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  #1  
Old 02-27-2014, 10:12 AM
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1/4 elliptical springs

I am cutting a lief spring in half to make a 1/4 elliptical spring.
The lief spring is rated @ 1000 lbs. Buy cutting it in half will the 1/4 spring be rated @ 2000 lbs since it is shorter therefor stronger?
I am using two 1/4 elliptical springs at each wheel.The project is a 26 roadster pickup.
Thanks
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Old 02-27-2014, 11:46 AM
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I have no real world knowledge but it seems to me that cutting in half would more than double spring rate because you now have another portion being clamped to frame that before was free to move.

Richard
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Old 02-27-2014, 12:11 PM
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Richard,thanks for the response.
That's the way I think about it but maybe that's to simple.
Fred
.
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Old 02-27-2014, 12:43 PM
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I thought I had saved some spring calculators but seem to have misplaced them. Try google.

Richard
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Old 02-27-2014, 05:30 PM
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Essentially your load pressure is in the same place but the weight is being adsorbed by only half the spring so wouldn't your load capacity be halved instead of doubled? Havent really thought it through ...
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Old 02-27-2014, 05:45 PM
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Youngs Modulus

Found this

http://www.calculatoredge.com/mech/l...gs.htm#quarter

How do I use Youngs Modulus ?

Fred
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Old 02-27-2014, 06:07 PM
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Quote:
Originally Posted by lakesmod View Post
Found this

http://www.calculatoredge.com/mech/l...gs.htm#quarter

How do I use Youngs Modulus ?

Fred
I understood this one.... I think

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Old 02-27-2014, 06:12 PM
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So if I'm understanding this, Young's modulus is psi. In the formula, you would need to convert psi to the metric equivalent.

From wiki...;
Quote:
Young's modulus is the ratio of stress (which has units of pressure) to strain (which is dimensionless), and so Young's modulus has units of pressure. Its SI unit is therefore the pascal (Pa or N/m2 or m−1kgs−2). The practical units used are megapascals (MPa or N/mm2) or gigapascals (GPa or kN/mm2). In United States customary units, it is expressed as pounds (force) per square inch (psi). The abbreviation ksi refers to thousands of psi.
On my Ranger, the front coil spring is ~ 380 psi

Last edited by alwaysFlOoReD; 02-27-2014 at 06:16 PM.
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Old 02-27-2014, 06:16 PM
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I am lost
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Old 02-27-2014, 06:21 PM
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I am too...I think...

I think it may be the terminology being used in the posted formula link. I've always thought of the stiffness of the spring as how far it will deflect, as in 100 lbs will deflect it 1 inch then it has a stiffness of 100 psi. But isn't that torque? So it should be lbs/ft or lbs per inch...ppi.?

Last edited by alwaysFlOoReD; 02-27-2014 at 06:27 PM.
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Old 02-27-2014, 07:14 PM
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Getting back to it's to simple.
Stand up and hold your arm out straight .
Have someone push down
Now hold your elbow to your side and push down,it's a lot harder .

But maybe I just have my head up my butt.

Thanks Fred
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Old 02-27-2014, 07:50 PM
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LOL.... I think some of us should of stayed in school and took Physics .....

Never realized that till this thread.....

..

Interesting I admit...
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  #13  
Old 02-27-2014, 08:33 PM
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I'm fighting a migrane... it's hurting to read much less to think. Post up what you get figured out.
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  #14  
Old 02-27-2014, 09:39 PM
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cutting a coil spring increases the spring rate. that's all I got
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Old 02-27-2014, 09:45 PM
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I think it remains the same if you don't change the number of leaves.

You have half the leverage, but also half the amount of spring to compress. And they cancel each other out.

My brother ran 1/4 elliptic on his FJ40 and the spring rates definitely didn't seem like they doubled.
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Old 02-27-2014, 10:45 PM
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...have fun

http://rspublication.com/ijeted/ijet...uly%2012/4.pdf

^ok, that is a bit of a joke.
In any case there once was a good write up on the web from back in about 2004 or so that covered the whole topic real well, on a jeep board BUT it appears to be gone.
Really 1/4 Elliptic haven't been used much since about then.
To many problems.
Why not a Coil spring?

E
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Last edited by entropy; 02-27-2014 at 11:23 PM.
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Old 02-27-2014, 11:15 PM
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Quote:
Originally Posted by entropy View Post
I knew you would pop up .. LOL... the link seems to not pop up for me.. but I'm sure it's good....

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  #18  
Old 02-28-2014, 10:14 AM
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Here is a basic layout but it is all in metric...
Someday the world will wake up

http://www.tribology-abc.com/calculators/t14_9.htm
&
http://www.engineersedge.com/materia...ing-design.htm

E
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  #19  
Old 02-28-2014, 12:21 PM
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Still confused on the "Youngs Modulus" thing but to muddy the water a bit more.I am using two 1/4 elliptical springs at each wheel.
That must double the weight from the 1000# to 2000# don't ya think?

Fred
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  #20  
Old 02-28-2014, 12:41 PM
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Quote:
Originally Posted by lakesmod View Post
Still confused on the "Youngs Modulus" thing but to muddy the water a bit more.I am using two 1/4 elliptical springs at each wheel.
That must double the weight from the 1000# to 2000# don't ya think?

Fred
You are doing this for the look?
Front or rear? Both?
What you are going to be doing is a sh!tload of experimenting.

At this point I'm thinking you can start using the typical onLine calculator that does not require the YM. Then as you said divide by two to get into the ballpark. Then divide that by two, that should give you a start point BUT I'll put money on the fact that you will be playing with leafs forever...
For instance you will likely want the lower pack to be different then the upper pack as in heavier. You may want the two packs to be oriented differently, such as in the rear the lower pack horizontal and the upper pack pointed down at the lower pack. That thought because when under power the lower pack will be in compression and the upper will be in tension.

Also you can tune the packs by cutting and or tapering the leafs.

E
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