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Hoot, I have a question about your "easy mounting HSF"

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FishDog3

Member
Joined
Jul 3, 2001
I wanted to know how much pressure the springs you put on create. I don't know anything about spring measurements so it would be nice if you could let me know how they gauge them.

I am worried about having a spring that either is too heavy and damages the die or too light and cant press the foam pads on the TB 1.2 down all the way and make contact with the die.

Thanks,

fd
 

cjtune

Member
Joined
Dec 18, 2000
Well, you can do some simple measurements to determine the force per elongation (ie. "stiffness") of a spring. Hang the spring some where, measure its length from a common reference level/point. Hang a known mass on the free end of the spring and measure the change in length by deducting the initial length from the loaded length. Hang another known (different) mass and do the same measurements. Now you have two points of force vs. elongation you can plot on a graph. Draw a straight line through the two line and take any future readings from it. That's it!
Note: Force=mass(kg) * gravitation acceleration (9.81 m/s2). The line should nearly touch the origin (0,0) of the graph but won't due to measurement errors and the self elongation of the spring due to its weight. Caution: try not to stretch a spring beyond 200% of its initial length.
 

cjtune

Member
Joined
Dec 18, 2000
BTW, AMD specifies 12 to 24 pound-force (53 to 106 Newtons) as a proper range of clamping force.

1 N = 1kg * 9.81m/s2
1 lbf = 4.45 N

Same springs (wire gauge, length, material, shape) have same stiffnesses. If you permanently deform a spring by applying too much force, the stiffness characteristic will also be changed forever and don't expect it to be linear anymore.
 

Hoot

Inactive Moderator
Joined
Feb 13, 2001
Location
Twin Cities
I've gotten half a dozen emails asking the same question. The springs I bought exert 18 pounds of force fairly linearly over a one inch travel region. At the hardware store, I bet I tested 20 of them to get the five that were closest to one another on the strain gauge. the clerk kept watching me around the end of the aisle, no doubt afraid I was stealing springs. What a maroon.

Hoot
 

cjtune

Member
Joined
Dec 18, 2000
Remember, guys, you'll need FOUR springs exerting a TOTAL of 12 to 24 pound-force at a particular elongation. To exert 20 lbf on the CPU core, you'll need 4 springs, each contributing a pull of 5 lbf AT THAT ELONGATION. ALL 4 springs MUST exert the SAME force or the HSF might tip to one side!

BTW, nice idea, Hoot!