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  1. RolMec

    Titan sub noise heard on board support ship.

    just a proposal to get some lessons learned from all this: if anyone here plans to do something new&groundbreaking, with passengers on board, then to do it from first principles with the balls to take in a / some devils advocate and to never rename a new and unknown subject like Ti-CF-bonding to...
  2. RolMec

    Heat treatment of 17-4PH separately cast specimens

    in my field all of the specimen are machined, and on a personal note I am not too fond of nono partners who put all the signs pointing their way.
  3. RolMec

    EN 10025-6: S690QL hardness

    Hi, this steel is dedicated to high yield high Charpy applications in welded structures, so hardness is not the standardized feature. What I'd do is to check for a suitable ultimate strength to hardness translation eg from EN ISO 18265 and then to prescribe a corresponding value to the steel...
  4. RolMec

    DIN steel casting test coupon

    For taking out or sizing test coupons of steel castings you may also refer DIN EN 1559-2. However, test coupons need to be agreed with customer, sizing of coupons dependent upon chosen / required final size etc as per previously mentioned standards. In the end, why not directly approach a steel...
  5. RolMec

    DIN steel casting test coupon

    Pls. check acc. to your purpose: references would be DIN EN ISO 6892 and DIN 50125. Roland Heilmann
  6. RolMec

    Hydrogen Embrittelment

    Hello OP, do I get it correct that these bolts have already been torqued into place once, then disassembled, and are now re-used? Pls. check, to what level / standard the original torqueing has been done: to yield (70 or 90 %) or beyond yield. If the second, theses bolts are imo as a rule not...
  7. RolMec

    Positioner for car dumper

    These positioners transmit a heavy horizontal force-couple into the rails, as well as their vertical g-forces. Requirements on positioning accuracy must be met. If drive is a rack & pinion, geared wheels-to-rack position requires sufficient stiffness. Roland Heilmann
  8. RolMec

    Doubt about steel

    Ck75 means it is a cold rolled spring steel. Could you verify your part being made of that material? Else, imo you need to contact a good supplier to make an assessment of your application / the material used. Roland Heilmann
  9. RolMec

    Higher strength materials compatible with hydrogen

    Air/space tech providers of the Shuttle program might be a contact, as liquid H2 was part of the fuel and mass a critical parameter, ie high strength materials had been used. Roland Heilmann
  10. RolMec

    makutea professional welding PM-4000DP

    https://makutea-eg.com Roland Heilmann
  11. RolMec

    Gears load

    3 pts of support: statically determined, you know where you are with the loading from basic mechanical calc. 4+ pts: statically indetermined, its more difficult to calc. or you build larger than strictly necessary. However: it is more stable, as the footprint is larger, there's a longer way for...
  12. RolMec

    Question about Bolt Preload and Proof Load

    Quote < Now let's swap the bolt with much larger one, and preload it exactly to the same amount of case#1 > unquote The larger bolt, not being preloaded to its proper percentage of proof strength, cannot be considered secure in sense of loosening / getting untightened. You'll have to take care...
  13. RolMec

    Is it safe to use cleaner to cleaner to fix bottom ash conveyor carry back ?

    Such scrapers / cleaners are common to fulfill the functionality you require. With ash, wear on belt and scraper blades as well as material buildup / sticking may be issues. Just contact that supplier (its a well respected one in the industry), describe your needs, they'll at least point you...
  14. RolMec

    Liebherr Orion crane failure under 5500t load test

    With such components of existential importance to the system and without redundancy, and especially when lives are at risk: Rules should require a pre-test in a safe working environment, step-by-step increase of load, thorough check for cracks prior and after. But I don't know whether this is...
  15. RolMec

    What should be in a reading list on failures, disasters and their prevention

    Yes, there's much more detailed investigation to be found. Actual distance from rim-pierces-compartment event to derailment was ~6 km, almost 2 minutes time (wiki) And yes, the manager was obliged by regulations to first assess the situation. However, what would one decide to do if a really big...
  16. RolMec

    What should be in a reading list on failures, disasters and their prevention

    NASA does safety messages on various incidents, always with an edge towards everyday's engineering works. This one is special to me: Link as it conveys, how human decisions influence the course of acion. I remember that time, the incredulous facts that the maintenance workers didn't heed the...
  17. RolMec

    Contact ratio between two surfaces

    there's similarity to brake design: brake disc and brake pad. so maybe that's a place to dig. afaik, the thermal conductivity coefficient is established in tests. a FEA thermal modelling might add insight, for a specific case. Roland Heilmann
  18. RolMec

    Looking for ideas for a Mechanical Engineering problem

    well, this is a forum, an OP rolls a dice in some way and let's roll it to the benefit of ... all. there's nothing more far off from engineering like an opinion about an opinion, perhaps its better to stay with the basic facts. i appreciate the question of the OP, to know how to ask a question...
  19. RolMec

    Crack like indication after machining of centrifugal casting

    The cracks are like equally distributed on the inner surface: Any more cracks subsurface further within the body? Are there handling operations involvimg a turning up of the ring, or even a sitting on its outer diameter? You say, you cut rings from cylinders: Then, due to ring form (inner vs...
  20. RolMec

    Ukraine airline crash Tehran

    I do so much grieve all these people, their relatives, friends. My sincerest condolences to them. To find out, what happened and how to prevent something similar: Put faces to Sparwebs (& others) questions, form a team which is not shy to stand up out. Demand competent and involved partners in...

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