Getting There With The FT Y6: Please Critique My Build

[Glenfilthie]

I just love these big multirotors the FT gang does. A year or two ago I bought one of those Bat Bone kits and built a V Tail out of it - and it was more fun than a barrel of monkeys! I got really good at flying line of sight and got so I was going out in fairly stiff wind - and I could still cut a rug with it. One day I had a run-away and I lost it in the woods and I was one broken hearted old fart! (It was all my fault; I got a swollen head and the aviation gods punished me for my arrogance!)

So I finally got over it and ordered the Y6 kit and electronics from the boys and I am so close to flying this bird - but for a few maddening obstacles. Cranial Rectosis got me straightened out on the wiring. When I plug the Y6 into the computer, all the inputs track as they should on the right channels. The motors all spin the right way... but the darn thing just can't seem to get off the ground!

I have a few concerns or issues for the gurus - your two cents is sincerely appreciated if you care to comment.

1. Loop time - this may or may not be an issue according to what I've seen on the new Naze 32 Rev 6. I tried to set it to 1500 as per Josh's video... but the board will not accept the value even after saving. It is "stuck" at around 1000. Some of the guys are saying the new boards and ESC's can handle that - if you've heard different I would like to hear from you!

2. Could the refusal to take off be the battery weight? I wanted a great big 3 cell in hopes of keeping the bird a little over on the slow side. I only charged it up to 3.8V for a quick hover test...would more voltage help it get off the ground? (I'm grabbing at straws here...)



3. The coaxial props have me foozbarred. All the motors are spinning in the right direction. The props are the standard EMAX ones that come with the recommended Flite Test Power Pack for their Y6. But they just don't make sense to me.



The top prop spins clockwise and you can see that it is pitched to push the air downward. The bottom prop will spin counterclockwise... but the only way to get it to push air down for thrust, is to mount it so that the thinner trailing edge 'leads'. Am I having a brain fart?

Any suggestions or remedies at this point are sincerely appreciated. I would really like to get in the air again...

 

[LitterBug]

If you are pushing with the thin side, you have the prop mounted upside down or your motor is spinning the wrong way. If you have a clockwise prop on top of a leg, you will use a counter-clockwise prop on the bottom of that leg. Can you post a picture of the motors/props on one of the legs?

Cheers!
LitterBug

 

[LitterBug]

Does the orientation your props look like this:

Top Clockwise, Bottom Counter Clockwise

Cheers!
LitterBug

 

[cranialrectosis]

"but the only way to get it to push air down for thrust, is to mount it so that the thinner trailing edge 'leads'"

Bet she howls when you run those props up.

The only way to mount props is with the writing facing top/forward. If you mount one upside down or backwards, it howls and you don't get the lift you want.

If your copter calls for 3CW and 3CCW props you have to use props designed for that task. You can't flip a CCW to make it CW.

You are running a thick lipo but it is only 30C and you didn't fully charge it. 30C may do it for you and should let you take off, but if your weight is causing the lipo to sag due to low C rating, you won't have any thrust.

Most ESCs will detect low voltage and slow down around 3.5v per cell. Charge that lipo for a better test.

 

[Craftydan]

1. If you're running a recent Cleanflight ROM (and if you're not, you really should update ) The loop time is now synchronized with the gyro data rate -- get new gyro data, process on new gyro data. Breaking that synchronization does ugly things to the math and introduces a sample rate noise you don't want. You can turn this feature off in CLI, but I recommend that you leave it be -- your board will be better for it.

2. Probably not, although it might hurt flight time. A 6400mAh pack is heavy, but not insanely heavy. The packs spec'ed should generate plenty of thrust.

3. Ok, if you're spinning a prop backwards, that will cost you the thrust you're missing.

Looking from the top, one prop should spin clockwise, one should spin counter clockwise, and you should be able to see the numbers on BOTH props from the top. This means the bottom prop should have the numbers facing the motor. It also means that on each arm will be a pair of normal and reverse pitch props.

The only weirdness with this is self tightening -- Since the motors are counter rotating, but you mount to the bottom of one and the top of another, "self tightening" nuts for this setup will have the same thread. Think of it this way . . . picture the motors spinning a long threaded rod with nuts near each end of the rod -- this is like the motor's spinning the same direction. The nuts would either both move up or both move down, depending on the direction the rod was spun . . . but they're not spinning the same direction, they're counter rotating. So one nut moves down (tightening against the top motor), and one nut moves up (tightening against the bottom motor).

 

[Glenfilthie]

Sorry guys - here is the only prop configuration that makes sense for downward thrust - they are pitched opposite to the top props but even so, the only way I can get any downward thrust out of them is to mount them as shown...and they only mount one way, i.e. I can't invert a CW prop to make it CCW....



I will go down and double check again... maybe I'm having a brain fart...

 

[Glenfilthie]

Oh - and thanks for your time! Fly safe!

 

[cranialrectosis]

The top prop is cool but the bottom one needs to be flipped over.

If that makes it spin backwards you need a prop that faces the other direction.

Seeing this thing up close, heavy lipo or no, I think it's gonna cook.

 

[Glenfilthie]

Just so, CR. It should look like that pic Litter Bug posted. But - here's the problem - those props only go on one way! If this were a standard quad copter, all ya need to do is get your CW and CCW pitched props correct - and you're in the air! But the lower motors are inverted - so with the supplied props, you won't get one that will direct the air downwards. If the bottom motor weren't inverted, I could use the supplied props.

Here are the props furnished by the Flite Test boys in their power pack:



Can a guy buy CW and CCW props for inverted motors?

 

[cranialrectosis]

Flip the bottom prop over.

Unless you have some type of special motor, the motor doesn't care if the top of the prop is against the nut and the bottom of the prop is against the bell. All that matters is how the prop hits the air. The top of the prop needs to be facing up according to the air, not the motor.

You have a CW prop on top and a CCW prop on the bottom. Good. If your motors are spinning the right directions, that part is right. Just flip the bottom prop over.

Think of it this way. You wouldn't flip the lower wing on a biplane upside down would you? Both sets of props need to face up just like the wings on a biplane.

 

[Glenfilthie]

That's exactly what I would like to do, CR - but here's the problem: with the supplied EMAX motors and props, the prop is basically 'keyed' to the motor shaft. Behold:



You can see the threaded shaft, and right close to the motor there's a circular hub that's flat on one side. The prop fits over that, and locks up tight with the motor shaft. I don't know if you can see it with these crappy cell pics - but here is the prop:



Can you see how it fits together? It's looking to me like the boys at Flite Test may have had a brain fart on this one... do you think I could drill it out maybe...?

 

[LitterBug]

Drill the props or get props with larger holes.

Cheers,
LitterBug

 

[cranialrectosis]

Ugh...

I see the problem.

I'd like to hear Dan's opinion on this one.

 

[Craftydan]

Drill the props or get props with larger holes.

(I agree with Litterbug)


The props should be able to take it, and if they can't . . . don't get too attached to any one prop. they die. frequently. Props should ALWAYS be considered expendable.

 

[Glenfilthie]

Well thanks fellas.

I drilled them out and put them on and now the thing has enough thrust to take off...but she wants to flip. I know back in the day when I was fighting the Flite Test Bat Bone V Tail with a Naze 32 - it had a quirk: in the Naze Board, it wouldn't fly in the V Tail configuration, you flew it as an A-Tail - and it ran like a champ.

To your knowledge, guys - has anyone encountered a similar quirk with the Naze in the Y6 configuration? I checked and double checked the props and motor rotation - so I know they're good. I have it set up for Angle Mode - which means 'self levelling' to me...do I have that right?

I'm making progress, fellas - at least she can get off the ground!

 

[Craftydan]

ok, by flip . . . how exactly does she flip? left/right/front/back? as soon as the skids lift or does she slowly build up to it? any wicked yaw or wobble?

Double check the ESC routings -- one pair of ESCs swapped with the wrong output and you're toast. Next double check your board orientation. Also check your board mounting -- if it can be wobbled by hand, the frame will wobble it and try to compensate . . . all the way over

Angle is indeed the strong self-level mode, and once she's sound it will work it's hardest at keeping her level . . . but until then she'll buck like a bronco.