Red Bull Soap Box Race

Insomnia strikes again! 07.50 and nothing better to do than post here? Sad or what?
Watching the videos on the website of previous runs, most vehicles had 4 wheels (although there were some 3 wheelers) and there were chicanes that require reasonable lateral grip and the ability of the vehicle to absorb sideways g forces.
This will, I think, preclude the use of bicycle wheels as the spokes will be subject to overwhelming lateral forces. Kart tyres on a kart chassis whilst good for negotiating the chicanes will not give sufficient ground clearance for the bumps. Ground clearance I think will need to be at least 150mm for the jumps / ramps
Other considerations for producing the fastest downhill time will include minimising rolling resistance. Kart tyres with a contact patch of c 100mm wide front and c 150mm wide rear would not be a good drag reduction option.
Minimising aerodynamic drag will also be a factor but less important I suspect at speeds lower than 50kph.
Obviously a low centre of gravity will reduce the possibility of rollover and should improve the confidence of the driver/pilot through the chicanes. The other important consideration will be centralisation of the mass between the available points of contact with the road. (2 wheels ?, 3 wheels ? or 4 wheels ?).
2 wheels whilst culturally correct for the Ducati forum would probably be anathema for the organisers as 1. the solution would inevitably be (or look extremely similar to) a bicycle and 2. the start would have to involve some sort of fudge whilst waiting for the go flag.
The real question therefore is 3 or 4 wheels?

A three wheeled vehicle will have the following advantages:
1. 75% of rolling tyre and bearing resistance
2. potentially lighter weight
3. potentially smoother aerodynamics as the tear drop shape???? is less constrained at the rear of the vehicle (assuming 2 wheels steering at the front)

A four wheel vehicle will have the following advantages:
1. More stable through corners
2. Better opportunity to spread the load between the wheels
3. Easier to accommodate pilot/driver
4. Wheelbase dimensions less critical.
5. Wheel bearing resistance may not be +33% as the additional vertical load on each bearing is only 25% i.e.total bearing rolling resistance may only be +8%. The rolling resistance of the tyres will still be + 33%.

Both a 4 wheeled vehicle or a 3 wheeled vehicle will require either a prone forward facing driver or a supine lying almost flat driver in order to achieve the lowest possible aerodynamic drag.

For a 4 wheeled vehicle the driver position/orientation is not difficult as he/she can be moved fore or aft/ left or right relatively easily. Obviously either optimum solution involves a centralised mass.


With a three wheeled vehicle the following considerations also need to be taken into account:
1. The most stable 3 wheeler will be an equilateral triangle (comparing the contact patches of the three wheels)
2. The centre of mass of the vehicle will need to be the mid point of the equilateral triangle.
3. A face first position in a 3 wheeler offers the best opportunity to achieve 1. and 2. above.
4. A face first position will be the most difficult to make crash worthy
5. A face first driving position is the scariest for the pilot/driver
6. Face first driving will involve a complex steering mechanism with the driver /pilot's head potentially forward of the front axle.

Despite the difficulties a three wheeler with prone driver/pilot seems to me to be the best option.

 

Lotus and Honda thought 4 wheels and came 1st and 2nd at Goodwood in 2004.
I wouldn't be surprised if every Red Bull winner since has been 4 wheels?

 

there are / were no jumps on the goodwood track.

 

They have added some jumps now, as well as fairly tight turns. 4 wheels is the way to go.

I haven't built of raced a cart for 30 years at least! Probably more 35...

 

When we were kids my brother had a cart running on wheelbarrow wheels with proper pneumatic tyres and greased spindles. It was heavy - took two of us to pull it up to the top of the hill but it went like stink. Stopping it was difficult. The traditional wooden friction brake just caught fire. You had to scrub off speed using the hedge or bank and then just hit something.
I know people who ride bikes in much the same way.

 

Doesn't have to win :Wideyed:
First you need to get an entry - how do you enter, how is it decided who goes through? There will be hundreds entering and a handful racing

 

I have e mailed for an entry and there is no point in entering if you do not want to win!!!!!

 

There are plenty of reasons other than just to win

 

@expired road racer.......Your post #21 has most things covered however I think favouring 3 wheels may be a mistake! like you I enjoy watching this stuff it's a bit of fun for most but if you look at the winning soap boxes they are pretty much all 4 wheel and quite heavy, seems it's almost a given that 20" BMX type wheels work best and you need the weight to keep the speed up

 

told you

 

Ok I give in, 4 wheels good 3 wheels bad it seems.

 

I agree with you now

 

Do the rules say anything about not being allowed 2 wheels? If not keep it quiet and obliterate the competition - push bike with 916 bodywork should do it

 

BMX would be perfect. But I think a 'cart' by definition is probably more than 2

 

Maybe, but is it in the rules, also it's a soap box and they by definition don't have any :Angelic:

 

I have not yet had the application pack returned by e mail , presumably they are on Christmas shut down, as soon as I do I will publish on here.

 

fish box with pram wheels used to be the way to do it, ( pre bmx tho )