EPIC nuts/studs loosening thread (reposting stupid stuff without reading = warning)
08-17-2009, 12:04 PM
#622
Boost Pope
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A cross-post here from the mirror topic at M.net, but did we abandon the belleville washer idea?
Seems that if one can be found that will retain its springiness at the temperatures we are dealing with (and is strong enough that we can apply enough torque to properly seal the turbo-manifold flange without completely flattening the washer) then it ought to solve that bit the the problem, yes?
As an example, these fine folks have spring washers rated for use at up to 700°C. From their own description:
Seems that if one can be found that will retain its springiness at the temperatures we are dealing with (and is strong enough that we can apply enough torque to properly seal the turbo-manifold flange without completely flattening the washer) then it ought to solve that bit the the problem, yes?
As an example, these fine folks have spring washers rated for use at up to 700°C. From their own description:
"Made to Din 6796 these discs are designed to prevent loosening of bolted systems due to vibration or thermal cycling. "
(my emphasis)
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08-17-2009, 12:07 PM
#623
Look, studs are cooler than the flange:
ITT we discuss why my brand new 2871R seized
ITT we discuss why my brand new 2871R seized
There was much rejoicing.... Yay....
A cross-post here from the mirror topic at M.net, but did we abandon the belleville washer idea?
Seems that if one can be found that will retain its springiness at the temperatures we are dealing with (and is strong enough that we can apply enough torque to properly seal the turbo-manifold flange without completely flattening the washer) then it ought to solve that bit the the problem, yes?
As an example, these fine folks have spring washers rated for use at up to 700°C. From their own description:
"Made to Din 6796 these discs are designed to prevent loosening of bolted systems due to vibration or thermal cycling. "
(my emphasis)
Seems that if one can be found that will retain its springiness at the temperatures we are dealing with (and is strong enough that we can apply enough torque to properly seal the turbo-manifold flange without completely flattening the washer) then it ought to solve that bit the the problem, yes?
As an example, these fine folks have spring washers rated for use at up to 700°C. From their own description:
"Made to Din 6796 these discs are designed to prevent loosening of bolted systems due to vibration or thermal cycling. "
(my emphasis)
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08-17-2009, 12:32 PM
#624
I'd say I'd try it, but I'm not running uber lap times. So even if my **** never failed it wouldn't be a good enough test. So far Sav and Hustler are going Tial so the potential pool of candidates has dwindled further. Looks to me like the issue will basically go unsolved.
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08-17-2009, 12:34 PM
#626
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If my through-bolt setup does not work (due to yielded bolts) then I may try Bellevilles next, made from a high temp alloy like A286. I could probably fit them on the manifold side of the flange under the heads of the bolts. No way they will fit on the turbine side.
So far my through-bolt setup is holding just fine at 20 psi boost pressure, but this is just on the street.
So far my through-bolt setup is holding just fine at 20 psi boost pressure, but this is just on the street.
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08-17-2009, 12:46 PM
#627
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In a most-extreme situation, it seems that the bellevilles, torqued to appx 50% yield, plus Travis' bolts (or studs) made from 100% pure ridiculoum, ought to hold fast no matter what you throw at it.
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08-17-2009, 02:53 PM
#628
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Yep, when unobtanium does not quite do it, then ridiculoum is the next step 
Seriously though I tend to agree with you. We'll see. Hopefully what I have now will do it.
Joe, check your PMs by the way
Seriously though I tend to agree with you. We'll see. Hopefully what I have now will do it. Joe, check your PMs by the way
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08-17-2009, 10:58 PM
#630
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17 ft-lbs to bottom an M8 Belleville; maybe back up 10 mils then Resbond to keep it in place. Read my posts:
turbo bolts wont stay tight!! - Page 12 - MX-5 Miata Forum
turbo bolts wont stay tight!! - Page 12 - MX-5 Miata Forum
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08-17-2009, 11:27 PM
#632
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If it takes 17 ft.lbs of an M8 to flatten one, then I guess the question is how many ft.lbs of that same fastener does it actually take to hold a turbo on? Assuming the bolt is prevented from rotating by external means (serrating the edges of the washer, using safety wire, pinning the threads, etc) does it need to be torqued that tightly?
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08-18-2009, 01:34 AM
#633
Truthfully 8-12 ft lbs will do it. The bolt preload must not exceed 10000psi, or it will overwhelm the bolt at load and temperature. You must use a quality stainless fastener, although the spring washer maybe any material that does not harden/weaken significantly with heat cycling.
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08-18-2009, 01:49 AM
#634
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If it takes 17 ft.lbs of an M8 to flatten one, then I guess the question is how many ft.lbs of that same fastener does it actually take to hold a turbo on? Assuming the bolt is prevented from rotating by external means (serrating the edges of the washer, using safety wire, pinning the threads, etc) does it need to be torqued that tightly?
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08-19-2009, 01:47 AM
#635
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As far as I know, nope.
Also, an update on my setup is in order. So basically tracked my car at Horse Thief Mile at Willow Springs on Aug. 2nd. Ran all day, EGTs (in the downpipe) were reading no higher than 1100*F all day (which I assume is 1400-1500*F at the turbo manifold) despite the 95*F ambient temps and hard pulls up and down the tight and steep elevation portions of the track. Since then, RoadsterTuner and I checked all hardware and the turbo brace he made; it's still all tight and snug and no leaks.
Now for the real challenge: Auto Club Speedway this weekend. I'll update afterwards and I'll also be there with Savington to ogle at his V-band setup in-person.
Also, an update on my setup is in order. So basically tracked my car at Horse Thief Mile at Willow Springs on Aug. 2nd. Ran all day, EGTs (in the downpipe) were reading no higher than 1100*F all day (which I assume is 1400-1500*F at the turbo manifold) despite the 95*F ambient temps and hard pulls up and down the tight and steep elevation portions of the track. Since then, RoadsterTuner and I checked all hardware and the turbo brace he made; it's still all tight and snug and no leaks.
Now for the real challenge: Auto Club Speedway this weekend. I'll update afterwards and I'll also be there with Savington to ogle at his V-band setup in-person.
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08-19-2009, 09:54 PM
#638
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Conversely, stacking them in opposite directions will cause each one to deflect by the same amount that a single washer would for a given clamping force (so the total deflection will be doubled) and you will have twice as much capacity to absorb expansion relative to a single washer.
edit: Neo beat me to it.
Agreed however that the correct technique is to set the fastener to a point that the washer is partially compressed, so that you are actually applying some clamping force, yet still have room for expansion. This seems intuitively obvious to me- was there a contrary opinion somewhere that I missed?
I wonder if there is a difference between torquing down the bolt to full flattening and then backing it off to achieve the desired deflection vs. simply torquing it down to achieve the desired deflection without flattening it first?
Reminds me of the procedure for half-masting a flag.
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08-19-2009, 10:03 PM
#639
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dont forget there is also >><<>><< if you want higher force AND deflection.
I had to email mcmaster.com and tell them their technical description was incorrect for alternating washers. ><><><>< is springs in series and will not equal the rate of one washer. I thought they fixed it but it is still wrong. effective rate is k/n where k is rate and n is number of washers.
I had to email mcmaster.com and tell them their technical description was incorrect for alternating washers. ><><><>< is springs in series and will not equal the rate of one washer. I thought they fixed it but it is still wrong. effective rate is k/n where k is rate and n is number of washers.
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08-19-2009, 10:06 PM
#640
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Agreed however that the correct technique is to set the fastener to a point that the washer is partially compressed, so that you are actually applying some clamping force, yet still have room for expansion. This seems intuitively obvious to me- was there a contrary opinion somewhere that I missed?
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