trex 500 intermittent jerk

[questerng]

Hi,

I've notice a jerk every once in a while..

it happen in the first minute or so..

i did the mod for the ESD for tail and body...

i'm running everything stock

motor + esc stock + 13T

GY401 + 9254 ( i thought this will cause tail heavy but mine has got nose heavy problem.. needed quite a few click to level this out) should i re-adjust my push rod to mechanical trim this so i dont need that much sub-trim...

Align 6S 2500.. this packs weigh about 400+g

it seems like a glitch.. but doesnt look like it.. and it also look like the motor just stop for a split sec..

has anyone got this problem.. advice appreciated..

thanks
quester

[Socal500]

Make sure you gyro is mounted as far back on the boom block as possible.. not near the bearing at teh front of the boom block. If you think the motor is cutting out this is probably not your problem but check it anyway.
http://www.socalsurfs.com/trex500/gyro.jpg


Do not use trim to get your heli to hover level. Move your battery pack up on the tray and shift the some weight back. To check balance, set the heli on hard, flat, level surface. Extend your main blades. Turn the rotor head so the main blades are running the length of the heli . The flybar should be across the heli. Make Karate hands with left and right hand. Stick left hand under flybar on one side and other hand under flybar on the other side. Lift heli up straight by the flybar slowly with the edge of your hands . Watch the skids and see if they lift level or if the front stays down while the back lifts, or vise versa. Adjust your weight accordingly until you can get the skids lifting level. This will give you a good start on your center of gravity.

You dont want to use trim because it will have the opposite effect on the heli inverted.

[c.penhallurick]

I had the tail jerk/kicking, moved the gyro back. Gone. I also added a tiny amount of teflonoil to the bearings(tiny). Hope it works.

[questerng]

hi,

thanks..

I did this lifting of heli to check CG.. it lift with tail heavy.. but when i hover up.. head heavy..

at first i thought its my swash plate not level.. but its not.. I'm at my wits now..

thks for the advice on shifting the GYRO back.. mine is I think too close to the bearing...



Make sure you gyro is mounted as far back on the boom block as possible.. not near the bearing at teh front of the boom block. If you think the motor is cutting out this is probably not your problem but check it anyway.
http://www.socalsurfs.com/trex500/gyro.jpg


Do not use trim to get your heli to hover level. Move your battery pack up on the tray and shift the some weight back. To check balance, set the heli on hard, flat, level surface. Extend your main blades. Turn the rotor head so the main blades are running the length of the heli . The flybar should be across the heli. Make Karate hands with left and right hand. Stick left hand under flybar on one side and other hand under flybar on the other side. Lift heli up straight by the flybar slowly with the edge of your hands . Watch the skids and see if they lift level or if the front stays down while the back lifts, or vise versa. Adjust your weight accordingly until you can get the skids lifting level. This will give you a good start on your center of gravity.

You dont want to use trim because it will have the opposite effect on the heli inverted.

[JCP SR]

Here is an option to move the gyro away from the bearings and I have had no trouble from being close to the servo: rdlohr tray: http://www.helifreak.com/attachment.php?attachmentid=40545&d=1204428783

[psindrup]

If moving the gyro does not solve the problem, try to replace the trust bearings in the tail blade grips with 3x8x4 mm radial bearings. There has been quite a few rapports that this solves the tail jerk problem

Peter

[rick m]

i had the same problem if my headspeeed was set above 2550 i found the fix was to oil up bearings ,ALL BEARINGS,now its as smooth as silk on stock, 13tooth ,100% throttle.love this bird...

[cudaboy_71]

another vote for lubing the tail thrust bearings.

on initial build i didnt check them because the screws were too tight to loosen the grips. however, after the 'jerks' in the first flights, i managed to loosen the grips--with a dremel ;) and found the bearings to be completely dry. i packed them full of lube and now the jerks are gone and it flies smoothly.

[questerng]

thanks guys,

definately re-position the gyro..

and lube everything that move..

[questerng]

seems the place that i was testing my set up is conjested with interfearance..

brought it to another place to test.. nothing happen.. no glitch.. no intermittent jerk anymore..

i must say i shifted my gyro down to the reciever tray.. move my reciever to the left outside of the heli, as my esc is on the right and the wire run inside the heli.. not too comfortable in putting my reciever next to the ESC wire..

thanks for everybody's help and suggestion..

Safe flying

cheers
quester