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06-10-2013 09:58 PM  5 years agoPost 1
arcticflyer

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Prince Albert, Saskatchewan, Canada

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Finally gave up and tore my G20 down today. The mid range vib got so bad I just couldn't spool up through the mid range without just about tearing the heli apart.
As several of you pointed out I am sure now it was caused by the fan!
In the pics you can see where it was coming in contact with the G10 plate and the hall sensor. The fan blades are ground off at a really weird angle.
A couple of you guys mentioned that the key will sometimes not allow the hub to seat properly and I think that was the case.
To be quite frank that plastic fan is a flexible piece of garbage and that is being polite.
Well...again it is sitting on the bench in pieces instead of flying!

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06-10-2013 10:49 PM  5 years agoPost 2
Billme

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MS

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"Finally gave up and tore my G20 down today. The mid range vib got so bad I just couldn't spool up through the mid range without just about tearing the heli apart."

No fan is going to cause this much vibration...Even though the fans are bending down, they are grinding down evenly.. once it has reach it limit, its over with...I"m not defending poor design, I'm letting you know its not that big of deal...Your problem is something else..
It sounds like you are not letting the clutch engage properly, or a big air leak..

How do you have your pitch setup in normal?

Do you run a gov? in normal, is it activated?

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06-11-2013 12:10 AM  5 years agoPost 3
arcticflyer

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Prince Albert, Saskatchewan, Canada

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vibs
Bill - The vibs are present with or without blades and a load. I ran it up Saturday without blades and it was jumping around like a jumping bean (should have taken video). It idles great and top end is great but just before mid stick and mid stick it is horrible.
I am running flybarless with an Ikon unit. The unit has 4 setting for three flight modes with the option to run gov (or not) in each.
I am not running the gov in the normal mode and have it set at 1500 for mode two and three until I finish the last few tanks of break in fuel.
I don't understand your question about engaging the clutch. I set up the unit per Ikon's instructions.
As far as an air leak what check can I run to find the leak and cure it.
It flew so good for the first three flights then everything started going down hill from there.

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06-11-2013 01:30 AM  5 years agoPost 4
Billme

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What gear ratio you running...1500 is WAY to slow for stock ratio , and you say you running this in idle ups? Are you running slower in normal? if that is the case, that could very well be your problem, lugging the engine... The clutch needs more rpm to work correctly, and if you don't have the pitch timed to keep from loading the engine to quickly, it just chatter, or not run smooth...

Now that we know this, I'll bet your not running enough negative pitch while trying to come up to speed and loading to quick...

Its best to run default pitch curves on the low end to make sure you have good engagement, if you are not sure...
Nothing to be a shamed of, most don't talk about this much, and in most case explains why some have problems, and others don't...

I always see someone getting in the air before it comes to operating rpm, and it really hurts the drive system.. On a gasser, its even more important, because each pulse is harder, and easy to let the clutch lose its grip coming up to speed...Here is where people blame the engine, when its the drive train most of the time and it will not stop till its corrected...

I ran into this myself, running the 29 big block, even more powerful pulses. I had always run -6 degs in normal with the gov off...Freaking machine look like it was beating itself to death..when I finally figured out what was going on, I changed to default curves on the bottom, briefly held the head, and throttle up to get the arms hot, then continued coming up to speed for a normal flight.. My minimum on this machine was 1700, so the more powerful may need more time, and rpm to engage properly...

Concerning the way to find leaks, i use whats on hand, from electronic cleaner or engine start fluid..Spray it around the carb insulator and on the Zenoah 20, around the head gasket...

If your machine is hitting hard at idle where you can feel it as you carry it out to fly, it can be leaking ..Once all leaks are sealed, you can tell a difference..
I use Honda #4 gasket maker to seal everything..
The Zenoah 20 needs to be sealed using this on the head gasket as well as the insulator gaskets, especially using the stock paper gaskets..
good luck
Bill

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06-11-2013 02:05 AM  5 years agoPost 5
arcticflyer

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Prince Albert, Saskatchewan, Canada

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Bill - here is a pic of all the gaskets between the engine and the carb. It came from Hanson like this.

My gear ratio is 6.42:1

As far as the head speed in normal mode I had a guy check it with a tach at a hover at 1310.

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06-11-2013 05:31 AM  5 years agoPost 6
Billme

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Why are you running such low rotor speed?

Did someone tell you to run this speed?

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06-11-2013 02:43 PM  5 years agoPost 7
bjacks

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Ft. Worth, Tex.

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Rad 20
Mines not happy at that head speed, I think I'm at 1700 or 1800 in normal. Bobby

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06-11-2013 08:15 PM  5 years agoPost 8
Gearhead

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Vt

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arcticflyer, as Bill said, people have complained about the G20 leaking air around the manifold, click on my photos,, this is what I found on mine, the intake flange on the G20 is not very flat, so the gasket doesn't seal well, the gasket crushes around the bolt holes, this allows air to leak
these photos were taking of a brand new engine, you can see where the paper gasket wasn't sealing

and get the head speed up to 1800 (or more), and lower the pich just as it starts to spool up so the clutch can bite harder

Jim
Buzz Buzz Buzz

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06-11-2013 10:44 PM  5 years agoPost 9
arcticflyer

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Prince Albert, Saskatchewan, Canada

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Just like mine!
Gearhead - Wow mine looks just like that (see pic). What I don't understand is why all the STUFF in between the motor and aluminum block and the block and the carb. Mine has five (2) silver paper stuff and (3) white plastic. Why not just one between the motor and block and one between the block and carb?

I don't know how to do (I am a newb to helis) what you guys are asking but I have some friends who are experienced that I will ask to read this thread and we will make the adjustments on the pitch.

I found a metal fan in the UK and ordered it today...the only other one left is at a shop in Germany.

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06-12-2013 01:52 AM  5 years agoPost 10
Gearhead

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Vt

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yee-up, and look at the upper right of the gasket, it loos like it may have been leaking, but form here I can't be sure LOL

Jim
Buzz Buzz Buzz

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06-12-2013 11:44 AM  5 years agoPost 11
thedrill

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Reno, NV, U.S.A.

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Grind about 2mm of the flat side of the woodruff key,get a new fan put it together. it will work. Mine vibrated like crazy until I ground down the key. It will make the fan off-center and wobbly.

Vote the bastards out!!All of em T-rex 450Pro, T-rex 500 Radical G20

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06-12-2013 04:49 PM  5 years agoPost 12
arcticflyer

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Prince Albert, Saskatchewan, Canada

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thedrill - that is on the to do list! That was mentioned on a couple of other threads I found on Vibs as well.
I think that mine is a combination of all the things you guys have mentioned.
Between sealing up the air leaks, getting the programming (pitch) right and getting that fan on properly (new aluminum fan coming) I should have a much happier heli to fly!
I don't know what NEWBS would do without these forums...give up and sell I guess.

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06-12-2013 11:00 PM  5 years agoPost 13
arcticflyer

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Prince Albert, Saskatchewan, Canada

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First things first.
Today I trued up the surface of the intake port with an aluminum bock and 600 grit paper. This was done very slowly by hand and I believe it will give a much better surface for sealing the gasket.
Next I have to decide what to do about the gaskets. I think the best approach would be to use (1) Teflon gasket between the block and the motor and (1) bwteeen the block and the carb.
Question is do these Teflon gasket need a sealer or do they seal themselves?

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06-13-2013 12:11 AM  5 years agoPost 14
Gearhead

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Vt

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nice job there,
I have some thicker gasket paper so I just made a new thicker gasket,

I don't see why the Teflon gaskets wouldn't seal, but don't blame me if they don't LOL

Jim
Buzz Buzz Buzz

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06-13-2013 07:02 PM  5 years agoPost 15
Gumbomb

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Northwest England, UK

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Arcticflyer,
looking at your photo on the upper right hand side is that a crack from the port to the outside or just a mark? or are my eyes playing tricks on me??

I know a lot of people use Teflon gaskets but for me they give a little too much and extrude resulting in air leaks.
just my observations, good luck

My gasser might not be light but it can fly better than I can fly it

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06-13-2013 08:47 PM  5 years agoPost 16
Gearhead

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Vt

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looking at your photo on the upper right hand side is that a crack from the port to the outside or just a mark? or are my eyes playing tricks on me??
I was wondering the same, but I can't see it in his other photo

Jim
Buzz Buzz Buzz

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06-13-2013 10:21 PM  5 years agoPost 17
arcticflyer

rrNovice

Prince Albert, Saskatchewan, Canada

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Just a mark!
That is a tool mark...went back and checked it again today and took it off.

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06-14-2013 12:58 AM  5 years agoPost 18
Gearhead

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Vt

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Jim
Buzz Buzz Buzz

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06-21-2013 03:17 AM  5 years agoPost 19
arcticflyer

rrNovice

Prince Albert, Saskatchewan, Canada

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New Fan Arrived!
Well the new fan arrived today from Midland Heli's in the UK.
I can now see why Century doesn't carry them anymore...it is a high quality part and I am sure expensive to make.
Got the heli back together and tomorrow will run it up in the garage. Will know as soon as I spool it up without blades whether or not it was worth it...fingers are crossed!

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06-21-2013 08:24 PM  5 years agoPost 20
arcticflyer

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Prince Albert, Saskatchewan, Canada

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What A Difference!
Ran it up today (in the garage, raining ) with the new fan without blades and noticed a considerable difference The engine was surging a bit in the upper end but I am assuming that is because there is no load.
Can't wait to get it in the air...has rained for over a week with a week more to come according to the forcast

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