• Some users have recently had their accounts hijacked. It seems that the now defunct EVGA forums might have compromised your password there and seems many are using the same PW here. We would suggest you UPDATE YOUR PASSWORD and TURN ON 2FA for your account here to further secure it. None of the compromised accounts had 2FA turned on.
    Once you have enabled 2FA, your account will be updated soon to show a badge, letting other members know that you use 2FA to protect your account. This should be beneficial for everyone that uses FSFT.

Mounting force & spring constants, did I get this right?

O

omaticrail

n00b
Joined
Nov 9, 2005
Messages
7
Here's the situation. I have a Swiftech Storm G4, and an ASRock 939Dual-SATAII motherboard. The two don't quite mix, cuz the mobo doesn't come with backplate spec'd by AMD. That backplate is required for stock mounting of the G4 on a 939 socket.

To remedy the situation, I'm going to remove the stock 939 bracket from the mobo, exposing those 4 mounting holes. I'll then use the Xeon mounting method and hardware supplied by Swiftech (or mostly so). The important part is the 4 black springs provided with the Storm. I believe AMD specifies 75 pounds of mounting force, which seems absurdly high, but I can't argue. I've calculated that I need to compress each of the 4 springs a total of 9.5 turns on a 6-32 bolt. That's 9.5 turns passedt just touching.

Someone please double check my work. Here's how I came up with that:

I created a jig that would allow me to measure the spring compression with a dial caliper while applying a known weight. I started with just the weight of the jig, and recorded spring heights of 0.509 and 0.502 inches. I needed to use 2 springs, side by side, to make it balance. After applying 8 pounds (an unopened gallon of milk), I measured spring height of 0.444 and 0.440 inches. The sum of the two compressions = 0.127 inches; the amount that 1 spring should have compressed if I could have done it with just 1 (this simultaneously averages the values). This gives a spring constant of 63 pounds per (linear) inch, per spring. When multiplied by 4 parallel springs, that gives 252 pounds (rounded) per inch. 75 / 252 = 0.2976. Multipled by 32 threads per inch (a 6-32 bolt), gives 9.5 turns.
 
I'd just put a drop of AS5 in the middle of the heatspreader, apply the waterblock and springs/washers/nuts then tighten them down a bit at a time until the springs are roughly 1/3 compressed, remove the waterblock and look to see how well and evenly the AS5 spreads.

If it's spread evenly and thinly I'd leave it at that, if not repeat but this time try 1/2 compression and re-check.

There's no need to go overboard with the pressure, you just want to apply enough to hold the block firmly and spread the thermal compound as thinly as possible.
 
Oh shit. Wow.

You went through an incredibly amount of work to figure that out.

Me on the other hand, all I do is just rotate till I feel that the block has made sufficient contact plus some with the CPU.
 
hehe....actually it wasn't that much work; just 10 minutes; It's a small price to pay for peace of mind. I just don't want to mess it up. This mobo is really flimsy looking, and these springs are so stiff I can barely compress them between my thumb and forefinger. I cringe when I imagine using the mobo and processor as pressure points to compress 4 of these babies roughly 60%. I still can't believe AMD wants 75 pounds on this thing. That's like supporting the mobo with 4 standoffs at the HSF mounting holes and standing one leg (half my body weight) directly on the proc. That's messed up.

Thanks for the replies.
 
Working through the calculations, I get the same numbers as far as spring compression goes. Have you tried it yet, and does it seem reasonable once you start cranking down on those springs? Like the other guys, I usually just wing it and tighten the hell out of them. My springs are actually completely compressed, but they're pretty weak (easy to compress).
 
zer0signal667 said:
Working through the calculations, I get the same numbers as far as spring compression goes. Have you tried it yet, and does it seem reasonable once you start cranking down on those springs? Like the other guys, I usually just wing it and tighten the hell out of them. My springs are actually completely compressed, but they're pretty weak (easy to compress).
Click to expand...
Unfortunately I have no comparable reference point. I've mounted many heavy HSFs, but this is my first WC system, and my first A64. For the mobo, I stopped after 4 turns (a bit less than half what is indicated). It's getting to the point where I can no longer turn the nuts with my bare fingers. With the IHS in place, the CPU is pretty indestructable. It's the mobo I worry about.

On a related note, my video card (also first-time watercooled) is visibly warped under the pressure of the DangerDen Maze4. Unfortunately the instructions for the Maze4 are incomplete, so it's tough to know exactly what they want in the way of spring compression. One quote says 60% (a common number thrown about), but that quote accompanies a mounting technique that utilizes only 2 of the 4 springs. There is no text to accompany the 4-spring method, but it would seem that half (30%) is appropriate.

I'm going to run some stress/temp tests before tightening any further, then repeat the tests after a couple turns. If I see no significant change, I won't bother going all the way. (what's the point?)
 
You must log in or register to reply here.
Back
Top