Trex 450XL problem

[headspeed]

Need help!

I suddenly realised that the rotor blades holder will hit the flybar control arms when you do an extreme left/right roll and/or forward/backward elevating. It causes the heli to vibrate so much that it can loose the control.

does anyone has this problem and how do you resolve it?

[Tele]

I don't think this situation could ever occur in flight unless you are doing some very hardcore 3d or possibly your head block is too loose.

Personally I would tighten up the head block so to minimise the movement of the main rotor blades. this will give the heli a more "crisp" feel when flying it.

[Super-Hornet]

That is because your cyclic throw is WAY TOO MUCH! Reduce your cyclic (end point) and it should be ok.

SH

[headspeed]

Thanks.

I tried to reduce the EPA of each cyclic - aileron and elevator(to almost <50%). I can't reduce anymore or it will be no cyclic at all. When using the aileron alone or the elevator alone the problem is gone. But when I used both together the swash plate vibrates and seems that the flybar control levers are hitting something(suspect the rotor blade holders).

Any expert in Trex 450XL can help?

[Super-Hornet]

BTW... yours is CDE or HDE? If it is CDE then u SHOULD NOT adjust endpoint. Instead should adjust swash plate AFR instead.

Super-Hornet

[Daniel Wee]

Actually I really can't imagine how the flybar will hit the blade holders at all since they're mounted 90 degrees out of phase from each other. If you base this from visually inspecting a rotating head you might think it could hit but it's an optical illusion. If your T-Rex is correctly set up, there is no way the blade holders will hit any other part on the head while rotating.

If you are feeling that the collective is not smooth at high angles, it is a sign that some of the links are sticky or binding. You need to work on your head links and mixing arms. Also make sure everything, including the swashplate, is as smooth as can be. It only takes one sticky ball-link to make it feel that way at extreme collective.

Daniel

[headspeed]

No, it is not the flybar hitting the blades holders. Is the flybar lever - the one that controls the flybar (for cyclic movement of the heli). When the lever goes up the linkage will hit the blade holder. I'll try to take some pictures. It happens this way - if you hit the control stick of the Tx to forward (for example to make the heli goes forward), in order to do that the flybar will need to be tilted forward by mean of the swashplate tilted forward. when that happens and Tx control stick moves to the extreme, the flybar control lever will move up to tilt the flybar. This is the point where it will hit the blade holders.

[Daniel Wee]

Ahh... I see what you mean. You must be playing with the head unmounted then. When you actually mount it, you'll probably find that you can't get that much elevation out of the servos anyway. Give it a shot, have it mounted up and see if you can get it to tilt that much. Depending on your setup, you may have to reduce your swash mix if it is in fact hitting.

Daniel

[Super-Hornet]

Yup it is the rectangular cage hitting blade grips. Only happen in XL or using rectangular cage. Normally it happen when your cyclic throw is way too much. Remember that Aileron cyclic too much doesn't cost much problem (except the cage hitting blade grips) but it is the Elevator that is more concerning. If u set Elevator too much, if u do flip or tic-toc or up hill when doing stall turn, u might encounter chances of blade hitting tail boom in mid air.

SH

[headspeed]

Super Hornet, u r right! How to resolve it? I have reduced the throw of the elevator and aileron to each less than 50% EPA and the problem is still there.

[Super-Hornet]

Hi HeadSpeed... u didn't mention your XL is CDE or HDE right? What servo u using for the cyclics and which servo horn hole using. Can show some picture of your linkages? Lets start checking with mechanical first before we go to electronics setting.

SH

[headspeed]

It is the HDE type. servo is Hitech HS55. servo horns are from Hitech tha came with the servos.

[headspeed]

1

[Super-Hornet]

Ahh... First time ppl post Acrobat instead hur...Hehe.

OK.... First of all, your cyclic is TOO MUCH. Reduce your cyclic throw. Remember that Paddles is like rotor blades and any aircraft wing. If your angle of attach is more than 20Degree, it actually experiencing turbulance effect. Thus no lift and thus not cyclic control.

Try reduce your cyclic control so that your paddles goes +ve/-ve 20Degree max. To reduce your throw, fix your servo horn first.

I can see that your aileron servo u using like 3rd hole from center. Hitec HS-55 free moving slop is considered quite high and its resolution is not as fine as HS-56. With that, try to use the closest hole to center as possible. Remember that the closer the hole u choose, the more finer the resolution, the higher the torque but the smaller it travel and the slower the overall speed.

Your Elevator looks ok to me.

Your Pitch wise... not properlly align. First picture in 2nd page, your pitch "see saw" is at the minimum throw (or in other words, at max -ve pitch) position BUT your pitch is like in 0 pitch (according to 1st page). This is considered a very common mistake first timer or new comer setting or unless u do it on purpose. By having such setting (your current setting), at full pitch, your blades pitch will be like 20Degree!

In TRex (and also in Raptor), the 0 pitch position should be the see saw is at mid point/position. With that, u can have full +ve swing (Goes up max) and full -ve swing (Goes all the way down). Realign your pitch where at 0 pitch (that is 50% in pitch curve for Futaba), your see saw is at middle. Your pitch servo horn to linkage is at 90Degree position. Then adjust your blades and mixing linkages so u have 0 pitch on your blades.

With the above settings, you then adjust your Elevator and Aileron End Point so that u have your paddles pitch is like 20Degree max or lower. If u do that, your rectangular cage should not hit your blade grips anymore.

SH

[Super-Hornet]

BTW... I forgot to add one thing:

Align Linkages (U know... the 0 shape that plug onto the ball) has a 'A' symbol/logo on it. That 'A' is to indicate that it is actually smaller diameter than the non 'A' side. With that, the 'A' side is always facing away from the ball. That means, u can only do adjustment of 360Degree turning.

Your linkages are mostly wrong! Slotting reverse direction of linkages actually damage. Your linkages will become loose or some free play. Please change it.

SH