28 replies to this topic

[JForce]

Hi guys

Here in NZ RedBull is holding a trolley GP, basically a 600m downhill course. I intend to enter, and to win. I'm waiting for my spec sheet pack to arive, detailing specs I must conform to, but my understanding at present is:

minimum weight (not including driver) 80kg

Maximum Height: 2.0m
Maximum Width: 1.5m
Maximum Length: 3.0m

Your trolley must be equipped with an effective braking system that functions independently of the steering and acts on at least two wheels.

Each trolley must have a suitable horn or warning device

I'd considered using an independant braking system on the rears, to enable tighter cornering, but given the reg says "acts on at least two wheels" I doubt I'd get away with it.

What I'm interested in is if anyone here has any experience in this kind of thing? I know many of you build race cars for private use, and for University projects etc, so any advice would be appreciated. From simple advice to complex ones, I'd like to hear it all. For instance, would a larger circumferenced wheel (eg bicycle wheel etc) be better/faster than a smaller wheel?

Thanks in advance

[red300zx99]

Is this a course where you have to turn, I read the tightening corners, just never heard of a unpowered downhill race with turns. Rear brakes, not sure how much good they do, escpecially a course with a downward slope. I know over here in the states the soapbox derby guys try to get the car designed so that they have a balanced wheel loads, it's funny in how so many different applications it is desirable to have this, as in a derby car this minumizes rolling resistance. Other then that I can't think of anything else at the moment, other then the wheel choice, I wouldn't think wheel diameter would mean too much, but a narrow profile may do some good in turns of aero eff., other then that try to find the wheel with the least rolling resistance.


wow, Jay-Z in NZ, he truely must be the best rapper alive

[red300zx99]

And would it be possible to map the course?

[Todd]

You definitely need the full spec package before you start designing and constructing your car. The course is also important, as you'll need to know how important cornering is, and also the slope of the hill, before you set your design priorities. Provided there are corners, you'll want to look at what wins in the Goodwood soapbox race, as some of those guys know what they are doing.

[Monstrobolaxa]

Well I build prototypes for the Shell Eco Marathon and we (almost everone) tend to use rear wheel brakes....the thing is that the idea is to run the maximum distance with only one litre of fuel....so we reduce the number of wheels to the minimum (3) - 2 in front and 1 in the back....so teams use the rear wheel as the braking wheel....we also have 2 independant braking systems....if one fails we still have another.

I was also going to participate in the Red Bull competition here in Portugal, but in my case I wasn't going to build something new...I was going to use the Shell Eco Marathon prototype, without the engine....and we were going to fill the car up with balast so it would have the 80 kg.....(then we'de let gravity do its thing);) the only problem is that we use mountain bike brakes....and slick tires (specially made for the Shell Eco Marathon)....and we don't wreally have too much sensitivity during braking.....so locking up the rear wheel usually happens without the driver noticing it....the dynamic friction coeficiente is smaller then the static....so simply the car would keep on slidding probably even spinning....so we decided not to race the prototype.....cause we could easily reach 80km/h....and spinning it or even rolling it....would be very dangerous.

[McGuire]

Studying Soapbox Derby practice is an excellent suggestion. They have been doing this for awhile, so I suspect that they have it pretty much down. I would also try to look into some of the vehicles built for the Reverse Hill Climb at Goodwood. Some pretty wild and imaginative stuff has been built for that event. "More creativity than an entire F1 grid these days," as someone put it.

[Monstrobolaxa]

Forgot to mention the wheels.....bigger diametre bicycle wheels have the disadvantage of cantillever loading....specially on high speed corners they might collapse. The thing is that bicycles tend to lean to the side which they're turning so that the sum of all forces is 0 during cornering. In this kind of car unless you have complex camber arrangement where the wheel leans into the corner, you'll get alot of cantilever forces on the wheel....so try going for small wheels!

[Paolo]

There are at least two downhill races with corners : Goodwood and Mount Tabor.
I find surprising there's not a maximum weight in the race you're interested in.
In case you have no corners, or few corners, more weight for a given aerodynamic resistance will have you go faster. Same as downhill skying : these guys usually weight around 100 Kg.
So : add 300 Kg of ballast and you win, provided the street is asphalt (no gravel) and there's no need for good braking or cornering.

I'd place some ballast low on the car anyway, in the form of a lead plate.
If it does not raise the Cg the effect on roadholding will not be terrible, in a car with no downforce.

[kober]

I was also thinking about this, Red Bull is holding those every year in Prague too. But speed is not the only thing that counts, I think the originality and image of the vehicle has the same weight. So when you have a fast trolley, be sure that it looks like penis or something to win

[Lukin]

Originally posted by kober
I was also thinking about this, Red Bull is holding those every year in Prague too. But speed is not the only thing that counts, I think the originality and image of the vehicle has the same weight. So when you have a fast trolley, be sure that it looks like penis or something to win

Funny you should bring that up. The dude who did an aero skin design for our FSAE car did it so the car looks like giant penis. It's a crack up. No way will the car ever get raced looking like that.

When I get on my own computer I will put some pics up.

The rules for the Red Bull Billy Cart for Australia also stipulate a min ride height of 80mm, to stop people bottoming out I assume when they try to turn. Given how SAE ended up in a heap for this year, I wish I had entered the comp for this summer.

[djellison]

Originally posted by Todd
you'll want to look at what wins in the Goodwood soapbox race, as some of those guys know what they are doing.

Spoke to the Bentley boys who were in the Goodwood race this year. Asked them how much they think their car actually cost.

They admitted that yes - in terms of material costs - it was under the limit set by the Goodwood Road Racing rules - but if someone had come to them asking for that to be built - it would be at LEAST £six figures.

Doug

[Todd]

Originally posted by djellison


Spoke to the Bentley boys who were in the Goodwood race this year. Asked them how much they think their car actually cost.

They admitted that yes - in terms of material costs - it was under the limit set by the Goodwood Road Racing rules - but if someone had come to them asking for that to be built - it would be at LEAST £six figures.

Doug

Speed costs money. How fast do you want to go?

[FrankB]

Originally posted by JForce
I'd considered using an independant braking system on the rears, to enable tighter cornering, but given the reg says "acts on at least two wheels" I doubt I'd get away with it.

You could go for a six wheel design (if the regs allow it) with braking to the pairs of wheels on each side.

But one of the other stipulations that you quoted said "...an effective braking system that functions independently of the steering..." so I don't think that any sort of fiddle braking would be permitted.

[zac510]

You could have two stopping brakes on the front wheels and independent turning brakes on each of the rear wheels (together with steering). Hopefully the stopping brakes are sufficient to pass regulation.

[red300zx99]

I can't understand any good reasons to use rear wheel brakes in this situation. First is the problem of the wheels locking up, as pointed out with Monstrobolaxa's problems. When breaking the weight wants to transfer to the front, lowering the effectivness of brakes in the rear, added to the fact that you are rolling down an inclined plane where gravity is transfering weight to the front more then usual. And then you must remember that you will probably be wanting low rolling resistance tires all around, further reducing the effectivness of rear brakes. For the rear wheel brake steer idea more info on the course would be needed. If you can take the turns simply by steering and not having to brake, then it woud probably be a bad idea to use rear brakes in order to tighten the turn as this is just scrubbing off speed. Not a good thing when your only other available force is gravity. Just my 2 cents

[baddog]

Jforce, where are they holding it?

Shaun

[red300zx99]

Don't tell him, that's only more competition

[golfball]

Originally posted by Todd


Speed costs money. How fast do you want to go?

The BAR F1 soapbox that won it's class (roadster) at Goodwood this year cost a few 100 pounds, was made in people's spare time in a few weeks and beat all the multi-thousand pound machines.

Money's not what you need, just common sense.

[Todd]

Originally posted by golfball


The BAR F1 soapbox that won it's class (roadster) at Goodwood this year cost a few 100 pounds, was made in people's spare time in a few weeks and beat all the multi-thousand pound machines.

Money's not what you need, just common sense.

Now BAR should try winning some F1 races. Or maybe the BAR crew doesn't have as much common sense as the folks at Ferrari, McLaren, and Renault?

[Monstrobolaxa]

In any case speed is not the only objective.....teams are analysed by the jury in 3 ways:

- cars design;
- speed in the course;
- team members dancing to the choosen music (at the start of the race) this is usually the funniest part!!!

in this case Red Bull judges usually don't give much importance to the speed usually the funniest design is what they're looking for....speed is the second most important thing....it isn't really a soapbox race....so try to make something funny/but not bullet fast.

Here in Portugal we had bath tubs, beds on wheels, shopping carts, sardine cans.....a giant Red Bull can...a dog, a cod fish,etc....the winner was:



Look at the wheels they really don't seem to be very go for high speeds...besides that the high cofg doesn't held while cornering.......but if you look at the car...it's a relativly funny design.

[JForce]

Originally posted by red300zx99
I can't understand any good reasons to use rear wheel brakes in this situation. First is the problem of the wheels locking up, as pointed out with Monstrobolaxa's problems. When breaking the weight wants to transfer to the front, lowering the effectivness of brakes in the rear, added to the fact that you are rolling down an inclined plane where gravity is transfering weight to the front more then usual. And then you must remember that you will probably be wanting low rolling resistance tires all around, further reducing the effectivness of rear brakes. For the rear wheel brake steer idea more info on the course would be needed. If you can take the turns simply by steering and not having to brake, then it woud probably be a bad idea to use rear brakes in order to tighten the turn as this is just scrubbing off speed. Not a good thing when your only other available force is gravity. Just my 2 cents

yeah the footage Ive seen suggests the course is wide and sweeping, nothing tight so no fancy braking tricks required. However they do show a few swapping ends when cornering so Im gonna work on getting cog and the weight balance as perfect as possible, plus maybe grip if I can.

[JForce]

Originally posted by baddog
Jforce, where are they holding it?

Shaun

It's on one of the steep roads going down from the domain.You want in? Know anyone with a gas welder?

[JForce]

Originally posted by Monstrobolaxa
In any case speed is not the only objective.....teams are analysed by the jury in 3 ways:

- cars design;
- speed in the course;
- team members dancing to the choosen music (at the start of the race) this is usually the funniest part!!!

in this case Red Bull judges usually don't give much importance to the speed usually the funniest design is what they're looking for....speed is the second most important thing....it isn't really a soapbox race....so try to make something funny/but not bullet fast.

Here in Portugal we had bath tubs, beds on wheels, shopping carts, sardine cans.....a giant Red Bull can...a dog, a cod fish,etc....the winner was:



Look at the wheels they really don't seem to be very go for high speeds...besides that the high cofg doesn't held while cornering.......but if you look at the car...it's a relativly funny design.

Yeah, so at this stage we're going for an authentic F1 car. Our entrance will feature a shitload of scantily clad grid girls, which should get the crowd on our side

[red300zx99]

Originally posted by JForce


Our entrance will feature a shitload of scantily clad grid girls

Brilliant

[AS110]

Originally posted by JForce


It's on one of the steep roads going down from the domain.You want in? Know anyone with a gas welder?

The one they use for the hillclimb?,goes down to what remains of Stanely st - some tight corners there,you'll need brakes alright.Do y'reckon the LTSA will put cheese cutter wire for course boundries,be a smart move for them,like someone could get hurt if they didn't eh?

Got gas,arc an MIG...

[djellison]

Originally posted by golfball


The BAR F1 soapbox that won it's class (roadster) at Goodwood this year cost a few 100 pounds, was made in people's spare time in a few weeks and beat all the multi-thousand pound machines.

Money's not what you need, just common sense.

They ALL 'cost' 'A few hundred quid' in basic material costs - thats the rules of the Goodwood event. But the value of the equipment used, the expertease employed, the talent base used, the experience called up - it's essentially uncalculatable.

That car was complete custom fabricated carbon fibre. Its not a few 100 pounds, it's TENS OF THOUSANDS OF POUNDS.

Doug

[alfa1]

I watched the Red Bull event here in Melbourne a few years ago, and so a
few hints are:

- As was mentioned earlier in this thread, speed isnt the only thing that the judges
take into account. In fact I seem to recall that since scoring was done at the time
of the run, speed must be almost irrelevent since they'd have no way of knowing
whether that run would end up being fast or slow compared to later runners.

- You are allowed a push start. Helpers can push start you, as long as they
dont cross the start line. Get some strong assistants, and install something
onto the kart that lets them push you easily. Practise. (all this just in case
speed happens to be important in your event)
Have your assistants in a 'uniform'. Make sure they can do a 'dance'.

- CRASHING spectacularly into the haybales at the end of your run impresses
the judges and the crowd! Have this as part of your routine. Make sure you
end up at least with the kart on its side. (gawd... the things one must do to
get a laugh)

- You are interviewed before your run for the local PA sytem. Have something
witty to say, not just the boring fact that you worked hard on this kart and hope
to do well.

- Practise beforehand. I was stunned to see that there were a number of karts
at the event I saw which had clearly never run any practise before. Axles
breaking, wheels falling off etc... on the start line. Some contestants never got
to do a run because of this failure to test.


For some inspiration/plagiarism:
http://www.redbullbillycartgp.com.au/

Remember, this isnt about motorsport. Its about selling drinks through
showbusiness and a 'good times' feel.

[clSD139]

The only thing you need your wheels for is the bearing function, not traction. Implementing brakes would increase weight, stronger axles are needed, torque resistant wheels,... Can't you just lower the frame and brake as it slides over the ground? Maybe some stop-power-tuning is needed... :-)

[clSD139]

You probably don't know Renault is founded this way... Brothers fabricated race-cars: bottom and suspention and bought engines in the beginning.