Soapbox tech

[campbell]

Inspired by our own istoo, as he and I (and others?!) prepare for the inaugural Royal Deeside Speed Festival (RDSF).

No competitive secrecy here ... I think

[Dominic]

What's the technical regulations?

I would think something aerodynamic would be advantageous. Low centre of gravity. Low rolling resistance, road bike wheels, pumped hard. I suspect that lightweight is not so essential, I am sure Robin will advise on that one.

[Stevoraith]

Yeah, I'd have thought if it's too lightweight it won't pick up speed. But if it's too heavy it won't change direction.

Best to make it as light as possible (without going overboard) with the ability to add ballast as required.

[rawsco]

Copy Guy Martin, he went for the world record soap box hingy. Nudged 100 I think.. The more weight to frontal area the higher your terminal velocity so heavy and slippery. Guy filled his with full water bottles. however hussling the weight round the corners will be a problem. From memory this was guys undoing resulting in a substantial crash. bike wheels aren't really built for lateral loads (loads of -ve camber.) and stub axles (apart from Cannondale hubs for the lefty fork.)

Skinny tyres and high pressure worked better for speed for Guy but again buggered up corners. It's gonna be a trade off between top speed and cornering ability. Know your course I'd say and your physics!

[Dominic]

Don't forget, good aero is as much about how you depart the air as much as it is about how you enter it. Tear drop FTW

[woody]

Wheel chair wheels and ply... however read the regs ages ago and seem to remember wheels are restricted to 14".

[campbell]

Regs are pretty open.

Quite frankly if Team FMC make it to the start line with something that stops and turns, I'll be delighted

Currently in pursuit of key parts. Blueprint drawn. Engineering help will soon be sought re bearings and axles so be ready guys.

[robin]

[Fluoxetine]

Nah - More like this, shirley?!

[alicrozier]

Is that tut and Scotty?

[Ferg]

I'd been hoping to do this, but keep looking at whats required and not sure I can commit with work and space and other stuff going on..

I had all sorts of beautiful fag packet type designs but had an attack of realism and went looking for the quickest route to a working kart. The rack and pinion steering is the main issue for me. For the rear though have a look at this kart for simplicity.



I was thinking similar to the above using two bmx forks facing rearwards with BMX wheels. Means the wheels are strong and the brakes are built in already. Didn't end up with a steering solution as I havn't found a suitable stub axle assembly yet.

[Ferg]

Simple steering.

[istoo]

There are relatively strict rules to stick to for size and footprint.
I will double check but fairly suire the regs stated no string or foot actuated steering.

but advantages are;
Low CoG
long, width is determined by the track we are racing down, so a longer narrow car will be faster (less drag) than a wide car if its just straight lines (think dragster) if its twisty will need some width.
Weight is your friend, heavier cart will accelerate quicker and have a greater terminal velocity than a lighter one in the same conditions. but see above comment on the track.
I have opted for BMW wheels on stub axle with semi slicks, agian dont know what cornering we are expected to do.
front wheel steering
rear wheel braking
Steering - sussed as per previous thread. I also found an old tractor mower which had some really simple pitman type setup, worth a scour of the local garden cente / tip / scrappy. The kids loved that by the way...


That all said and done. I am with Campbell, just making it would be an achievement!

Team 'Duct tape and hope'

[Sanjøy]

Seriously nearly 24 hours and nobody has posted these?

[istoo]

Seriously nearly 24 hours and nobody has posted these?

cartie can go on a diet no fecking chance i am!