Hi Folks

Just found this site whilst researching aerodynamics on behalf of the teams I assist in the  Greenpower Challenge, www.greenpower.co.uk over here in the UK. Lots of good info so hoping to find a nugget that will make all the difference.

Very interesting to see the way a different set of rules literally shapes the cars. Over here we run a four hour endurance format, the motor and batteries (2 pairs of 70Ah SLA) and motor are set by the formula. Many cars now use internally geared hubs, yet last year the UK final held at Goodwood was won by a single speeder with a very clever controller, more than one way to skin a cat.

It would seem that we also have the same discussions regarding safety and the ever increasing speeds.

-- Edited by Orinoco on Saturday 17th of July 2010 10:13:05 PM

-- Edited by Orinoco on Saturday 17th of July 2010 10:13:43 PM

Welcome Orinoco Your right about the way rules shape vehicles but there still are enough similarities to make both formates interesting. I think we are too fast for one hour but you are too slow for four hours. Perhaps a two hour format with manditory pit stops would be the answer but so much is dependent on track type and lay-out that it is difficult to say for certain. Four hours just seems to be too long -- like watching major league baseball --

Considering this is the country that  invented Test Cricket with each game lasting five days the four hour race format is into "blink and you'll miss it" territory!

Seriously though, because we have to use at least five drivers and change batteries the races are very interesting; and it's surprising how close the finishes are, I think there have been two races this year where the winning margin was less than 10s.

It sounds like tyre life can be a real issue for you due to the higher speeds and tight corners on many tracks? We're quite fortunate that the majority of our races are run on large race circuits with wide sweeping corners so very little stress on the tyres, although I believe this has allowed the development of a number of narrow cars with enclosed wheels and shaped underbody which have a high C of G; as a result there have been several rolls this year; are rolls a common ocurrence over there?

Yes we have far too many roll-overs, some due to poor design( bad CG), and some from racing other cars instead of racing the track.  Some other roll-overs are caused by ramping off curbs and bails.  Almost all occur on street or parking lot tracks with nearly none on speedways or roadcourse tracks.  Fortunately none have cause any injuries which is  a credit too very well designed set of rules and rule enforcement.

Tire wear is pretty much a non-issue.

We have four races, and probably 5 hours of practice on one set of tires, so they're at at least 9 hours of wear so far.

We've also been fortunate that none of the rolls have resulted in injury, also thanks to adequate protection and enforcement. A new rule states that a car suffering a roll cannot race again until the team can prove staility has been improved, this seems to have arisen due to some of the rolls being caused simply by the driver turning too violently; not a situation I'd like to put any of our drivers in.

Tire wear is a huge issue for us when we are running on a trach that is very rough. I can remember a number of races where we started out with brand new tires and the cords showing at the 50 minute mark. Hot weather, rough tracks and tight corners lead to very fast tire wear. I have seen a number of cars rolled over the years too. Hitting a wall or a curb is always bad, but ironicly I have seen many cars rolled when going straight and have hit nothing. A three wheeled car on a straight track will flip right over if it is moving fast and blows a rear tire. Front tires are not really an issue. I don't have time now but I want to read through all of your rules and compare them to ours. Aaron

Probably where the rules vary most is with regard to motor and batteries, both are fixed by the formula for us and the combination means we have an absolute maximum output power of just under 750watts although if you try to do that for more than a minute of so the motor will be damaged through overheating. Over the course of a race we're averaging 400W whereas the Etek motors many of you seem to use over there look like they should average 1000-1200W? So a really big difference there.

We've just had the batteries changed for next year so that we'll only be drawing around 18A at 24V, maybe 300w output which will reduce the faster cars to probably 100miles for the four hour race.

-- Edited by Orinoco on Wednesday 21st of July 2010 10:04:01 AM