T-Rex 450 head vibration

[Rich J]

Had a small bump with my 450, but still managed to bend main shaft! Have replaced blades, flybar, main shaft and checked feathering spindle is true. Balanced new blades so they should be ok. Flybar weights are exactly same distance along each side of the flybar.

However, when I spool up the heli, there seems to be more vibration in the head than before. As you increase the speed, the vibration decreases, but it does seem to bounce the helis around quite a bit on spool up.

Can anyone shed any light on this?

Thanks

Rich

[heliward0]

are the blades too tight??

[JeromeF]

Perhaps replace the feathering shaft too.

[Rich J]

Have replaced feathering shaft and problem still exists.

Does anyone have any other ideas? What amount of vibration are others getting on spool up?

Thanks

[Tim Procter]

Dampers could well be shot mate, Replace and surround the whole dampers with silicon grease and try again.

If they are dry this could cause the vibration.

I must admit it does seem like your Feathering shaft is bent, You say you have replaced it with a new one.

I have had similar troubles in the past and rolled the suspect shaft down a mirror and seen no bend in the shaft yet if I replace it with a new one the shaking goes.

[JeromeF]

Dampers could well be shot mate, Replace and surround the whole dampers with silicon grease and try again.

Good point. I must admit I over look the dampers and have only recently started to check them and replace if need be.

I doubt it, but perhaps check the main shaft bearings too - they could have taken some damage?

[Rich J]

Still struggling!!!!!

I have replaced the feathering shaft again just to be sure.

I have checked the new main shaft. I spent the extra and got some High Tensile ones. It would appear that neither of them are 100% straight but are very close. The only way I can tell is that I can see a fraction of daylight when running them down a granite surface.

I have ordered some standard ones to see if this will cure the problem, but I just wondered if anyone else has had problems with HT ones.

Thanks

Rich

[Tim Procter]

Doesnt sound good if you can see any light at with the new shafts Rich..

Check everything is running true and free from any binding.

Fit new dampers and smother them in silicon grease (if you already havent)

Check your main blades have no cracks or dents from the crash and are correctly balanced

Is it the head thats shaking or a tail wag, Be sure.

Lower the gain on your gyro and try that.

Various things to try and eliminate the shake you mention mate.

[Blackrat]

bluetack two stanley blades onto the table with the sharp side up and roll the shaft on that ..

use a hard block of wood, or a mallet if you got and give the shaft a good wack to get it 100% straight

[Rich J]

bluetack two stanley blades onto the table with the sharp side up and roll the shaft on that ..

use a hard block of wood, or a mallet if you got and give the shaft a good wack to get it 100% straight

You're kidding aren't you! I'd rather just go and buy a new pack for £6.00.

[Tim Procter]

bluetack two stanley blades onto the table with the sharp side up and roll the shaft on that ..

use a hard block of wood, or a mallet if you got and give the shaft a good wack to get it 100% straight

Absolute rubbish..

You're kidding aren't you! I'd rather just go and buy a new pack for £6.00.

Quite correct too Rich.

[Rich J]

Ok, so far have replaced.....
Blades - now have Radix carbons (balanced out of box)
Main spindle and bearings
Flybar
Feathering shaft
Dampers

Have cheched blade grips and they don't look bent
Have cheched head and nothing is loose.

However, the vibration is still there. It is when I spool up the heli. At full headspeed it does seem to disappear, but it makes the heli bounce around at about half speed.

Anyone have another suggestion?

Thanks

Rich

[robgt]

There's definitely a difference between the heli wobbling through spoolup and a vibration once it's up to speed.
It sounds to me like you're just seeing spool up wobble - but maybe not?
Can you video it and host online somewhere so we can take a look?
If the main blades are too tight in the blade grips, this can cause a head wobble until there is enough centrifugal force to throw them out straight (fighting the friction in the blade grips).

Just thinking out loud really - these things can be very frustrating! It might be something, or it might be nothing? A vid would potentially help.

Cheers,
Rob

[chipbury]

I had a hard arrival with my 450SE and thought i hadn't damaged anything. The next time i flew the vibration was very bad so i went down the same route you have in replacing all parts. In the end the aluminium headblock was slightly out and nothing else had been damaged! It cost £20+ for a spare so i didn't really want to buy one unless i was absolutely sure as you can imagine but solved all problems.

[Rich J]

Thanks chipbury

Going to give that one a try. It must be about the only thing left that will cause this problem. Let's hope this is the fix, otherwise I'm stumped!!!

Rich