I'm in ABQ.
I'll be at Taos most of the time this season(its going to dump, damnit), but A-basin is the best thing in the space between Taos and Little Cottonwood Canyon.
It is an engineering competition, so in the competion itself it is understandable that attempts are made to minimize the effects of driving. The rules include a (somewhat halfassed) ringer exclusion to that end.
I know several FSAE teams attend local autocrosses in the US, there have been magazine tests, and some teams go to SCCA nationals. For most teams the money and desire to operate an ongoing program is not available.
If the conveyance in question is a performance automobile or motorcycle, that is quite correct. Not the case in a variety of other realms.
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My personal experience suggests that tread depth is the most important factor with liquid water, in that a full depth crap tire will often perform much better than a great dry/wet tire that is more than a few thousand miles old. With frozen water, good siping and the narrowest practical section width seem to do the trick
No, obviously they aren't.
I'm saying that the biggest difference between drys and wets is the compound. You can cut treads into drys and they will still be awfully slow in the wet.
Ahh, I sort of expected that type of reaction.
Slick tires with fairly round casings that are properly designed for their application will not hydroplane at sane speeds. Adding a tread pattern to these tires (for on road use) will only decrease their performance. This is counterintuitive and hard to fathom for some, though it sounds like many of you have experience with it.
MotoGP (and other racing motorcycles) change tires when it rains because they want a better suited compound, not necessarily because the dry tires hydroplane, although they are definitely seeing rather insane speeds, so I'd guess they might hydroplane as well in standing water. The intricacies of how and why wet compounds differ from dry compounds would make for a nice senior project.
Slick tires with fairly round casings that are properly designed for their application will not hydroplane at sane speeds. Adding a tread pattern to these tires (for on road use) will only decrease their performance. This is counterintuitive and hard to fathom for some, though it sounds like many of you have experience with it.
MotoGP (and other racing motorcycles) change tires when it rains because they want a better suited compound, not necessarily because the dry tires hydroplane, although they are definitely seeing rather insane speeds, so I'd guess they might hydroplane as well in standing water. The intricacies of how and why wet compounds differ from dry compounds would make for a nice senior project.
Yeah, 9-11 second old drag cars aren't uncommon in the US, but 7 second ones with valid registrations are still probably something you can count with fingers.
I've ridden in 10 second cars and can only imagine how sweet it would be to hit the loud pedal in a 7 second car.
I've ridden in 10 second cars and can only imagine how sweet it would be to hit the loud pedal in a 7 second car.
They don't point it out in the vid, but I imagine that it runs those 7.8s on street legal drag radials. I know there are a few drag radial cars in the states running 7's.
Personally I agree with Bob. I'd much rather drive a 14 second car with a thoroughly sorted suspension. Even 14 second cars require a good deal of self restraint to avoid driving at felony speeds.
Personally I agree with Bob. I'd much rather drive a 14 second car with a thoroughly sorted suspension. Even 14 second cars require a good deal of self restraint to avoid driving at felony speeds.
In real life it isn't as simple as LFS. The point at which the tire will have the best (dry) grip is usually achieved by shaving much of the tread off when new, and then heatcycling the tyre X number of times before it ever sees the road.
In general, the less tread depth there is, the greater the dry grip. The problem with this is that most compounds have been seriously damaged by less-than-optimum (and too many) heatcycles by the time the tires get worn that far, not to mention uneven wear. This is why "road" tires used for dry racing should be shaved when new; it actually increases their usable life.
A properly prepared tire with 4/32nds of tread depth will perform better and last longer than the unprepared tire with full depth.
Your knowledge of physics should suggest that the surface area (commonly called "contact patch") should not matter.
Your knowledge of chemistry, that wonderful subset of physics, should provide the reason for greater surface area being generally better. That is "adhesion and cohesion." The interface between the rubber compound of the tread and the road surface is not simple friction. As a result of all this, tires have a non-linear force/grip curve. Increasing the normal force doesn't increase the maximum grip as much as simple physics would suggest.
The fact that a car can benefit from a larger contact patch inspires engineers to fit the widest feasible tires. The side effect of such a large contact patch is a low aquaplaning speed. NASA developed a rule of thumb formula for aquaplaning speed in standing water: 7.5 times the square root of the tire pressure in psi gives onset of aquaplane in knots. This is for an aircraft tire which has a long/narrow contact patch instead of a short/wide one, although I doubt that makes much difference Ultimately, slicks on cars would aquaplane over standing water at around 50mph. Before the tire gets all the way to the dynamic aquaplaning stage, grip will be dramatically reduced at lower speeds through several mechanisms.
As a result, ways must be found to prevent a "wedge" of water from building up under the face of the tire. That is why your vehicle tires have treads. If you look at a long haul truck, you'll notice the common tread pattern is simple circumferential grooving. These truck tires operate at far higher pressures than car tires, and thus can get away with it.
In situations where the largest contact patch isn't the most important factor, tires are shaped in a round fashion with no tread pattern. No road motorcycle or bicycle should have a tread pattern on the tire, if it does it is only for looks and detracts from performance. Airplane tires are similar. Completely "slick" airplane tires stop airplanes hard even in the wet.
Your knowledge of chemistry, that wonderful subset of physics, should provide the reason for greater surface area being generally better. That is "adhesion and cohesion." The interface between the rubber compound of the tread and the road surface is not simple friction. As a result of all this, tires have a non-linear force/grip curve. Increasing the normal force doesn't increase the maximum grip as much as simple physics would suggest.
The fact that a car can benefit from a larger contact patch inspires engineers to fit the widest feasible tires. The side effect of such a large contact patch is a low aquaplaning speed. NASA developed a rule of thumb formula for aquaplaning speed in standing water: 7.5 times the square root of the tire pressure in psi gives onset of aquaplane in knots. This is for an aircraft tire which has a long/narrow contact patch instead of a short/wide one, although I doubt that makes much difference Ultimately, slicks on cars would aquaplane over standing water at around 50mph. Before the tire gets all the way to the dynamic aquaplaning stage, grip will be dramatically reduced at lower speeds through several mechanisms.
As a result, ways must be found to prevent a "wedge" of water from building up under the face of the tire. That is why your vehicle tires have treads. If you look at a long haul truck, you'll notice the common tread pattern is simple circumferential grooving. These truck tires operate at far higher pressures than car tires, and thus can get away with it.
In situations where the largest contact patch isn't the most important factor, tires are shaped in a round fashion with no tread pattern. No road motorcycle or bicycle should have a tread pattern on the tire, if it does it is only for looks and detracts from performance. Airplane tires are similar. Completely "slick" airplane tires stop airplanes hard even in the wet.
No, you are quite correct that the barrier deforms without acting as a spring. The track facing "wall" is four or five steel extrusions welded together vertically and joined at the end of each SAFER section to the next section. In the space behind the steel "wall", there are bundles of foam every so often. The size and shape of the foam bundles can be tuned per application, but more recent SAFER walls claim to have struck a compromise that works well for single-seaters as well as 4000lb stock cars.
The barrier has very little elasticity. It absorbs a tremendous amount of energy as it deforms, but it doesn't "bounce back" per se. It uses the foam in the same sacrificial way a bike helmet does, after it takes a good knock the track crew will quickly replace a section before getting back to racing. Watching NASCAR races it seems that cars are directed back downtrack with less vigor than they were by the original unforgiving concrete walls.
Fair enough. I do think it makes sense to invest in the facility when it benefits all drivers, even if they aren't able to afford the ultimate in driver safety equipment. I agree that the layout shouldn't be dramatically altered, but moving the driver even three or four inches toward the center could have a significant impact (no pun intended) on safety. There are certainly layouts where such a move would not be feasible, and again this seems to support the installation of better barriers/runoff areas.
The crash was so particularly damaging because the car hit the wall so squarely.
ajp, you say there is no need for better side impact protection, but then go on to point out that the crash you witnessed would have been worse were it not on the passenger side.
You cannot make a seat solve a basic physics problem. If the car hits an immovable object squarely on the driver's side, the most important safety criteria by far is how much room there is between the driver and the outermost structure. This is even more critical in steel/aluminum vehicles because of the way they deform in an impact.
You can either redesign the cars with a more central driving position and greater use of composites, or you can do what the oval racing Americans have done and install modern energy absorbing barriers.
Had this gentleman hit a safer barrier, he probably would have walked away without brain injury.
It is my opinion that it is not acceptable for high level motorsports to be carried out on circuits that have needlessly shoddy runoffs and walls. Products like the SAFER barrier aren't that expensive in the context of high level motorsports. I'm not arguing that motorsport should be some risk-free activity, just that its silly not to take advantage of technology to protect drivers when it doesn't adversely effect the racing.
ajp, you say there is no need for better side impact protection, but then go on to point out that the crash you witnessed would have been worse were it not on the passenger side.
You cannot make a seat solve a basic physics problem. If the car hits an immovable object squarely on the driver's side, the most important safety criteria by far is how much room there is between the driver and the outermost structure. This is even more critical in steel/aluminum vehicles because of the way they deform in an impact.
You can either redesign the cars with a more central driving position and greater use of composites, or you can do what the oval racing Americans have done and install modern energy absorbing barriers.
Had this gentleman hit a safer barrier, he probably would have walked away without brain injury.
It is my opinion that it is not acceptable for high level motorsports to be carried out on circuits that have needlessly shoddy runoffs and walls. Products like the SAFER barrier aren't that expensive in the context of high level motorsports. I'm not arguing that motorsport should be some risk-free activity, just that its silly not to take advantage of technology to protect drivers when it doesn't adversely effect the racing.
Last edited by skiingman, .
You should get out more, and/or pick up a history book.
The SRT4 is a mildly amusing Neon. Not something to be particularly awed by.
I was actually looking for that graph to post. Nice work.
NOx includes all of the oxides of nitrogen, some of which do have different deleterious effects than plain N02. Running leaner than stoichiometric creates dramatic (orders of magnitude) increases in NOx emissions.
Running lean does not dramatically increase CO2 emissions as far as I can remember.
Hah. I rarely have more than a pint in a sitting, so high alcohol content beers don't bother me too much.
One of my favorites if I'm restless before dinner is here:
http://www.unibroue.com/products/3pistoles.cfm
I'll have to try that. Not a "micro" brew per se, but do you like any of Magic Hat's beers? They are out of Burlington VT. In a similar vein I enjoy some of the brews from Unibroue up in Quebec, available pretty widely through the US now at good beer stores.
There are a bunch of decent micros in my area of Upstate NY. Good stuff for sure.
Word. I've put about 1500 miles on my commuter bike so far this year. Bike as in one with pedals. My car is certainly not particularly friendly to its envrionment, so I drive it only when I need to. Helps keep me at a reasonable weight, cuts down on costs, and generally makes me feel better. Its nice to spend the money on the autox car instead.
Of course, I suppose over there you don't have the proliferation of regular-debt-ridden middle class people driving 6500lb trucks because they are "cool" or whatever. Jeebus, the smallest cars you can even buy here are still generally 2500lbs or more, most "small" cars here are around 3000lbs these days. Companies like Honda even specifically engineer bigger, fatter versions of their cars solely for our market.
...
You know, it is much easier to find a job when you know how to read and write. And don't whine like a little bitch. There are hundreds of people on this forum posting in a second or third language with far more eloquence than you do in your first.
When I was 12, a US dollar bought considerably more than it does today. I bought myself a $2000 PC after earning money providing on-site tech support for various people who were referred to me. A strong lesson in the power of word of mouth advertising. I saved that money in about a year.
And then we have Americans who do speak English that somehow think our current debt problem is largely due to World War II, which really couldn't be further from the truth. In fact, we made out like bandits on that deal. Not only financially, but technologically as well. I know that most Americans find history intolerably boring, but perhaps you should google "Redstone Rocket" and learn something interesting.
Despite what auto magazines repeat ad nauseum, 50/50 is not the perfect weight distribution. The "perfect" weight distribution very much depends on a bunch of other factors, and indeed a FWD car well setup and designed will always have more than 50 percent of the weight on the front wheels.
At the same time, mid engine RWD vehicles should always have a good bit more than 50% on the rear wheels.
RWD has a lot of important advantages for sure. However, some of those advantages are academic when you have a very sedate power to weight ratio.
Except that you are wrong on some important counts.
On BLGP, for instance, when the longest straight has an entry speed far higher than the speed at which the FWD or RWD slow-cars are traction limited, the FWD car will be faster with all other things equal. It weighs less and has smaller drivetrain losses.
The FWD cars will understeer like pigs if you set them up like some typical crappy American road car. Go ahead and try reducing damping to near the minimum, then reduce the rear spring rate to practically nothing and then triple that figure for the front spring rate. Oh, and either no rear anti roll or very little, but a big fat front anti-roll bar. More rear than front camber. Barely any caster. The list goes on.
Set a car up like that in LFS, and it will understeer like a pig. Set a car up in LFS like you would to run it around a track in real life, and it will be far more balanced.
All of this over 12 pounds?
Robbson, I've earned more than that sitting here reading forums in the time you've taken to write these silly posts.
WTF is anyone feeding this troll for? I got my money's worth from my S1 license in the first night I owned it. I didn't buy it as early as many others did. I could have bought it a single day before S2 was released and not felt even slightly bad about ponying up another 12 pounds.
It costs me more to go to a movie with my girlfriend than it costs to buy a S1 license. If I buy dinner as well, I've then covered the cost of the S1, S2, and S3 licenses.
Get a job pal.
I remember when I used to need to plan ahead to spend 15 dollars on the next chapter in an Apogee game. That was nearly fifteen years ago, and I wasn't quite old enough to mow lawns...
Robbson, I've earned more than that sitting here reading forums in the time you've taken to write these silly posts.
WTF is anyone feeding this troll for? I got my money's worth from my S1 license in the first night I owned it. I didn't buy it as early as many others did. I could have bought it a single day before S2 was released and not felt even slightly bad about ponying up another 12 pounds.
It costs me more to go to a movie with my girlfriend than it costs to buy a S1 license. If I buy dinner as well, I've then covered the cost of the S1, S2, and S3 licenses.
Get a job pal.
I remember when I used to need to plan ahead to spend 15 dollars on the next chapter in an Apogee game. That was nearly fifteen years ago, and I wasn't quite old enough to mow lawns...
Wow.
You are one cheap guy.
I don't even want to think of how you explain other things in life to yourself.
You are one cheap guy.
I don't even want to think of how you explain other things in life to yourself.
LOL I noticed that on a hotlap page, FE Club maybe? Definitely kinda bizarre
Uh, hell no.
X-Plane uses blade element theory. That might be appropriate for car wings, but car wings are in a realm of aerodynamics simply not seen in airplanes, so the model would probably have to be rather impure to be "realistic". At low angles of attack with single element wings theory is very accurate. Modern multi-element car wings operating at the verge of stall are not going to be accurately aerodynamically modeled by any reasonable theory AFAIK.
CFD=not going to happen. Calculation for a single moment with a single set of conditions would take a typical PC minutes to hours, depending on the complexity and amount of iteration. Not only that, CFD over a "low poly model" is far more worthless than table lookups or things like blade element theory.
As to suggestions that the advertising endplates are going to give the car longitudinal stability, consider that any vertical surface forward of the CG does the opposite. The moments are small and the areas fairly small. On the other hand, taking a wing that is on the verge of stalling and yawing it even a couple degrees (like, less than five) away from the flow will dramatically effect its performance. Anyone that has ever kicked a rudder pedal in a Cessna thats about to stall knows this.
Last edited by skiingman, .
When I read that, I just think of all my tax dollars that could have been spent on something useful to real people.
FGED GREDG RDFGDR GSFDG