A nose for all occasions (a crazy idea)

[Jonny Hotnuts]

OK, here's the deal.
I decided to start a new topic in the tech side but is really a continued discussion of where the wheel base, steering question on another thread.

I wanted to firstly say thanks for the comments and the work that sum put into editing the pics.
THanks....seriously.

Now for my crazy idea, take into consideration that I am not the smartest guy in the world (barely graduated HS!!!) and what I am about to suggest goes agents the grain of traditional thought in LSR.

It is a well known train of thought that in LSR it is a good idea to keep all air from going under the car. And I understand the reasoning and principles that make this common idea a good basis for most LSR cars.

In my quest to design a nose for my car I continually ran into a design problem. For some reason I think I an aerodynamically blanced nose would be a good thing. I think I have found a solution for that problem that seemed to have at, least in my mind, some merit.

Because I am not an aerodynamic engineer or have never seen this done I have a feeling that it is not done for a reason. I would like to know what that reason is.



My car, unlike a streamliner, is basically twice as wide as it is tall (referring to the front end of the car).

This means that if I were to build a nose that diverted the airflow 50/50 over the front of the car (25% down each side and 50% over the top) this would mean that 50% of the flow over the top would be generating downforce.
For some reason I got in my head that having a car in motion being 100% aerodynamically neutral in the front would be a good idea. This would mean that the 50% flow over the top would need to be balanced by apposing pressures of equal values.

My idea is to have a small area under the nose to allow a small amount of air under the car.  This air would generate a given amount of pressure that would be then directed to the side by a dam the same or near profile as the front. The area between the nose tip and the "under dam" should generate a ground effect and could be very small in comparison to the amount of surface area and angle of deflection of the air going over the top. I listed a raise of 4" on the drawing but it could be less then that and should not significantly increase drag because of the small amount of air going under the nose and the efficiently of the lift generated by the ground effect.

This in my mind would, or help equalize the pressures on the front of the car so when the car would be in motion that each side would get a 50% of pressure and the top and bottom would get equal pressures and still prevent the air from actually going under the car....at least beyond the front wheels.



Is this a crazy idea and should I just stick with a standard nose shape like the examples pictured in the other thread.

-JH









http://www.fiatforum.com/gallery/data/500/medium/lowered_with_nose.jpg?2741

[Unkl Ian]

So where is the benefit ?

Seems like more work,just to send air around the car.


The factories might do something similar,to create a high pressure area for a rad inlet.

[hotrod]

That is a well tried solution, for examples, look at the short air dam used under the nose of the Dodge Daytona/Plymouth Super Bee's, very simular to your idea.

A more modern example take a close look at some of the modern Corvette's they have a nose profile very similar to what you are discribing, and a short air dam buried mostly out of sight just in front of the front wheels, and suspension components.

In fact for your car a copy of the late model Corvette noses might be a good idea to work from, they should be easy to find for you to take measurements and pictures of and the car has a proven low drag body.

http://upload.wikimedia.org/wikipedia/commons/7/75/ChargerDaytona.jpg
http://upload.wikimedia.org/wikipedia/commons/8/8a/DSCF2897_c4_corvette_lg.jpg
http://upload.wikimedia.org/wikipedia/commons/2/20/1996_Corvette_Grand_Sport.jpg

Here is another proven nose shape you might look at to use that would be a good starting point for what you want to do.
http://upload.wikimedia.org/wikipedia/en/9/98/P997_carrera_s_frontview.jpg
http://upload.wikimedia.org/wikipedia/commons/a/a8/Porsche911997.jpg
http://www.rsportscars.com/foto/11/911turbo07_07.jpg

The Cobra Daytona has a very similar nose to what you are discribing but no air dam

http://www.ultimatecarpage.com/car/2/AC-Cobra-Daytona-Coupe.html

Larry

[Sumner]

First the air over the top could be creating lift.  Maybe downforce on the nose, but maybe overall lift.  If it is getting to the rear spoiler it might be creating downforce there.

   

This is a picture of Tom Burkland's old Datsun that set a record (still a record) at 294.  His nose has some of the features you are talking about.  I've always meant to talk to him and get his reasoning for the shape it is, but always forget.  There are a number of streamlines also that have more the shape that you drew.

Also note the tunnel the Datsun had under it.  An expanding tunnel under the car can help get the down-force where it is needed.  You just need a slight rake on the car with a belly pan slightly higher in the rear than the front and side plates under there to keep the air from spilling out the sides.  We might try this on the Stude.

Those skirts at the back of the Datsun that I think make-up the back of the tunnel also help to move the CP rearwards (good).

Trying to do what you suggested in the drawing might work fine, but without wind tunnel time I think I wouldn't go that way.

And don't try and act dumb  .  Just because you might of barely made it out of High School has nothing to do with you IQ only the fact that you were probably messing with cars, girls, or some other activity that you didn't get credit for  ,

c ya,

Sum

[Sumner]

Larry I see your point with those cars, but I'm wondering, if the designers didn't have to design them to work on the road and clear driveways and other obstacles that require a nose that is not flat way out in front of the front tires would they still have made them that way??

They have to raise the front to clear things and make the car practical and then the air dam back under there to me looks like a band-aid to help keep air from under the car.  Just my thoughts...

I finally got to look at the pictures you gave me and you have cars on the CD that I don't have pictures for, so that will help.  Thanks and they are nice.  Now I just have to find time to go back to that project.

I have a problem remembering faces    and already forgot what you looked like, so please re-introduce yourself the next time we are at the same place.  After a couple times I usually remember.  That goes for the rest of you guys too,

Sum

[hotrod]

Yes I think they would have (maybe very slightly longer). Long and pointy does not really do that much for you at low supsonic speeds. Those porsches are 200 mph capable cars, look at the NASCAR noses on the old style cars, even if they could make them longer they would not push them out all that far.

Another example, This GT-40 nose was also on a 200 mph capable car, but note it was a high front lift design until they put an air dam under the nose.

http://upload.wikimedia.org/wikipedia/commons/c/cd/2005_Ford_GT.jpg

Years later the Ferrari still has a very similar nose on the Maranello and Ferrari 550's

http://upload.wikimedia.org/wikipedia/commons/d/dd/Maranello.JPG
http://upload.wikimedia.org/wikipedia/commons/e/ed/05Spa_5152BMS550s.jpg

The main reason the F1 cars have a long pointy nose is to make it as narrow as possible so the can put more front wing on it without exceeding max width dimensions.



===
Glad the pictures are useful, will strip some out of the newer pictures after WOS.


Larry

[Sumner]

Yes I think they would have (maybe very slightly longer). Long and pointy does not really do that much for you at low subsonic speeds. ................Larry

I'm not advocating longer, but lower and rounder at the front.  If you are having a problem with CP then longer can help that.  I'm not saying that those cars aren't fast, but they were all built to either navigate city streets or meet the rules of the organizations they are running under.

Johnny has the option of making the front almost anyway he wants in the class he is in without any of the design problems that faced those designers.

Good conversation,

Sum

[hotrod]

Right, I think we are both thinking of a similar nose style it is just difficult to express in words, you initial photo tweak in the other thread is very similar to what I have in mind.

The NASCAR nose is a good example  push the front valence down in the dirt and you get a high down force nose, as you move that air dam back from the front and put more nose ahead of it the front becomes progressively neutral, until you start to cram too much air under the front (ignoring ground effect systems) then like the early GT-40 with no airdam it generates about 300# lift at 200 mph.

In my mind the ideal front for Bonneville, used on a more or less street car body, would be something like those Porsche turbo noses (old style NASCAR nose),if it is pushed out a bit in the front center for a rounder front, with the front edge that transitions to the hood raised just enough (making the hood flatter for less down force) to make them near neutral lift and a nice round transition to the hood. You want just enough down force to keep the front tires on the ground and not jack the front end up at speed, and have it come back down promptly if it does take a funny bounce and get lifted a few inches.

Sharp pointy noses, especially wedge shaped noses are good low drag shapes as long as their angle of attack (nose angle to the ground) is right, but they change lift/down force rapidly as that angle changes and if they lift up a bit too much the car flies, and if they get a bit too low you plow up the road way with your air dam.

The Ferrari 365 has a more wedge shaped nose that manufactures moved away from in the 1970's because of this attitude control issue.

http://upload.wikimedia.org/wikipedia/commons/6/68/SC06_Ferrari_Daytona_Coupe_silver.jpg

The thing folks need to remember is the nose is not the most important part of the body with respect to drag. Once you get any sort or reasonably clean nose, probably 2/3'ds of your drag comes from the rear and under body. That is why Tom has that nice diffuser and side plates on the lower rear body.

Larry

[Sumner]

I like this one you posted, but fill in the openings.  Round with some going over the top, basically back to the Blowfish again............

http://upload.wikimedia.org/wikipedia/commons/d/dd/Maranello.JPG

c ya,

Sum

[hotrod]

Yes that is what I am thinking too, block off most of the grill, and put the bottom of the nose a tad lower.

You would also end up with essentially the same shape if you did the same modifications to this Porsche nose.
http://upload.wikimedia.org/wikipedia/en/9/98/P997_carrera_s_frontview.jpg

The you can tweak the final front lift by using an easily detachable front splitter lip like on the Maranello. If you need more down force increase the size of the splitter, need less trim it back.

Larry

[Jonny Hotnuts]

Unkl Ian:    So where is the benefit ?

I am in a hurry and cant even begin to read the replies yet but did want to respond to this:

The reason, at least from what I can see, to have an aerodynamically balanced nose is because if you have a car that generates unbalanced downforce the faster you go the more force is created, it is exponentially increased scale something like:
Say you have a car that's nose is making 100 pounds of downforce at 50 mph (these figures are for example only but do represent how forces increase with speed) it can make 400 pound at 100mph and 2000+ pounds at 200 mph.

If the nose is blanced then no matter what speed you are going and how much downforce is being made there is an equal force being generated to counteract it.

This would make the car weigh the same no matter what speed you are going....at least from the front and not get progressively heavier the faster you go.

[interested bystander]

Talk about opening a can of WORMS!

Walter Korff's Summers Bros (1965) nose is PERFECT (and there's an SAE paper on it and the rest of the car) PROVIDED the rest of the car is the Summers Bros car.

There are otherwise so many variables that I have nothing more to say as it's making my brain buzzz!

Help. help help, JackD and Rex.

[1212FBGS]

anybody get a pix of the splitter i installed under my liner nose?

[Unkl Ian]

Production based nose designs have to allow for radiator inlets,brake cooling,
minimum height for headlights and bumpers,and "brand" styling.

A Bonneville car doesn't have to include these compromises.

[tortoise]

Say you have a car that's nose is making 100 pounds of downforce at 50 mph (these figures are for example only but do represent how forces increase with speed) it can make 400 pound at 100mph and 2000+ pounds at 200 mph.

1600 pounds, really. Still a lot, and you're right about avoiding excessive downforce; if nothing else it creates drag. The problem with some neutral downforce designs is that a little change in angle of attack, like from a bad bump, could put you into lift.