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Soapbox derby set
A Wood Car Racing Event is slated for Saturday, March 23, on the North 15th Street. For more information on rules and registration, contact Jaeger at 245-3362 or e-mail firstname.lastname@example.org. Email; Share; Print. Arkadelphia Siftings Herald ...
One awesome race from the top all the way down to Battle Abbey gatehouse, this will be a race of speed, daring and of course, amazing costumes!
The track is 266m long and the race will be held on June 30th, start getting excited!
See https://www.facebook.com/pages/Battle-Soapbox-Race/491485564221444 for details.
Aerodynamic drag is by far the largest factor affecting a carties top speed, but how big an effect is it? I've been doing some maths and have come up with some interesting typical figures. the three sources of drag on a cartie are;
- Aerodynamic drag
- Rolling resistance
- Wheel inertia
Rolling resistance is almost constant at all speeds, and wheel inertia actually decreases as speed increases (or - more correctly - as acceleration decreases), but aerodynamic drag increases as the square of the speed. It starts off very low, but soon becomes the dominant factor.
As the graphs on the right show, at 10mph the aero' drag is just 19% of the overall drag, but by the time the cartie has reached 20mph, aero' drag is nearly half of the total. (Click on the graphs for the full size versions).
Aerodynamic considerations are often overlooked when building a first racer, in favour of things that are easier to see and quantify. Teams will often spend much time and money on tyres, bearings and brakes and treat the shape of the bodywork as little more than aesthetics. Spoilers, wings, external cameras, etc, will be added because they "look cool" without any thought to the effect they will have on the cartie's overall drag. But physics says that at aerodynamic drag the most significant at factor at speeds over about 20mph.
Solar car racers have many of the same issues as gravity racers. They have a limited amount of energy and need to be able to use it as efficiently as possible. Their energy is sunlight, and our is gravity, but both are finite and fixed, and the team that most efficiently converts that potential energy into kinetic energy will be the winner. And, as detailed in The Leading Edge by solar car designer Tamai Goro, solar racers know a thing or two about aerodynamics.
The Kop Hill Soapbox Derby Challenge is intended to provide the opportunity for our younger racers to design, build and compete in a soapbox event.The event is open to two age groups of competitors; under 15s and under 17s.
For contact details, entry form, etc., see the Kop Hill Climb web site.
I've got a disc brake compatible SR Suntour XCT-JR 20" Suspension Fork, and upgraded the brakes from single action mechanical disc brakes with a 160mm rotor to a Shimano twin pot hydraulic caliper and 203mm rotor which I picked up for "not very much darling" on eBay.
I am really chuffed. The only thing I need to find now is a 1 1/8" head tube. Can't wait to start building.
It would appear I never did really fix that wonky wheel problem, and the day started with so much hope, aspirations and dreams….
The 4am start leaving Nottingham only heightened the sense of venture as we travelled over to Cadwell for our first folly into soapbox racing, with the car in the back and free Sunday Times CD of inspirational speeches on the cd player, preparations couldn’t have been better…
The Dayton 1 passed scruiteneering at its 2nd attempt. Failing initially on its brakes (they didn’t even move the first time)
As we milled around the paddock area, we got various comments regarding our dodgy wheel angles, something that became apparent due to every other team’s cars having nice vertical wheels with no angled bits. People even stopped to take photos, although not out of admiration but im guessing out of shock.
A typical conversation in the paddock went something like this,
Me: “I’m a bit worried about my brakes”
Old man: “Yeh, I would be”
Old Man: “You ever been down a hill in that yet?”
Me: “erm.. No”
Old man: “You know that’s a 35 mph hill, don’t you”
Anyway, pushing these lingering thoughts about my imminent death to the rear of my mind, I had passed scrutineering and found myself tieing the soapbox to the back of a van along with 5 other soapbox to be towed to the top of the hill.
I made it to the top of the hill. It was here that problems started to surface.
The Dayton 1 took one look down the hill, shivered, panicked and in one quick shriek collapsed to the ground. Actually the front left axle bolt bent as the car was moved from trackside ready for the first run. Quickly followed by the front right axle. Gutted.
The soapbox was swiftly taken back down the same hill on the back of some quad bike trailer combo, like a really cheap royal procession, with me sitting on the back, with my pathetic looking soapbox, waving to the spectators.
So I did manage to get up the hill, and go down it again. It’s just a shame that both times were aided by another vehicle….
Something that stood out throughout the day, was the support, advice and help from the other soapbox teams. Helping me load my soapbox onto the quad bike trailer, giving me advice about better axles to use, and encouraging me to come back next year.
So I failed to race. I guess thats quite a major failure, but the day was peppered with other smaller successes, I passed scrutineering, and made it up the hill, and for a few moments I was just another soapbox waiting to run with everyone else….
Already there are ideas and plans annoying buzzing around in my head for the Dayton II.
It’s the Eve of the race.
I’ve managed to fix the wobbly wheel problem, which is a relief, by drilling and fabricating a shape out of a cap nut, that then fits snuggly into my wheel. They now run smoothly and straight. Hurrah.
My brakes are still causing me a few problems, and its the only element of the car im unhappy with. I have an idea which I will try tomorrow morning, before I hand my car over to be scrutinised, currently they only grind the car to a halt rather than stop briskly, which I feel unless I can improve them may be a problem with the race organisers.
The car is packed in the van ready for our 4:30am start tomorrow morning, travelling over to Cadwell park will probably take 1:40 mins or so.
We tested the car outside for the first time, running it down a road which is on a slight slope. To my astonishment the soapbox ran like a dream, it’s a smooth ride, the steering feels good and it picks up speed quickly. The body work is on the heavy side, which I always thought would have a negative effect, but it grounds the car nicely, and doesn’t fling all over the place.
Good luck to all the other teams and cars tomorrow!
Finally I would like to thank the following for their help / advice / time / effort of the past few weeks.
Amelia Beavis Harrison / Sam Mercer / Liam Aitkin / John Chambers / Simon Withers / Guy Brown / The music guy from upstairs / Steven Ingman / The fish man downstairs / all the Nottingham Contemporary GA’s /
Starting to add various bits of detail onto the bodywork. A nice big Tethervison logo, who gave me some money to fund the various bits of the car.
I am number 49 on Saturday. So keep a look out for me, and if your racing or just watching come on over and say hello / give advice / be nosey. Or if a car with 49 on the side is wobbling in your direction, I apologies in advance!
If I come 49th out of 50 i would be really pleased…
There are two days till race day, and i’ve got so many small niggling jobs to do, to give the car the highest possible chance of passing scrutinising. So off to the studio….
I will update later tonight.
A little video!
The soapbox’s first outing, making tentative but lumbersome rolls around the studio. It handles similar to what I image handling a cow would be like.
Quite a lot of progress today. Which is nice, considering there are only 4 days left.
I finished making the front nose, and almost finished the bodywork, I’m quite happy with it. Also managed to start putting on some undercoat, which provides the first glimpse of what it’s going to actually look like. Here are some pictures.
Is’nt she lovley?
My brakes are causing some problems, they are not releasing properly when used, meaning they are almost ’one use brakes’, which is of actual little use if i need to brake twice.
Also im still concerned about the weight: wheel ratio and whether the wheels and axles will cope. I wheeled the soapbox around the studio, and various problems seem to arise, this needs moving, or this bits too small… whats going to happen when i get it outside on the road?
Thought I would list some of my worries, as the race gets nearer, im feeling more worried about various possible scenarios. Here are my current worries (they change). Biggest worry first.
- Wheels falling off
- Brakes failing, and me crashing into a hedge, person or both
- Not moving when that race starts… and everyone else rolling into the distance
- breaking a bone (from crashing)
- just general humiliation amongst the soapbox regulars
Maybe all soapbox racers have these worries?
I had some help today from a work friend, has been good to get all those small jobs that require more than one pair of hands to complete…. thanks John.
Finally…. a question for wordpress. Why is this text small?
I’ve attached one of the back wheels, along with a rear brake. It took a while to attach, after faffing about with fixing the brake to the frame. I now have 3 wheels attached.
I am planning my first ‘test run’ around the studio on Friday. I’m Nervous.
I was reading a blog yesterday about someones soapbox, and their tweaking of the suspension…. TWEAKING ?! I don’t even have a suspension, and tweaking is something i’m a world away from. I consider just having four wheels an achievement.
I’m going to upload a little video of the first test run on friday… hope your ready.
9 days to race day.