Landracing Forum
Tech Information => Technical Discussion => Topic started by: hawkwind on October 07, 2005, 04:09:24 AM
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some resources to check out :D
http://www.ae.su.oz.au/aero/contents.html
http://homepage.usak.ca/~drs694/fluidmechanics.htm#bluff-body%20aerodynamics
http://princeton.edu/~asmits/Bicycle_web/bicycle_aero.html
http://www.rmcs.cranfield.ac.uk/aeroxtra/exb2pdbase.htm
enjoy :D
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Thanks for the links. Learned some new stuff.
I think Jon should deduct 1/2 of your points on this post as I could only get 2 out of the 4 links to work 8) .
c ya, Sum
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One of those surprised me quite a bit. According to the graph, with speeds under Mach .6 a sharp point (conical section) has lower drag than a rounded leading edge or "bullet" (ogive) shape.
(http://www.rmcs.cranfield.ac.uk/aeroxtra/e338dragfig8.jpg)
Ddn't Carroll Smith (among others) rant for years that any any speeds a race car will see on a closed course an elliptical section is preferred?
Well if you found it on the internet it must be true.
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one of our racers (dlra) adapted a ultra light fairing to his bike using shape B and with the same HP added 12% to his top speed, so in practice it obvisously works quite well
Http://photobucket.com/albums/y108/dlra2/speedtrials2005-010.jpg
I was very suprised as I expected very little if any inprovement , as this is the prefered shape for supersonic speeds :oops: it appears to increase the bikes Cd without to much frontal area penality
Gary
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think about the numbers the dustbins were running in the 40's and 50's. it wasnt clean hp making those numbers.
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When they learn of this heads are going to roll at Cessna, Beech, Boeing and at other manufacturers after they learn that their engineers have spent years and hundreds of millions of dollars developing those blunt nose shape of their subsonic aircraft. Try this link for information on parabolic nose shapes.
http://www.aerospaceweb.org/question/aerodynamics/q0151.shtml
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One of those surprised me quite a bit. According to the graph, with speeds under Mach .6 a sharp point (conical section) has lower drag than a rounded leading edge or "bullet" (ogive) shape.
(http://www.rmcs.cranfield.ac.uk/aeroxtra/e338dragfig8.jpg)
Ddn't Carroll Smith (among others) rant for years that any any speeds a race car will see on a closed course an elliptical section is preferred?
Well if you found it on the internet it must be true.
I think we need to put the above data into perspective , looking at the data AND reading the points its making , the author is stating that at low subsonic speeds ,in this graph below mach # 0.6 which equals 445 mph , there is not much difference between the shapes maybe 0.03 Cd( and I assume they are balistic projectiles ) , the main point is at what mach # drag starts to increase ( due to the nose shape ) ,in the information from the site you supplied ( which was also on the internet :lol: ) the data is missing an important bit of information what mach # the model rockets achieved as this has a large influence on the drag created , also the picture examples where of subsonic jets and a rocket , the crusing speed of a 747 is 0.86 mach # or 670 mph at this speed the shape of the nose is important .,all interesting stuff
I look forward to meeting you in person and having a chat , your liner is a blast :)
Gary
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it seems hard to believe that you can isolate one part of an aerodynamic body and consider it's performance without any association to the entire body. looking at the example motorcycle it would seem the base drag is the predominent factor in the aero losses. A 0.03 change in Cd of the nose seems pretty hard to prove. it certainly seems like it would not account for a 12% improvment in performace unless the original nose was a large flat plate. I had always thought the first place to clean things up was the base drag as it is generally the largest component of drag in land based vehicles. That is other than poking the smallest hole in the air to start with. The old CdA thing..
Dave
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Dave that is correct , most improvements will be based around a reduction in base drag , and yes the overall picture tells the story ,where the CdA figure is paramount ,in my opinion as a keen amateur , the front shape of those 3 examples is not important provided that there is no detachment of the boundry layer before the widest part of the vehicle especially at the low mach # we run at , a good experiment would be for my friend to replace the cone shaped nose for eitheran ogive or spherical nose and see if there is any improvements .
Gary
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Hawk:
When I started the project a couple of years ago I knew almost nothing about aerodynamic theory (and still don?t). My approach was fairly simple, don?t be influenced by any prior designs and look to other vehicles that travel at mid range subsonic speeds and have had many years and millions of dollars spent on R & D i.e. aircraft, missiles and bullet trains. One thing that always struck me as wrong during my previous two trips to Bonneville was the sculptured shapes around wheels and other chassis parts on most of the streamliners. My thoughts were that you don?t want to disturb the direction of the moving air any more that is necessary. You won?t see bulges bumps and protrusions on aircraft fuselages missiles or even boat hulls for that matter. I thought the ?cool look? might have a lot to do with it or ?that?s the way other streamliners look? train of thought. When the project was getting to the stage where we were ready to start finalizing the body shape a friend of mine brought Ken Mort by. Ken had worked on the wind tunnels at Ames NASA in Mountain View for a number of years and had much practical knowledge of various designs. Ken liked the project and volunteered to help with the design. He liked my initial design but had me make a number of changes. First he liked the parabolic nose but did not like the symmetrical design. Ken wanted to change the cord to about a 10 degree downward angle for some down force. I just kept moving the curve down on the computer until Ken said I like that then built the nose tank. Next we discussed the shape of the windscreen I had two designs one with a long tapered windshield similar to Sam Wheelers and the other a more conventional upright design. Ken said that up until almost supersonic speeds either design would perform about the same however on the upright design it was very important to have the proper shape at the body transition areas. When we built the plug for the mold Ken came by and we just kept changing the transition area until he liked it. The major change he suggested was to add a couple of feet to the rear of the body to move the center of pressure back and he concurred with my conclusion that a tail would just add drag and increase the effects of a cross wind on stability. Ken also wanted the bottom profile to be narrow and rounded as opposed to any type of flat surface. Also with the body as close to the ground as possible. By accident ,rather than design, the body ended up about 1 ? ? higher in the rear than the nose. This seems to work well as it seems to produce down force at the rear. Ken estimated that an open tail would add 10 -20% to the total drag however if the overall drag was low this would not be a great penalty especially with the power we had available and it simplified the design. We never did any wind tunnel testing. Ken wanted to tape a few hundred pieces of string to the body and follow it at about 100 mph to observe the air flow however we never had time to do this. As luck would have it the design has worked very well and we have seen almost no wheel slip at up to 336 mph. I don?t know if any of this will be helpful in your endeavor but I wish you the best. I guess my point is that common sense, practical knowledge and luck can often trump theory or commenly accepted principals. As Ken says ?I would rather be lucky than good any day?.
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Panic:
Rude? Im not as rude as Jack D but I will try harder. What I thought you meant by your post was Carroll Smith and others were obviously wrong based upon this graph. What did you really mean? Dave Dahlgren has it right I believe you can not take a finite element such as ballistics data and come to conclusions about a streamlined body. Thats why I posted the nose cone link for Hawk.
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Like speed, rude has all manor of expression, reaction and results. One person's rude/speed is another person's cause to stop and think. The end result should be that a lot of the stopping and thinking has been done before you and the value will be in the results. That is all that will last past today anyway is results.
To fold easily and edit out your remarks often means you are not comfortable with the information in the face of any other ideas.
What works for one might not work for another, but still has to work.
If everybody failed to stop and think and were afraid to try something the result would be a lot closer to the tried and true Highboy Roadster that has not been perfected yet.
You can be nice and rude or mean and rude. In the end, the results will establish the value.
You wanna see rude? Spend a bazillion dollars and get a 2 bit result. That is rude. :roll:
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some interesting points there Ack :wink: cheers , nice to have a friendly neigherhood aerodynamist willing to assist :)
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Yes Mike thank you for that post, it is very nice of you always to be so open about your project. If there is anything that I have learned from you is that you have no secrets about your project. And you are open to what, why and when you have done everything on your project. When talking to you I find that you took the simplist approach to everything, make it simple is what you keep saying.
Thanks
Jon
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Hawk:
When I started the project a couple of years ago I knew almost nothing about aerodynamic theory (and still don?t). My approach was fairly simple, don?t be influenced.........................the best. I guess my point is that common sense, practical knowledge and luck can often trump theory or commonly accepted principals. As Ken says ?I would rather be lucky than good any day?.
(http://purplesagetradingpost.com/sumner/temp-pictures/899%20ackattack-em.jpg)
Ack thanks for sharing Ken's and your thoughts. That pretty much sums up what I'm trying to do with the body on my lakester. The only picture I have (have been able to find) of your liner with the body on is the one with this post. I would sure like to see some frontal, rear, top, and/or side pictures. Are there any posted on the Internet? If not and you would like to share those with us I would be glad to post them on my site or you could post them here. I was so busy with Hooley and his Stude 2 years ago that I missed seeing you on the salt and you weren't there this year.
If there are any pictures of your liner, with or without the body on somewhere on the I-net could you please post an address. BTW the liner looks great :D .
Thanks,
Sum
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Cut and paste from Tony Foale, motorcycle designer article circa 1997
http://www.tonyfoale.com/Articles/Aerodynamics/AERO.htm
CONCLUSIONS: Aerodynamic design of motorcycles is more than just a matter of producing a low drag, low lift body with a C of P. behind the C of G. Stability is harder to achieve with well streamlined low drag bodies, this is due both to the greater side area present with such fairings and to more efficient production of "sideways lift" due to the angle between the airflow direction and the direction of travel. So ideally we want a combination of sometimes conflicting requirements:------ Minimal drag for performance. Low frontal C of P. to reduce drag induced weight transfer. Low and rearward side C of P. to reduce the unbalancing moments, and give directional stability. A shape and value of side area that minimises the side force produced. A high and forward C of G. combined with a large weight to minimise the effect of whatever side forces are generated.
If any of you out there were thinking of designing your own bodywork, don't let this put you off. Often the amateur with limited resources shows up the large companies, who do not always get it right, even with their wind tunnels. Just look at Ford's attempt with the Sierra (European model only), initially there were stability problems until they fitted spoilers to the rear quarter lights. In the bike world, back in 1981 a road test on BMW's Futuro fully faired concept bike, showed it to be very bad in this area too. _
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I sure hope that this all works, because my head hurts.
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the biggest reduction in drag comes from enclosing the front turbine er I mean WHEEL. Have ya ever seen flow visualization of a spinning mass? It's pretty ugly. try all ya want with band aids like slippery looking body coverings the best you'll get is 5 to 7%. look at the records, compared an open bike to a ps record, do the math, it's all about 5 to 7%. The smaller ya make your bodywork the less affect it will have on possibly stabilizing or reattaching the turbulent wake made from the front wheel. until they allow us to run dustbins again its gonna be pretty hard to lower CD. So think all ya want 'bout making your bodywork smaller and smoother in a misguided attempt to lower cd. but history and the records show it wont make all that big of a deal. Kawasaki was on the right track when they put those little wing-lets on the side of their bikes. those were to stop the wash from creeping up the side of the bike. They were just a little too small, heck who would buy a bike with big stupid looking wings on the side of their bike? Now Hawk don't run out and put big wings on your bike! do not put any aerodynamic loading devise on an inherently unstable vehicle. Unless you want us to see a pretty spectacular crash. Like my 93 speed-week crash.
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Pics removed
J
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Great pictures John :D . Thanks!!! Do you plan on running Speed Week next year?
Can I ask some questions/make some observations and feel free not to comment if there is something you would just as soon not be made public.
Looks like both motors exhaust to one turbo? Where does the water for the intercooler come from? Is the tank at the very front of the liner for cooling and/or intercooler? Is the tank under the chutes gas?
It looks like the front motor drives an intermediate jackshaft that connects to the rear jackshaft via a chain on the right side of the car? Then the rear jackshaft by the swingarm is also driven by the back motor and that jackshaft drives both sides of the rear tire/wheel?
The workmanship is fantastic :!: :!: :!: .
I hate to comment on someone else's car/bike, but I would really like to see the area by your helmet more closed in to stop lateral movement of your head. Also maybe a bumper at the front of the helmet to stop forward movement. I guess Tom Burkland has made a big influence on me in this area.
He just sent me the following links that I would like to share:
http://www.joieofseating.net/2005_stories/randy_reacts1.html
and
http://www.joieofseating.net/seats.html
The second one with the seat info wouldn't apply to you, but we are looking at options to confine Hooley's upper body and head area in his Stude and that page, especially the part at the bottom "SAFER SYSTEM" might be good to study for some of the car guys.
I think Randy Lajoie sums it up with the following statement:
Being involved with NASCAR?s Tech Center (Concord, NC); sitting in on their crash tests and receiving the data from the black boxes onboard NASCAR Trucks, Busch and Cup cars has been helpful to all of us and I have learned plenty. The old saying, ?You have to move inside a racecar (when you get hit),? well, let?s just say that is BS. No points loss here I hope. The industry has never hurt a driver that did not move.
Well anyway thanks for the pictures and I want a picture of it going 350 mph or more next year.
c ya, Sum
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Thanks for the compliments, I will answer a few of the questions and see if Mike wants to answer any others.
1. Yes
2. Yes
3. A tank with ice under the rider
4. Cooling
5. No tank under chutes, the Black "tank" is the fuel tank.
6. Above that is the Intercooler.
That first article was very nice and had great information thank you, the liner was inspected at Speedweek (and passed) and also by the FIM stewards while we were at the Bub's event last month, the chassis I am sure is stronger than most if not all other liners (bikes) as Mike is first concerned with safety, simplicity and then speed.
I would rather ride the streamliner (with regards to safety) than the open bike at 260 with nothing more than leathers, boots and a helmet.
Pic removed..
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I'd like to see John Noonan's photos but from here it just says "Photos removed". How do I see them?
Thanks
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To see Noonans pix you need a really big monitor. Like a 19" or 20" cuz his head won't fit into a 17" monitor anymore. Little A is pretty good with shrinkin heads but is reluctant to practice his voodoo on Noonan as yet
kent
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To see Noonans pix you need a really big monitor. Like a 19" or 20" cuz his head won't fit into a 17" monitor anymore. Little A is pretty good with shrinkin heads but is reluctant to practice his voodoo on Noonan as yet
kent
Yeah, no need to look at that swoopy bodywork either...
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cool I just passed Noonan for points with that last post. Now if I can only gain speed to catch Doland.
kent
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cool I just passed Noonan for points with that last post. Now if I can only gain speed to catch Doland.
kent
Yeah, now I have more points than (insert name here) not about points, about good info... 8)
PS. I now have more points...again.
J :lol:
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I'd like to see John Noonan's photos but from here it just says "Photos removed". How do I see them?
Thanks
Sorry, some people in small tribes still have dial up at 2600 baud rate and cannot clock in to view the future.. :cry:
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Stop that and go to bed! I hear Michelle calling!
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are pointless. 8)
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Stop that and go to bed! I hear Michelle calling!
She is calling...my name..... 8)
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are you sure.........
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are you sure.........
Yep, it sounds like grass hole..thats me.. 8)
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Still nothing on how or where to see the photos. Anyone?
Thanks
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working on it,
Jon
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Jon if it isn't a problem with you, John or Mike here are the pictures that John posted the other day. If anyone has a problem with this please delete the post.
c ya, Sum
(http://purplesagetradingpost.com/sumner/ack-attack/ack-1.jpg)
(http://purplesagetradingpost.com/sumner/ack-attack/ack-2.jpg)
(http://purplesagetradingpost.com/sumner/ack-attack/ack-3.jpg)
(http://purplesagetradingpost.com/sumner/ack-attack/ack-4.jpg)
(http://purplesagetradingpost.com/sumner/ack-attack/ack-5.jpg)
(http://purplesagetradingpost.com/sumner/ack-attack/ack-6.jpg)
(http://purplesagetradingpost.com/sumner/ack-attack/ack-7.jpg)
(http://purplesagetradingpost.com/sumner/ack-attack/ack-8.jpg)
(http://purplesagetradingpost.com/sumner/ack-attack/ack-9.jpg)
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No problem.
John
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Looks good, im still working on a fix for pictures, ones that are oversized for the limits of the page, it will automatically reduce the image so the poster does not have to worry about it....
Its coming I promise.
Jon
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I liked the larger pics of the liner with the body off so you could see the details and craftsmanship that went in to it. Jon, can you make the pics so that you could double click on them to increase to original size?
John