Chrome on Carbon Fiber

Last crawled date: 1 year, 10 months ago

My motivation for this entry is to improve on the durability of the current design and fix some of the common issues that users have experienced, as well as add drifting flair through chrome on carbon fiber.

I started my research with a visit to the Razor Crazy Cart facebook page. The uploaded videos mostly consisted of what appeared to be sponsored skaters and drifters either at skate parks or California drift competitions showing off the amazing capabilities of the cart. They were professionally made (some with GoPros) by grown men in front of big crowds with access to lots of smooth pavement, with plenty of carts on hand in case one went down. As a father of two razor-loving children, of course after seeing such a great product, my first instinct was to look into buying one or two myself. A quick Google search later, and views became more grounded. While the cart is fun and has some amazing capabilities, it is clear from the 91 reviews on Google, that the product is in its infancy and needs a few simple fixes to improve its durability.

The first and most obvious issue that consumers are having is that the wheels wear out too quickly. Razor lists the wheels as standard wear items, and they are therefore not covered by the warranty, so consumers were regularly voicing complaints about having to replace the wheels. This would not be an issue if it were a once-a-year occurance, but more than one consumer had complained about having the replace the wheels within a few weeks, with some even having issues after the first hour of use (one father even suggested buying a pack of rollerblade wheels along with the product). Buying a $350 product for your kid for Christmas that he gets to use for an hour is every father's worst nightmare. A quick glance at the Solid Edge model, and the issue was obvious. The polyurethane rollerblade wheels are not right for the application.

Polyurethane wheels revolutionized the skateboarding in the 70's as an asphault-grabbing alternative to the previous bone-jarring clay wheels. Rollerblades then took the experience a step farther with tapered polyurethane to be able to handle both forward linear motion and tight turns. Razor then put the rollerblade wheel on a scooter and a whole new genre was born. Rollerblade wheels are very well suited for forward motion with limited lateral load on the wheel; however, this is not the type of load that the Crazy Cart wheels see. The Crazy Cart is a heavy hunk of steel with a powerful, high-torque electric motor. It gets moving at 10-12 miles per hour, then the user pulls the "emergency break" and all of the energy of that forward motion is transferred laterally to the wheels, which quickly wears them out. My solution to that issue is a simple set of COTS dual wheel casters. The ones I'm showing are McMaster-Carr abrasion resistant black rubber (90A Durometer) dual-wheel (more maneuverable) with a threaded stem. These will last for years, with no sacrifice in capability.

The next issue that consumers are having is that the chain drive constantly pops off and requires maintenance. This is something that almost every consumer (even the ones that gave 4 stars) lists as an issue. One reviewer mentioned that a chain tensioner should be added, but then I saw a tensioner in the model, so I wasn't sure if this is still an issue or not. This can easily be fixed by going to a more heavy duty COTS tensioner. I've included a generic (not made by me) screenshot of one that would help tremendously. I didn't include it in the model because again, I wasn't sure if this is still an issue or if I was just reading an outdated review.

My third design change was to go to a carbon fiber bottom tray. The purpose of this is threefold: it increases performance, adds to the drifting spirit, and generates marketing hype.

The performance advantages of going to carbon fiber are significant. A lot of reviewers listed as a con the term "heavy," and of course a huge steel plate is a very heavy item. By going to carbon fiber the weight is significantly reduced. This is an additional plus for the issues above in that reduced weight means reduced load on the drive assembly, and less chance of popping the chain off. It can also mean less lateral load on the wheels, which will increase their lifespan. The main performance advantage of going to carbon fiber is of course increased speed and longer battery life.

Carbon fiber also isn't as expensive as it seems, especially for this part which lends itself well to switching. Since it's a simple flat plate, you could use a classic laminated plate, or for even more weight reduction, include a honeycomb core. In place of welded on nuts for machine screws, you could add simple click bonded nutplates. There are several companies out there that can easily do an equivalent strength analysis to the current steel plate, and would even go so far as to design/build the mold, and cure and trim the part if you don't want to invest in your own infrastructure.

Another advantage of going to carbon fiber is the marketing attention and hype it would generate. It would likely be the first large-scale, high-end toy made by a major company to include Carbon Fiber as a primary build material in a prominant part of a kids toy. Carbon fiber enthusiasts would go crazy, and just as the razor scooter pioneered the use of inline skates on a scooter, the Crazy Cart would go down in history as the first to make use of carbon fiber as a performance-enhancer on a kids toy. It also looks cool, and it would be as much of a must-have for drifting enthusiasts as for the neighborhood kids on the block.

The final details I added are the chrome parts and the carbon fiber engine covers. This is not so much a design function, as it was easy to do and Keyshot and made it look nice. I included one with chrome seat, and one with the classic crazy cart red. Sure it looks nice, but it would be needlessly cost-prohibitive. Maybe it could be offered as a special edition?

Anyways, so that's my design improvement. Fix the two most common consumer durability complaints (chain popping off and wheels breaking) then change the deck to carbon fiber for added durability and performance. Thanks for reading!