Sunday, 10 February 2013

Do YOU want to build a gravity racer?

As I explained in my last post, the gravity racer project that was the subject of this blog, ground to a halt for reasons that have nothing to do with the engineering challenges. Actually the design is still a sound concept and, more than that, there was still much more of the deign to come that had not been aired in the blog.
With this in mind, and as there has been so much interest in the blog, I thought it might be worth floating the possibility of getting the project going again. However, right now I’m not in a position to build the car myself. Yet a blog featuring a stream of engineering ideas unsupported by practical experience is not a very sound basis on which to advise others. So, no car, no blog and this really is the end.
However, if someone out there is considering building a gravity racer and is wondering how and where to get started, they would be very welcome to adopt this design. In fact I would happily work with them, sharing ideas in return for their experiences. Then, the results would be the basis for more entries in the blog.
If you fancy this, please get in touch and let’s start talking to see where it takes us. But, for now, thank you for dropping in and goodbye.

1 comment:

  1. Looks like I found this blog just at the right time.
    I want to build a billy cart (gravity racer in Australia) and have similar constraints to you – little or no money, semi-interested kids and probably a wife who complains about the time wasted building kids toys.
    Here in Australia we have billy cart races held annually in some of the small towns. In Braidwood where I live the winning cart for the past 2 years has been an out-of-townie so I want to build something competitive for next year to return local pride to the event. For this year I converted a Jason recliner lounge chair to a billy cart and clocked 37 kph down the hill where we run the annual Braidwood Billy Cart Derby. That would have been fast enough to win 3 years ago but unfortunately the fastest cart on the day did 47 kph so I have a long way to go.
    Because the hill is a straight road and only 450 metres long I can get away with solid axle steering but when this cart is completed I’ll look at building one with Ackerman steering so I can play on some of the twisty roads.
    So far the plan is to use 12” or 16” bicycle wheels (less inertia) depending on what tyres are available that can take 100 psi. The winning cart this year was called Whistler and had 12” inch wheels running 90 psi. Unfortunately that cart (and wheels) are 25 years old and finding old 12” tyres that take that pressure may be impossible – curses to modern manufacturing methods that incorporate built in low standards.
    Because my new cart will only need to go in a straight line I’ll run a solid rear axle with the wheels bolted on. The axle will run in 2 bearings attached to the body. This will allow me to fit a braking system within the body and therefore reduce aerodynamic drag which is my main design constraint. It also reduces rolling resistance by only needing 2 bearings, not 4 (2 per wheel). Body design will be streamlined with as little frontal area as possible. I’ll use separate fairing for the wheels.
    To see the track, look at Gillamatong Lane, Braidwood, New South Wales on Google Earth. We race from the intersection at Sandholes road down to Araluen Road.
    If you go to the Braidwood Times site you will see some pictures of the event including my racing lounge chair and Whistler.