A-Level Project

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Hi, i am currently studying for my A-level D&T projects for A2, and i have decided to design and construct my own 'Gravity-Racer' and incorparate a few 'F1-Style' tech into it.my leading ideas at the moment are to include a 'brake-steer' system that can help the car corner easier and use less friction, and a movable rear wing, taking inspiration from the DRS currently used in F1 this year.

What i am asking is for any of your opinions on starting up my project and what problems i will encounter during this project.

also if you could answer these few questions as part of a survay i have had to devise:

1. How much budget would you be looking to spend upon building a Gravity Racer from     Scratch?
2. What technique is better, more or less weight?
3. How low to the ground should the car be to achive maximum performance?
4. Disc Brakes or rim-brakes?
5. What is more important, straightline speed or cornering performance?

thanks for your time,
Sean 

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1. £2k 2. For most events

1. £2k 2. For most events more weight is faster however if there are large numbers of corners then less weight maybe advantageous. 3. A lower CoG will improve handling and cornering performance however making the body too low to the ground will cause interference drag between the cartie and the ground. 4. Definitely Disc Brakes either on the front only or all 4 wheels, rim brakes require a substantial structure to support the callipers which adds drag. 5. Depends very much on the event, for events like dalby forest straightline speed is best as there are no corners as such, most other events have some degree of corners.
Lee w (not verified) | September 15, 2011 - 18:00
scottishcarties's picture

What makes a good cartie

It's probably fair to say that Lee's £2K is the top end of the scale in terms of cost. Most people take pride in building using spare parts and recycled materials and usually quote figures much lower than that. There was a poll a couple of years ago that'll give some useful data - check it out here.

For any given cartie, more weight means faster. However, that doesn't mean that the heaviest cartie always wins. 1st and 2nd place at Cairngorm this year went to machines that were quite light compared to others there. As a general rule, I'd tend to aim for a cartie that was around 60 - 70% of the maximum allowed, and then use ballast to bring it up to the maximum and control the weight distribution at the same time. Adding weight to a light cart is much easier than removing weight from a heavy one.

The only place that extra weight doesn't help is in the wheels themselves. They need to be as light as possible whilst making sure they are strong enough to cope with the side loads caused by cornering.

Ground clearance needs to be enough to make sure it doesn't ground out, and that will depend on the course. Generally speaking there is no real advantage to making the cartie really hug the ground like an F1 car would. Centre of gravity is a different issue, however - that definately needs to be as low as possible.

Cable disk brakes or hub brakes are best. It's difficult to get enough braking force from rim brakes, and they are very bad in the wet.  Hydraulic calipers drag slightly on the disk because of the way they work so are not as good as you might imagine. Care needs to be taken with disk brakes, as they can overheat and fade to the point of being useless if used for too long.

It depends on the track as to whether you need an all out speed machine or a nice and nippy slalom buggy. No two tracks are the same, and carties that do well on long fast drag runs don't necessarily do so well on tight twisty technical tracks. I don't know any one machine that does well everywhere.

I don't think F1 is a particularly good place to start for inspiration, as a lot of the things they do are very different to what works in cartie racing. For instance, the single most important thing in cartie racing is aerodynamics - making your cartie as slippery through the air as possible. Although it may not seem so, F1 cars are actually extremely poor aerodynamically because they have to generate down force to help keep them on the track and that in turn generates a great deal of drag. A cartie with the same drag factor as an F1 car would be an utter dog. Downforce would help carties to corner faster, but if the cost was extra drag and lower top speeds on the straights it wouldn't be worth it on most tracks. A DRS system might work quite well though.

Another alternative you might like to think about would be an energy recovery system like KERS that would somehow store energy from braking before a corner and restore it on the way out. That is currently outside the scope of all the rules I know about, but an interesting idea nonetheless.

A fast cartie will have most if not all of the following characteristics;

  • Very sleek and smooth
  • Low frontal area
  • Well balanced
  • Strong, light wheels
  • Good brakes
  • Good steering
  • Firm suspension - just enough to soak up the bumps
  • As heavy as the rules allow
  • The right tyres for the conditions... 
I hope that helps. Please don't hesitate to ask if we can help any further.

 

scottishcarties | September 15, 2011 - 20:34

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