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Project 4x4 Commuter Mazda


legoms013

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Also your alternator is borderline over-chargeing, anything over 14.5 or 14.6 is considered over charging and is bad for your battery.
Naw if it was 15 or higher i *might* be concerned. 12.5 means alternator is shot, 12.5-13.5 means it might be working right, and anthing between 13.5 and 15 is perfect. Different vehicles, and temperatures all affect charging voltage at idle. 13.8-14.2 is PERFECT at least for this vehicle.

half price and lasted 3 years thus far... i'm okay with it. :D

hey legoms, how hard is it to tell what height springs will be with certain weights on it? is that something you can explain on here or PM me? or is it to complex to explain it.. several local people have asked about it before and i don't guess we have anyone that knows the math.
It is pretty simple, see if all my school is about to pay off:

The equation for a spring (specifically a linear coil spring) is: F = -kx

This is commonly referred to Hooke's Law.

F is the force (in Newtons, or Pounds: N or Lbs)

K is the spring constant, in Newtons per meter, or Lbs per foot: N/m or Lb/in.

Typically we offroaders refer to a springs K property as the PPI rating of a specific springs. For example, my Skyjacker springs are 415PPI (pounds-per-inch), or more accurately, 415 Lbs/in.

Basically what this means is that in order to compress the spring 1", it takes 415lbs of force to do so (neglecting the 1:1.5 lift ratio of the TTB beams b/c of where the coil sits on the beam in relation to the pivot point and the distance to where the weight is applied at the wheels).

The beauty of the above equation is this. If you know any two of the 3 variables, you can find the missing one. And most of the time you will know the K value, so that means you only need one other property, either the force or the X.

X is the distance the spring has been compressed or stretched, in Meters or Inches. Expressed as Delta X, or the change in spring length between free length and compressed length.

The negative value out front of the K is there to indicate that the spring always WANTS to return to its free length. Compression is positive X values, and extension is negative (for trucks you won't need to know the second statement since we are only interested in finding the compressed length).

So, as an example, using my springs:

I know several things.

The free length of my spring: 21"

The compressed length as it sits in the vehicle at static ride height: 17"

The PPI or K value: 415Lbs/in.

This means I can easily solve and find out how much my truck weighs at each wheel (times two to get total nose weight at front tires).

Original equation:

F = -KX --------> Assume compression is the positive direction, and drop the neg. value out front eliminate places to mess up.

Sub in my known numbers:

F = (415lbs/in)(21in-17in)

F = (415lbs/in)(4in)

F = (1660lbs) <------Notice how the "in" units canceled out (in/in = 1)

That's the force at one coil (if I was SAS)...but since this is TTB we are interested in, it gets even better:

The TTB suspension has (roughly) a 1:1.5 lift ratio, meaning that it takes a stiffer coil on TTB than on a SAS rig to accomplish the same thing. Meaning, if I was SAS and wanted a coil that acted, and road exactly like my current coils do, I would need a linear coil with a rating of around ~280lbs/in...this would guarantee that the ride I perceive sitting in the driver's seat would be exactly the same with both types of suspension.

415lbs/in / 1.5 = 276.67lbs/in just like I said above.

To get the true weight at the wheels (for TTB) you would need to take the 1660lbs calculated from above and divide it by 1.5:

1660lbs / 1.5 = 1106.67 lbs at each wheel. Meaning between both tires, my front end on my truck weighs ~2213 lbs (1106.67 x 2).

Keep this in mind.

Now if I wanted to calculate how much my truck would compress a coil of 190 lbs/in (K value of EB deaver superflex coils) I would do the following for each coil:

True weight at one coil (leverage effect of beams): 1106.67 lbs

1106.67lbs = 190lbs/inX

Now solve for X. Divide both sides by 190lbs/in to isolate the wanted variable to its lonesome.

1106.67lbs / 190lbs/in = X

5.82458in = X <------------Notice the "lbs" units canceled out (lbs/lbs = 1) leaving you with inches, the correct unit for the change in spring length.

So If I were to run the above mention coils, each one is going to sag ~5.8in with the weight of my pickup on them.

For SAS rigs, you neglect the 1:1.5 ratio step. But for TTB rigs you will need to multiply or divide to get certain values.

As you can see, you can solve for whatever you need, as long as you have 2 pieces of the 3 for the puzzle...


How'd I do? Did anybody follow any of that :icon_confused:

Who wants to hear my lecture on triple integrals that calculate electric flux through a three dimensional volume? Or work produced from a steam driven turbine with inlet and outlet parameters? lol good cuz I forgot



And that isn't all of them either :(
 
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88_Eddie

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isnt it amazing how easy it can be to understand something when it's applied to something you actually are interested in?
 

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isnt it amazing how easy it can be to understand something when it's applied to something you actually are interested in?
yea seriously..
its 8am on a thursday and i actually learned something i cared to learn. :icon_rofl: thanks legoms
 

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i was going to buy the same lift kit but i didnt know what they ment when they said i need a lift kit Components. can u shed some light on what that is.
 

legoms013

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i was going to buy the same lift kit but i didnt know what they ment when they said i need a lift kit Components. can u shed some light on what that is.
Not sure what they mean either.

Some common components you want to include when you buy: longer brake lines, pitman arm, shocks ect.

If you are referring to Skyjacker's kit, they come in different stages for different budgets. The more you spend the more complete the kit is.

For a non-linear spring the equation gets more complicated since now as the force varies the compression of the coils is not linear for each 1" traveled, it starts to become less and less as more compression results.

Don't ask me how to calculate those, I'm not sure how to do it (yet) :icon_twisted:
 

prerunnerwannabe

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That is some handy-dandy math right there! Gotta love math. Repped!
 

nooch450

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Im liking the truck!
 

nb11

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+repped indeed. ME, I'm guessing? That's what I am. How far along are you in your degree?


p.s. I like your truck.
 

legoms013

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nb11

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I'm actually going in Mechanical Engineering at USU in the fall:D I'm so excited!!!:icon_bounceblue:
Haha yea just wait. It'll get tough. I'm in my 2nd year, so just getting into engineering-related classes. Calc2 and C++ particularly have been kicking my butt.
 

legoms013

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Its hard....no doubt about that. All of the material is practical though. And the way the world is with computers and programs, once you are out of college you are basically done doing all the really hard math...that is the computer's job. You just have to know conceptually what is going on and how to use the tools at hand.

That being said, I had five semesters of math: Trig, calc 1, calc 2, calc, 3 and diff. equations. I made all C's except in diff. equations in which I got a B+. It was pretty much living hell but with the math out of the way, now the rest is more applied and practical. I am by no means a brainiac...I'd like to think I am more down to earth and sociable than the average engineering major. For that reason though I never excelled in math and had to work my butt off just to pass....glad those days are over and I can enjoy my engineering classes for what they are now. Once the math classes are out of the way that is more than half the battle (at least for ME degrees here at CSUS).

Good luck fellow ME'ers, it is a great degree with lots of opportunity in the job world, and best of all most of it can be applied to our trucks in one way or another! :icon_thumby:
 
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legoms013

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Not much of an update, but at the end of April or early May I'm gonna have a new driveline made (or possibly just my current one balanced, which I doubt).

Might buy this as a fun toy:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=230778383282#ht_500wt_1050

Swap my electronics and motor over from my 2wd, and sell of my 2wd chassis as a beefed up roller with many spare parts to cover the cost of the 4x4...I could potentially upgrade to the 4x4 one for as little as $120-150.

End of May early June I am planning to put an AGR box and an AGR pump as well as new powersteering hoses to completely do away with the 233,000 mile worn out stock stuff that is on there now.
 

88_Eddie

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oh geez, dont start posting pics of an RC car you're playing with. that's just gonna end with me pulling mine back out of the closet and dumping cash into it.....STICK WITH THE 1:1!!!! lol
 

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