coeffecient of friction

[hawkwind racing]

Fr=U*N
Fr = resistive force of friction
U = CofF of the two surfaces
N = normal/perpendicular force pushing the objects to gether

by changing U or N we can decrease or increase our 'sliding friction'
not much we can do about U, surface is salt and tyres are rubber , but we can do some things ,use a treaded tyre over a slick ,the grooved patterns of the treaded tyre change the roughness which increases the friction ,but our most potent weapon is to increase N the greater the force pushing rubber to salt the greater the friction ,thats why I will be using up to 200 kg's of lead ,but be aware not to go beyond the load rating of the tyres and be carefull where you place the weight ( but thats another story
Gary

[Dr Goggles]

Nicely put Mr Whippy.....The very first time i had a squiz at Landracing.com there was a thread started by Franklin Ratliffe ( for those who haven't come across him he is the most argumentative and abusive character you'll come across in the on-line LSR community) he was on a similar rave but busy calling people nicompoops and idiots amongst other things ....the "thrust" of what he was saying was that ballast WON'T increase your traction only your thrust......you've put it well there Gary and for the first time I saw how simple it can be explained.....Of course the traction doesn't increase.....because it describes the surface...the relationship b/w the tyre and the track is changed by the force pushing them together......thus you can accelerate beyond the point where the air resistance on the vehicle was equal to the force that the available "grip" would allow....it's all so much clearer now...

now , chuck in F=MA and V=D/T and we're nearly there......

oooh me head hurts

[PJQ2]

How about a crawler track system on a high speed vehicle? Substantially increase the surface area of contact between the two surfaces. Or is that the similar to increasing the diameter of a thin tyre?

Sounds bloody dangerous, but would be an interesting traction experiment.
Like these good-old-boys running on ice instead of salt...
http://www.radarruns.com

[PJQ2]

I'm on the wrong track with the idea of surface area contact. The force of friction does not vary with the size of contact area.

Great explanation here:
http://en.wikipedia.org/wiki/Friction

And discussion using Dragster example - validates Hawk's ideas - here:
http://www.newton.dep.anl.gov/newton/as ... s/PHY2.HTM

[grumm441]

On the wrong track. Ho ho ho

[momec]

Taught us in trade school friction is independent of area.
Brake pads or clutch a good example. Bigger rotor same size pad better brake force.
Chris

[DirtyDave]

The NHRA now have 1000 frame per/second video fotage of race vehicals at high speed you can see every fire of the cylinders but the most amazing thing was the tyre deflection on the fuel dragsters, the leading edge of tyre cantact was hitting so hard that it was bouncing back off the track the contact patch was stuff all, and the amount of vacuum between the rear wheels pulls the back edges of the tyres together. it was on ESPN2
A good example is if you have ever seen a motorcycle chain whiping up on the top return run and it still does this on the section that has the power drawn thru it.

Dyno pulls with a 175mph dragbike in top gear are awsume to watch..

[Dr Goggles]

Taught us in trade school friction is independent of area.
Brake pads or clutch a good example. Bigger rotor same size pad better brake force.
Chris

bigger rotor equals greater leverage or applicable torque against the wheel.

bigger contact patch on tyre equals lower force per square centimetre , thus less thrust

[hawkwind racing]

I will also throw the cat among the pidgons , maximum grip under acceleration will occure with the tyre /s sliping at between 10-20% ,how do you like them apples
Gary

[gazza414]

Building up wedges in real time

[hawkwind racing]

I would like to continue on this subject , after reviewing what I consider the big 3 in achieving a high terminal speed ( power , aero & traction ) at least for the records Im chasing (naked & partially streamlined motorcycle) I have come to the following conclusions.
POWER
I am able to make far more than is possible to use , as such there is no problem here , but there is a lot of scope to make it reliably without breaking parts ,there are many solutions to achieve this
AERO
Limited by rules only( argueably imposed by safety concerns ) these should be reviewed as a matter of urgency and relaxed where possible ,there are many practical ways to achieve far superior aero for the partial streamlined class , few for the naked class
TRACTION
this is a severe problem with very few partial solutions (for motorcycles) many for cars if using brute HP only to obtain high speed ,IMHO the only solution is through altering the above two
Also for those of us chasing the sepo's records in blown classes they have a very significant advantage aero wise, (density altitude) they are better off to the tune of 15% less dense air .
I would like to here from one and all on solutions and/or sourses of data, to place us (Aussies ) in a better position to go faster than those damn yanks

cheers

[David Leikvold]

Just a few random thoughts about traction and ballast. I've never tried any of this, I'm just hypothesising. I've noticed that John Noonan's very fast Hayabusa has heaps of lead strapped to the rear swing arm. It obviously works but I've often wondered if it's the best way to add ballast. I believe that unsprung weight isn't a good thing, even on salt. I think the ballast would be better placed under the engine. This should achieve a few things: it would put weight low down in the bike and hopefully make it slower to get out of shape on slippery salt, (Moto GP bikes have their weight higher so they can change direction faster) the weight would be more evenly spread between the two wheels thus avoiding that annoying light steering feeling when all the weight is at the back, the added weight would still push the rear tyre into the salt but the lighter swing arm would track on the salt better. Use a good shock and spring to control it and the bike should be fast and good to ride as well (I hope!)

[hawkwind racing]

thanks david ,vairing weights have been tried in different locations , some background , since the Hayabusa arrived on the scene speeds have increased rapidly ,especially with the turbo varity , the yanks got the jump ( many events ,very cheap parts and bikes and their mostly rich SOB's ) speeds have now stagnated as limits have been reached with aero( as per rules) and traction , the only solution I can figure is to allow much more radical streamlinning, cars have the advantage to use excess power in aero downforce to increase traction ,motorcycles do not
The next step for us Aussies is allow in special construction classes ,improved aero ( dustbin ,boatail fairings) this has the benifits of affording a decrease in power output which will make building engines cheaper and more reliable , less power means traction becomes way less of a problem both in acceleration and drag limited modes ,its a winner all round

[David Leikvold]

I haven't looked too hard at the bike rules yet, is there anything that specifically prohibits the use of wings? Would there be any good reason why you couldn't build a form fitting fairing that streamlined your legs but still let you put your feet on the salt? Could you run a wide wing where a pillion might normally sit? Or have a downforce generating windscreen? Could you get a set of custom leathers made with a hump like the Moto GP riders use but much longer so that it incorporated a good back brace and lots of padding and tidied up the airflow over the rear wing?
Or go completely nuts and build a bike where you sit in front of the engine in a chopper style riding position with the fuel tank under your knees and your bum about 6 inches off the salt? That would be easy to get good aero because you would eliminate all the compromises that a conventional motorcycle has. If it works put my name on the side of it! Dan Gurney built something just as unusual, I think he called them Gators. I'll go looking.

[Rob]

Is this the one Dave?

http://www.allamericanracers.com/alliga ... _home.html

Rob