Every MET student at Central Washington University that graduates, recognizes an engineering problem significant to their interests. From there the student seeks out the answer by designing, building, and testing their own unique project. My project was motivated by a need for a device that would allow a person to ride a dirt bike in all the seasons encountered in Washington State. Most people ride a motocross bike exclusively from spring time through fall; the plan is to change that so an individual can ride during the winter season as well. The final product consists of a front-mount snow ski assembly that fits front tire on a motocross bike currently is, whilst utilizing a sand tire on the rear wheel to keep costs down.
The motocross bike was bought about two months ago (August 2014) and has only seen the sight of dirt, mud, and large puddles with its current owner. The bike doesn’t realize it will be encountering snow in the near future. This is cool because MX bikes have never been bought with the intentions to be used in snow, until the past few years. There are only a few companies producing snow kits for MX bikes and the designs will continually change and adapt to the needs of the riders.
This calls for multiple different designs that will allow the rider to choose the kit that fits best for their needs or if the purchase is strictly for a kit that is more aesthetically pleasing. Being involved and greatly interested in motorsports is the main motivation for this project. As a rider and dirt bike enthusiast only the best materials will be utilized in the development of this project. The plan is to use a strong-lightweight metal for all the basic components (ski-mount, spindle, fork Linkage and support). As for the ski, one will be purchased online to allow more focus and emphasis on the other components of the project.
The demand for lightweight components in motorsports is large. The reasoning for lightweight components is so the overall weight of the bike remains low, since the weight distribution towards the front of an MX bike (steering column especially) determines how easily the bike is going to handle without having to wrestle the handlebars to get it to turn and track smoothly. The other reason and motive behind utilizing a lightweight metal is for when the rider hits a large obstacle covered by snow, such as a stump or rock; this is essential to keep the steering and suspension from being ruined or needing to be replaced, since new fork suspension costs an upwards of 2000 – $3000 versus a ski spindle and mount that cost 50 - $100. The metal will be built with the intention of being light-weight and strong.
Motivation
Introduction
Function Statement
Requirements
Scope of Effort
The MX bike platform that will be used for the design and testing process will be a 2005 Honda CR 250R and it will utilize a sand tire (or tire with equal or greater grip) for the testing process of the project. The project must be capable of performing a few simple tasks with ease of the operator:
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Must support a motocross bike and rider, whilst tracking through the snow.
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To allow the rider to make turns at low and high speeds.
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The ski shall not inhibit proper function of the front suspension/forks.
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The spindle shall not rotate from its original mounted position.
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The ski must slide forward in the proper direction with ease.
The MX SnowSki will hold tight tolerances in the manufacture process to ensure proper function ability. The design shall not be overly complex so that an average mechanic can easily install the finished product. The project must pass more technical criteria which involves proper mechanical function and structural integrity:
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The total weight of the assembly should be less than 10 lbs.
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The ski should be able to rotate to a 20-45° incline past horizontal equilibrium (when the bike is on flat ground).
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The ski should be able to rotate to a 15-30° decline past horizontal equilibrium.
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The spindle shall not rotate >2° when properly installed onto the pre-existing front forks of the motocross bike.
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The column must be able to support a 500 lb load
The scope of the project will be focused upon making the bigger components, such as the spindle, ski, mounting bracket, and the components to restrict unnecessary movement. All the necessary hardware (i.e. bolts) will be bought or provided by outside sources. The evaluation and testing part of the project will focus mainly on the components produced during the design process by using some of the pre-existing hardware or parts.