Landracing Forum
Tech Information => Aerodynamics => Topic started by: hawkwind on April 12, 2013, 01:34:07 AM
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If one was creating downforce via an inverted wing and that downforce was acting directly over the axel in a vertical direction ie. at 90 degrees to the direction of travel would it alter the CoG ? then if one was to move the wing so that it was forward or rear of the axel would that change the CoG? or generally does the added force of negative pressure add weight to a car like adding lead ? or does it create pitching moments only?
And if you add enough downforce to stop any wheel spin, would soft compound tyres then help further with traction?..... for arguments sake lets say the vehicle is very traction limited and nowhere near enough space to add enough lead.
cheers
Gary
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My guess Gary is that it wouldn't effect your COG, it would move your COP though.
I would be wary of generating a lot of downforce on a single track vehicle.
Only my opinion.
jon
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Gary, you can pour 1/2 inch lead plates that you can form to fit as required if you use fairly pure lead. You might be surprised how much weight you can find room for.
I'm thinking you are asking for trouble with a wing...
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To geneerate the down force you imply, the wing would also generate a considerable amout of drag at speed. drag bad.
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If I'm thinking straight this morning . . . .
Applying downforce to the wheel/axle is better because there is no need to alter spring rates. This, however, does NOT mean that drag won't be present. One canNOT get downforce without drag.
In my mind, drag from a wing increases with speed. Wt. (mass) is a constant no matter the aero conditions (speed, or not) giving the same added traction at all speeds.
Does that make any sense?
It seems enough folks have proven the added wt. theory . . . .
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Al Teague tried a wing and went slower, you will see very few streamliners with a wing.
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the problem with a wing at velocity (downforce) on a single track vehicle, is that it will want to steer ya if at an angle to the horozintal plane,,
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The first car to go 500 will use down force , wings or body shape or both . Wings can have 30:1 lift to drag if they're slender and tapered .
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Thanks ....yes im well aware of the drag penalty in providing down force...like all things in life there is no free lunch :cry:...under certain circumstances all things must be considered ...the search for traction will continue ...the problem still remains ....time to investigate solutions that most for there reasons reject......Facts trump speculation...... research continues.
Stainless1 I have gone to extraordinary lengths to utilise every square inch of available space ...lead shot is inhabiting all the frame rails and every where else it could be secured safely somewhere around 60 Kg...there is only so much space on naked bikes....available horsepower is well in excess of available traction so adding some more drag to what is a very high drag platform is not as bad as it looks ....finding a balance is the solution. excessive spinning of a tyre only gets you a ruined tyre not a record ....need to exceed 230mph now.... up from 208....as stated before available traction is the limiting factor.
cheers
Gary
P.S. who dares wins :evil:
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You might improve your traction if you shave your tires (to reduce its ability to carry high pressure air and loose salt, wrapping around to ground contact). You could mount your battery box as low as you can, directly in front of the rear tire. This will cut off airflow into that very high pressure air that the tire is dragging around the circle. Part of the problem is marbles from the front tire, perhaps?
Those big sidewalls are pretty good at throwing air under the front of a tire. Our roadster would drag salt, in the tread grooves, all the way around in front of the rear tires. The side of the body, in the upper forward quadrant of tire area, had the paint really abraded from that 180 mph salt meeting 180 mph air for combined speed of ....some big number! It was obviously the highest pressure point on the whole car.
This effect is so significant that many production cars are now using spats/spoilers in front of all four tires, and using tighter shoulder tread patterns. It starts to matter at as low 50-60 mph! I run a spat in front of my rear tire, and you can bet it will be deeper this year. :wink: It had a LOT of salt stacked on it, last year, that blew back from the front wheel....and it was the hammered-in hard kind that you get at speed (and i'm only going 160 on my 650 pushrod bike).
Maybe a cheap and safe improvement for you. The way the rules read for open class, a rear tire spat isnt streamlining because its not ahead of the rider, and doesnt cover tire or wheel.
Regards, JimL
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Thanks JimL..... :-D yes I have the batteries down low and directly behind the rear wheel ...I tried to post a pic but the file is to large and it was rejected :oops:.
I have been doing a lot of research and its hard going to find much about inverted wings on motorcycles BUT there is some and its not the doom and gloom most make it out to be.
"In a straight line, any aerodynamic features that create extra down force will load the tyres more and make available more traction. Provided that our brakes are good enough and that we have sufficient power, this greater grip will allow for better acceleration and braking"...quote from Tony Foale...also the other bike experts I have read Gaetano Cocco & Vittore Cossalter also agree in principle that the idea is a sound one albeit limited in scope or at least what has been tried before.
If you fitted a fixed 'wing' to a bike it would generate down force relative to the vertical axis of the bike, and when leaned over it would generate not only force in the true vertical plane (to enhance grip) but also in the true horizontal plane, increasing the force trying to push the tyre away from the centre of the bend. Net result, no increase in grip but power lost in aerodynamic drag.What we're talking about is increasing the down force and hence grip, F=mu*N.If you fitted a wing with a gimbal mechanism so it always created down force vertical to the ground you could increase the grip without increasing the cornering force so any leaning for apparent wind direction would not limit or negate the down force.
There are any number of top fuel drag bikes that use inverted wings of several types and designs and a surprise find was a Kiwi physics Dr. Roger Freeth who in the 70's raced a TZ750 with inverted wings until the sanctioning body outlawed it. so its not in the realm of science fiction.
Both wrist induced and electronic traction control is usefull to a point but sadly trying to outsmart the laws of physics is doomed to fail, so for me its a no brainer to use down force albeit at the expense of extra drag and search for a balance.
cheers
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Resize your pics to "large web" size before you try to load them to this site.
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Thanks Jack but the pics are on my puter not a web hosting site and 500kb is all she wrote, all mine are many mega pixels : :cry:
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I like the idea Gary. If the wing has negative dihedral it should help to keep the bike upright as well.
Dave.
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Thanks Jack but the pics are on my puter not a web hosting site and 500kb is all she wrote, all mine are many mega pixels : :cry:
Let's try one last time then we'll move on. All of my pics are on my puter too. I right click on the pic and pick "edit" from the list that appears. there should be opions to choose from. Just trying to help as a lot of folks here function better with photographs.
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here are some of the examples I have found
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This one is from the 70's
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JimL .....here are some pics of my bike .....total weight all up with me on and ready to race is 1000lbs made up of lead 200lbs.....me 216 lbs and the bike 575 lbs it has a weight distribution of aprox 60/40....as you can see the batteries are low and behind the rear wheel ......last time I raced there was about 17% difference between recorded speed and tacho redline speed ..im adding sensors to accurately record real tyre slip.
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Looks nice Gary.
Are there any areas that at filled with shot that you can melt lead into or slide an ingot into?
The best stacking of spheres possible gives about 21% airspace.
My concern of a wing is not around running straight, it's around a crosswind.
Cheers
jon
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Me 216lbs???? Not trying to be nasty but brother that is a huge amount of ballast. Try Marco Melandri. :-D :-D
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Looks nice Gary.
Are there any areas that at filled with shot that you can melt lead into or slide an ingot into?
The best stacking of spheres possible gives about 21% airspace.
My concern of a wing is not around running straight, it's around a crosswind.
Cheers
jon
Powdered tungsten will fill the space between the balls... I think it is a little heavier than lead... and a lot more expensive.... although a pound of both weigh the same... :roll:
same wing concern here, the downforce in a cross would seem to want to push the tire out from under the bike.
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I was going to say something about re-sizing photo files -- how it's done in your computer, not on the web - but Cpt. THun beat me to it. Another way around those large files is to use a photo-sharing site (Photobucket, etc). They accept any size file and link to your post with just a line or so of text. Yes, if the photo site goes down your Forum post would lose the photos, but that's a minor concern if you ask me. It's happened once or twice to me in the past five years, and then the missing stuff came back soon anyway.
A plus is that the entire post loads faster.
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Just a thougt about a wing on a two wheeled vehicle. The down force generated by the wing is always directly down from bottom of the wing, i.e. 90 degrees from the bottom of the wing, so if you happen to be going fast enough to generate some serious down force and you happen to have to lean the bike over a little then he wing down force is no longer perpendicular to the ground instead it is trying to push the tire out from under the bike. Could this really happen, got me? but just a thought.
Rex
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These are as far as I know, are the two fastest and quickest Drag Bikes at present.
Korry Hogan the fastest 250+mph
(http://i1023.photobucket.com/albums/af354/RGV866/A%20bit%20of%20Fun/KorryHogan250mph_zps70ab2985.jpg) (http://s1023.photobucket.com/user/RGV866/media/A%20bit%20of%20Fun/KorryHogan250mph_zps70ab2985.jpg.html) (http://i1023.photobucket.com/albums/af354/RGV866/A%20bit%20of%20Fun/Hogan7burnout_zps64e7e0d3.jpg) (http://s1023.photobucket.com/user/RGV866/media/A%20bit%20of%20Fun/Hogan7burnout_zps64e7e0d3.jpg.html)
Larry McBride 5.6 secs
(http://i1023.photobucket.com/albums/af354/RGV866/A%20bit%20of%20Fun/McBride1_zpsd6bd596f.jpg) (http://s1023.photobucket.com/user/RGV866/media/A%20bit%20of%20Fun/McBride1_zpsd6bd596f.jpg.html) (http://i1023.photobucket.com/albums/af354/RGV866/A%20bit%20of%20Fun/McBrideHogan_zps9285f27e.jpg) (http://s1023.photobucket.com/user/RGV866/media/A%20bit%20of%20Fun/McBrideHogan_zps9285f27e.jpg.html)
Both are McBride built bikes and have that rear "Spoiler" set up rather than a Wing maybe there is something in that???
Pete :-D
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Rex that's the problem there is so little information out there ....everything I've read says its possible ...methinks its time to explore the possibilities :-D.......maybe it will start a trend if it works :cheers:
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what happens if an aeroplane trys to fly straight ahead if the wings are at an angle to the horozintal, :?, will want to steer in a circle,(more angle, tightens circle, less not so tight), have to have some pedal in there to keep it straight, :wink:,,
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Just a real distant and casual observation from a slow-poke rookie..............could it be that the flat-tray is creating lift? You appear to have a lot of air-space under the motor and no air-dam effect in front of the tray.
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One variable I cant figure out is what speed you begin experiencing the 17% slip. I guess you mean you are running 208, and turning the rear wheel 243? That has me wondering if there is a particular speed range where this much tire spin begins to occur. That might give some clue to what is happening.
....an interesting puzzle, indeed.
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Looks nice Gary.
Are there any areas that at filled with shot that you can melt lead into or slide an ingot into?
The best stacking of spheres possible gives about 21% airspace.
My concern of a wing is not around running straight, it's around a crosswind.
Cheers
jon
Agreed--- For example I filled my front bumper with lead shot, added about 85lbs that way. Then went back and poured molten lead in thinking I'd get a little bit more weight and would use the molten lead to seal the shot in the bumper. I got another 34lbs of molten lead into the 'already filled with shot' bumper!
Additionally, when you melt the lead, all of the impurities float (you can float a steel bolt in the stuff actually) and you remove the impurities from the top leaving just the more dense, molten lead. When it came time to fill the framerails I didn't even bother with shot, just went straight to molten lead and filled them up. Put another 220lbs in just the front sections of the framerails (firewall forward) in my car. I