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Astar Main Rotor Balancing


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I was tracking a 204 one time...those that have done those know how high those blades climb  from ground to hover...we are talking a lot!!! So they had these mixed up set of blades...pain in the butt...I spent almost all day getting those things to fly somewhat acceptable...then the chief wrench says ...the heXX with it ...he order a new set of blades...5 engineers and 10 hrs of flying later he finally saw the light!!!

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7 hours ago, IFlySometime said:

Thanks for all the info guys. Much appreciated. So this definitely happened, a bit by accident though. The heli had a bit of a hump, we just got our brand new Microvibe and I was more than thrilled to burn that old chadwick....anyway. Only two runs later it's butter smooth, almost scary smooth. Then we descend back to camp and the 3per is there. I ask the pilot, has that always been doing that? Answer was, "I dunno"  

I've check over the usual 3 per culprits, it's been through a 600 and I'm pretty sure the swashplate friction was fine but I may just have another peak at that. If that's fine might just be that it's too smooth it was showing under .2 hover and MCP straight and level was around .1. lt's really nice, other than on descent. The starflex ball bearings were worn and I hoped that new ones would fix the 3per. No luck.

As SuperWrench also mentioned the shocks. I did have those off and did the pull test as best I could, they seemed nice and tight. The leafs are deflected a fair bit and have some on order now. It has a decent wobble on the ground at flight idle. Tail rotor is nice and smooth. It was a windy day and the tail was pointed into the wind at the time, so that might of caused some of the wobble.

The leaf springs have little to no effect on the ground vibrations.  They are there for landing just as the skids first touch the ground.  On the ground they have no effect in my option.  They can be in limits and not even touch the ground with bearpaws on.  As long as they are equal or lower then the bottom of the skid tube they are within limits for delection.  I have seen plenty of shocks feel fine but still need fluid.  If you have the old style pop up the black seal and fill that cavity with hyd fluid, then shack the tail.  It will draw the fluid in, keep filling and shacking the tail till to doesn't take anymore fluid.

Depends of airspeed and rate of descent you will get a natural 3per you can hide.

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With the B3e, it’s impossible to get the 3-rev level low in both hover and full speed because the different RPM. 
 

If 3-rev only in descent, check Windshield screws torque as they always get loose. Loose hammer’s blades attachment screws 1 by 1 by 1/4 turn and retorque to standard torque value.  It can be the frequency adapter bearings, especially if there’s a big play difference between them. Check play on AVA rod lower bearing with a big flat screwdriver between bolt and spring/weigth. I’ve also found a machine that had an excessive swashplate uniball play causing 3-rev.

I assume the suspension bars play has been checked if just out of a 600.

Vibration on ground can be cause by the pilot that don’t put the cyclic stick on the right spot, if not, like the other said, check leaf springs and oleos. Leaf springs attachment screws always comes loose. Check, if equiped, the bear paws, I’ve already found couple of machines « dancing » on excessively loose bear paws. If it’s all good, keep in mind the machine is made to fly, it’s more important to get it smooth in hover, usually, I don’t even check values on ground and in hover in ground effect and go directly out of it. Try to balance as heavy as possible as the 1-rev in flight tend to get worse with coning. 3-rev usually get worse when you go light, lower than 30% fuel. Going lower than .08 will make you feel only the 3-rev and make it inconfortable.

 

hope it can help you!

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The MVA bearing worn can cause all types of weird problems.  Lateral balance is important for a smooth machine.  An increased lateral vibration can actually induce/excite a vertical component.  

Loose equipment, windshields, cowlings, tail components can also amplify the vibrations.

 

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Not sure what they call the 3 very large spherical bearings at the ends of the star in the head but I got a ride in an astar one time with our chief pilot at the time...it didnt take me long to tell him to get us back to the barn before this thing self destructs...never rode in a ship that was that ruff....they pulled the head apart...those 3 big bearings were so loose you could almost pull the inner race through the outer race!

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Hi Guys

I really like to have a look at this forum. The problem analysis from all of you is always very interesting. And thus the conclusions that can be drawn from the normal rotor system.Since I am working on a different rotor system that is surrounded by a sheath current and no more variable pitch adjustment is required, your communications with each other are very helpful. Since a previously defined angle of attack is used that matches the torque curve of the drive unit and the 1 - 2 second delay time is negligible, vibrations and superimpositions will appear very little.

The prerequisite is, of course, an absolutely exact section-by-section measurement of the individual flukes. Hence the application of the overhang minimum weights determined on the asymmetrical rocker.  The fluke is only released for installation in the hub if the smallest individual amount of mass has been removed before dynamic balancing. And so nothing stands in the way of using four or eight flints.

Greetings Peter Türr

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11 hours ago, DGP said:

Not sure what they call the 3 very large spherical bearings at the ends of the star in the head but I got a ride in an astar one time with our chief pilot at the time...it didnt take me long to tell him to get us back to the barn before this thing self destructs...never rode in a ship that was that ruff....they pulled the head apart...those 3 big bearings were so loose you could almost pull the inner race through the outer race!

Yeah I’m not a fan of flying in a rough machine. I changed those bearings as they were super sloppy. Definitely helped a bit but still some 3 per there. Only really when landing. Slow forward speed collective down.

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This means that 1,000 Nm are applied to both hubs. The agility of the control around the longitudinal axis is the same as with the normal rotor.Since there are lamellas in front of the sheath flow inlet, it is obvious to modify one of them in order to influence the negative pressure as a percentage. And so the question of unnecessary pitch is answered. The control pressure can therefore be precisely determined with the asymmetrical suspension. So the selection of Tieblinge and differential crown gears is just an easy task.

Greetings Peter Türr

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10 hours ago, IFlySometime said:

Yeah I’m not a fan of flying in a rough machine. I changed those bearings as they were super sloppy. Definitely helped a bit but still some 3 per there. Only really when landing. Slow forward speed collective down.

I would say you are just noticing ground effect roughness as the air under the ship builds and spills...that is pretty normal in all landings...try hovering out of ground effect for a comparison.

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