Almost A Contender

OKAY! So i realised that we never ended up posting this when it happened! But i thought i may as well now. So yeh, this happened almost a year ago!

The eV Challenge race was almost a week ago now and here's how it unfolded.

We knew the bar had been raised when cars like this showed up

We got out to the new track at 8:30 and as we drove past some of our competitions pit stations it hit us that we would be in for some serious competition this year with some other cars looking very professional indeed. The second thing that hit us as we got out of the car was the wind. Boy was it gusty! Even the registration people found it difficult as they hopelessly chased rego papers across the entire carpark. In the end the wind did play a big role in the way the race played out.

Guy and Steve in Pit Lane Before the Race

We then set up our pit area and started to get the car, race ready - tightening and checking all bolts and electrical connections, attaching the skin and air scoop and applying sponsor and race number decals. Our car passed the scrutineers in flying colours and our wiring 
even received a compliment. We met with our sponsor representatives from SKM who also had many nice things to say of our car.

 Originally there was only going to be one race in which all classes competed in. But then the organizers decided to book the track for the whole day allowing for the usual two race format. We were entered in Class C (open category with own batteries) which ran in the second race. This allowed us to watch the first race and see how the new track and windy conditions would effect tactics.


The new 1km track is about double the length of the previous track and allowed for 3 - 4 cars to go side by side which along with run off areas instead of curbs improved the safety of the event immensely. Unfortunately the wind was unfavorable for the track as it gave a headwind down the long main straight - the more aerodynamic cars seemed to reap the benefits from this however.

The eventual race winner

^ THIS is where i got up to when writing it last year!

So what happened in the race?

Well, We decided on our driver 3 stints, Guy would drive first as he was the most cool headed driver out of us and so would not get into a tangle that can often happen in the congested opening laps. I (Oscar) would drive second as the car would now be in its peak performance and as i was the lightest, we felt we could benefit from this. Stephen drove the last stint because, well someone has to.

Stephen brings it home. 

Guys stint went fairly well. He drove steadily and kept up their with the main competitors for most of it. But then we realised something was wrong. Half way through his turn we realised guy hadn't come past the pits in a while and then we noticed on the very far side of the track he was stopped. The chain had fallen off. He got it back on and kept driving. It fell off once more during his stint and we were back at least 2 laps from the leading car. Our hap dash drive train was letting us down... Another problem appeared around this time. We think we may have lost 2nd gear. Either the power of our motor had killed it, or we had not tuned to gearbox well enough and it was misaligned. In second the car made a bad clicking noise and gave no more speed than first gear.

Then i got in. Under team orders to just go almost all out and see if we can take back some laps, i did just that. I didn't drive at full throttle the whole time as I didn't want to ruin the batteries but even at 95% we could see our car was pretty fast. The chain didn't come off once during this stint. Perhaps we thought because I was the lightest and thus put less stress on the chain. We regained about a lap during this stint.

 

 In Stephens stint the chain problem re-appeared... 7 times.... The combination of our slightly shoddy drive train which by the this stage would have developed a bit of slop due to the stress of racing and perhaps Stephens unfamiliarity with the car could have been the reason we had more trouble in this stage. We lost more time on the field even tho it was obvious our car still had the speed to compete. It was frustrating to say the least and we could tell our batteries still had juice after the race.

 

L-R Oscar, Guy and Stephen after the race

So where did we finish?
9th
I wont lie. It was disappointing. Seeing as we had never finished lower than 3rd in a car we had built. Still a top ten finish in a field of 50 with a chain falling off 9 times, is a fair effort.
Our car was almost all we had wished for: innovative, fast, efficient, good looking, BUT, it lacked one majorly important thing every car needs. Reliability and consistency.

We were almost a contender

Tomorrow, We Race!

A lot has happened since the last post and finally tomorrow is the day we have building up to. The Race!

We have test driven the car now 5 times and only the last time did we decide to end testing, the other times the car decided it wanted to stop. So there have been many bugs to fix and finishing touches to apply over the last few weeks.

The drive train has been playing up with loose chains, chains falling off, bent sprockets and more. After a lot of tinkering and fine adjusting it is working fairly steadily now. The chain tension is not 100% how we'd like it, but we are confident it will last the hour.

The main fault has been with the... well errr, we're not entirelt sure, but it has cut the power to the motor more than once during testing. Is it an ESC temperature cut off? Or dodgey wiring? Or maybe its the fuse holder? We're not sure what it is so we adressed all our theories with some cooling systems - an air scoop and a whole bunch of heatsinks on the motor - a redo of the wiring and a new bigger better fuse. The cut off problem did not rear its head during the last testing session so we are hopeful our electrics will go the distance.

The Skin is Finished and an Air Scoop is Added.

 The lycra skin has now been finished and really completes the car. We put a lot more effort into the appearance of the car this year giving it a bit of a paint job and some finishing touches.

Steven Drives the Car for His First Time

The Car Corners Very Well Indeed

Guy Picks Up Some Speed Down the Straight

Tomorrow is Race Day, where we put our car to test against many others with the same goal of winning the eV Challenge! Tactics come into the race a lot but it should be a level playing ground this year with a new track. We'll get to the track early tomorrow morning, register and get the car scrutineered then check and double check the car over. By 11 we should be out on the grid ready to start the eV Challenge 2011.
How well we'll do, we're not sure, but from my point of view im just stoked we're going into the race tomorrow with a car we designed and built ourself. Now Lets Race!

Oscar

Drivetrain

Sit back and relax, coz this is a long one.

From the very start of this project, we knew this years drivetrain was going to be a beast to complete. After many, many designs and layouts we finally decided on a motor > gearbox > rear wheel arrangement, all chain driven. Sounds simple? Unfortunately, far from it.

Here are the specs for our setup.
Brushless Motor with inbuilt ESC - 400w, 24v, 2500rpm
Sturmey Archer Gearbox - 3 speed (1st - 33% reduction, 2nd - 1:1, 3rd - 33% increase)

The main difficulty was that the motor revs at a nominal speed of about 2500rpm and we want the rear wheel to max at around 450rpm (40km/h). This means a huge amount of down gearing is needed. So we needed a small motor sprocket to large gearbox-in sprocket then a small gearbox-out sprocket to large rear wheel sprocket. Unforutatley no one really makes the extreme parts we needed, like a 53T rear freewheel sprocket! We had to make one out of a regular bicycle freewheel and 2 large chainring sprockets. In the end (after a bit more bodging) we had a 9T motor sprocket, a 28T gearbox-in sprocket, a 21T gearbox-out sprocket, and a 53T rearwheel sprocket. This gave us roughly the ratios we were after.

The other difficulty was that we now had 2 chains to align, whilst keeping them taught and all inside the rear triangle of the bike frame. Chain alignment is very important in terms of efficiency. Not only can a badly aligned chain fall off, but it will also grind on the sprockets causing friction that will slow the chain down and make the motor do more work. It will also wear away the chain and sprockets faster. Its preferable to have the chains nice and tight so there are no losses to vibration and slipping.
A lot of patience was involved in this process of adjusting the positioning of the gearbox and motor into alignment and then making sure the chains were tight. It actually took 2 goes...

Guy Welding in the Gearbox Mount

Good Job

Rear Supports

We also added some support members to the rear of the chassis to strengthen it during cornering.

Bicycle Dropouts Were Used for the Gearbox Mount

Motor Mounted in Place with a 9T Sprocket

The Drivetrain Setup

For a bit of fun I decided to make a teaser vid of us testing out the drivetrain.

Now to fine tune the setup, fit cooling systems and finish the skin. With the race only 20 days away now things are coming together nicely.

Oscar

The Aero-Skin

As you may know, you need 3 drivers to compete in the eV Challenge, and well... there are only two of us at the moment. So it was a good sight to see Stephen from our last ev project come and help us out again.

From the start of last year I've had the idea of using a flexible fabric skin on an EV to create the aerodynamic body. I'm not going to take full credit for the idea because really BMW provided the inspiration with there concept car, GINA - BMW GINA Concept. This idea is still an original idea for the eV challenge however with most other teams using aluminum or corrugated plastic panels, foam and even fiberglass shells. Last years car was far from aerodynamic with a modest amount of rear paneling, so this year we had to go for the Aero-Skin. After a trip to spotlight we had decided lycra/spandex was the material of choice.

The Beginning of the Wire Frame

We decided we would make a wire frame from thin aluminum rod and stretch the fabric over it to form the body. We placed wire 'ribs' going cross ways with a wire 'spine' down the middle and thinner wires on each side. Next we needed to know how much lycra we would need, so we layed an old sheet over the vehicle and cut out a rough template. To see if the material might flap or bellow inwards we tested the sheet cover out by fanging it downhill.

All Wrapped Up

It may have looked a bit like a cot, but it seemed to work well and didn't flap much at all. With the lycra instead of sheet and more framing it should have better rigidity and aerodynamics.

Stephen Getting Accustomed to This Years Car

We have also now mounted our batteries in a very nice slide in/out arrangement so we can get to them quickly and easily.

We had hoped to have the motor and gearbox in place by now but are still waiting on the motor sprocket to arrive. They'll be the next step.

Oscar

Brakes & Tyres

Brakes. They're one of the most important parts of any vehicle, although brakes waste energy they're vital for safety (they also let us go down really big hills without crashing). For this reason the cost of the brakes is not included in the limited cost of $1200 that we have for the competition. This weekend we completed fitting two caliper brakes to the back wheel, not a simple exercise at all. The bicycle frame that we fitted to mount our back wheel is designed for a larger wheel than the one that we are using, because of this the brake mount does not line up! You may have noticed that the seat stays on the bicycle frame are made of Carbon Fibre. It may be light and strong but it's not good for welding brake mounts onto! Mounting the brakes required some clever plates bolted onto the frame.

 We chose to use caliper breaks because they are easier to mount and require less adjustment than V-brakes or disc brakes. Vehicles in the eV challenge require two brakes, during scrutineering the brakes are tested to see that they provide adequate braking force.

Final adjustments

New tyres!

 Finally the new tyres arrived, we chose these tyres for their low rolling resistance, an important factor in making the car as efficient as possible.

Oscar

And Now It Can Do Turns!

Steering is a critical component of an EV. Not just for the obvious reason of turning around corners, but because it can effect your efficiency substantially. Get one piece out of line and your wheels can "scrub" when turning, giving the car a bad rolling resistance and thus making the car work harder. Which is why designing and constructing the steering gave us many headaches from brow frowning and head scratching. But it is now complete (pretty well) and so we braved the rain to take it for another spin.

The car is now fitted out with some fine steering devices

Focus

REEEOOOooowwww

Return Of The Rope Tire!

Last year our car used plain old billy cart steering, and even though it could cleverly lean the vehicle into turns, it still felt a bit agricultural. So this year we have decided to use ackerman steering (the type of steering all road cars use). This makes it harder as there are much more angles to consider, many distances to calculate, a lot of levers to account for and these strange things called rose joints. The reason why we have chosen to use this steering system is because its very efficient, if you get it right. So far all is looking well and with a bit of "trimming" she should turn true.

The steering layout with a lightweight ply-wood steering wheel

Taking the car out for a spin with a fully operating steering system certainly was a lot more satisfying and we can now see the car really taking shape. Although we have not reached speeds of more than walking pace, we can suddenly feel the potential.

Guy gettin some gnarly speed!

okay, so we didn't go quite as fast as this looks, but some crafty camera work helps

Next step - to focus on the drive train. Motors and gearboxes, should be simple?

Oscar

Rolling For The First Time

On saturday we welded on the front wheel hubs which are made from two old bike bottom brackets and cranks. The car was rolling for the first time! But we had a problem; three wheels and only two tyres! Our solution? We used rope instead of a tyre of course! (and two F clamps for steering)

Wheel hubs made from bicycle bottom bracket

Oscar- Check out that rope tyre

This guy's enjoying himself