Mounting force & spring constants. Did I get this right?

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 passed 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. Multiplied by 32 threads per inch (a 6-32 bolt), gives 9.5 turns.

Bump.....anybody????

Is 75 pounds actually correct? Seems an aweful lot for this flimsy mobo.

Did I get the calculations right for # of turns? (assuming the compression test is accurate)

dude. Your cpu has an IHS so you aren't going to crush it. The only worry is warping the socket area on the mobo. You're reading way too much into it. Just mount the block, and tighten down the nuts until the springs are compressed an equal amount, and the block is making good contact with the IHS. Start the machine up and go into bios hardware monitoring section. Start turning the nuts 1/2 turn at a time in sequence so that you are tightening them all the same amount. Wait a few seconds after each round and observe the temps. When the temps stop dropping, you have it tight enough .

J.

four mounting holes + IHS = you can't screw it up

crank down the thumbscrews until you can't turn em anymore

I would just crank it down until its firm, like the others have said.


But for the record I checked and your math is good. I think the spec is something like 75-90lbs pressure. Of course this also assumes perfectly linear springs (might change a little over the length, and if your jig was heavy and caused a good amount of initial compression it could be off a bit...)

But still, you did enough thinking, just try it.

Thanks for the replies.

I'm actually not concerned about the chip (IHS, as you said) so much as the mobo/socket. This is my first time with WC, and first time with A64. I"ve never seen anything warp circuit boards like this before. I guess it's just my inexperience. I see the same behavior on my 6800 under the pressure of a Maze4. I've still not tightened everything down as far as indicated. I'll crank up the pressure once temps start becoming an issue (not overclocked yet).