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  1. tmoritz

    Generator cleaning

    I am looking for companies who provide generator cleaning services. The lower end turns on one of our pumped-storage units were contaminated by turbine oil mist when our mist extraction fan failed several years back. The oil has since collected brake dust, metals, and some asbestos fibers. We...
  2. tmoritz

    Russian hydro dam failure

    Hydro units of this vintage are generally controlled by a mechanical governor. In our plants the maximum wicket gate speed is ultimately limited by the hydraulic oil flow rate through the main spool valve. But if a hydraulic line between the servos and the governor were to fail then gate...
  3. tmoritz

    Suction line accumulator vs. pump-down w/ hard start kit

    I would like to relocate our residential 3-ton A/C condensor so I can build a patio. I'm planning on running the line set underground in a 4" PVC chase. The underground run will be 15' to 20' long and sloped back towards the evaporator. I'm debating on if I should have the contractor install...
  4. tmoritz

    latest miracle aircraft

    I wonder if you can do something equivelant to autorotate or glide in this thing. I for one would like to have some means of safely landing an aircraft if the engine(s) crap out. Tom Moritz Mechanical Engineer US Bureau of Reclamation
  5. tmoritz

    thrust runner design

    My oversight. I didn't see it was five mils/inch. Tom Moritz Mechanical Engineer US Bureau of Reclamation
  6. tmoritz

    thrust runner design

    Hmm...a 5 mil interference fit would be a loose fit between the thrust collar and shaft on one of our hydro units. That leads me to suspect the scale of ginsoakedboy's thrust bearing is a bit smaller than what I'm used to working with. GSB, can you provide any information on the dimensions of...
  7. tmoritz

    Winglet aerodynamics

    Remember, the winglets are set at an angle to the wing. It's lift vector is more horizontal. You can have a winglet with an angle of attack that will generate a force outward which will counter the vortex generated by the circulation around the wing. An outward force generated above the wing...
  8. tmoritz

    Winglet aerodynamics

    Actually winglets serve many purposes, it extends the effective span of the wing without impacting the physical span of the wing. This means you don't have cut notches in your hanger doors when you buy the extended range 737. They can be pitched slightly outward to reduce both bending moment...
  9. tmoritz

    Winglet aerodynamics

    Your right btrueblood. They probably design multiple winglets so the customer can select the optimum for their flight profiles. I do recall on glider pilot at Harris Hill that had three wing tips, one straight and two winglets. He said something about selecting the tip based on forecast...
  10. tmoritz

    Golf ball dimples for cars

    Everything I said above was tongue-in-cheek. The best way to reduce drag on a vehicle is to reduce your speed. Aerodynamic drag is a function of velocity squared. Reduce your speed from 75mph to 65mph you will reduce aerodynamic drag by about 25%. Jimmy Carter was pretty darn smart when he...
  11. tmoritz

    Winglet aerodynamics

    The winglet angle of attack is a function of the wing tip vorticies. Change the loading on the wing and you change the circulation around the tip of the wing which will change the angle of attack on the winglet. I haven't heard of adding winglets to improve climb rates. This is usually such a...
  12. tmoritz

    Golf ball dimples for cars

    How to dimple your car for aerodynamic efficiency: 1) first spray the surface of your car with blackened oil. This will work better if you have a white car. 2) drive down the highway 3) note the transition area from laminar to turbulent by the change in oil film 4) locate a line about 5-10% of...
  13. tmoritz

    Winglet aerodynamics

    Winglets are designed to be effective for a very narrow range of angles of attack, usually to optimize cruise. Since your angle of attack will be higher for glide and turn you will probably find winglets are detrimental to performance. Tom Moritz Mechanical Engineer US Bureau of Reclamation
  14. tmoritz

    Radial forces due to uneven air gap

    Thank you all for your responses. This is a very interesting discussion. We will be rewinding this unit. It is currently scheduled three to four years out. We have decided not to risk damaging our fragile winding at this time by moving the stator. In the mean time I will be monitoring...
  15. tmoritz

    Radial forces due to uneven air gap

    We can move the stator. It's just there's a camp of experts telling me not to move it. This is a 30 year old winding on a pump-generator. It's past it's prime and a recent PD test is showing weakness. I'm trying to learn all I can about the implications of not moving the stator. Regards...
  16. tmoritz

    Radial forces due to uneven air gap

    edison123 - We took a total of 80 air gap readings, 40 at the top, 40 at the bottom. At each elevation we took 20 readings from a fixed point on the stator and 20 readings from a fixed point on the rotor. The readings from the fixed point on the stator were used to compute the eccentricity and...
  17. tmoritz

    Radial forces due to uneven air gap

    esee135 - The stator frame sits on twelve sole plates with radial dowels. The stator is comprised of three sections bolted together. I am concerned the uneven heating will result in the uneven stator frame expansion. This could cause the stator frame to bind on the radial dowels resulting in...
  18. tmoritz

    Radial forces due to uneven air gap

    Clyde38, The rotor weight is 575,000 lbs as it sits on the pedestal. This is a reversable vertical synchronous machine, 136MW pump, 106MW generator. The eccentricity may seem like a small issue but it is a contributing factor in an extended outage on this unit. In November of 2008 I found...
  19. tmoritz

    Radial forces due to uneven air gap

    esee135, Our objective is to center the stator but keep distortion to a minimum. We do have an epoxy/mica or polyester/mica insulation on these windings so brittleness is an issue and the primary concern of those in the "DON'T MOVE THE STATOR" camp. I'm trying to get my mind around all the...
  20. tmoritz

    Radial forces due to uneven air gap

    Electricpete, Thanks for confirming my suspicion that the radial forces are attractive not repulsive. I can't tell you how many engineers here at USBR believe in the concept of magnetic center. As I indicated in my original e-mail, I think they recall hearing something about axial restoring...

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