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  • Users: LL631
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  1. LL631

    Hall Speed Sensor

    Do speed + direction sensors for back-biased / gear-tooth applications, such as Honeywell SNG-Q Series, use two separate hall IC's? I cannot find any single hall IC's for back-biased applications which provide speed + direction detection with quadrature output, other than the Allegro ATS605...
  2. LL631

    What system could replace a spring?

    Take a look at Compliant Mechanisms, this is essentially what GSTP has suggested : https://www.youtube.com/watch?v=97t7Xj_iBv0. You could combine parts 1,2 & 3 into a single molded component saving costs and will get bonus points from your school for being innovative.
  3. LL631

    Die Cast Overmolding

    7,000 - 10,000 rpm. The only reason for choosing high strength steels is they are the only options I can get from 3D printing suppliers, I guess there isn't much of a market for spending £000's to manufacture cheap low strength steel. We plan to sinter the production version in a low carbon...
  4. LL631

    Die Cast Overmolding

    Unfortunately an all steel rotor is not an option as it's used within an EM brake where it tends to be pulled to the magnet causing heat and wear issues - the relatively small amount of steel in the rim and it's shielded location make it less of a problem. There is also the bother of...
  5. LL631

    Die Cast Overmolding

    Thanks for the replies, I'll contact some suppliers to see what they think.
  6. LL631

    Die Cast Overmolding

    It doesn't have to be a rim but it will be 48/64 tooth so individual pieces will be impracticable and give bad tolerances. I had considered a rim with internal teeth which would be overmolded, the outer rim would then be machined away leaving the teeth inside, but I still have to figure out how...
  7. LL631

    Adding an attachment point to a plastic material

    If the problem is just the cover bowing then a simple fix could be to make something like part 21 to apply more even pressure between the bolts. Two lengths of flat bar with holes either end that attach to the outside of the cover with the bolts would do.
  8. LL631

    Die Cast Overmolding

    Sorry trueblood I missed your reply. The idea of overmold casting was to eliminate additional production steps to keep costs down, but I think your right that the shrinkage is not going to work in this application. I hadn't thought of welding the rim I'll take a look at that. Cheers
  9. LL631

    Die Cast Overmolding

    Is die cast overmolding possible? specifically, die casting aluminium to overmold a steel part? A quick scan of google suggests not, possibly due to the high shrinkage rate of aluminium? We have a die cast aluminium rotor that we would like to incorporate a steel rim into to act as a target...
  10. LL631

    Shaft Clamp Torque Capacity

    Yes, in reality this will play a role but for simplification it is assumed they are the same, the equation already uses friction in 2 places so is probably only good for ballpark work anyway. In reality the clamp ID is typically 0.005" larger than the shaft OD to ensure a fit. The clamp is...
  11. LL631

    Shaft Clamp Torque Capacity

    Was out by a factor of 2 but I understand my mistake now, 2 screws does not create twice the clamping pressure. In practice the 2-screw split design can give more clamping pressure but only due to the fact that less force is going into bending the clamp.
  12. LL631

    Shaft Clamp Torque Capacity

    Is this derivation correct for the torque capacity of a 2-piece shaft collar clamp? The axial force formula is from Shigleys for a 1-piece clamp, but the derivation is not given.
  13. LL631

    Phenolic Molding Problems

    Sorry the 180s cure is referring to the time in mold, their usual procedure would then be to post-cure in a graduated oven cycle for 10 hours. Delamination due to steam pressure looks very plausible, thanks for pointing this out. I think the material is pre-reacting during pre-heating, they...
  14. LL631

    Phenolic Molding Problems

    I'm working with a supplier to produce a compression molded phenolic resin based friction rotor. They had some problems with the first trial; the part has splits (mostly at tool mating line) and the flash had a strange sponge/honeycomb structure. We have no experience in molding so are looking...
  15. LL631

    Interference Fit Splined Hub Stress Questions

    I am looking into the design of interference fit splined hubs i.e. a plain bore hub with external male spline, in particular how to design for stresses in relatively small / thin walled designs. I posted something similar a while back but I haven't manage to get to the bottom of it. My question...
  16. LL631

    Post Drivers - Effects of Air Pressure, Mass and Springs on Impact

    Assuming a perfect system (no losses, friction, 100% transfer of energy etc.), no damping effect from the cylinder as it out-strokes and your spring is set so it has 0 tension at the point of impact you can equate the total energy in each system. For the first system (E1) energy is only the...
  17. LL631

    De-magnetization with LC Circuit

    Thank you all for the replies, can't test anything this week but hopefully can get get time next. There seems to be conflict whether this should work or not so I'll provide more detail in the hope to get a better understanding. So, the problem is the magnet will sometimes fail to disengage due...
  18. LL631

    De-magnetization with LC Circuit

    I have a DC electromagnet which has problems with residual magnetism, is it feasible to place a capacitor in parallel with the coil to act as an LC oscillating circuit in order to de-magnetize the magnet when the power is removed? i.e. if I sized the capacitor so that when the supply was removed...
  19. LL631

    Interference Fit Plastic Stress Help?

    Thanks for the reply, I've redone the calculation by hand but can't see where I've gone wrong; for +0.007mm interference & 8mm ID I've calculated: - Pressure = 65.916N/mm2 - Radial Stress = -65.916N/mm2 - Hoop Stress = 95.958N/mm2 - Von Mises Stress = 140.99N/mm2 These results match the...
  20. LL631

    Interference Fit Plastic Stress Help?

    I have a small interference fit hub that I need to find the acceptable range of internal diameters for. I've calculated that for loosest case (+0.007mm) a hub ID range of 8.5mm - 13mm should provide enough torque. However, due to machining tolerances on the shaft and hub the minimum tightest...

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