Well, it's been a pretty hectic week or so, but the car is built and running. It's had a few practice laps of the tennis courts and should be getting paint tonight. We're very much looking forward to getting it on the track on Sunday.
Well we got it to the track, and it was painted - only one coat but it's mostly white. The stickers were applied and scruteneering passed! Whoo.
As for the race, a successful day was had by the HTC Eco team. Eco-3 finished in 10th place, having covered 86.4 miles, with Eco-4 covering 76.8 miles. Both cars (as will all the others at the event) will have their totals increased by around 8% to take account of a stoppage to clear the track from an accident between two other team's cars. Fortunately none of the students involved were seriously injured. Eco-3 looks likely to have qualified for the National Final from this performance, Eco-4 is probably borderline. However we hope to improve at the Greater London regional in September
Eco-4's wheels are already being stripped down, to build the hubs up into 16" rims. There'll also be some reshaping around the nose and tail. The smaller wheels will also help with enabling the tops of the wheels to be covered, aiding airflow over the car. A free wheel has also been put on order too, we're abandoning any idea that the re-gen has any edge over the benefits of lower rolling resistance.
Well our car was "sold" on e bay (£250 which is a bargain - Greenpower charge £2750 for a kit with the same running gear!) but when the buyer finally appeared he said it was not quite what he expected and that he should have read the advert more carefully ..... and walked away!! Doh. So I will be putting it back on the bay in a couple of weeks.
Hi , loved reading this and seeing how the different cars have just got better and better . Perhaps you could save some weight on basic finishing of the metal components though . I saw quite a few bits you could just put a radius on corners of etc to save a few grams here and there . Also have you thought of getting the subframe made from bent aluminium tubing , using bonded in 't' shaped bosses ? Tube bending has come along a lot so multiple bends can easily be formed and small bonded bosses would be adequate to hold components [ use ICI double bubble epoxy ]. Would the rules allow some sort of switching system which rapidly switchs the motor on and off ? If so you would get more distance . Also what about a constant variable transmission thing , like used on Those old DAF 33 cars ? Think its quite simple in priciple , based on cones which are linked by a belt which spreads out further the faster you go ? Might be talking rubbish but thought i would throw some ideas at you . Well done for all your effots , i think you do a admiral job of getting youngsters interested in technology and engineering
Hi Grumpy I agree with you that the cars can be made lighter and the rules allow a reasonable room for innovation but "advanced engineering" becomes a bit of a problem when getting our pupils really involved. When I said to my pupils - "you could pop rivet the floor to the aluminium ladder" ...What is a pop rivet? so I showed them. "So drill the hole there".... How do you drill the hole? "Well you centre punch....." All of a sudden a lot of time has gone by with not much work done.
Yes Mark , i take that into account , you have to balance up what you apply to whats teachable to kids and at the end of the day its ment to spark there interest and get them hands on and involved . Either way your doing a sterling job and its a very interesting thread to read - keep up the good work !
Our Greenpower car is now relisted on E bay but to broaden its appeal I have realised that it could be "Detuned" as a 12 volt car by just using a single battery and connecting across the other quick release battery connector. That should reduce the power to a quarter? ie half the volts, half the current, therefore power = volts x amps 1/2 x 1/2 = 1/4.....?
We've been busy, but as usual, not soon enough. We just about managed to get the new car modified to suit the new 16" wheels. It was a long and late day Friday, but the body work is together, but a lot has gone on under the skin.
The axles have been modified to sit lower, the front geometry has been evened up after the hastily assembled job before led to some interesting handling characteristics - it dived to the left with no hands on the steering. The motor has also been moved from being mounted on the very rear of the sub-frame to being mounted under the seat in a similar fashion to the open wheeled car. This caused a lot of problems because the new mounting points were flexing, and the revised motor mounts were also, leading to the chain jumping and jamming on the caliper bracket (there's very little clearance between the bracket and the rear sprocket. The bracket was stiffened up as were the mounting points. We've also added some graphite impregnated nylon guides, to help keep the chain in it's proper place.
It's not quite finished yet, there's some infill panels to make for the open sections around the bottom wheel wells and it doesn't have a full set of wheel disks yet. They are being worked on, by one of the chaps who helps, he's taught himself to spin and made a former for them, being shaped from 0.5mm. It'll end up looking more like it should e racing on the salt rather than UK airfields and club circuits.
The Race at Dunsfold went well for us, both cars improved their national final qualifying position. The (currently) better of the two cars - Eco-3 - has qualified in position 25 out of 76 starters, and it's the first year we have qualified with two cars. Data analysis post race showed that the newer car (Eco-4 above) was pulling about 24 amps at 25mph, which is massively higher than we need to run at, target is 16A. After playing with the drive train and some testing the two cars on the rolling road we decided it must be the motor. A call to Greenpower put us in a bit of a panic - they had none in stock! Fortunately a delivery was expected and we managed to get a new motor and get it fitted Friday afternoon - two days before the final.
During the week previous some of the team and an assortment of Y9 engineering students got the car painted.
Which just left the stickers, Friday was a busy afternoon getting the new motor in and revving up the vinyl cutter.
The finish is pretty poor and it could have done with a bit more shaping on the styrofoam, but it'll give us plenty to do next season, as we don't intend to build a car from the ground up.
The Final is a Goodwood on Sunday (13/10/13) you can see the race pan out through this link fo the live timing: www.bbk-online.net/gpt/race159.php and if you fancy coming down to see what it's all about you be able to find us luking in paddock 27 & 28.
Yeah, we're fairly pleased, 23 from 25 and 52 from 52, not as good as the 19th and 40th we were listed in at the end of the race. They had to re-jig the results to take account of each of our cars being recovered during the race when the batteries expired before we would have expected (it's such a long lap a Goodwood that you can come unstuck if you miss calling a car in - or they miss the pit board). For those recoveries we lost two laps for each car. We weren't the only team affected in that way.
Here's a few pics,
Our driver was passing these two as they were getting closer together...
No.9 car taking a chance on the gap not getting any smaller this time...
Needless to say by the end of the day we were all very cold and wet. The kids put up with it brilliantly. We have currently go quite a young team so hopefully they can develop with the cars over the next 12 months and aim for a top 15 place next year.
There's not going to be a new car build from scratch for 2014, but there's some modifications to do to Eco-4 to get it up to the same performance as 3.
Brilliant stuff, just read through again and caught up on last years antics! Man, I wish we'd been able to do this type of stuff when I was in school! Looking forward to seeing how the car develops over the next year. Is carbon fibre allowed or is that a bit to techy/expensive?
Looking at the wheels, coming as a biker, I'd say swap out the hubs to something like Hope Pro2's and change out any bearings you can for ceramics. There is virtually no resistance to ceramic bearings, and hope hubs are some of the most free rolling hubs you can get.
Unless the existing wheel hubs can take sealed cartridge ceramic bearings anyway, but I doubt.
One of the cars does have ceramic bearings, I cant remember which! They are all 20mm hubs, but low end to keep the costs down. Cheers Phil. It's all change for 2014. No 4hr endurance with 3 sets of batteries. The race format has been revised and is now two 90min races, with one set of batteries for each, races 1 hour apart and counting for qualifying purposes as two events.
Eco 4 is having some changes ready for the Goodwood test day in March. Last Tuesday the kids pulled the rear subframe off so that it can be modified to fit the motor where the batteries used to live (when getting them out quickly was important. This will keep the chain run shorter and eliminate the extra tension that we had to put in the drive train because of the slightly flexible mounting point.
The batteries will move into boxes either side of the driver, improving the weight distribution and keeping the small drivers in their seat.
There's also the possibility of some serious funding that could be put to use buying vacuum bagging equipment and materials, to build a composite tub, or a tig welding set so we can have a go at welding aluminium.
The Eco-3 car may also get modified during the season to use the same 16" wheels, but we'll buy four more with less spokes to use as front wheels on both cars.
Last Edit: Jan 24, 2014 20:33:32 GMT by markbognor