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View Full Version : The shakes... a couple of questions


ghtracey
10-29-2007, 01:09 PM
Sorry, another long post, but since this is the only access I have to experience... :)

So, as I posted earlier, maidened the Titan this weekend. Everything went great, came of the ground nicely, actually did a 10 sec stint with no right hand before I chickened out as it was drifting forward slowly. But, I have a few small issues that I wanted to ask you those of you with more experience than me.

1) When I spool down after landing, there is one RPM range where the chopper starts to dance for a couple of seconds... shaking about, the first time it did it I thought it was going to flip over. Is this normal, and if not, any ideas how to get rid of it? It happens when I throttle right to idle (even slowly moving the stick) or hold the stick at about 0 pitch and hit throttle hold, or hold 0 pitch and cut the engine. Something may be out of balance but I don't know what, will do the blades today and check them.

2) I'm still breaking in the motor (3 tanks now) so I'm keeping it pretty rich. I think I am anyhow, after a hover through an entire tank, I can hold my hand on the head for more than 5 seconds, its hot but not burning. I have two issues with tuning though:
- if I land and idle down, the engine will idle fine for 15-20 secs then "burp" and die (quick 1/2 sec rev). I think its too rich on the low end (pinch test takes quite a while to idle it up). That sound like what would happen?
- when I am in a hover there will be an occasional quick RPM increase (again a little 1/2 second jump) that pops the tail right a tad. There's no other effect to this, the heli flys fine and has never stuttered or seemed like it was about to die, I can pull pitch from a hover and put it into a full out climb with no hesitation at all. I'm thinking that this may be a comnbination of two rich on the lowspeed, and perhaps too little headspeed (my pitch meter is in the mail, but visually I am guessing that I am hovering with more than 5 degrees pitch at center stick). I don't know what 1600 or so should sound like (woodies still) but I am going to drop the pitch and up the throttle a tad and see if it smooths out some.

3) Finally, and this one worries me most... when I cut the throttle duing the spool down, I can hear a ticking sort of noise. It almost sounds like the belt slapping inside the tailboom, but the belt tension looks fine (about 1/4" of slack). I don't have the 0499 TR shaft yet, it too is in the mail. Is this a normal thing?


Again, sorry for the long post, trying to be descriptive. Hopefully someone can give me a little bit of help.

Mike SVOR
10-30-2007, 08:05 AM
1) When I spool down after landing, there is one RPM range where the chopper starts to dance for a couple of seconds... shaking about, the first time it did it I thought it was going to flip over. Is this normal, and if not, any ideas how to get rid of it? It happens when I throttle right to idle (even slowly moving the stick) or hold the stick at about 0 pitch and hit throttle hold, or hold 0 pitch and cut the engine. Something may be out of balance but I don't know what, will do the blades today and check them.


Main blades are probably too tight in the grips.

ghtracey
10-30-2007, 11:53 AM
Main blades are probably too tight in the grips.

That's what I love about the internet, on RCU someone thinks they aren't tight enough LOL
I had them set to where I could turn them fairly easily, they would stay up if I tipped the chopper on its side, and fall down if I gave it a whack in that position. So scientific, someday someone should post a torque rating on some of these things. :P

wren1702
10-30-2007, 12:07 PM
One of our 600E's developed the same problem, after half a day of work we swapped out the blades and the problem went away. They were V-Blades and were in balance. They have been sent back!

Strange......

ghtracey
10-30-2007, 12:16 PM
Well, as I mentioned, I did balance the blades last night. 4 TT woodies and do you think I could find 2 that had a CG that was close AND where one was not way heavier than the other? GAH! I should just order some Radix and be done with it. I also removed some of the slack from the TR drive belt, that should get rid of the ticking sound (it did when I spun it up by hand).

I wish I had a temp gun and an optical tach, but they weren't in the budget. I'm sure I'm running way too rich without enough headspeed, but if I'm wrong...

Seeker
10-30-2007, 08:05 PM
On my raptor 50 there are 2 things that cause the wobble and they are related...

First is the main blade tightness... the tighter they are, the higher the headspeed needs to be to stop it... with real tight mains and nylon dampeners with O-rings (harder then the red dampeners) the heli will wobble at anything under 1500 ish.

If I loosen the mains a bit (I normally run them pretty tight) I can run the headspeed at around 1450 with the hard dampeners.

If I change the dampeners back to red or blue ones, I can run the headspeed at 1400 with blades that are not real tight.

I think the normal for the mains would be tight enough to not move when the heli is held sideways and bumped down.

With red or blue dampeners and normal blade tightness and just starting to spool up, many raptors I see (as well as mine) wobble as they spool but it stops once you get over 1000 rpm (ish).

Hope that helps some.

tailStrike
10-30-2007, 11:22 PM
I just picked one of these up for $25 as I am still working on getting my motor tuned properly myself:
https://secure.mcminone.com/content/productimages/s3/58-12050.jpg

https://secure.mcminone.com/product.asp?product_id=58-12050&catalog_name=MCMProducts

poerqwa
10-31-2007, 12:15 PM
You seem to know the pinch test so when you have a gallon or so through the engine use the pinchtest(you pinch, within 5 secs the engine revs up to quit within 3 secs or so, if it dies immediately it is too lean, if it takes ages to rev up it is too rich) to find your idle spot. You apply the temp rule pretty well so also take that into account with further tuning.

tailStrike
10-31-2007, 01:02 PM
Are you supposed to completely pinch off fuel when doing this or just constrict the flow a little?

ghtracey
10-31-2007, 01:03 PM
You completely pinch it off to see how much full has built up in the crankcase waiting to be burned.

tailStrike
10-31-2007, 02:29 PM
Cool, thanks.