APS/BF- ???

[hawkwind]

Sitting here waiting for parts to arrive ex japan ........So time to bite the bullet .....Today starts project impossible or at least highly improbable ??? ...as all projects need a goal to aspire to, mine will be 300 mph sit on partial streamlined APS/BF -something on the salt ...yes I can hear the and the .....nothing ventured nothing gained....I have a plan .....time and empty pockets almost.....all the back of the envelope calcs are done ...some untried theories to test and no motorcycle specific land speed tyres....plan is to be ready speed week 2016 God willing.

cheers
Gary #282

[hawkwind]

Land speed racing rests on the 3 pillars of aerodynamics /traction / power...some might argue a forth being that of cubic dollars.......there a bit like the fire triangle ,in that you take away or have a deficiency in one of them you don't go fast...or at least as fast as you ought.....so lets look at each of them in sequence.
For arguments sake I'm biasing all my theory and calculations with regards to partial streamlined motorcycles, but with some mods they will stand true for most if not all land speed vehicles.
Firstly aerodynamics.......It has been said that this is the paramount consideration when attempting land speed racing...I say yes and no .....if you are talking streamliners yes ....BUT .... all others classes have limits applied to them by rules, which limits how slippery you can make your vehicle ..... in the case of motorcycles in general and partially streamlined in particular, the rules are not very generous when it comes to streamlining ....... comparing PS bikes to cars both a very good PS bike and roadster are around the Cd of 0.5 …..yes frontal areas are very different but Cd's are similar and with the current rules as they stand I believe that partially streamlined bikes will not progress to any lower Cd's than they have now …...I believe there is some wiggle room for lower frontal areas from different designs ….. so unless the rules change or some genius comes up with something different, gains from aero are about at there limit.......So where to next …...Traction.

Im interested in Cd and CdA numbers from members and any imput you feel like weighing in with.

Cheers

[momec3]

Hawk,
Our F100 had a frontal area a touch over 52sq ft and a cd of .54. It ran 184mph.
I think this breaks 1 of your pillars:)

Chris

[Stayt`ie]

all my theroy/calculations were initally based on the information given in "The Racing Motorcycle" by John Bradley,, i done the calcs, read up on different articles and came up with figgers that at the start were close enough,, ok, eighteen passes later at an average of 190mph has the figgering tweeked pretty close, with my bike naked i see 3.67 sq' frontal @ .775 c of d,, with the oem ZX12 fairings, same frontal with .604 c of d,, i do not use computer generated formulars or calcs, because you do not know the base calculations thay are based on,, i do "everything" longhand,( pencil and paper), that way i know everything is relevant to my situation,, record everything, keeping charts and graphs helps you zero in,,

you going this year Gary ,,

[dplecko]

your formula is very correct: aero = traction = HP ie half the aero is the same as double the HP, assuming you have traction. But then double the weight on the tyre = almost double the possible tractive force.

two wheel drive would also help the traction problem...hydraulic...electric...

[internetscooter]

Gary - I also suggest you get this http://www.amazon.com/Aerodynamics-Road ... 0768000297

The motorcycle part is small but it does provide measured Cd/CdA values for a number of motorbikes. Also it is a BIG book and therefore might help with traction should you need extra ballast

[hawkwind]

Hey Chris good to hear from you ......I reckon you are making between 1000 to 1200 HP at the wheels and if I knew the weight of your ride I could see if you are traction limited....interested to see if im in the ball park with the power estimate

Ronnie Im very surprised at the frontal area of your bike naked ...that's aprox one third less than with fairing, would never have guessed that .....Yes im going this year all paid up ...but im really against the wall getting the bike finished.....its still in pieces and im waiting on engine parts that were promised before Christmas.

Paul ....I think I will need a library for ballast

[hawkwind]

OK next we have Traction this is the biggie and the real problem child with high powered bikes more so than any other vehicle...eg short wheel base, low weight and one tyre ….here is a quotation from another forum that sums up the situation better than I.

“I suggest that maximum forward thrust is equal to the coefficient of friction multiplied by weigh on the rear axle. When forward thrust equals resistance from all operative factors power can only spin the drive tires. You will need more weight or less resistance to gain speed. I have heard it said that the coefficient of friction on the salt is .45 to .5. Does anybody actually know?”

Your vehicle is either power limited ,this is when all the drag forces equal the available power and no further speed gain is possible or Traction limited which is stated in the above quote. Traction has a very intimate relationship with your tyre/s also throw into the equation suspension, CoG, weight transfer, vehicle weight and number of drive tyres ect....it is a complicated business of which I hope to cover more fully as I progress through the build.
To date at least for bikes the conventional wisdom is to just throw more weight at the problem, it helps but again only up to a point, bikes are very limited in how much weight can be physically accommodated within a very limited space and the load limit placed on the tyres we use. So we are limited aerodynamically by the rules and limited physically by limited space to carry extra weight and by tyres, also we are limited where that weight can be carried without upsetting the handling and stability of the bike. Just a quick heads up you will be very surprised by just how much weight has to be added to provide acceptable traction, its way more than what anyone is using WWWWay more but that adds another less thought about problem of length limited which is a story for the streamliners.
And talking about tyres ...there are zero motorcycle tyres rated for 300 mph.

I have 2 possible solutions for the traction issues ...one has been tried before with limited and mixed results the other has never been tried by LSR bikes ….interesting days ahead.

That leaves power next.

Cheers

[Stayt`ie]

so I have heard it said that the coefficient of friction on the salt is .45 to .5. Does anybody actually know?”

there is no "one fits all" number, every machine is different,, imho, the c of salt is whatever the indivual makes it, traction can be in the first instance controlled by the wrist or foot, ballast, gearing, when applied correctly will mitigate, ,,

[Greg Watters]

Gary if its any use to you
my busa weighs 381 kg, 216 at the rear wheel
thats dry without rider or bodywork
add a full dented busa fuel tank 16 l x.78 , 20l water, 80 kg rider 10kg gear, 10kg bodywork
roughly 500kg with around 43/57 split
that was heavy enough to get ~400hp (19 psi on the gauge)to the ground with just about no wheelspin at 257mph
it had no hp spare at that point and you can even hear on my 256mph video the wheelspin caused when the front tire started shredding probably littering the track and reducing the traction
I think here i can achieve similar speeds, the thicker air offsets the better traction, just take a few more psi

Tires are the biggest issue, i have tried the car lsr tires, even shaved for a more motorcycle profile, but while they felt good on a std busa at 185mph , between them and the bodyworki had handling issues that made me put it back to previous settings with no further testing,
slight side wind causing the bike to lean put me on the shaved edge and much narrower contact patch , this caused wheelspin and a rear end occillation
I still intend trying the tires again, brought more of them as they are our only real option , but need a new top trippleclamp with wider spacing to fit one on the front and probably limit the side wind speed to 4mph , 6 was too much
I hope you get your 300, i think its possible , , something with the frontal area of a F1 outfit without the chair
i'm aiming for 280 then i think i'll retire the bike , then step up the liner plans and see if we can run with the big dogs

[Stayt`ie]

along with Gregs, heres some more facts and figgers to ponder,, my bike with me on it at the startline weighs in at 850lbs with 461lbs at the rear giving a 54/46 split, this is constant,, at Gairdner last year 198mph with approx 6* "calculated slip"(good salt), 411'lbs driving force at rear wheel,, Bonneville last year, only change was gearing to compensate for loss of horsepower due to altitude, 191mph with 4.5* "calculated slip" (bad salt, remember all the spins at Speedweek), 352'lbs driving force at rear wheel,,(note, wheelslip is not calculated into these driving force figgers),

you are going to have to lobby the DLRA to extend their run up from 2 to 5 miles, theres no way you will get 300mph on salt with that short runup,, ,

just remembered,, to add more confusion,, Chris Bryson had bugger all, if any ballast, less hp with a slippery tail, = same speed at 198, ,,,

[DLRA]

Ron, I just need clarification on your thinking.

For this year the start line will be at the 1 mile again so we will only have 2 mile of run up, as has been the case for the last several years that we have run. ( The surveyors mark out the same 10 points each year)
The track is configured for 5 sets of lights (when we have 5 sets to use) the first at the 3 mile (really to 2), then 3.25 then 4, 5 and the 6.
Your last attempt at setting a highest speed is between the 5 and 6.
So you're saying that 4 miles of run up is not enough and that you need 8 miles (5 + 3) to get up to speed?

[Greg Watters]

Current bikes should be up to speed in 2 miles or so,takes me 2.25 its Garys proposed bike that probably would need more, as the faster you go in a particular mile the less time you have to accelerate in the next mile

[Stayt`ie]

ok, i had forgotten that we had been starting at the one mile, my bad, ,,

current bikes at 250 to 280, not such a problem,, sit on, partially streamlined motorcycles will struggle to get 300mph even in five to six miles, not sayin thay wont, but the physics tell me "it aint gunna be easy",, apart from the "big three" motorcycle liners and Vesco, no other m'cycle based liner has ever done it, let alone a sit on bike,

[momec3]

Hawk,
760 HP.+
Weighed 2280kg

Chris