Sricketts

I posted a message about 2 weeks ago about a blade pitch problem that my helicopter developed after a small crash. After Replacing the Main blades, the Oval Stabilizer Bar control rods, and the Landing Gear, It appears that every other part is defect free. However the pitch of on of the main blades is totaly incorrect, it is at a negative angle. I have disassembled the rotor head, and removed the spindle, it appears to be fine, not bent or broken; however one of the bearings that is on the side of the defective blade grip (or the blade grip with the negative pitch) is stuck. The bearing still rotates, however the inner ring of the bearing seems to be stuck on the spindle. Could this be the source of the problem? Even if the bearing still rotates? I have also checked the push rods to ensure they are the same length all around, and they appear to be, only one is out by approx 2mm. Is that enuff to cause such a great pitch difference? I'm really at a loss, If someone could help me out, I would be very greatful.

-pkh-

My Feedback: (2)

First, can you explain exactly what your problem is? How are you measuring your blade pitch? Why do you think one blade has the wrong negative pitch?

2mm off on a control link can cause tracking problems, and you might be able to measure a pitch difference. I matched all of my Raptor links exactly (sub-mm, anyway) and didn't have to adjust the tracking at all with the stock TT CF blades. When you adjust your tracking, 1/2 to 1 turn of the link end makes a difference, this adjustment in the mm range...

Charlie

If you have something "stuck" on the spindle, you definitely have something wrong, There shouldn't be anything stuck on the spindle, you have to figure out why it is stuck and fix it.

Is there any way for you to take a picture and post it so we can have a look and try and help you figure out what the problem is?

Sricketts

The Problem is that when the helicopter is set in a neutral state (i.e. The swashplate and stabilzer bar,are level and neutral, and the collective at the lowest position) the rotor blades appear to be at the same pitch. However, When the helicopter is turned on and the collective/throttle increased, it appears that one blade maintains the correct pitch, white the other oneseems to droop to a lower pitch, where at full collective/throttle, the blade is only at about 0 degrees of angle of attack/pitch. However, I have noticed that the entire rotor head rocks side to side along the same axis as the spindle, I actually don't remember if prior to the crash it did this, but like i said in my previous post, nothing else appears to be damaged, perhaps in correctly calibrated - but even so nothing APPEARS to be different that before. I have begun to wonder if this rocking side to side is the problem, as i don't see what contols that.

With regards to the "stuck" bearing on the spindle, It is the outer most bearing on one side that seems to have gotten a layer of some unknown substance between it and the spindle that has cause the inner ring to become fixed to the spindle. However, the bearing still works as i assume it should, the outer part of the bearing still rotates, and from my observation of the other bearing, it appears that this inner part of the bearing would ordinarily remain stationary on the spindle for the bearing to work, so i'm not sure that is the cause of my problem, even thou I have not ruled it out. But I don't know how to unstick the bearing with out possibly damaging it. Any suggestions as to how i might accomplish this are welcome.

I actually haven't had anytime this weekend to investigate further, but I will try to take some pictures and post them. I am still very stuck, still looking foir help/ suggestions/ advice, Very greatful for some help, and thank you for the feedback I have already gotten.

-pkh-

My Feedback: (2)

I'm still not following you at all...

1) you say at min collective it looks OK... this should be a negative pitch, or zero pitch at most.
2) you say it actually decreases pitch as you raise collective.
3) you say it's at zero pitch at full collective.

This doesn't add up... if 1 & 2 are true, then you'd have a very negative pitch at max collective.

Here's what you should do...
1) match all of the ball links for each blade to less than 1mm difference (as closely as you can measure/adjust)
2) make sure that you assembled the head and the ball links properly according to your instructions
3) at min collective, level the swash and flybar, and set the bottom end of your pitch curve to the min pitch you want
4) at max collective, level the swash and flybar, and set the top end of your pitch curve to the max pitch you want
5) hover the heli and check/adjust the tracking of the blades

BarracudaHockey

My Feedback: (11)

You say the feathering shaft isn't bent but how did you tell? Looking won't always show a bend.

Remove a blade.

Put the other blade straight out.

Put a hex driver on the feathering shaft bolt of the blade you removed and turn. If the tip of the other blade goes up and down remove and replace the feathering shaft.

Go and visit http://www.raptortechnique.com and follow his steps for putting the grips and thrust bearings back together.

Sricketts

Firstly thanks again for the help.

Ok one at a time, -pkh-:

Okay, I don't think that it is that the blades are very negative to start, when everything is neutral (swashplate, flybar, and at min. collective) the blades are fine. However when the collective is increase, it appears that in stead of both going to the correct pitch, one goes to maximum pitch while the other seems to do very little, almost as if the entire blade assembly is rotating as opposed to the pitch of the blades. I'm sorry if its hard to understand, its quite difficult to describe in words. So if i don't resolve this soon, i will upload pictures to help dipict this.

barracudahockey:

I have Completely disassembled the rotor head, removed the spindle (what you are refering to as the feathering shaft) and rolled it on the table with the stuck bearing just off the edge, The table is a drafting table and is very smooth, and there is no bend in it. But i have gone to the website you recommended, (thanks, great resource), and i think i may have found a possible problem...i think the rubber dampners that the spindle goes thru aren't lubricated enuff (one was stuck on the spindle when i removed it) If it is that the spindle/feathering shaft is meant to rotate, then this maybe the problem....what do you guys think?

Thanks again

BarracudaHockey

My Feedback: (11)

Dry dampeners cause wobble and other problems so its possible but not the most likely cause but you correctly ruled out the feathering shaft or spindle.

We use Silicon Dielectric grease on the dampeners, well lubed, and available at any auto parts store.