Mechanical Topics

[claire]

Specific question re: mechanical aptitude stuff.

Does anyone remember having a question regarding "overdrive ratio"? if you haven't, then study for it. b/c there is a question on it on one of the versions - i don't know which one.

Anyway - what the hell is it? i just remember having a question that mentioned "overdrive ratio" and it giving the size of two different tires. Either that, or there were two questions - one on overdrive ratio, and one asking a question regarding two different sizes of tires. The point is - do you remember anything about any of this? I have found some stuff online that seem to touch on it but I'm just not sure. Does anyone remember this question? This topic? Did you know the answer? Can you steer me to where I need to go to learn about it? So frustrating!

 

[nugget61]

Overdrive ratios are the ratios of a working gear to a gear being worked on.
Example: In your car just driving around town, you'll notice your tach is higher (angle) than the speedometer. However when you jump onto the interstate and get into your top gear the RPMs will be lower than the speedometer (again, in angle). That's because in the lower gears the engine is having to spin faster (or at the same rate) as the tires. However in the top gear the engine is spinning slower than the tires (which is why you might see an 'overdrive' switch near the shifter in an automatic). So the overdrive ratio in this example is engine crank RPM to tire RPM.

 

[Scoob]

Overdrive is just a gear ratio of <1. Input speed is less than output speed, simply put: the wheels are turning faster than the engine.

 

[Scruff]

Overdrive is just a gear ratio of <1. .

This is why you don't tow with your vehicle in overdrive. It puts massive strain on the engine/torque converter/transmission (a/t apps).

Overdrives in vehicles are beneficial to fuel efficiency and higher top speed, while throttle response is drastically decreased.

Sorry....back to OP's original question

 

[claire]

thanks!

wow, you all, thanks! i did read up on this concept and i learned about the whole fuel efficiency idea. i also found a page that had an equation that you are supposed to use, on this website:

http://tops4less.com/tire-size-gear-ratio.html

which ultimately is: RPM = mph x gear ratio x 336/tire diameter.

i can't help but want to dig in my heels and think, "for goodness sakes, am i really supposed to know this equation for this test?!" but maybe i am. but i do wonder if there are some basic relationships here that, if i know them, that i don't have to do any equations. you know, just based on certain numbers, i could pick a correct answer based on those certain relationships. the whole explanation about the rpms versus tire rotation makes sense. i will have to make sure i understand that concept.

anyway, i'm open to anything you all want to offer. i just wish i could remember more about that question so i could know better what exactly i was supposed to do. b/c i remember reading it and thinking, "there is some kind of math problem i'm supposed to know here, which i don't!" like i said...frustrating.

 

[HeyJoe]

i can't help but want to dig in my heels and think, "for goodness sakes, am i really supposed to know this equation for this test?!" but maybe i am.

IMO, they don't always expect you to know this type stuff off top of your head, but they want to know your aptitude in figuring things out with clues they give and in set period of time.

So Claire, you ready for your obvious callsign of "Planet"?

 

[claire]

hilarious, heyjoe! priceless, truly. and it would be perfect if i was trying to get my wings. but i don't want to have to give a damn about overdrive ratio when trying to become an Intel. officer, that's for sure! ;-)

 

[claire]

here are some websites with helpful mechanical review:

edquest.com (Grade 8 Resources)
sparknotes.com
technologystudent.com
eformulae.com

FYI!

 

[Shpion1]

Claire, good luck in your quest to become an Intel Officer. You may be surprized how handy seemingly "weird" pieces of knowlegde can be as an intel officer. Store "overdrive" someplace in the back of your head and someday it may come in handy. Do that with a broad set of knowledge and you'll be surpized.

Oh, it's also really good info to have when at 3 am some morning, when you're on watch somewhere, bored out of your mind from reading message after message, there may, just may be a game of jeopardy on a TS chat room that doesn't show up when you ask for a directory of chatrooms. And maybe the question is "overdrive". Aww hell, I'm just giving fodder vs Intel Geeks here. In any case, the new "warfare pin" is really awesome. :sleep_125

Good Luck