August 07, 2006
Reinventing The Bike Wheel With SolidWorks
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Jeff Rowe - Managing Editor

by Jeff Rowe - Contributing Editor
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A Rocky Mountain company is using SolidWorks software to reinvent the bicycle in what it hopes can be part of a global solution to rising gas prices, high vehicle costs, and congested cities - as well as a way to keep in shape while having fun.

Although many have attempted to motorize a bicycle in the past, the company says, none of the solutions have been as elegantly designed as the RevoPower Wheel. Profiled recently in Popular Science, the wheel attaches to a standard bicycle fork like any other front wheel. However, it incorporates a 25-cc gasoline engine boasting 200 miles per gallon, easy installation, light weight (12 lbs.), and intuitive operation with a single throttle/starter interface. The rider can alternate on the fly between engine power and traditional pedaling.

"SolidWorks has been a tremendous tool in helping us overcome some steep challenges to design a better transportation product," said RevoPower Wheel inventor and company founder Steve Katsaros. "We had to pack an engine, fuel delivery, controls, transmission, and a starting mechanism into the 130-millimeter width between standard bicycle fork ends. Additionally, we had to deal with a spinning carburetor and engine, which has never been the case in any other environment. Modeling our solution in three dimensions using SolidWorks software has helped us develop, iterate, and refine ideas with our focus on the design challenges, as opposed to the workings of the software tool.
It's easier and more intuitive than any 3D CAD software we've tried."

Katsaros, a patent agent who does engineering work for the ski and home improvement markets, found SolidWorks software's assembly tree especially helpful in quickly and efficiently developing documentation for the first patent on the wheel, which was granted on Dec. 6, 2005. He is hopeful that the unique qualities described in the patent will gain the interest of clients and customers from a sizeable worldwide potential market.

More than 100 million adult bicycles are produced each year, but they take considerable effort to propel over larger distances, the company reasons. With the addition of the RevoPower Wheel in 2007, RevoPower thinks that a new lease on life is in store for the bicycle.

"We understand that companies like RevoPower need to focus on their design work and not the CAD system in order to succeed at bringing great ideas to market," said Rainer Gawlick, SolidWorks vice president of worldwide marketing. "Our efforts at creating intuitive, high-performing software are designed to remove obstacles and let our customers design truly innovative products that can even change an entire industry."


by Jeffrey Rowe, Editor

Being a bicycle enthusiast myself, this is a very interesting development and one that I believe has a lot of potential. RevoPower is a Denver-based company whose main purpose and objective is to bring unique, affordable transportation to emerging markets. The RevoPower Wheel has a place as both a lifestyle product, as well as a transportation product for both developed and third-world countries. RevoPower intends to service that market and make the technology available in a variety of forms.

We spoke briefly with the founder of RevoPower, Steve Katsaros, about his company, his product, and his design method. He uses SolidWorks exclusively in his shop for conceptual design and refinement, and hands the design data over to manufacturing where UGS NX CAM is used. In the early stages of the company when he was attempting to raise capital, Steve found the photorealistic capabilities in SolidWorks enabled him to convey concepts to potential investors.

So, how exactly did the whole RevoPower Wheel come about?

In 1997Steve visited a pedicab manufacturer who was experimenting with an electric-powered version of their pedicab (bicycle taxi). From previous projects, he knew that electric vehicles were impractical in terms of range, recharge time, and weight; the only advantage he could see was their attractiveness from an in-use emissions perspective (ignoring their environmental impact during manufacturing and recycling/disposal). In the case of the pedicabs, the electric motor and batteries added a massive 130 pounds to an already heavy vehicle. Most of this weight was due to the low storage density of batteries. In fact, most common form of batteries, lead acid, have a storage density of about
35 watt-hours/kilogram (more expensive batteries such as lithium-ion, only store about 150 watt-hours/kilogram), while the energy stored in gasoline is 12,000 watt-hours/kilogram.

So, he thought to himself, "How do you power a bicycle with a clean gasoline engine?" He continued to think, "Would it is possible to design a bicycle wheel with a gasoline engine built right into the wheel?" The trick was to have the entire engine, gear train, starter, gear train, and starter be so thin that the whole assembly could spin between the forks of a standard bicycle. This spinning assembly (that is, wheel with engine) could be cooled because it spins and not by a massive flywheel with a fan. In addition, Steve sought a solution that would allow anyone to install it on most bicycles, as well as be easy to use.

Thus began a journey of discovery and experimentation. From the earliest prototypes, Steve's company progressed from stage to stage over a period of several years. In 2002, he filed a comprehensive patent, and just a year later in 2003 RevoPower was founded. In 2003 he was able to go to work full time on the project. The first patent was issued in 2005, and a number of additional patents are currently pending.

The technical challenges and obstacles the company faced involved delivering fuel to a rotating engine, throttle control through the axle, and miniaturization of ignition system.

From a raw idea in early 2003, the team of engineers at RevoPower has developed breakthrough technology to incorporate an entire engine and gear train into the width of the normal bicycle wheel. Many early skeptics are now becoming believers.

A number of prototypes have been constructed and tested, and the final design is close to completion. Extensive testing and refinement are planned prior to proceeding with high-volume manufacture. The product is expected to be available in early 2007 with an expected MSRP of $399.

So, how does it work?

A small motor, turning at up to 7,500 rpm, drives a gear train that causes the wheel to rotate around a fixed axle. Reduction gearing within the hub delivers the appropriate combination of torque and speed to the wheel. The bicycle can be ridden as normal when the motor is off, or when the bicycle is traveling faster than the engine speed. The motor only engages when the speed of the bike is slower than the engine is traveling. The Wheel can be used manually or motorized at any time.

The Wheel will travel at a top speed of 20 mph or 32 km/h in its initial form; future models will include a higher torque lower speed model for carrying loads.

The Wheel uses a mixture of gasoline (petrol) and oil. The prototypes we are working with now weigh between 12 and 15 pounds (5.5 to 7 kilograms), but after production weight will decrease.

The controls are designed to operate on an automatic-off principle, meaning that if you release the throttle, the engine will shut down immediately. This should ensure that there is very little risk of injury or a runaway bicycle should the rider fall off. Even though this is our initial option, further design will ease this with possible considerations such as a kill switch.

We've all seen bicycles, mopeds, and scooters, but the RevoPower Wheel could truly be a reinvention of the wheel.

The Week's Top 5

At MCADCafé we track many things, including the stories that have attracted the most interest from our subscribers. Below are the five news items that were the most viewed during last week.

BUNKSPEED announced the release of HYPERDRIVE, a new software application for creating photographic imagery of 3D digital models in real time. The solution, described as the "3D interactive photograph", allows users with no expertise in CAD software or any other imaging software application to create photorealistic images from 3D digital data. It is the first software application of its kind that completely removes the complexity that is traditionally associated with creating photorealistic imagery. HYPERDRIVE is an environment that is fully raytraced in real time, combining and, therefore, eliminating the traditional time-consuming setup of a scene and
image processing. HYPERDRIVE uses High Dynamic Range Images (HDRI) to capture accurate lighting and shadow information within the environment. Similar to a digital camera, the user has control over the lens size, the brightness of the image, the environment itself where the design should be located, and the orientation of the design inside the environment.

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-- Jeff Rowe, Contributing Editor.


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