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Lama 4 swinging like a pendulum at hover?


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prof_fate
Flying Inverted
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Joined: 31 Aug 2010
Posts: 59
Location: beaver, pa

PostPosted: Sat Sep 04, 2010 8:43 am
PostPost subject: Lama 4 swinging like a pendulum at hover?
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I picked up a used and built lama V4 (180 bb motors, all metal heads, extreme blades, adjustable flybar..perhaps more).

The seller seems to have known his stuff, but one never knows for sure.

Anyway I fired it up and two things - one is minor, the nose wants to go left. I adjusted the proportaonal and it's better, but not perfect.

The bigger issue is if I hold it in a hover it will be begin to make a circle, counter clockwise, like a pendulum or rock on a string would. As in a 5 or 6 foot diameter circle. Sometimes I can move the control properly to stop it but it's easier to fly it out and return to a hover where it sites for 15 seconds or so and begins this odd pendulum thing - nose forward just fine (i'm giving a bit right rudder to hold the nose).

Otherwise it seems to fly fine - very responsive!

Any thoughts? I'm thinking a weight trim issue but it seems to hang true from the fly bar.
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prof_fate
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Joined: 31 Aug 2010
Posts: 59
Location: beaver, pa

PostPosted: Sat Sep 04, 2010 11:19 pm
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More trimming and then I took things apart to check...found two things, one I"m correcting the other I have a question on...

The heli was in storage in a box of peanuts for 6 months and the top blades are 'arched' - when laid flat on a table the ends touch and the centers are about 1/8" above the table. At least they're even, right? Laughing

OK, the other issue. On the swash plate there is a pin that sticks out to keep it aligned. It goes into a slot. The slot on this heli is part of the frame and it's been abused for some reason - attacked with a soldering iron. So the slot is way wide and the pin on the swash moves about with every servo action. I suspect this can't be good for stability and control...

I can of course replace the frame (not a cost issue, more of a PITA really). But it would be easier to make a new slotted piece out of styrene and just sister it to the existing part...can it glue it and will CA hold? If it falls off the original one is there so control will remain unless the part falls into moving bits of course.
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prof_fate
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Joined: 31 Aug 2010
Posts: 59
Location: beaver, pa

PostPosted: Mon Sep 06, 2010 3:41 am
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Update:
googling shows that the TBE can be a too-tight top head, so I checked and it is (was) too tight.
The lower was too.
Fixed both (filing the alum holders was required).

The slot may or may not be a problem...can't find a definitive answer. Since it flew 'loose' I'm sticking with that for now. I have an idea on how to fix it but I assume the chassis is Delrin plastic...coolchem and loctite make something that might work...no rave reviews on it so perhaps not.

Gonna go fly it in a bit and re-trim the 4 in 1 (did that on my big lama and made a big difference in hovering). I'll report back the results.
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prof_fate
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Joined: 31 Aug 2010
Posts: 59
Location: beaver, pa

PostPosted: Wed Sep 08, 2010 8:32 pm
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OK, it flies much better with the head rebuilds and some gyro tuning.

Now I have a vibration..never ends, huh? I have a blade balancer on the way but it's coming slowly from the west coast.

I think the flybar is OK balance wise - how does one balance that anyway? I"ve tried using the rotorhead has the pivot but I"m not happy with the results - seems inconclusive.
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platinum
Extreme 3D
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Joined: 31 May 2011
Posts: 272
Location: Bangkok Thailand

PostPosted: Tue Jun 14, 2011 12:22 pm
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Hi prof_fate,
How about your V4 now?. I'm interested in your information. I also renovated my old bird so far. Now it's my favorite one.
Thanks for sharing very useful information.

platinum
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/Gaol : relaxed flying with the least fixing. Very Happy
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