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T-REX 500 › Vertical tail bounce
08-12-2010 03:51 AM  8 years agoPost 1
Cavnatkguy

rrNovice

Puyallup, WA

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Alright then I seem to have this problem now after a crash early this week.

In the crash I had to replace the Tail boom, link assembly from rudder servo to rudder and the Main rotor blades. I also had to replace all the cyclic links and then it was off to the field for run ups.

I noted the weird vibration coming from the helicopter and shutdown, so I went and changed the main shaft..no luck then I went to changed the feathering shaft and my buddy who doesn't have a RC helicopter picks up one of blade grips and out falls the thrust bearings LOL. Remember how I said I was at field yep they are lost in that field now. Alright so it off to LHS to get parts.

I came home and finished replacing the shaft with new parts one screw on the shaft was very hard to come out and looked warped when I did get it out. So I was pretty happy and I am sure I fixed it now. Out to the backyard for run ups, no luck again

Looking at this does anyone think it could be the grips or the main head assembly itself because after that I just don't know, thanks for any help on this problem.

Charles

EDIT: I have already changed the dampers.

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08-12-2010 04:18 AM  8 years agoPost 2
Heli 770

rrProfessor

USA.

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Have you checked the tail shaft?

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08-12-2010 04:33 AM  8 years agoPost 3
Cavnatkguy

rrNovice

Puyallup, WA

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When I replaced the tail boom the shaft inside seem fine and everything is moving very smoothly. My Trex 500 is a ESP so it does have the TT. Also the movement is up and down and not a left to right.

Charles

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08-12-2010 11:46 AM  8 years agoPost 4
LeszekJ

rrNovice

Poland

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Blade balancing and tracking done?
Have you checked RPM?

Is it FB or FBL machine?

BTW it's quite easy to check torque shaft. Remove the tail unit, spin autorotation gear and observe tip of the shaft. Then mount tail unit, take TT out from the boom case, spin tail blade holders and observe shaft again.
If it dances like crazy...

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08-12-2010 04:11 PM  8 years agoPost 5
Cavnatkguy

rrNovice

Puyallup, WA

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Yes I always balance and check my blade tracking. I would in the future like to get something to check the head balancing.

This is a FB system am way too new to deal with a FBL yet. As it stands right now after another tear down and inspection it look like one of the blade grips is damage and holding one the blades too tight. Going again to the LHS to get parts today and will update if this fixes the problem.

Thanks for all the input so far!

Here a picture before the crash...

Charles

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08-12-2010 04:30 PM  8 years agoPost 6
dlakeside

rrNovice

Deering NH

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I had the same problem with my mini titan.
I tried every thing and my tail still bounced then a friend said to increase my head speed.
I tried it and the bounce went away. Rock solid now.
I hope this helps you............

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08-12-2010 04:51 PM  8 years agoPost 7
Warrior58

rrNovice

TX

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Tail bounce
And here is a picture after the crash

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08-12-2010 06:00 PM  8 years agoPost 8
LeszekJ

rrNovice

Poland

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Is it the balance or tracking tape near the blade tip?

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08-12-2010 06:01 PM  8 years agoPost 9
Cavnatkguy

rrNovice

Puyallup, WA

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Yeah this what friends are for...lol. I went to get the helicopter and he says WAIT.... I need to get pictures for the accident board team. What would we do without our friends!

Yes the tape is near the tip as I always done.

Charles

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08-12-2010 06:09 PM  8 years agoPost 10
LeszekJ

rrNovice

Poland

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You have to put balance tape in the blade CoG (somewhere in the middle of its length). Except the situation when you want to move CoG.

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08-12-2010 06:24 PM  8 years agoPost 11
Cavnatkguy

rrNovice

Puyallup, WA

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Am sure you have more time in the hobby, but I had to replace blades 3 times (over a 6 month time frame) and have always had the tape at the ends. Each time I done this it has balance and tracked great.

I use a blade balancer on all blades before they are installed. Hope am not coming off pig headed but this bird didnt have this problem till this last crash and am sure it not the blades. Thanks again.

Charles

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08-12-2010 09:36 PM  8 years agoPost 12
kingair

rrKey Veteran

Utah - USA

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Sure sounds like low headspeed and or tight dampers to me.

There is a very fine line between "hobby" and "mental illness."

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08-12-2010 10:18 PM  8 years agoPost 13
LeszekJ

rrNovice

Poland

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Each time I done this it has balance and tracked great
I'm sorry for having bothered you but it's fairly important to have CoGs of blades at the same distance from the main shaft.

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08-13-2010 04:05 AM  8 years agoPost 14
Cavnatkguy

rrNovice

Puyallup, WA

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Ok changed the main grips and the first flight back to normal, change battery and it's came right back.

One I'll listen to HeadSpeed but I dont understand how it can be that unless the motor or esc was damage during the last crash right? No I dont have a tach meter to check it So open to how troubleshoot this without replacements lol.

EDIT: I guess I could try a higher Motor Pinion, am using a 13T right now I guess I could try a 14T or 15T.

And LeszekJ your not bothering me your taking your time to try and help me, Thank you and everyone else on this thread so far.

Charles

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08-14-2010 02:24 AM  8 years agoPost 15
Cavnatkguy

rrNovice

Puyallup, WA

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Well no luck with 14T or 15T seems to be very intermittent at times. Forward flight will be smooth then back to the bobing up and down with tail. Also moved the balance tape to middle of the blade.

I started a total tear down because I really dont know where to go now on the troubleshooting this problem, just hope it doesn't keep me grounded to long.

Charles

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08-14-2010 01:55 PM  8 years agoPost 16
LeszekJ

rrNovice

Poland

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If you don't use a governor try to adjust pitch and/or throttle curve at the point of hovering. Up with throttle, down with pitch. It is very unlikely but could happen - a perfect coincidence for every pinion.
I have had the same problem once - rpm too low, collective pitch too high.
Check also flybar paddles - zero angle on both of them when you send zero pitch from TX.

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08-15-2010 04:16 AM  8 years agoPost 17
Cavnatkguy

rrNovice

Puyallup, WA

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Well just got done with the complete tear down and the only thing that really stands out so far is the main shaft bearing blocks seem to be a tad gritty, and does anyone know how long this part is supposed to last. This helicopter was built six months ago and I've crashed it two times.

But my question for tonight is with the bearing being gritty do you think this way my RPM may be low? It seems to me to long shot, like I said above it's a tad gritty and am sure over time it does get dirt inside the bearing. Do you have to change the bearings often on this part? Thanks for any input on this question.

Charles

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08-15-2010 07:38 PM  8 years agoPost 18
Cavnatkguy

rrNovice

Puyallup, WA

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Well I changed shaft bearings and it up good as new, really couldn't tell the bearings were bad till I took the head off and the weight from it. With just the shaft installed I would spin it and then I could feel the grit. Again thanks to all who posted here and I got some good information out of it and will use it in the future.

I order a BAN-CHECKMASTERII Optical Heli Tach & Multi-Function Tester, this would been great if I would of already had it but next week I will.

Charles

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09-23-2010 05:42 AM  7 years agoPost 19
sprintr

rrNovice

chicago il

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bounce
did you ever get this figured out i just got a year old old 500 and it does the same thing, when i put it together tail bounces up and down not left to right.
if i put it in a hover at low head speed it seems to do it less when the head speed comes up so does the tail.
it gets so bad that i think it would snap off the tail boom if i did not land it. moves up and down about 6in help.

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09-23-2010 06:27 PM  7 years agoPost 20
Romak

rrApprentice

Scotland

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Hi Charles

The trex 500 does not like low headspeeds! I had tail bobbing with mine at 1800 - 1900 rpm. raised the head speed to 2100rpm and tail bobbing gone. Most guys seem to use 2300+rpm depending on the type of flying. Align main shaft bearings do not stand up well in a crash. I keep a couple of spares and if I have a bad landing (LOL), I change the bearings.
I have found that a tachometer is the most useful bit of kit in the tool box. You won't regret your purchase.

cheers

Rod
14sg....... ;-)

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