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Old 08-31-2009, 08:48 PM   #1
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How tight should they Be

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Ok I have looked in the manual and either my eyes are painted on or its not there. How tight should the blades be on the head. Tight enough that they can swing freely or tight enough you have a slight amount of resistance when folding them together. One on my heli is tight and the other is sloppy ,it has plastic pieces where they mount on and yup you guessed it the place where the nut goes is stripped so it can't be tightened,or loosened come to think of it. So do I buy an new complete cnc aluminium head replace those plastic pieces with more plastic or get metal pieces instead of the plastic. My choice is leaning towards a total head as when the motor is run up ( to no real speed) it has a bad vibration,could be blades needing balancing could be the loose blade,could be a bent head. Thinking if I can remove the head pieces that are no good and replace with the two new ones I have I could then see if the head was bent. There is no way of doing this with blades flailing around
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Old 09-01-2009, 07:54 AM   #2
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Re: How tight should they Be

1 They should have a slight amount of resistance 2 replace the blade holder 3 The bad vibration is the blades are not centered yet it happens on spool up at low speeds
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Old 09-01-2009, 09:35 AM   #3
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Re: How tight should they Be

The blades seek and find their own path as they rotate around the head in response to outside forces such as relative wind. This is the reason those rubber dampers are in the center holder. The blades therefore have to be loose at the pivot bolt to allow them to Lead/Lag.

However, you do not want them so loose that on spoolup they flop like dead fish. It will only occur until the RPM increases enough that centrifugal force throws out the blades and keeps them there, but at low speeds this is an invitation to one of them dropping and hitting the boom.

So, as a rule of thumb you should be able to hold the heli over on its side so the blades extend out horizontal. The blades should remain there until the slightest jounce, then break loose and drop.

Another little trick I learned was to lube the blade roots with the same beeswax I use on the main gear, (can be found at a leathersmith or dive shop and goes a very long way to extending the life of your pinion and main gear). If you put a lot of time on your machine you would notice the grips wearing grooves in the root and/or wear out the slot. Either creates slop and reduces control response. Since you are working in fractions of a degree blade pitch change you want the control system free of any play.

NOTE: Even though I use and recommend a teflon based bicycle chain lube on all of the linkages and along the main and tail shafts to allow for free movement, you want to avoid any petroleum based lubricants since they have a tendency to attract and hold abrasive dirt particles. That's why using beeswax on the main gear works so well. It is relatively dry once it seats, (you will get some initial throwoff of excess, but it pretty much falls off) and does not attract dirt or dust.

As part of our training we had to maintain a rotor RPM range when auto rotating. The high end, (107%) was there due to rising mechanical loads. The low end was just as critical since RPM equalled stored energy, but too low and the blades lost that centrifugal force and the tips would start to bend upwards.

Last edited by Cougar429; 09-01-2009 at 09:45 AM.
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Old 09-01-2009, 12:39 PM   #4
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Re: How tight should they Be

While you are replacing the parts it would not hurt to remove the shaft and roll it on a piece of glass. That way if it is not bent it just gives you another place to look if it keeps happening.
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Old 09-01-2009, 12:59 PM   #5
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Re: How tight should they Be

Finally found the link to the guide:
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Old 09-01-2009, 07:20 PM   #6
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Re: How tight should they Be

Your out-of-balance shake/wobble is likely because the blades just haven't been spun up to full speed, and aren't quite centered.

As far as buying aluminum parts...I'll tell you exactly what was told to me. Don't bother. The tolerances are no better, and the plastic/composite parts can be more forgiving in a crash situation, absorbing more of the energy and breaking less overall pieces.

I don't know what you are flying, but on my 90 machine, I crank the hell out of the blade bolts. It takes quite a bit of RPM to get them centered for the first flight of the day, but I don't worry about them collapsing in autos, or folding on themselves when hitting the throttle. More bad can happen when blades are loose than the other way around.

My Vibes both have plastic/composite blade grips and have flown with them in the F3C Worlds that way (not by me).

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