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BVS at the Green Power Corporate Challenge

Posted: Tue Apr 29, 2008 11:46 am
by Russell
Over the last three weeks I've been working with John Lilly on an electric race car that was to be the Battery Vehicle Societys first entry to the corporate category of the Green Power electric car race for schools. The idea of the event is to see who could go the furthest on the regulation motor and two sets of regulation batteries in four hours. Its aimed at school children from 9 to 21 years old but there are various age categories and once a year corporate vehicles are allowed to race the best of the school winners so as you can imagine the competition is very tough. I'm serious, they had to alter the regulations because some of the cars started averaging over 50mph from the same power motor and batteries that push your disabled granny around the shops! so this year they banned totally enclosed body shells to slow them down a bit.

More about the races at

As I was involved it naturally turned into a rat car very quickly. It was built entirely by John and myself out of scrap bits in six days in the three weeks leading up to the race but we also had a lot of help on the day before race day from Kelvin who spent hours mending punctures and Gadget who got the fiddly brakes working. We got all the bits assembled and had it rolling but untested at 4am and a mear 4 hours before scrutineering started. I did almost all of the constructional work whilst John prepared the bits for next step as he also had most of the ideas. He'd been trying to organise a team for a year and I got involved exactly a month before the race and in just enough time to lash an entry vehicle together. There was some confusion over who was supplying some efficient wheels which left us hunting out suitable replacements a week before race day and some vintage motorbike and BMX wheels were rapidly found. Over the six day build in the three weeks leading up the the race day we successfully welded together an abortion of parts into an electric racing car that got the approval of the scrutineer (who was a very nice man) and raced it around Goodwood racetrack last Sunday. After an initial chain alignment problem lasted the rest of the 4 hours endurance / distance race without major problems.

The machine was a Frankensteins abortion of parts most notably...
Two kiddies bike rear ends, both from skips,
The rest of the kiddies bike frames cut up and used for bracketery,
A broken childrens climbing frame pinched from a neighbours garden,
A Sturmey Archer 3 speed bicycle hub gearbox,
A second-hand microlite body shell,
More cable ties than you can possibly imagine,
A sack truck handle,
Some office chair legs,
A pair of car rear view mirrors,
Some impact foam scrounged from another team on race day - regulations I'm afrade.
A 3 point racing harness covered in mould and bird poop - Should have been a 4 point harness but the scrutineer was a very nice man.
Two old c90 (?) wheels with mis matching tyres that were about 35 years old and VERY old looking and cracked and were a bit larger than regulation allowed - did I say how nice the scrutineer was.
And of course the regulation unmodified 24V 240W motor and batteries.

Instrumentation was a bicycle speedo that gave random speeds but the clock worked which was very useful for timing laps and changing driver at agreed times and at the speeds we reached seconds weren't so important to us :). An accurate ammeter was used to keep a note of current and allow control of motor temperature. A temperature gauge on the motor because over 80Deg C the glue holding the magnets would allegedly fail and destroy the motor. Control was via a microswitch cable tied to the steering wheel that operated a large contactor.

This is the drive train that consisted of a pair of kiddies bike pedal sprockts, a Sturmey Archer 3 speed hub as a geared lay shaft driven from the regulation motor. The Sturmey Archer geared hub gave ratios of about +33% 1:1 and -33% and were essential to get up the hills around the track. It was very successful despite failing some 200 yards from the start line and us being the first to be recovered by the recovery trailer. However some more bits of chair leg and some quick welding to brace the motor mount and keep the chain in alignment had us back in the race within 15 mins.
The steering bits were from some failed electric project from years ago. It originally had some new 26 inch wheels and braked hubs but those wheels had to be abandoned after we checked the rules that stipulated a max wheel size of 20 inches. Even though we used 17" motorbike wheels the overall diameter was more than 20" but as I have already said the scrutineer was a very nice man.
Did I say how nice the scrutineer was. :)
The finished thing, with John in the driving seat, Kelvin sporting his pink sleeved faded hang gliding suit and Mike the head scrutineer who spent much time reminiscing about how all the cars were like ours when the event was first started.
Queuing up for the start line. The wheels only went on the car at 4am that day and the only time it had driven under its own power was from the paddock to the scrutineering bay which was about 25 yards.
On the start line with Kelvin being the designated pusher as you are allowed a two step push start. I was able to get this close because I had to sprint onto the start line with a spanner and two forgotten 8mm nuts for the track rod ends and took the photo whilst retreating under the protest of angry marshalls :)
Some of the other marvelous machines.
Some more marvelous machines.

The day was not without excitement as several cars spun out exiting the bendy bit. This one rolled on its first lap and I believe another one lost a wheel after a spin and was the only car to retire from the race.
There were many cars there that ranged from one that Bently made that cost them £80000 not including labor and design time of their trainees to one (above) from the Blue Peter team (I'm trying to find when they are going to air the race on the TV show)
This me passing the finishing line. The girls are grinning like idiots because we were the slowest car in the whole race and actually passed the finishing line almost 15 mins after the race had officially ended due to a binding brake and resulting over heated motor and lack of power. The bored commentator had kept him self amused during this time by winding everyone up to the point that ensured a heroes cheer from the spectators when the finish line was eventually crossed at a snails pace :)

Anyway you're probably wondering about the results. Well considering we built the beastly thing in 6 days I was surprised it lasted the full 4 hours of the race and was still working well at the end of the race. But predictably we came last with the second to last being almost twice as fast as us and was being driven by a team of 13 year old girls :roll: !
The fasted lap time was about 3 1/2 mins which was an average speed of about 40mph and the max total distance in the four hour race was 122 miles or 51 laps. We on the other hand had an average lap time of about 12 mins which gave us an average speed of about 12mph and a total distance of 36 miles or 15 laps.
More results at.

It was interesting that we used less than half the battery capacity in the race but we were limited to how hard we could run the motor because we didn't have motor cooling and overheating would have resulted in instant failure, a fate of so many other earlier race cars and looking around the paddock most of the teams have rather elaborate cooling apparatus on their motors. So theres scope for more power and vehicle refinement even if theres a small budget available for next year.

Considering that we had no motor cooling, the tracking was out and we had just about the most inefficient tyres possible I consider the whole thing a total success despite coming last.

The main highlight of the day was receiving a surprise trophy for Innovative Use of Recycled Materials! The category was introduced this year by the IoM3 at the last moment and we had no idea that it existed until the prize ceremony.

I'm already looking forward to being involved in next years race when hopefully we will have a stronger team and a more competitive vehicle.

Posted: Tue Apr 29, 2008 12:48 pm
by MalcolmB
Great report Russell! Shame you came last, but you did a grand job considering the time available. I'd love to build and race something like this. Looks like a fun event.

Just a couple of questions:
Are three-wheelers not allowed?
What batteries are you allowed to use?

Posted: Tue Apr 29, 2008 1:11 pm
by clnbrtltt
Excellent report :D

Well done everyone involved :lol:

Cheered us both up reading about it :D

Posted: Tue Apr 29, 2008 7:46 pm
by ChrisB
Fantastic report there , but we really need to do better next time dont we :oops: we are after all the battery vehicle society 8)


Posted: Wed Apr 30, 2008 7:28 am
by qdos
Well there you have it see guys you too could have a go so come on and join in! the gauntlet is down. and I promise I'll wear a different flying suit next time only we kept having heavy showers and my other flying suit I'd thrown in the car had been shreaded on a barbed wire fence on a dodgy landing.

Batteries and motor are very much what you are supplied with by GreenPower and you are not allowed to change them in any way though you can use no end of genious to make all sorts of inovations to the other items on the vehicle which are external to these items. Yes you are allowed heat sinks but I don't think you can add any fans (other than those on the terraces cheering you on!) Yes we had lots of them! Thank you Yvette Oliver Henry and William! Oliver is now dead keen to get his school to build a car and We'll see if we can help him convince his school friends and teachers Mum certainly wants to see him have a go!

We may have come last but our main goal was to encourage people to take part and we most definately succeeded there in getting youngsters very keen on having a go and building their own EV. Needless to say we are very glad we took part Well done to John for being determined to get there. and Russ did a superb job in using all the resources he could get his hands on including ropeing in his friends in Sussex to give us hands on support building the car in the small hours of the morning of Saturday/Sunday night. We were still up welding at 4am just 3 hours before we had to be at the track!

My father was very shocked when a motley crew of cars trailers and rat bikes arrived at his very middle class home on a private estate to shock the neighbourhood with furious welding. grinding and drilling. But he is very proud to have been able to help the gang by loaning the use of his garage. He wishes to say Well done to the BVS and he's now looking forward to seeing it published in the next Plugged In so he can show all the neighbours that there's a growing movement of people behind this who are indeed serious about doing things rather than just talk.

Posted: Wed Apr 30, 2008 1:02 pm
by bobc
Superb report - particularly liked the photo of "phoenix" on it's side!
There were a few nice photos of my team's car "brian" - the slug lookalike.
Like he said ^^^^^ it's a fun hobby, I'm associated with a girls' school team - we were laying up a fibreglass mould for this year's car last night, me an 5 year 7 & 8 girls - and they all love everything about it, and learn LOADS to boot. Over the last couple of years we've worked our way up the 'pecking order' and I expect great things of this year's new car (should be racing in just over a month.....)
PS watch blue peter next wednesday at 4:35

Posted: Wed Apr 30, 2008 1:10 pm
by bobc
must be 4 wheels (and as you can see some still roll). Obviously safety of the kids is top priority.
Batteries are supplied by the organisers - 70Ah lead acid automotive batteries. You get 2 pairs of 2 for the 4hrs

Posted: Wed Apr 30, 2008 5:51 pm
by MalcolmB
Thanks Bob
I just read through the regulations. They look pretty straightforward.
It should be possible to get 100Ah from those batteries over four hours, which should be ample with that motor. I wonder if it would be worth sacrificing some efficiency to step up the voltage to 36V, or possibly even 48V? :twisted:

All I need now is a fourth wheel and some bin bags...:D

Posted: Wed Apr 30, 2008 6:24 pm
by bobc

Posted: Wed Apr 30, 2008 6:26 pm
by bobc
Yes you get bang on 100Ah. I've done the sums...... peak efficiency for the motor is at a touch over 24V so if you use a boost converter the motor efficiency gain gets lost in the converter (that's with 600W going in). You'll appreciate this is an efficiency contest, not a power contest! The winning car (on its side pictured above...) wins because of its aerodynamics. To get low frontal area and enclosed wheels they've ended up with a narrow track & so it has a tendency to fall over. Visibility is very poor for the drivers too, but apart from that it is an exquisitely engineered piece of kit. I am SO looking forward to kicking its @rse later on this year....