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On February 24 2015 08:38 FiWiFaKi wrote:Show nested quote +On February 24 2015 03:59 farvacola wrote:
You're a mechanical engineering student, surely you know someone at your school better versed in automotive engineering than TL's general population. There is not a simple answer to your question lol. Surprisingly not. I've asked several peers and two professors, and the best answers I got were hypothesizing reasons and radiated shaky confidence at best. I was almost mad that my prof for Advanced Mechanics of Materials had no idea. Seems like such a fundamental concept, but I cannot find very much meaning information easily. Feels like my best bet at this point is to take some Automotive Design textbook from the bookstore, and try and find something. Show nested quote +On February 24 2015 07:23 Acrofales wrote:On February 24 2015 03:49 FiWiFaKi wrote:On February 24 2015 01:39 ThomasjServo wrote:On February 24 2015 01:23 FiWiFaKi wrote:
Why are wheels and tires the size they are on cars (in diameter)?
What factors do you consider, and has there been any research and papers that can be linked on proving why the way it is now is ideal? Depends on the type of vehicle and the surface it is meant to drive on. Take the tire below from a Ferrari 458, this would likely only ever see surface streets in a metro area and or racing tracks. Which means there doesn't need to be as much tire, because the terrain it is designed for isn't terribly demanding. Take this out to the country on low profile and or track tires and the right kind of bumpy, country road, and the thing will crack a rim no problem or generally fuck itself up ![[image loading]](http://i.imgur.com/k212Vnb.jpg) You can compare this to a pick up truck tire, or even that of a mid range sedan and things are more all purpose, hence the name for the tire, "all weather" or what have you. Good at most things, but it is meant for broad strokes. The bigger vehicle you get, into pick ups and I would imagine 18 Wheelers even, is that wider tires equal more grip, more grip plus the way that those vehicles are designed means they can pull, push, tug, and generally fuck up more shit, and make use of all of the power available. I am no car expert, but that is kind of it in a nut shell. As to why precise ratios or diameters are ideal, I have no idea. Thank you for the reply. However, I'm not talking about the thickness of the tire, I understand the thinner the tire, the less dampening ability. I am only talking about the outer diameter of the tire. Like winter tires, summer tires, all season, it doesn't matter, the wheel itself is still roughly the same diameter. I'm not asking about the thickness, or the grooves on the tire either. I understand the concept that a thicker tire means more grip, hence better transfer of torque into linear motion. Simply asking, why is the rim for a car of diameter x. Why aren't the wheels larger, why aren't the wheels the size of skate board wheels (well that one is clear). Just wondering how you'd go about optimizing the wheel size of a car. What I understood when I did a brief research on the internetz because I had to replace my tyres and the factory model was not available (for some reason, my car/model is one of the very few using 195/60 R16 tyres in Brazil). You CAN switch your tyres (I almost bought 205/55 R16) and even the diameter of your rims (take them off and put on others), but car manufacturers (have to) do quite a lot of tests to figure out what combination is best for the car. What exactly they test for I don't know, but stability and durability under varying conditions is an obvious one. Thanks for the info. That's the problem, all the information is too vague. Yeah, the tires must have proper dampening, so be thick or wide enough, material properties of the synthetic rubber must withstand the tire pressure under all dynamic conditions. The internal stress in the rims must withstand any impacts, and so forth. But it's all hypothetical and very vague. You want big wheels to be able to smoothly pass through potholes, and your car will be more efficient in terms of needing smaller gear ratios at a certain rpm. But on the other hand, you have more mass in the car, potentially slower acceleration, more force needs to be applied to turn the wheel, just to name a few. But nothing is quantifiable. Anyway, maybe I shouldn't ask here, but I've had people be really smart in answering my silly quantum mechanics questions that I find interesting but know nothing about.
I think the point you bring up is one reason why more concept vehicles are looking at other options. Basically in the late 40's early 50's Goodrich developed the tubeless tire and since then everything was designed around that basic element.
It's not like people generally get the 'most efficient' option when they purchase vehicles anyway, so it would make sense that a lot of design was focused on what people wanted their tires to look like rather than if they were optimized for their actual driving conditions.
New efficiency demands have brought to the attention of engineers the issues with less than optimal tire/wheel options.
Airless tires and high efficiency expectations will definitely make answering questions about the most efficient options with new wheel and tire combinations a lucrative endeavor.
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On February 24 2015 08:38 FiWiFaKi wrote:Show nested quote +On February 24 2015 03:59 farvacola wrote:
You're a mechanical engineering student, surely you know someone at your school better versed in automotive engineering than TL's general population. There is not a simple answer to your question lol. Surprisingly not. I've asked several peers and two professors, and the best answers I got were hypothesizing reasons and radiated shaky confidence at best. I was almost mad that my prof for Advanced Mechanics of Materials had no idea. Seems like such a fundamental concept, but I cannot find very much meaning information easily.
I can give you some shakily confident reasoning as well... 
A big wheel rolls better than a small one, in the sense that small bumps will break a big wheel less than a small wheel. That would be a reason to make the wheel as big as possible.
A big (thus heavy) wheel has more inertia to accelerate to a certain speed than a car with the same total weight but smaller wheels, as you have less energy stored in the angular momentum of the wheels. Can't imagine that being a huge effect for normal cars, but would be a factor if you tried to build a vehicle where the wheels take up a significant fraction of the mass.
More importantly, large wheels take space, in the sense that they you wouldn't fit in seats above too large back wheels, and the front wheels would go through the top of engine lid which probably isn't a good idea for a number of reasons (vision, stability and shooting pebbles at people comes to mind). I get the impression that most car wheels are essentially as large as they can get without going through the top of the car while still leaving space for suspension.
Actually, after some google image search for "car", I see that many sporty cars have little bumps over the front wheel, allowing for as large wheels as possible (reducing ground friction) without breaking through the top.
Also, if you want to go in rough terrain, it is more important to have big wheel (as you can expect larger scale bumps), which is why city-cars can get away with smaller wheel than a more terrainy car, but I think you already knew that.
edit: and the reason you don't just build high cars is that you get more drag at high speed. Although some certain cultures seem to prefer to do that anyway, and just stuff in stronger engines to make up for the drag... >_>
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When's the next homestory cup?
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What sum do you want, the sum of the numbers 1-52? The sum of 1*50+2*50+...? (Firstly, you don't need Wolfram Alpha for any of those, you can easily calculate them as 53*26(*50) using the gauss summation trick, and pulling a constant out of a sum)
The problem in your code is that you use n(50), which the code interprets in a way that n is a function, not the summation variable, and thus it can't simplyfy anything because you didn't specify the functions 1(x), 2(x)...52(x) beforehand. If you want n*50, simply use the same code and replace n(50) with n*50. If you want the sum of n, replace n(50) with n.
Edit: You could also simply use this page: http://www.wolframalpha.com/input/?i=sum and input the values you like.
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thank you. i was looking for 50+100+150+...+n(50). I changed it from n(50) to n*50 and it gave out the total sum. thanks a lot!
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As i said, you don't actually need any summation functions for that.
Firstly, your sum(n*50)=50*sum(n). Then, using the gaussian summation trick , sum from 1 to k of n = (k+1)*k/2, meaning your total sum equals 50*26*53
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i didnt know about that haha. i was thinking how much i couldve possibly saved up if from week 1 I save 50, then previous + 50 or (50 + 50) on to the next week so forth and so on. so i tried to get a function then summed it up with summation. that gaussian trick is useful tho!
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Are you asking how much you would save if you saved 50 a week?
Or if you save 50 more than the week before.
E.g.
Are you saying:
Week 1 I save 50
Week 2 I also save 50
Week 3 I also save 50
...
Week n I also save 50.
Then it's just 50 * n
If you're saying
Week 1 I save 50.
Week 2 I save 50 MORE than I saved week 1 (so, I save 100 week 2).
Week 3 I save 50 MORE than I saved week 2 (so, I save 150 week 3).
...
Week n I save 50 MORE than I saved week n-1 (so I save 50*n week n).
Then you're saving 50*(n*(n+1)/2) in total.
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i already got the answer a few posts ago i was explaining what i was doing but yeah, your 2nd scenario is correct.
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You did, but I was confused when you gave your example.
At some point you're going to hit a limit on how much a month you will save!
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On February 26 2015 23:48 Gowerly wrote:
You did, but I was confused when you gave your example.
At some point you're going to hit a limit on how much a month you will save!
Well, apparently not before the 50th month, when he will be saving 2500 a month. I wish I had a salary where I could do that!
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On February 26 2015 23:48 Gowerly wrote:
You did, but I was confused when you gave your example.
At some point you're going to hit a limit on how much a month you will save!
it's gonna be relative who knows it might be 50 cents or 50 zimbabwe dollars
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On February 27 2015 07:47 icystorage wrote:Show nested quote +On February 26 2015 23:48 Gowerly wrote:
You did, but I was confused when you gave your example.
At some point you're going to hit a limit on how much a month you will save! it's gonna be relative who know's it might be 50 cents or 50 zimbabwe dollars
Take the cents 
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Mexico2170 Posts
What I wonder is if people are really seeing black and blue/white (instead of the bluish white and gold) or are they just trolling.
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On February 27 2015 13:31 [Phantom] wrote:
What I wonder is if people are really seeing black and blue/white (instead of the bluish white and gold) or are they just trolling.
All I can say is that my GF is a RL troll and I thought she was trolling me saying she saw blue and black until I saw the image of it photoshopped blue now I can't see the white and gold anymore. (Well a little gold at the top but it's blue as blue gets now)
I could see the blue maybe but I thought people who saw black were just being trolls.
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I can't see white at all. I can understand black or gold for the trim, but it's definitely a pastel-ish blue color. See the cow-print shirt in the bottom left for white.
After seeing the picture edited so it's white I can see how people saw it as white, but even in that picture you can tell it's not quite right (blue highlights still exist). Here is the wired article:
http://www.wired.com/2015/02/science-one-agrees-color-dress/
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On February 27 2015 14:13 Najda wrote:I can't see white at all. I can understand black or gold for the trim, but it's definitely a pastel-ish blue color. See the cow-print shirt in the bottom left for white. After seeing the picture edited so it's white I can see how people saw it as white, but even in that picture you can tell it's not quite right (blue highlights still exist). Here is the wired article: http://www.wired.com/2015/02/science-one-agrees-color-dress/
Now I just need to know why it changed, but I can't see what I saw at first anymore?
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It definitely looks white and gold/dark orange to me.
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EPT![[image loading]](http://i.imgur.com/gKs5lbe.jpg)
