Landracing Forum
Tech Information => Technical Discussion => Topic started by: Screwdriver on August 29, 2006, 04:52:22 PM
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Hi guys, I hope this is the right section of the forum and that this isn't too cheeky for a first post...
With regards to naked unfaired motorcycles and specifically those with upright handlebars:
Is it possible to ride such a machine with wide bars sitting upright at, say, 180mph?
How stable would the bike/rider system be?
Anyone here ridden a non-specialised roadbike at these sorts of speeds?
The question comes from a road riding motorcycle forum (VisorDown.com) where many members are "streetfightering" their hyper-sports machines; stripping off the fairings and fitting wide upright handlebars. While that makes a fun machine, I am wondering just how safe and stable they would be at high speed.
Many thanks
Screwdriver.
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Well you may not find the right answer, because I dont think there are many who even consider riding that way at 180 mph.. I think it would be a little unstable... Most riders over 180 naked, tuck handlebars in...
Wish I had an answer for you but im not crazy enough to try it to find the result.
Jon
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That's an answer in itself thanks!
Personally I think modifying these super high speed motorcycles in that way is a recipie for disaster. The forces involved must be immense. Anywhere on this site with some tecchy numbers? Pounds per square inch wind pressure etc?
Screwd.
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Is it possible to ride such a machine with wide bars sitting upright at, say, 180mph?
May be the bike could reach this speed :wink: .....but than, fore sure.....the rider will be not anymore sitting on bike....... :D
......if he is fast enough (walking) he will catch his bike 1/2 hour later :shock:
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What sort of forces would be involved on an exposed torso? Is there a calculator?
Thanks for the replies.
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Try putting your hand out the window of a car at 80 mph and feel it slap the side of the car. The body has a lot more area to push on and as Pork Pie says it will take a while to catch up.
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Yes I've done that at 160+ on a bike, putting my hand up into the airflow. Almost ripped my arm off. There's a craze in the UK currently to strip perfectly good 180mph sportsbikes of their fairings and fit upright handlebars. Great fun but i'd like to get the hard facts and figures behind the bravado. I simply don't believe it would be possible to hang on to the bars at that speed, sitting upright.
If you have to get into a racing crouch, then there could be a product liability issue if the manufacturers ever produced a naked bike with that sort of awesome performance...
Screwd.
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There is alot to be said of Jason McVicar going 235 mph on a naked Suzuki Hayabusa turbo charged. He however was in a full tuck and arms weren't out in the wind. A nice tuck he had... I still dont think he knows how the hell he hung on for that ride... But as you stated arms out in the air and situp bike... Nahh ill pass...
Jon
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Any good sources for facts and figures for aerodynamic forces? Specifically on the human toro (this is a long shot!)
Screwd.
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The last pass I made on my TZ 750 was 180MPH. It had no front brake and since the back pads were dragging we bled off all the fluid to eliminate that problem. So the bike had no brakes.
As I exited the 3, I chopped the throttle, grabbed the clutch for a plug check and sat straight up. It took my breath away but I had no problem in staying on the bike. I wanted to see how quick I could get off the course so I didn't wait long and leaned it off to the right. That was when there was a single course and the return road was to the right. The road race slick jumped over the pressure ridges and the back end was pretty loose but manageable. I was at a dead stop, pointed back to the starting line at the 3 1/2. My pick up fellow waited at the 4 1/2 and I never got there so I sat on the bike for quite a while before he found me.
I hear people talking about hanging on to an open bike and just think about that experience. Somehow their imaginations don't match my experience.
Scott has probably done it also, but he's smart enough to keep his mouth shut. Jason talks Canadian and there is no way to translate his experiences. That's one of the problems with letting foreigners run with us.
FREUD
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I think you answered your own question when you wrote taking the fairing off of a 180 mph bike. Remove the fairing lose the speed. I think the bike may be stable but it seems like it would be very uncomfortable to be traveling at say 160 sitting bolt upright.
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In 1979, I made over 30 passes at Bonneville in excess of 180 with
a Z-1 Turbo street bike with the only aero changes made with the change to ATC-90 bars and no tuck in.
The luggage rack and turn signals were in place.
I think we used 12 gallons of gas that week.
In 78, AMA made us take the fairing off the Z1-R to run in production.
It was a blessing because the bike ran 4mph faster and handled better.
Some times a bad fairing can make things worse.
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A few years back ( lake Gairdner), a couple of members of a well known outlaw bike gang showed up with some hotrod big inch Harley's, complete with forward controlls and ape hanger bars ,they were not shy in informing all and sundry how they would be the fastest vehicles of the meet,as it turned out they posted the slowest speeds of the meet, one bloke actually took some advice about streamlining and returns each year with improved aero and increasing speeds ,the apehangers did not show again :wink: ,hint ,human windsocks and high speeds are as rare as rocking horse shit
Gary
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Screw.....What are you bringing; A Big Dog Beach Cruiser???? Or maybe OC Choppers has group ready to come to B'ville...Now THAT would fun!!!!!
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Any good sources for facts and figures for aerodynamic forces? Specifically on the human toro (this is a long shot!)
That info probably exists in the skydiving community. A simple way to look at it is the terminal velocity of a skydiver in the normal arched back posture is near 120 mph, if he weighs 200+ lbs (body weight plus weight of equipment) that implies 180-220 lbs of drag at 120 mph. Most of that drag would be off the upper body, so a good guess would be near 100 -140 lbs drag on the upper body at 100 -120 mph. If drag increases at the cube of the speed, 200+ mph would give a drag number of almost 4.5x that or something in the 800+ lbs of air drag, trying to shuck you off the bike if you sat up suddenly.
Larry
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how much pressure :?: you ask, on my zx12 with all fairings fitted (frontal area `bout 4s'),,,, i have calculated that at 180mph it is pushing approx 275flbs :) naked up around 315flbs :?
ya know how to position that screwdriver and sit, may help :lol:
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how much pressure :?: you ask, on my zx12 with all fairings fitted (frontal area `bout 4s'),,,, i have calculated that at 180mph it is pushing approx 275flbs :) naked up around 315flbs :?
ya know how to position that screwdriver and sit, may help :lol:
Ya know, he is probably pretty close, with a large % on the white knuckles and newly stretched arms. :wink:
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I've ridden naked bike a couple of times -- a couple of records, too. First comment:
As I completed my first run down the long course, with best speed around 185, I endured some amazingly serious psychological concerns about holding my head where I wanted it to be so I could see and control. I worried that if I let my head turn to the side -- that I wouldn't have the strength to turn it back to straight ahead again, and then I'd either get my head ripped off -- or I'd have to lift. Dang, it's windy out there at a buck--eighty-five. So I finished the run, and when Cris and Ed Shearer met me they helped me take off the helmet -- and didn't say hello, didn't say "Good Run", they jumped to the back of their pickup to get cold cloths to put on my head and neck. That's how stressful that ride was on me.
So the next year, when I bumped the record in M/F 1350 to 191+, I learned -- and rode the short course! Still lots of wind, but at least not for so long.
At the end of a run I'll roll out of the throttle and begin to slow down, then start lifting my head slowly at (maybe) 160-170. At about 140 I can start to sit up, and form then on it's all easy.
At Maxton we don't have the luxury of a long deceleration run, so as I approach the first light I start to grip the bars REAL TIGHTLY, and when I'm in the second light it's out of the throttle and sit up straight, holding on for dear life! You don't get blown out of the saddle -- but it could happen if extreme care isn't taken to be comfortable in the manuever.
Would I want to sit upright and make a naked bike run at speeds over 180? Well, it'd be nice to have enough horsepower and traction to be able to get to those speeds while sitting up, that's for sure.
As an aside, I've occasionally thought of asking for a rules modification that would allow a vertical stabilizer on the back of the helmet -- to help keep it straight during high-speed runs. The wind forces are so high up at high speed that it'd be nice to use the wind to help, not to scare the rider.
Best wishes to those guys. At least it'll give their deodorant a chance to be refreshed...
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I was watching one of those chopper shows once and the famous builder was bragging on the motor in his bike, how it made 160hp, and how he was considering taking it to Bonneville and running 200mph with it. I about fell out of my chair. It's amazing the assumptions people make about horsepower and speed, most folks have no clue what it takes to go 200.
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OK guys thanks for the comments and the experiences. It does get pretty damned windy at high speed (!) and I have a better perspective on the forces involved. I'd forgotten (or never knew) the cube law and had been assuming a square. I guess that's a killer for those last few mph hey.
People do throw numbers around especially when it comes to motorcycle performance; casually, in exaggeration and often without any personal experience. It's nice to hear from those who know wherof they speak. I'll be popping in and out of here I reckon, thanks again. :D
Screwdriver.
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Watch the MotoGP guys and they sit up to help breaking at 200 mph.
On the other hand, Ron Cook sat up at 200 mph at El Mirage and was blown off the bike.
Accelerating up to speed while sitting up, and sitting up at speed are two different things.
Going 180+ while sitting up is gonna take some real horsepower!
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Watch the MotoGP guys and they sit up to help breaking at 200 mph.
On the other hand, Ron Cook sat up at 200 mph at El Mirage and was blown off the bike.
Accelerating up to speed while sitting up, and sitting up at speed are two different things.
Going 180+ while sitting up is gonna take some real horsepower!
Ron Cook was thrown off the bike after control was lost and bailed.
He had the same problem at Muroc the month before and worked on the wrong end of the bike.
Rear steer as it hooked up at speed was the problem.
If you want to test it at a much slower speed , drive out of a water burn out and see it pull sidways when it hits the dry stuff.
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Watch the MotoGP guys and they sit up to help breaking at 200 mph.
On the other hand, Ron Cook sat up at 200 mph at El Mirage and was blown off the bike.
Accelerating up to speed while sitting up, and sitting up at speed are two different things.
Going 180+ while sitting up is gonna take some real horsepower!
Uh, Ron Cook never went 200mph nor did he "sit up" while running his KZ1000, however he was and is sill an inspiration of mine that I think of everytime I make a top speed run....
Rons website is www.pureguts.com
J
PS, sat up well over 200 with no problem, place feet firmly on the pegs, open up knee area to aissist in air braking, sit up with a firm hold on the bars and I have stopped at the 6.5mile with no brakes after running over 250+
Jason has run over 240 on gps on an open bike with no front bodywork at last years Bub's meet so hanging on is possible..
J
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One thing for sure, it is a lot easier to pick up stuff from the ground. :wink:
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We ran a standard dirt track handlebar in 2003 on our XR-750s on the short course. The best pass was at 138, Don Camlin did all the riding. He was up to about 135 at the start of the measured mile in a dirt track tuck and was really beaten up badly at the three mile. That helmet attached to his flexible neck was the biggest aggravation, even at 135 the slightest movement went to twist it off. You're not just going at speed, your maintaining that speed for thirty seconds. We could have found a little more speed but we clearly had the wrong set up.
In 04 we added a fairing to one of the bikes and set a few more records. We had another XR in the trailer and Don never got it out.
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Here is a 208mph blow-off video from the RB Racing site:
http://www.rbracing-rsr.com/cinema/topfuel5.mov
Note that the rider was not tucked in (just crouched over), but was still apparently blown off due to losing his grip on the left hand handlebar.
I was almost blown off at a much lower speed. I wasn't thinking (as usual) after making a fully tucked-in dry lakes run and abruptly sat up at something over 120mph. If I hadn't been holding on, I would have gone off the back end. I went from NO wind to the full blast in just a couple of seconds. If I had raised up slowly there would have been no problem, but the unexpectd surprise was what did it. That's the problem with brain lock.
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I have molds for several different helmet tails. We made them for the hang gliding people years ago. They are the only people that are brave enough to use them. The tails are outlawed by most motor sports organizations because of neck accelerations in an accident. The hang glider/parachute people stopped using them cuz they couldn?t turn their heads.
The head is only a small aero problem with an open bike
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Their estate will put yourself and everything you own up for sale. :wink:
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A few years back i ran a 1327 prostocker ( oz rules back then ) we ran around the 170 mph range, and my home track had a real short braking area, we got real used to jumping up and jamming your body into the air to help slow down. but that was still a full fairing bike,
I got boarded with prostock and put the same donk in a stock efe 1100 lowered street bike, no fairing, man i forgot how powerful the full force of air was like, One run i got a powerstand up in top gear at close to 160mph I got of the gas close to the traps and it just floated there for a while and came down "O" so softly, the air was holding her up there .Lost a small end next pass, So i started building my 1642 landspeed open project,, DLRA 07 ,,,, :roll: :roll: :shock: :shock: :lol:
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I can only say from personal experience (on fully faired bikes) that I have no problem standing on the front pegs of my 12 on the street @ around 170 mph indicated.....keeping it pinned I note the bike can not pull much more because my entire torso, arms, neck and head are out in the wind and above the windscreen. I make sure to have a strong trip on the grips of course....
...I only do this while toying with dellusional literbike guys :lol: I'm 5'6 125 lbs.
A.
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I thought you were coming to the salt..?
you can "toy with dellusional literbike guys".....there...
Joe :)
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Bring generous quantities of anal lubricant that you can self apply when you challenge the " dellusional literbike guys" at B'ville.
It may ease the pain.
If you can find Goodies Headache powder in two pound containers I would advise several of those also.
Read the history of 998 cc at Bonneville.
FREUD
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Nobody seems to have asked this so I will.
Why the hell do you want to ride a 180 mph bike sitting bolt upright?
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It appears that "dellusional" is working both ways now.
DW
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I'd forgotten (or never knew) the cube law and had been assuming a square. I guess that's a killer for those last few mph hey.
Actually, you assumed correctly. Aero drag is proportional to the square of speed. Hotrod was probably thinking of power required to overcome aero drag, which is proportional to the cube of speed.
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Watch the MotoGP guys and they sit up to help breaking at 200 mph.
On the other hand, Ron Cook sat up at 200 mph at El Mirage and was blown off the bike.
Accelerating up to speed while sitting up, and sitting up at speed are two different things.
Going 180+ while sitting up is gonna take some real horsepower!
Uh, Ron Cook never went 200mph nor did he "sit up" while running his KZ1000, however he was and is sill an inspiration of mine that I think of everytime I make a top speed run....
Rons website is www.pureguts.com
J
PS, sat up well over 200 with no problem, place feet firmly on the pegs, open up knee area to aissist in air braking, sit up with a firm hold on the bars and I have stopped at the 6.5mile with no brakes after running over 250+
Jason has run over 240 on gps on an open bike with no front bodywork at last years Bub's meet so hanging on is possible..
J
W/F,
That was 1 of the Coolest Passes I've ever seen! The Flash Flood & Your FIM World Record was The BEST Though!!!!! I sure Learned allot from watching Jason and You! Thanks again Worlds Fastest :wink:!!!!!
S/K.....