maniago

Quote: nels The prop might be bent but the spinner's look very aerodynamic.

Attached Images I would like to note two things about this picture that PK posted. 1) What Mooney model is this, because I want one! 2) The propeller on her head is bent. Someone must have been pushing and pulling by it (BTW, on reflection, my above comment is entirely out of line and un-professional. I will delete it...later)

Quote: N4352H This can happend applying power too quickly, overspeeding or other....not just a prop strike.

Quote: scottfromiowa Naw, it was the last gasp of this pathetic thread...

Quote: jetdriven Or is this another bullshit wives tale?

Quote: 201er ....I don't have the physics degrees to justify my explanation but to a layman like me it would seem that an essential/functional surface like the prop would be stronger and better supported than a mere aerodynamic/aesthetic item like the cowl?

Ok I concede. I'll tell Sean Tucker that to stop doing that aerial trick where he hangs the airplane stationary on the prop in mid air because the prop can't take all that load. The prop is going to bend in half and he'll die. After all its only 2000lbs the prop is holding up. Silly Sean.

In todays ePilot is a link to Engine and Prop short course, ASI credit. Note that inthe prop section it doesn't say anywhere that you "mustn't" pull on the prop when tugging the plane by hand. Of course lack of mention of something doesn't prove anything, but I just thought I'd note it here for argument sake. It does however have a neat pic of where stresses are on a rotating prop, ie max and min flex stresses... https://www.aopa.org/asf/osc/loginform.cfm?course=engine_prop&project_code=&WT.mc_id=120203epilot&WT.mc_sect=sap

PK, You can usually find anything on You Tube, but I struck out on crankshaft flex, which is odd since its totally cool to see. Probably have to dig into a drag racing forum. However, I then looked for camshaft flex as they do the same thing and got this: Personally I had to stop it as I began to hurl! Your mileage may vary haha

PK, They are not totally different. They are totally related. Static tests and stressors are related to dynamic tests and stressors. When we torque the bearing cap bolts on the crank, the crank is static. But we know that those torque settings will provide the correct amount of "holding power" when the crank is flinging around dynamically. So is the same with the bolts that hold your prop to the flange. A really good slide rule engineer would probably model that moving prop as just a prop that is stationary for a micro second, then is in a new stationary position a micro second later. And the two positions and stressors in those positions are interrelated and can be recreated in a much more static modulus test. Harmonic stresses are much harder to test for, and tend to be empirical (tho a nod to computers must be made these days). That said, pulling on your prop is far more akin to the static testing, for which the entire assembly (ie the whole airplane) has been modeled and tested. But I understand what you are trying to say, and it is important to approach the subject cautiously and "safety-wise", as you are. Some people use caution where its not necessary, but that's a whole lot better than throwing caution to the wind instead. Similarly, I hope you change your oil more often than 50hrs and fly every two weeks to keep the water off your cylinder walls. But its not required! haha M.

But isn't that what we are doing? Trying to dispell wives-tails and rumors? Not long ago, this would have been a heated discussion on "to lean or not to lean", having forgotten what our round motor breathren knew long long ago... But, I don't see personal attacks or name calling. That is clearly beneath us.

Quote: allsmiles I don't think so. I respectfully disagree. You know, what is really disturbing is that we have these engineers on here who should, in theory at least, have a different perspective on things. You, an engineer, can't understand the real physical issues introduced when a localized force is applied on a small area of the blade of a prop at rest? You don't see how this can potentialy "bend" the blade and at the very least throw it out of track? You don't understand that that the prop relies on centrifugal force to stay rigid? Which only happens when it is spinning and not present when not spinning? You as an engineer don't undestand that the phenolic links are not very strong in tension such as when you push on a static prop but extremely strong in compression such as when spinning? You don't see that applying a localized force on a static prop can cause misalignment of the actuating pin mechanism and upset the blades in the hub? Really??!! Let me attempt to enlighten you. A spinning prop is indeed very different than a static one. It relies on centrifugal force and draws its strength from the compression forces of this force. To make the argument that the prop withstands much greater loads in flight than can ever be applied to it by pushing on it is ludicrous. Unless ofcourse you try to push on it in flight and compare the forces. I never handle my airplane by the prop nor will I allow anyone else to do it. But each to his own. And these are my two cents.

Quote: 201er You could. We're having a New Jersey Mooney Pilots Fly in at KVAY tomorrow from 11-2. He's based there and said he'll drop in. He can have the beer but you probably can't

Quote: 201er I didn't realize this would be such a mathemetically sophisticated topic that it would stir such intellectual debate beyond mortal comprehension so now I'm curious if a majority does or does not handle plane by the prop on the ground. I couldn't add a poll to the original topic so I guess just keep discussing it there but find out where we stand on this poll.

Quote: jetdriven Do give us a proper analysis of the physics involved... please!