oops

Hi All,

Just a question about those who are familiar with the Walkera 22A or Dragonfly 22A

I've been debugging mine. while learning to fly it... And I found it was a bit loose- in that I would tune it to bring in collective *after* full throttle,
so as to emulate 3D positive flight settings, however, I found that it would have no lift, then it would suddenly go mass-collective.

At first I thought this was poor positioning of the lock on the mast, however, on further consideration, it appears that the 22A design is using the
pinion gear which drives the tailshaft, as a thrust bearing.

This probably explains why it flies so poorly and binds up under power...

It seems it really needs a lock at the base of the shaft, and possibly a thrust bearing there also, to take the lift, since the main gear/pinion is a poor load bearing item, and would generate a LOT of drag in the process, as well as reducing the life of the gear.

The height of the pinion gear also prohibits me from fitting the main gear up against the existing bearing.

Is it just my model that has this issue, or have others on this forum experienced the same with either of those models?

(This probably wouldn't affect the 22D as much - other than a reduction in flying time... )

Regards
David

quaker1

Maybe a spacer between the main gear and the lower bearing just thick enough to take up the space would work, beleive it or not I had the same problem with an MS Hornet.

oops

That makes sense, since most of the design is the same... But it seems like such a simple oversight... Most of the design looks right except for that...

I've seen things like that in a production environment, where the prototype was designed correctly, but the production run had a slight variation which no one notices because the whole thing still works...

Did you put the spacer/thrust-bearing on your hornet? How well did it work?

Regards
David

cptsnoopy

i was just looking at my 22d to see what you're refering to. my main gear is about 1/32" from the bottom of the heli body were the main mast goes through. what is holding it from rubbing is the tail shaft gear. if the heli were capable of inverted flight using the system it has now the main mast collar would prevent the mast from moving down. is there a chance that your tail shaft gear is too far to the rear letting the main gear ride higher?

oops

Hi CptSnoopy,

I was more concerned that the load from flight is taken up by the tail-shaft gear. That's just plain wrong ! I'm going to use the bottom bearing in
the shaft tunnel as a load-bearing by sleeving the top with some brass tube, between the bearing and the main gear.

It's not a great upgrade, but it's a LOT better than using a gear to take the load of flying!

Regards
David,

p.s. Yes, you are correct in guessing that the slack in the gear when I set it up was enough to allow for about 1mm of movement when it puts pressure
on the gear. Since I set up the collective as 0 degrees until 50% throttle, then it comes on through the remaining 50% until at maximum. I figured it would give me a better response, and let me build up to 3D throttle speed on the ground, with stability. (ie, at 50% throttle, I can switch to 3D mode on the ground without difficulty, and without it drifting. .

That means that as I add collective, at full throttle, it generates enough lift to lift the shaft, then that adds a few degrees extra collective, so the helicopter suddly "jumps" into the air... Rather violently.

cptsnoopy

thanks, I can picture that... sounds like a recipe for trouble... i will have to look at shimming mine also. thanks for the idea.

quaker1

shimming works fine.

oops

Yep, with the shim, mine actually flew today...

Now I just need to complete repairs

There is also an engineering flaw in the tail gearbox mount design.... Seems like with a few minor changes, these work OK

David