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  1. tlee123

    Click Type Torque

    If you using a toque wrench like the one shown in unclesyd's post, then yes, the torque will change with a different "head" length. In my earlier response I was thinking of this type, a torque limiting screwdriver...
  2. tlee123

    Click Type Torque

    If you haven't changed the adjustment (locked by a setscrew maybe?) then I would think that the torque at which the wrench will "click" will not change. In other words, it's still calibrated. Any way you can do a quick check which of course is not the same as a calibration?
  3. tlee123

    Contact stresses/permanent deformation

    This is similar to Brinell hardness testing or Rockwell B. I would look into the theory behind these tests for guidance on how you can calculate this. Is the ball material tungsten carbide? It probably should be.
  4. tlee123

    Tube Crimping

    Look into how the gas spring manufacturers do it. Suspa, Stabilus, IGS. They're dealing with high (>2kpsi) pressures. I've heard (from a manager, not an engineer) that they crimp right on the end of the tube for some important reason that I can't remember. Tom
  5. tlee123

    Speed Damping Mechanisms?

    sreid, I was surprised to hear you got that much damping from the eddy current device. Thanks for the info. I looked into the magnet track from Parker/Trilogy. It's pretty neat that you can buy long lengths or modular. However, the tracks are expensive. A 48" long pc is $2500-$2700 (210...
  6. tlee123

    Speed Damping Mechanisms?

    First, an eddy current damper (the "magnetic damping") can be useful but is not appropriate here. This frictionless damping will be too low unless you use huge neodymium magnets with thick copper or aluminum plates. Second, a rack driving a rotary damper is a great idea. I think you won't...
  7. tlee123

    Compliant Mechanisms

    It seems like your are looking for snap fit design help. Compliant mechanisms are really another category where the intention of the design is to provide defined repeatable motion with flexures. I own the first edition of this book for snap fits and it is pretty good...
  8. tlee123

    Inserting Steel Allen Socket in Aluminum?

    Drew, How about a Hollow Lock Socket Set Screw? Screw it in to a tapped hole. Secure with Loctite 680. This will give you the socket running all the way through. McMaster-Carr sells them. Tom
  9. tlee123

    Questions regarding adjustment screw method and push nuts

    We use Loctite 680 for production threadlocking with good success. Just because your test showed that a prototype cured without primer doesn't mean you don't need primer. We learned the hard way. We originally tested some sample stainless-to-stainless parts and had good bonding. However in...
  10. tlee123

    Anyone recommend a subscription service for specs?

    rb1957, Yes ASSIST is very good (and free) for MIL specs, but what about ANSI, ASTM or other non-governmental specs? I don't think they're available thru ASSIST. Tom
  11. tlee123

    Trouble with PE exam sample problem

    OK, I agree with you that you weren't wrong. Thanks for the explanation.
  12. tlee123

    Trouble with PE exam sample problem

    I found zekeman’s idea to try to satisfy all the criteria of the question including the 1 second launch time to be very interesting. I think he also got the correct answer of a lever ratio of 260, but there were problems. The differential equation he used is wrong which you can tell by setting...
  13. tlee123

    Trouble with PE exam sample problem

    tg, Spring rate of one spring = 0.5 lb/in * (12 in/ft) = 6 lb/ft. The 0.5 lb/in was from the original post. Also, the total 144 lb/ft in my last post was a typo. It was corrected lower in the analysis as 114 lb/ft.
  14. tlee123

    Trouble with PE exam sample problem

    jistre, Interesting idea to look at an impulse analysis. However, the average force of one spring is 1.25 lb, not 2.5 lb. F(av)=(5*0.5)/2 = 1.25 lb Following your argument with this change, I = F(av) * Delta t = 1.25lbf * 1 sec = 1.25 lbf-sec. The change in velocity of the balloon...
  15. tlee123

    Trouble with PE exam sample problem

    JB, OK, I also stand corrected. I must have never actually read your entire post. I apologize for that.
  16. tlee123

    Trouble with PE exam sample problem

    No, rb1957, the "magical" part was proposed by JamesBarlow and seconded by telecomguy. This is the quote that had me bothered:
  17. tlee123

    Trouble with PE exam sample problem

    Using the energy based solution, the 5 inch acceleration phase takes slightly less than .004 seconds. This is so small compared to the 1 second "launch time." The 1 second "launch time" has to do with the loading of the balloon or releasing of the latch or whatever. And now people are saying...
  18. tlee123

    Flexible drive shafts

    Sam, I have never used flexible drive shafts. However, I remember reading that the torsional stiffness is very good if the shaft is straight or follows a simple arc (constant radius). If the shaft has to form an S-shape, the stiffness suffers. I can get the reference for this if you need it...
  19. tlee123

    Trouble with PE exam sample problem

    JamesBarlow, Just because the acceleration is decreasing, it is still positive thru the entire 5 inch stroke, and therefore the velocity increases throughout that stroke. The indestructible, perfectly rigid water balloon stays in contact with the massless sling.
  20. tlee123

    Inventions You Would Like To See - In Your Lifetime

    How about cars that don't crash (sensors, computer controls)? How about a robot driver so I could work, play, or sleep during the commute?

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