So, my concept is to create small rental stations for this scooter at each Bart and CalTrain stations to make them available for a small fee, so that people (car commuters) can try it out and see if it works for them.

As for the rear cargo pod, I am thinking about making it modular so that one can attach something suitable with one's needs. The pictured is the biggest size I designed, and it is designed to fit an airplane carry on luggage for frequent flyer's, but you are totally right about center of the gravity, so I will try to move it around if it is possible.

And the front pod is actually attached to the frame. Here is the side view.
SIDE-VIEW.jpg

Oh, and thanks for the great link. I will look into it!

Chiro

colin9876
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Re: Need some help designing a electric scooter

I really like your design,

A 1000w hub motor (48v 20amps ) in the front wheel would be enough. The hub motors look similar to what youve drawn.
You could have a 48v 40ahr LiFeP04 pack in the space down near the rear axels / under the seat, thus giving u a low centre of gravity and keeping the other two boxes spare for storage.

Hub motor $200, battery pack $300+
With such nice drawings - do u also have the people available to make the plastic mouldings / aluminium frame?

chas_stevenson
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Re: Need some help designing a electric scooter

Colin9876,

Where can you get a 48v 20ahr LiFeP04 pack for only $300.oo????????????? The best price I have seen for a LiFeP04 pack that size is about $1200.oo.

Grandpa Chas S.

wheelie
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Re: Need some help designing a electric scooter

Hey Chiro...

I like your design and images... I hope it's a tilter / leaner (check out the Honda Gyro if you havn't already)... I like the adjustment in seat height and handlebars.

I too am designing a utilitarian trike (which tilts)- have been working on it for 3.5years now - and I am at a point where my plans are drawn, and construction is about to commence... Having got to this point, I offer a few suggestions..

Knowing the size of your battery pack is a must - before you get too far down the track with your design - also knowing what controller and BMS you will use is essential in determining your frame setup. This forum has great links to all the electric bits and pieces you will need to build this.

Use Lithium batteries. Use as many "off the shelf" items as you can to reduce your production costs..

Keeping weight low is essential - especially for people who don't ride a lot - overpacking the luggage compartments will lead to undesireable handling characteristics, especially when that weight is high up on the bike.

good luck, it looks like a winner to me.
look forward to seeing more as you develop it.

starrychloe
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Re: Need some help designing a electric scooter

I don't have time to look up the formulas, but based on experience I would guess 1500W would be minimum for 30MPH and going up steep hills for a fat person. The batteries/motor is a trade off - any combination is OK. The more the watts of the motor, the faster the batteries are drained of juice. The Ah is the capacity, or volume, of the batteries. Think of the batteries as a bucket, with more Ah = larger bucket.

Oh, and like others were saying, make sure you can't tip backwards going up a hill!

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