hi all. I know i should really post this on an rc heli forum, but i figure there are more than a few fliers on here so i will start here

After a small bump, my heli isnt flying right. The rotor wobbles slightly even on the lowest speed, so its either not balanced or i have a bent shaft The rotors are new and the paddles appear to be exactly equal, so i suspect the shaft. However, by eye, it looks perfect. On a slow speed in my hand, you can feel it wobble back and forth.

Also, as it start to lift off it runs to the left. If i try to correct it to keep it still, it tries to fall over to the right even as its still moving left. Any ideas about this one?

Cheers! I have the heliadict and rcgroups forums in my favs so will ask there if no joy here.

Hi joel, if its one of the small electric helis, the torque reaction from the tail rotor sometimes pushes them to the left (depending on head direction) thats why they often fly with the right skid lower in level flight, but if you mean its only just started doing it then dont know. Have you access to a DTI and some V-blocks to check the shaft? That would be my first guess for the wobble

Hello Jeol,

Can't really tell what size heli you have but I get the impression it's a small electric one. Welcome to the world off balance…

Things to do -

1) Check blades are ok, not split or missing a bit that could unbalance them. Did you balance them before fitting?

2) Check the paddles are exactly level when the swash plate is also level and that they are exactly the same distance from the centre of the hub.

3) Check the tracking of the main blades, that is do the blades rotate in the same plane as each other i.e. there's not one 'flying' higher than the other when your are at hover throttle. To find out which one it the highest put a very small dab of tipex on the tip and you soon see. Adjust the pitch control rod to adjust.

4) To check the balance of the head assembly if you can, pop off all the control rods (pitch control & paddle rods) and let the paddles swing loose. If balanced they will remain level. This is very difficult to do on some mini heli's but is easy on the larger ones.

5) To check the shaft on a mini heli. Remove the blades and run the motor up. Looking down over the shaft you will clearly see it wobble if it’s bent. On large sizes with metal tube shafts, remove the shaft and roll it on a smooth surface. Any bend will then be easy too see. I have found that straightening them completely is pretty much imposable and you'll probably have to replace. There cheap anyway.

All heli's have a tendency to roll, usually to the left due to torque effect until actually hovering, even then heli's usually have a slight 'lean' when flying anyway. I have noticed that this can be quite pronounced on the mini ones and far less on 30 upward machines. Higher head speeds also reduce this. If possible reduce the pitch off the main blades to increase hover rpm, though be very careful with larger machines as you can over speed them even push the tips supersonic on the largest 90 size heli’s.

If after all that it’s still wobbly let us know and we work out what’s wrong.

Scott.

[Edited on 13/1/07 by macnab]

i have the same heli as joel and i can say i have experienced similar probs though not quite as bad.

mine wants to roll to the left all the time and generally seems very unstable but i have managed to hit the hover butter zone on a number of occasions though but not for more than a few seconds

Its a micro electric one, same as what liam got.



1) Check blades are ok, not split or missing a bit that could unbalance them. Did you balance them before fitting?

The blades are new after i bust the old ones. They appear to be identical, but when i remove them i will check weights on a balance.

2) Check the paddles are exactly level when the swash plate is also level and that they are exactly the same distance from the centre of the hub.

Level as in no pitch? After the crash they both ended up vertical, i levelled them off to horizontal but they do sometimes wander. They are free to rock up and down as they go round though.

3) Check the tracking of the main blades, that is do the blades rotate in the same plane as each other i.e. there's not one 'flying' higher than the other when your are at hover throttle. To find out which one it the highest put a very small dab of tipex on the tip and you soon see. Adjust the pitch control rod to adjust.


im thinking of using a dot of tipex to see if the flybars are symetrical. The main blades appear ok though


4) To check the balance of the head assembly if you can, pop off all the control rods (pitch control & paddle rods) and let the paddles swing loose. If balanced they will remain level. This is very difficult to do on some mini heli's but is easy on the larger ones.

The balance falls either way depending on where the main rotors move to. Im gradually tightening them until they resist the torque, but the battery has now died. Looks a bugger to get the rods off, very fiddly!

5) To check the shaft on a mini heli. Remove the blades and run the motor up. Looking down over the shaft you will clearly see it wobble if it’s bent. On large sizes with metal tube shafts, remove the shaft and roll it on a smooth surface. Any bend will then be easy too see. I have found that straightening them completely is pretty much imposable and you'll probably have to replace. There cheap anyway.


will remove all blades and see how the wobble looks. I can feel a very definate wobble as i hold it in the air, the tail shakes with it. However, the shaft looks perfect when viewed from the side. Will experiment tomorrow when the battery is alive (and when i find my damned screwdriver )


All heli's have a tendency to roll, usually to the left due to torque effect until actually hovering, even then heli's usually have a slight 'lean' when flying anyway. I have noticed that this can be quite pronounced on the mini ones and far less on 30 upward machines. Higher head speeds also reduce this. If possible reduce the pitch off the main blades to increase hover rpm, though be very careful with larger machines as you can over speed them even push the tips supersonic on the largest 90 size heli’s.


Im beginning to think it might be the screws that hold on the main blades, however it seems to vibrate before the blades have a chance to move off centre. Need to experiment. Then buy a heli that is already set up!

Cheers for the help guys. I did get it almost to hover (as in balanced on one skid for a few seconds) but so far, by the time i finish fiddling the battery is too low to make it take off even on full throttle!