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I know... I corrected this in future videos, but I can't change the location of the subtitles, so this older video will remain like this. I really appreciate the feedback. This is a popular video, so I may redo the video to correct the poor placement of the content.

Thanks ✌️

I understand... I added text that conflicts with the autogenerated subtitles. I won't do this for future videos, but I can't edit previously posted videos. Thanks for taking the time to let me know! I like this feedback, because it helps me improve these videos.

Did you mean "Spicer"? That's a company that makes a lot of these... I see them sold online as "Spicer" joints. Maybe they are like the "Kleenex" of U joints.

thanks for the comment. I did this faceless, no-narration video, of a centrifugal governor... eventually, I'll do another video with some context behind it. This machine was the control system that had a lot to do with the start of the industrial revolution.

nah... that vibrates also :)

U joints have cyclic loading as the output shaft speed varies. I believe they use CV joints where cyclic loading is badness, such as front axels on front-wheel drive cards. Surprisingly, CV joints are pretty inexpensive, even though they are more complex. (although more cost to replace them due to the maintenance hours).

thanks!

yes, I modeled this in Auto desk Fusion

Harry Reasoner wrote, "The thing is, helicopters are different from planes. An airplane by its nature wants to fly, and if not interfered with too strongly by unusual events or by an incompetent pilot, it will fly. A helicopter does not want to fly. It is maintained in the air by a variety of forces and controls working in opposition to each other, and if there is any disturbance in this delicate balance the helicopter stops flying; immediately and disastrously. There is no such thing as a gliding helicopter. This is why being a helicopter pilot is so different from being an airplane pilot, and why in generality, airplane pilots are open, clear-eyed, buoyant extroverts and helicopter pilots are brooding introspective anticipators of trouble. They know if something bad has not happened it is about to"

No

Yes, there is a grease fitting on the cross; that's what I intended. I'm sure there are u joints with sealed bearings, and no grease fittings, but I know for sure that a 1992 Jeep has grease fittings on the cross. I also used parts from McMaster-Carr as a reference for creating the 3d model and all the ones I saw had grease fittings... Although I didn't look at every available part.

@@bzig4929 In my experience, they do have grease fittings.

A joint with a grease zerk fitting is called greasable, while one without the fitting is called sealed. Typically speaking, a greasable joint is more prone to failure and a sealed joint is more favorable. But, that's all dependent on whether or not the end user is good at regular maintenance and also what the application of the joint is. When applying to vehicles, a stock application (no modifications to engine power output or suspension) with regular maintenance will benefit greatly from a greasable joint. A heavily modified vehicle (even with regular maintenance) won't see the same benefit, due to the cross of the joint being hollow and therefore less strong. It's something to consider when selecting the right U joint for the job

Great suggestion!

Glad you liked it!

Thanks again!

Obrigado! And thanks for watching.

It's not that you want the max displacement to occur at a certain point... it's that you need it to do that in order to control the aircraft. To fly forward, you need the tip-path to tilt forward, so that means each rotor blade needs to be at it's highest point of flapping at the six o'clock position (over the tail boom). To achieve this, you have to apply the lift to the blade 90 degrees prior. Maybe a way to think of it is all the blades produce (almost) equal lift. It's not the lift on each individual blade that controls the helicopter, rather it's the overall lift and the tilt of the tip-path-plane that points that lift in the correct direction. I've flown a lot of formation flight in helicopters, and it's cool to see the entire rotor disk respond to control inputs as a single entity. It really doesn't look like individual blades, but rather as a single disk that tilts in the direction the pilot wants the aircraft to go. It may also help to think that the hub isn't capable of reacting moments at the flapping hinge; lift from the individual blades can't apply a moment to the mast to maneuver the aircraft. The overall lift vector, applied through the plane of all the rotor blades, is where the control comes from. The leaf spring looking thing is a tension torsion strap that reacts CF loads. The model of the rotor head came from images of the Boeing CH-46 Sea Knight helicopter and the TT strap when through the lead-lag hinge this way. I reused that 3d model for this animation. Good eye for detail!

it's not really a simulator, although I may refer to it as that in some of these videos. This is done in 3d animation software called Blender. Blender is free and open source... anyone can download it and install it. Although it's animation software, I treat it like a simulation for making these videos. There are almost no animation key frames involved in making these videos. Instead, I program the equations of motion for real-world motion and aerodynamics into a feature of Blender called "drivers." Drivers allow me to interact with my 3d models using Python code and it's much better for this type of video than key framing the motion. Blender has a steep learning curve, but it's an amazing tool. Particularly since it's completely free.

That's the actual RPM of the Sikorsky S92 helicopter. Larger helicopters have slower RPM. The design goal is to keep tip speed below mach 1. So you want rpm*blade radius+max forward flight speed < mach 1.

@@bzig4929 The blade tip air speed below mach 1 thing is very informative, and do need to add the forward flight speed, many thanks!

You are welcome!

Thanks! I appreciate the comment.