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Registered Member #56
Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445
I torque wrench wouldn't really help, since it is nearly impossible to calculate the force down from the bolt from how tight it is. You could start by looking at the mechanical advantage of the thread, and look at the force required to tighten vs losen, subtract... But I still don't think you would get any reasonable numbers
Registered Member #69
Joined: Thu Feb 09 2006, 07:42AM
Location:
Posts: 116
Yeah the torque wrench won't do it, I read up on this stuff when I was assembling my SCR stack. You don't get enough precision, too much stick-slip friction variation I think to translate torque into tension accurately. SCR manufacturers specify a fairly narrow pressure range below which you can have hot spots and above which things break. Probably not a big deal if you have cheapo throwaway SCRs.
I would use a compression spring so you can apply the force more accurately. Something like these.
Registered Member #690
Joined: Tue May 08 2007, 03:47AM
Location: New Jersey, USA
Posts: 616
The bolts on the heatsinks that actually did the clamping all had a particularly thick "spring washer" between them, at least I think thats what they are called. Looks like a normal washer, but it is split and the ends are slightly offset each other. Is this what you are referring to?
Registered Member #146
Joined: Sun Feb 12 2006, 04:21AM
Location: Austin Tx
Posts: 1055
Shaun, i was indeed refering to a split washer, but i dont know how accurate they are. What Eric linked to is probably a more proper solution. I had a feeling the actual clamping force would be critical, but i didnt know what sort of tolerance it had.
Registered Member #546
Joined: Fri Feb 23 2007, 11:43PM
Location: Albuquerque, NM
Posts: 239
...I was actually just thinking about the torque wrench so you can get even pressure.... you'd still have to know what the pressure is I guess.
on washers:
a "split" washer, is technically (in the US anyways) a Lock washer. It's a regular washer when a slit in it and opened a bit is indeed a lock washer, and they're to keep the bolt from spinning...yes... they dig into the surface and mar it - so if that matters don't use them.
a Spring washer is a very short spring, that is closed on each end, and is used like a washer, but allows for some vibration dampening, tensioning, or spotting (seeing when a certain predetermined force is reached).
the problem is, a spring washer on an scr stack would have to be rather large to compress properly at the multiple tons of force needed on an SCR, and would take up significant space that would have to be calculated into the length of the bolt... not hard, but bulky.
...
I guess you could always find a used load sensor on ebay and hook it up... shim it do it's the same thickness as the scr, and clamp it in next to the scr, and then ..I dunno... loosen each bolt n turns and remove the load sensor and reset the bolts....? ...
I's just go with the 12 bolts and a torque wrench to make sure each bolt is the same....and give it everything it's got to tighten the stack. If you break a puck...well... you know you went too far?
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OMG TEH 1337 SCR (x4!)
