Scooter
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=Design for Environment= | =Design for Environment= |
Revision as of 05:35, 8 February 2012
Group Information
24-441 Spring 2012, Group 10
Product: Razor Scooter
Executive Summary
A kick scooter is a simple human-powered vehicle, composed of a small platform to stand on and handle bars to hold onto and steer, used as a means of transportation over short distances. As a case study, our team is analyzing the Razor brand scooter, one of the most popular in the United States. The scooter will be disassembled in order to gain an understanding of how it is manufactured and put together. Competitor products will also be examined in order to understand various solutions the manufacturers face. An initial user study will be conducted to determine shortcomings in the overall design. The goal of the project is to come up with an innovation to make the scooter easier or safer to use, to make the construction simpler, or to change its purpose by adding a utility attachment.
Major Stakeholders
Manufacturing
- Simple parts that can be mass produced
- Small number of unique parts
- Assembly with minimal effort
- Fast assembly time
- Environmental effect of materials used
- Product re-usability
Shipping
- Maximum compressibility
- Low weight
- Low volume
- Reduce empty/wasted space
- Durable enough to withstand damage with minimal padding
Retailers
- Appealing colors to customers
- Cheap product cost for maximal profit
- Minimal store floor-space usage
- Efficient packaging for minimal storage space
Potential Consumers and their concerns
Parents
- Low cost
- Reliable
- Safe
- Durable
- Something their kids will want and think is cool
Kids
- Fun
- Cool
- Light weight
- Trick friendly
College Students
- Portable
- Collapsible
- Light weight
- Easy to carry/store
- Energy efficient
- Cheap
- Durable
Product Details and Observations
Product Specifications
These product specifications are provided by the RazorUSA Company.[1] The particular model analyzed is the AW. This is the same as the model A, with the only difference being the addition of a wheelie bar.
- Material: Aluminum, Steel
- Number of Wheels: 2
- Front Wheel Material: Urethane
- Front Wheel Size: 98mm
- Rear Wheel Material: Urethane
- Rear Wheel Size: 98mm
- Wheel Base: 20.0 "
- Bearing Type: ABEC-5
- Maximum Weight Capacity: 143.0 Lb.
- Manufacturer's Suggested Age: 8 Years and Up
- Dimensions: 34.0 " H x 26.0 " L x 13.5 " W
- Weight: 6.0 Lb.
Product Observations
This particular model scooter has a rubber shock installed on the front wheel assembly (see image in the Bill of Materials Section below). The collapsing mechanism on the front of the scooter has locking grooves as a safety precaution when folding/unfolding the scooter. The operation of the folding mechanism is initiated with a very simple release lever that can be operated with one hand. This particular scooter comes with an optional wheelie bar. While arguments can be made that this is added to be able to do tricks and stunts, it mainly serves as a foot rest for the rider. It also adds a slightly "extreme" look to the scooter. In order to prevent the riders foot from sliding on the deck of the scooter, the Razor company added a sandpaper like sticker. While this has an important function, it also makes others aware that this scooter is in fact an authentic Razor, something that might appeal to younger children. The handlebars were coated in a comfortable cushy material in order to make riding more enjoyable for the user. The spoon brake system proved to be somewhat effective in slowing down the scooter, and is fairly easy to operate, making it stand out to parents who may be buying the scooters for their children and concerned for their safety.
Product Operation and Preliminary User Study
Product Operation
- The rider places hands on the handle bars and the inside foot on the deck for stability
- To propel the scooter, the rider pushes off with the outside foot and repeats this step until desired speed is reached
- The rider then lifts the outside foot off the ground and either lets it hover in the air or rests on the deck along with the inside foot until more speed is desired
- In order to stop, the rider either jumps, runs, or walks off the deck of the scooter or safely uses the inside foot to press down on the hinged fender that begins to stop the back wheel from any further rotational motion
Preliminary User Study
- The scooter is difficult for larger users. While there are bigger models, an adjustable universal model would be an optimal solution.
- The deck is too small for larger shoes to fit on fully
- Even at the maximum setting, the handle bars are too low for tall users
- Larger users can easily miss the brake while trying to stop
- A 143lb weight capacity limits the customer base severely
- Brake proves to be ineffective for stopping very quickly
- Sudden heavy braking can lead to locking the rear wheel, which in turn will wear it down
- Leaning back slightly can cause the user to fly backwards off the scooter
- The turning system proved to be difficult to use
- The direct connection to the front wheels causes a safety hazard at speed if the user turns the handlebars sharply
- User must turn really wide, or stop to turn
Potential Innovations
- Wheel innovations
- Smoother ride
- Omnidirectional capable wheels
- Collapsible wheels
- Greater energy output with less effort input
- Easier/simpler collapsible mechanism
- Reduced weight
- Reduced volume when collapsed/increased potability
- Adjustments for larger users
- Telescoping handlebars
- Adjustable deck dimensions
- Multinational use
- Ski attachment for snow use
- Anti-lock brake system
- Hand operated disk brake
- Foot operated disk brake
- Removal of hard-to-use release buttons on handlebars
- Added utility attachments
- Broom/mop attachment for novelty cleaning product
- Ease of use modifications
- Foot operated collapsing mechanism
- Kick-up collapsing mechanism
- Foot deck rotational lock for more comfortable carrying
- More environmentally friendly materials/production process
Bill of Materials
In order to make the BOM more comprehensible, it is split up into separate subassembly BOMs. Repeating components share the same part number across subassemblies.
Front Wheel Subassembly
Shock and Wheel Attachment Subassembly
Lower Tube Subassembly
Collapsing Mechanism Subassembly
Front Deck Subassembly
Rear Wheel Subassembly
Top Tube Subassembly
Part No. | Part Name | Material | Quantity | Function | Weight (oz) | Dimensions | Manufacturing Process | Picture |
---|---|---|---|---|---|---|---|---|
46 | Bottom Tube | Steel | 1 | 5.1 | Extruded and Machined | |||
47 | Top Tube | Steel | 1 | 4.8 | Extruded, Welded, Machined |
Handle Bar Subassembly
Top Tube Adjustment Subassembly
Frame and Brake Subassembly
Design for Manufacturing and Assembly Analysis
Design for Manufacturing
When analyzing our competitor's product, the Razor scooter A2, we found a lot of room for improvement of its manufacturability. In order to minimize the part count, it would be possible to design a collapsing mechanism that uses fewer parts than the current design, which has 18 parts. The plastic covers especially are mostly for decoration, with a secondary purpose of preventing young children from sticking their fingers into the locking mechanism. Even so, they are not essential to the design of the collapsing subassembly, and so only add unnecessary steps to the manufacturing and assembly processes. Throughout the whole product, plastic parts were added instead of using metal finishing processes. While this was resulted in fewer finishing steps, it added steps both in manufacturing and assembly.
The Razor scooter we disassembled also showed opportunities to standardize components, commonize the product line, and standardize design features. A lot of the screws used as fasteners were the same size, but several differed by one size, and a few even switched from Imperial to Metric sizing. By unifying the size and length of screws used, the scooter could take better advantage of economies of scale and utilize fewer tools in the manufacturing process.
Another area for possible improvement with respect to design for manufacture is the creation of multifunctional parts. No parts of the scooter are currently multifunctional, but there is a definite opportunity for the creation of such parts in our redesign. For instance, designing a brake that doubled as a lock for the handlebars when the scooter is in its collapsed position could remove the hassle of the handlebars swinging about loosely when unlocked.
A final place where manufacturability of the scooter could be improved is in its secondary & finishing operations. Every single aluminum piece that is visible on the outside of the scooter has been polished, and a sandpaper sticker was glued onto the deck when it would have been much easier and probably as effective to extend the extruded ribs across the deck of the scooter to add friction.
Despite all these areas for improvement, there were many ways the current design had kept maufacturability in mind, which we will remember as we consider our redesign. Some of the locking mechanisms on the scooter had minimized their part counts to about 2 parts (for example, the handlebar locking mechanisms each consisted of a button and a spring). Similarly, the scooter had some fairly sleek and simple designs, like the braking mechanism which, while not 100% functional, also only consisted of about 4 parts. In terms of ease of fabrication, most of the scooter was made of aluminum, which is easy to manufacture (when the aluminum is recycled) and very easy to machine. Most parts that were not aluminum were plastic, and the few remaining parts were made of steel or rubber. The plastic parts were all colored black by color dyes added to the injection molding process.
Overall, there are a few good designs we will keep in mind during our redesign, but even more opportunities for improvement which we hope to take advantage of in the next phases of our design process.
Design for Assembly
Our product was fairly complicated to disassemble, and in our limited experience attempting to reassemble some of its subassemblies, we discovered much room for improvement in its design. First of all, there were a lot of components for such a small, simple device. Some of these were flashy add-ons for marketing and design purposes, such as the shocks and wheelie bar, but others were useless or not essential to the function of the device, such as the numerous plastic pieces used as covers to hide unfinished parts. As well as removing unnecessary components, another way to minimize the part count is to remove fasteners, and utilize snap fitting or other means of attachment. A lot of screws were used in this device, and as we've discussed, they were already a hindrance for a number of other reasons.
Another area that could be improved upon is the ease of handling of parts for human assembly. There are a lot of ambiguous parts, such as screws and levers, which can be very difficult to tell apart and could easily be unified for easy assembly. Some of these parts are also symmetrical, but only work in one orientation. These parts should be made obviously unsymmetrical, so that it is obvious in which orientation they should be attached to the product. The orientation in which parts are attached is not uniform, either. Many parts have fasteners on multiple sides, and most of these are attached horizontally instead of the ideal attachment direction of straight down. A final cause for concern is that many of the parts of this scooter are assembled inside its small-diameter tubes, which are tight and do not facilitate easy movement or sight.
The main way in which the scooter utilized good design for assembly was its use of subassemblies that can be assembled and tested separately or outsourced. The wheel subassemblies are almost certainly tested and purchased separately, and most other subassemblies, such as the telescoping tubes, brake assembly, and handlebar assembly, can easily be tested without the entire product.
There are many ways to improve the ease of assembly in this product, many of which we will probably explore in the next phases of our project.
Failure Mode and Effect Analysis
Item and Function | Failure Mode | Effects of Failure | S | Causes of Failure | O | Design Controls | D | RPN | Recommended Actions |
---|---|---|---|---|---|---|---|---|---|
Design for Environment
External links
Brake device for a skate cart - Patent number 6139035 (stamped on brake of the scooter)