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  1. Dan Thomas

    Why are alternators so heavy?

    Copper is heavy. There is a bunch of it in the alternator's field in the rotor. Is that starter-generator you are fooling with a permanent-magnet affair? If so often lighter. But the output is regulated via variable resistance or clipping the AC waveform, both wasting some input energy.
  2. Dan Thomas

    Bronze vs. sealed precision bearings for control surface hinges

    Steel on steel is not good. It tends to gall, and is very much aggravated if any grit gets in there. Gippsland Aero's GA-8 airplane had aileron control issues due to a steel control wheel shaft in a steel bushing, requiring an AD to force changes. For most, this involved the substitution of a...
  3. Dan Thomas

    Bronze vs. sealed precision bearings for control surface hinges

    The smaller Cessnas used bronze bushings in the rudder and elevator. They used piano hinges in the ailerons, and unsealed needle bearings in the flap rollers. The bigger Cessnas (180-182-185) used small sealed ball bearings in the tail stuff. The 206 and 210 used small ball bearings in the...
  4. Dan Thomas

    Puzzling out my electrical system

    The starter usually has to be disassembled and the armature turned in a lathe to clean up the commutator. The oxidation got there in the first place due to the arcing of the brushes on the commutator. Spinning the starter won't clean that off. Oil leakage from the engine can get into the...
  5. Dan Thomas

    Puzzling out my electrical system

    That one only measures AC amps. For DC amps you need this one: https://www.harborfreight.com/cm610a-600a-t-rms-acdc-clamp-meter-64015.html The cheaper ones work by picking up the varying AC-generated magnetic field around the wire. The expensive ones have to generate an AC signal that creates...
  6. Dan Thomas

    The Johnson Twin 60

    Imagine trying to land in just about any crosswind.
  7. Dan Thomas

    The Johnson Twin 60

    "Powerplants can be changed while the gas tanks are being filled." Sort of says something about the longevity of the engines. "Change the engines and check the gas."
  8. Dan Thomas

    Auster autocar fitted with hydroski or "pantobase"

    Way back in the 1960s several folks tried water skis on airplanes. I saw a magazine article, with pictures of several different attempts. One was a Bellanca Cruisemaster, I remember. One needed a good beach to build speed on before hitting the water, and for stopping after landing. Risky. I...
  9. Dan Thomas

    Drilling metal tube

    Some one mentioned using the highest drill press speed. NO. Don't do that. Far too much friction is generated, resulting un uncontrollable heating, and heating ruins the step drill's hardness. High speed also results in cuts shallow enough to make the cutter always cutting through work-hardened...
  10. Dan Thomas

    DA11?

    From Riggerrob's post. I think he meant aspect ratio of 5:1. A 5:1 aspect ratio is not a good glider. A Piper TriPacer has that aspect ratio, but has a thicker wing better for low speed flight. It sure isn't known for its glide. The sole example I few wasn't bad, but we were nowhere near gross...
  11. Dan Thomas

    DA11?

    From a 172 POH: 20 miles from 12,000 feet is 8.8:1. Far more than the DA-11's 5:1. A Rogallo hang glider, the old triangular kite, was at about 4:1, a VERY steep descent. Short wings glide more steeply. It's why sailplanes have long wings. My Jodel, at 27 feet, about 164 square feet, and a...
  12. Dan Thomas

    Resurrecting the Dyna-Cam

    I would expect the roller/swashplate interface to be the weak spot. It's a line of contact, totally unlike the wide surface area of a connecting rod bearing on a crank journal. Even a piston's wrist pin has considerable bearing area. And the rollers: they are necessarily small, and on a small...
  13. Dan Thomas

    DA11?

    Yup. Wing loading of nearly 12 pounds per square foot can be deadly on a short span like that. Not for a low-time homebuilder. I just came across this link. Davis built more models than I knew, and I was a DA-2 fan! https://www.angelfire.com/ks2/janowski/other_aircraft/Davis/
  14. Dan Thomas

    Puzzling out my electrical system

    That's what the book said.
  15. Dan Thomas

    Puzzling out my electrical system

    There's your 1.5V drop across the master with the master off. A very tiny draw, as a digital voltmeter would have, will run a few microamps though the voltmeter when you bridge the master contactor, just enough to make it indicate a small voltage. Take the voltmeter leads off the contactor, and...
  16. Dan Thomas

    Rethinking Propellers?

    Billski would have input on that, too. He has a fabulous amount of knowledge about Torsional Vibration. Used to make his living dealing with it. A lighter propeller will alter the resonant range of the engine, gearbox and propeller, and destructive vibrations might show up with propellers...
  17. Dan Thomas

    Rethinking Propellers?

    The only "data" I see there are some impressive static thrust numbers. But one can get those using a prop with very low pitch so that the engine reaches redline in static condition. Just try taking off with that prop; it will stop accelerating the airplane before you get to takeoff speed, and...
  18. Dan Thomas

    Rethinking Propellers?

    You must be young. We old guys got tired of being sucked in long ago. We got smarter and wiser. We want to see certified test results confirming the marketing claims, not a lot of "fluff," as Billski puts it. What I see there is just composite props and blades. Nothing more. Such props have...
  19. Dan Thomas

    Rethinking Propellers?

    No, but they stall. Surely a different phenomenon. Propeller cavitation erodes the prop. Water is incompressible. Air is compressible. They behave differently. In a wind tunnel, using smoke streams to trace the airflow over an airfoil, we can see the air being compressed and decompressed. Its...
  20. Dan Thomas

    Rethinking Propellers?

    I think that the loop props, taken to an aviation level, would experience problems generated by centrifugal force and thrust. The "loop" would want to flatten out as the blade stretched under the usual high centrifugal forces. The blades would want to twist as their offset put the thrust from...
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