Hehe, it's OK, it took me a 4 year degree to learn what I know now
The 'standard aerodynamic equations' you mention probably assume that the fluid is incompressible (and isentropic and adiabatic, etc...). It's much simpler if you don't have to account for the change in density of a fluid as the pressure changes. A standard rule of thumb is that a density error of 5% is usually acceptable...that takes you to about Mach 0.3 (approx. 200 mph at sea level).
Reynolds Number is a non-dimensional number based on flow velocity, fluid viscosity and some reference length on the object. It can be thought of as the ratio of inertial forces to viscous forces. At low Reynolds Numbers, the viscous forces (i.e. skin friction drag) dominate the drag forces, while at high Reynolds Numbers the inertial forces dominate (i.e. pressure drag - the 'wake' behind an object).
Drag coefficients change because of changes in boundary layer behaviour at different flow velocities.
The 'width x height' calculation should give an approximation to frontal area, not side area!
Edit - I should probably point out that these effects (probably) aren't relevant to VHPA as it stands at the moment...the usual drag equation is fine unless you want super-accurate figures at very low speeds or above 200mph.
Last edited by StewartFisher, .
Cd is a empirically-calculated constant which relates an object's properties to its drag. 'A' is simply a relevant reference area. It needn't be a frontal area, just an area. The real value of calculating Cd comes when you want to compare objects which are similar in shape but different sizes...in that case, the reference area you choose must be consistent in all cases, but it doesn't really matter which area you use.
For example, there isn't really any need to know the exact frontal area of each car. A simple width x height calculation would give you a good enough reference area to calculate a Cd in order to compare cars. The only requirement is that you are consistent in your calculation of 'area'. I've probably needlessly complicated things...sorry about that!
Assuming you choose a consistent definition of area then, yes, Cd is constant with area.
BTW...A sphere only has Cd = 0.1 at high Reynolds Numbers, once the boundary layer becomes turbulent. Cd is constant with area but it is not constant with flow velocity.
Sitting the car on a weighbridge with individual weight measurements for each corner would help with a lot of things. This way you could calculate the overall mass of the vehicle and the CoG location in the X-Y plane, as well as the fuel tank mass and CoG if you use Tristan's drain/refill method. You could also get a friend of known mass to sit in each seat in turn to calculate the CoG of passengers.
Finding the height of the CoG is going to be tricky.
A rolling-road dyno will be required for engine testing, and you can also use it for testing the brake strengths (and, therefore, brake balance). Rolling roads are fine if used correctly...we've got one here and I've not heard of any problems with it.
Finding the rotating mass of a wheel isn't as simple as weighing it as this doesn't take into account the radial weight distribution. What you'd need to do is to apply a known torque to a wheel and measure how fast it speeds up or slows down. Then use Torque = I * angular acceleration to work out I, the moment of inertia.
In aerodynamics, the value 'CdA' can often be taken to be a single parameter, for the simple reason that 'Cd' can only be defined once you've defined an 'A'. Cd is usually measured using a coast-down test. This includes rolling resistance, obviously, but there are equations which can be used to seperate out the effects.
If the wings are infinitely thin then you can measure the wing angles by placing a ruler between the leading and trailing edges and measuring the angle. If the wing has thickness then you will have to use a ruler with a cut-out to match the profile of the wing at the leading and trailing edges so that the edge of the ruler lies along the chord line.
Finding the height of the CoG is going to be tricky.
A rolling-road dyno will be required for engine testing, and you can also use it for testing the brake strengths (and, therefore, brake balance). Rolling roads are fine if used correctly...we've got one here and I've not heard of any problems with it.
Finding the rotating mass of a wheel isn't as simple as weighing it as this doesn't take into account the radial weight distribution. What you'd need to do is to apply a known torque to a wheel and measure how fast it speeds up or slows down. Then use Torque = I * angular acceleration to work out I, the moment of inertia.
In aerodynamics, the value 'CdA' can often be taken to be a single parameter, for the simple reason that 'Cd' can only be defined once you've defined an 'A'. Cd is usually measured using a coast-down test. This includes rolling resistance, obviously, but there are equations which can be used to seperate out the effects.
If the wings are infinitely thin then you can measure the wing angles by placing a ruler between the leading and trailing edges and measuring the angle. If the wing has thickness then you will have to use a ruler with a cut-out to match the profile of the wing at the leading and trailing edges so that the edge of the ruler lies along the chord line.
No. The car modelled in LFS is the F1.06. No modifications are necessary.
Wings which generate downforce modify the incoming airflow such that it is actually moving very slightly downwards as it hits the front of the wing. The leading edge is curved upwards in order to allow this flow to move onto the wing smoothly. A perfectly horizontal leading edge would cause the wing to stall at a lower angle of attack.
Well, I was using a 300mm lens on my 400D, so that's a 35mm equivalent of 480mm...1/320 isn't so easy at that focal length!
You'd be surprised what sort of shutter speeds you could use to get the moon properly exposed. My best shot of the moon so far was ISO 100, f/7.1 and 1/320 secs shutter speed. OK, I did use a tripod, but only because I was in the back garden and I had one handy. Bump the ISO to 200 and you should be able to hand-hold that without a problem.
Yes, in your opinion! Opinion counts for nothing against the letter of the law.
Well, I am, as it happens
I understand your point but I still don't see how this justifies breaking the law to get what you want. There's plenty of free music out there.I maintain that any price is fair if people will pay it. That aside, I have no problem with people purchasing music by download on legitimate sites. Your reasoning appears to be "I can get it free...that's a fair price!", without regard to the fact that it is illegal.
It's still subjective though, which means that it's impossible to account for in law. It's not a good defence to claim "My personal belief system makes it OK, so you have to accept this.".
Aside from that being a ridiculous statement, just turn on the radio, where music is free. What if I truly believed that 'a big TV is life' and stole one? Would I be justified because 'it is life'? Somehow, I doubt it.
What is a fair price? As far as I'm concerned, no luxury item can be overpriced. If people are willing to pay the price, then it's a fair price.
The problem with 'karma', as you put it, is that people define it differently, so there are no absolutes. If I took it upon myself to decide that the government were corrupt and that it would be 'good karma' for me to blow up Parliament, would my belief in 'karma' justify my actions?
No alternative? The alternative to having a luxury item is to not have that luxury item and get on with life. You claim that you've paid 'extortionate prices' for music. You would have been aware of the cost at the time of purchase and if you handed over the money, you decided that the value of the item to you was equal to or greater than the price you paid. The only person you have to blame for the 'extortion' in this case is yourself.
OK, so you admit that what you're doing is wrong. Interesting, then, that you continue to do it. There is nothing 'wrong' with what the music industry has been doing. How can you claim that the music industry has 'shafted' you when you were the one who walked into the record shop and opened your wallet? If you don't think music is worth the price the record companies are charging for it, don't buy it. It won't be the end of your life just because you can't listen to a particular CD.
Right...so theft is now the fault of the victim? I'm not denying that the record companies should change the way they do business, but that is for them to decide, not you or me. The point here is that the record companies haven't changed the way they do business, so it's still theft!
Why isn't it a like for like comparison? A company sells a product which you desire. You seem to think it's legitimate to steal it if an opportunity is made available.
Mugging old ladies is infinitely easier than mugging professional boxers...Tough break, but that's capitalism for you.
It is not our decision how to run record companies. You seem to have misunderstood my point. I also note that you conveniently ended the quotation there to avoid having to answer my question.
How does that legitimise stealing their product? If you don't like the way a company operates, the response of the market should be to stop doing business with that company. That does not make it acceptable to acquire their product by illegal means.
Did you read the correction at the top of the article? The RIAA were not trying to prosecute someone for ripping CDs for his own personal use, they were trying to prosecute him because he was sharing them on a P2P network!
Did anyone actually read the article? The RIAA are not trying to stop people ripping their CDs for their own personal use!
When you buy a CD, you buy the CD and the rights to listen to the music contained thereon. You do not buy the rights to copy or distribute said music. The copyright holder alone (ie the performers or record label) gets to decide how their music is distributed.
True. I have a desire to own a Ferrari...do I have the right to 'indulge it freely', should an 'opportunity' be created?
That's not our decision, The record companies don't have to do anything. Why do you think you have the right to steal from companies just because they don't do things the way you want?
I am aware of that, but if you read what I posted, the article makes it very clear that music companies are not attempting to prosecute people who do this.
Hankstar is, of course, correct in his assertion that the music labels have missed out on massive profits from early adoption of DRM-free downloads. However, that's entirely their own choice and it is their right to run their business as they see fit. Just because people don't agree with the way record companies run their businesses doesn't mean they have the right to steal music.
It seems you all missed the correction at the top of the page:
The rest of the article makes it quite clear that the record companies don't care if you make a copy of a CD or rip it to your PC for your own personal use. They only get irritated when people distribute their copyrighted works to others free of charge.
I have no problem with these lawsuits. All the music I have was legally purchased on CD and I've got no time for freeloaders who think they have a right to steal music. I used to be one of those freeloaders, but a few years ago I got rid of all my downloaded music and started buying CDs.
The rest of the article makes it quite clear that the record companies don't care if you make a copy of a CD or rip it to your PC for your own personal use. They only get irritated when people distribute their copyrighted works to others free of charge.
I have no problem with these lawsuits. All the music I have was legally purchased on CD and I've got no time for freeloaders who think they have a right to steal music. I used to be one of those freeloaders, but a few years ago I got rid of all my downloaded music and started buying CDs.
At the moment I'm reading 'We Come Unseen', a history of the Royal Naval submarine service during the Cold War.
Fiction is for sissies
Fiction is for sissies
I've got a memory card reader in my PC so I don't use any special program to import pictures. I avoid installing the software that comes with things like cameras and phones because I don't like clutter on my PC.
For all my photo editing I use the GIMP (www.gimp.org). It doesn't quite have the power of Photoshop but it's free
Batch cropping sounds like an odd thing to do...surely you'd prefer to crop your photos individually so that you control the framing. Do you mean re-sizing?
You mean his one and only race, during which he set 5th fastest lap?
I reckon it will be Raikkonen again this year.
Well, my 400D does this in full-auto mode if it decides it needs flash. I agree it's irritating, but that's the punishment you should expect for using full-auto
I should probably confess at this point that my kit lens was very quickly rejected in favour of the 17-85mm. Looking back through photos taken with the kit lens, it was clearly the idiot behind the viewfinder who was limiting the quality of my shots, not the lens
mcintyrej, you've got some awesome shots there!
I just don't get this. I have large hands (no comments, please
) and I find the 400D fits in my hands just fine. If I had to be really picky about it, I would prefer it to be slightly larger, but there's nothing wrong with it as it is. Oh, and the kit lens isn't that bad. It's obviously cheap, but if you can't take good photos with it then that's not the lens' fault.I agree with Stregone entirely on this one. Almost every adjustment I want to make can be done with the thumb and forefinger of my right hand while my left hand simply supports the weight of the camera and lens.
Downforce.
Just out of interest, how effective is the in-body stabilisation? I've often heard that it's not as good as in-lens stabilisation.
Well, if you want to ignore all the advice in this thread then by all means go for it. I assume your uncle also uses Canon equipment? If you're going to expect help from him, it's probably worth going with the same brand as he uses.
Bear in mind that the standard 400D kit doesn't come with a memory card. You'll need to buy a CF card seperately. A case might be also be a good idea unless you want to leave your £400 camera sitting around loose.
The smaller sensors on Canon cameras are APS-H (1.3x) and APS-C (1.6x). The 350D, 400D, 30D, 40D etc... have APS-C sensors (hence they can take the EF-S lenses) while the low-end professional line (the 1D series) has the APS-H. Only the top of the line professional cameras (the 1Ds series) and the 5D have full-frame sensors.
Do you hand-hold or use a tripod? The problem with sticking to higher f-numbers is that the exposure times go up, making camera shake more difficult to avoid. I've got IS on both my main lenses (17-85 and 70-300) and I love it, though it's a bit wasted on the standard zoom until you get past about 60mm.
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