Blade 400 - new servos and tail wag

[dam74]

Well I've purchased some new AcerLab servos a few weeks ago and with the weather the way it's been today was the best day to try and test out the new setup. It almost ended up in disaster with the strength of the wind but I managed to keep from breaking anything.

I pretty much just did small hops and see what was happening eg. spinning, banking or forward/reverse travel. I made note of what the heli was doing and countered it by disconnecting the motor and centering the sticks. Then I'd move the servo horns until they countered this travel. I've got it within the best position on the servo as going to the next cog/tooth results in greater travel in the opposite direction. It's not perfect at the moment and at the moment I have it trimmed out on the TX. I guess now to get it perfect I could adjust the lengths of the linkages/pushrods to remove the trim settings on the TX.

Something I noted was the heli had a bit of slow tail wag and I take it that it's down to the gyro gain? I never tried tweaking the gain settings but will attempt to adjust before the next time I go out. I do have another replacement gyro just a cheapo AcerLab one but at the moment I want to get the servos setup so that it results in (close to) level flight with zero stick input.

Also the rudder movement linkage/pushrod seems to be greater then the stock servo and servo horn. To the point that the linkage/pushrod hits the slider on the tail and causes the rod to distort. How would I go about stopping this from happening? Should I change to one of the other holes on the servo horn to decrease travel? There is a threaded section on the pushrod which I think you can reduce the length of the rod. Which is the most prefered method???

Regards
Darryl

[p4ddy]

Up the gain to sort out the slow wag, & it sounds like your end points need reducing to stop binding. Also with the drift i don't think you should replace the horns to counter act it. You need to place the horns on with zero trim or subtrim then centre them with subtrim if they are slightly out. Have you got a way of checking the swash plate level??

[dam74]

I've got no way to check swash plate level. I'm only eyeing it up.

The manufacturers horns had to be replaced as they didn't fit the AcerLab servos as the metal gears/cogs/teeth didn't match up. At the moment with center stick they're centered and it's drifting to the left and back, plus it has a bit of rotation to the left. However if I change the horns to the next position on the teeth it drifts at a higher rate then the other direction, same with the rotation. So it's closest to center I can get it on the horns. However due to the servo and horn hole positions being different to the manufacturers I'm gathering all of the rods will be out aswell so will need shortening/lengthening to get it relevelled. As I said the rudder has way more travel then the manufacturers and over travels causing the rod to bend.

[Holst]

I've got no way to check swash plate level. I'm only eyeing it up.

The manufacturers horns had to be replaced as they didn't fit the AcerLab servos as the metal gears/cogs/teeth didn't match up. At the moment with center stick they're centered and it's drifting to the left and back, plus it has a bit of rotation to the left. However if I change the horns to the next position on the teeth it drifts at a higher rate then the other direction, same with the rotation. So it's closest to center I can get it on the horns. However due to the servo and horn hole positions being different to the manufacturers I'm gathering all of the rods will be out aswell so will need shortening/lengthening to get it relevelled. As I said the rudder has way more travel then the manufacturers and over travels causing the rod to bend.

You need to get the horns at EXACTLY 90 degrees using subtrim.

Then level the swash by altering the links if its not right.

If you start running the horns off level and then trying to fix it by altering trims and links you will end up with interaction between your collective and cyclic inputs and the heli will be much harder to fly.

A swashplate leveling tool is very handy, although you should be able to get it pretty much right with a MK1 eyeball.

You need to sort out that rudder servo horn ASAP.

If necicary redrill the holes so that they are the same as the stock ones.

If you ask a digital servo to travel too far and it pushes against something then they can burn themselves out in seconds trying to get to the correct position!!

The tail wag is caused because by lengthening the servo horn you have increased the mechanical gain in the system.

[dam74]

Cheers Holst. Will put the helicopter on a table and adjust the servos so that they're 90deg to the body. Although some of the horns/double ended won't be that due to their orientation. However I think I know what you mean center is the vertical line along the long side of the servo body. At center stick the horns should be centered along that line.

With the rudder servo I will get the original horn out and look where the ball used to sit in relation to the new horn and remount to try and get it within the same distance from the pivot point. I didn't fly it much this morning, just lots of hopping and then some short flights of about 10-15sec to test level. I hardly used rudder/anti-torque in these flights as I had trimmed it to stop it spinning.

[Mart61]

I've got no way to check swash plate level. I'm only eyeing it up.

I have found the allen key method to be very reliable.

See my post here.

[Holst]

I have found the allen key method to be very reliable.

See my post here.

I had forgotten about this martin,

Although a little more fiddly than a swash leveler it will work just as well.

[p4ddy]

I use a spirit bubble which i got out of a pen type spirit level from the Hardware store in portswood.

[dam74]

I'm going to try doing the allen key method tonight.

Darryl