View Full Version : Flybarless hardware question
10-27-2007, 09:26 PM
Sometime in the (distant?) future, I'm considering going to flybarless. After some time studying pics, I finally understand why the washout levers remain in place. (acts as a swashplate driver/synchronizer) But most of the setups I've seen keep the rocker arms from the old teeter mechanism, but I don't understand why.
Why don't people just run a connecting link right from the swashplate to the blade-holder arm? I realize that would require reversing the collective. I'm guessing it's not a good arrangement for 3D maneuvers requiring large amounts of negative pitch, thereby placing large compression loads on the link, and inviting the likelihood of bending. Perhaps too much load for the servos?
I already have a Cyclock, so it's a little like marijuana, the gateway drug to bigger things! :rolling
10-27-2007, 10:17 PM
Yeahh, I would like to see some flybarless 450s. That would be cool. I see myself getting very interested in that direction. The mechanics seem so clean and simple. I wonder if a 3 rotor-blade head would be better? Hmmm....
10-28-2007, 12:50 AM
I have a scale setup in the works. Its ccw rotation and flybarless with no gyros on cyclic. the mod is easy and with out gyro stab is still flyable but damn fast. so with cylock or other setup you will have a rocket and will need to be fast but true on the sticks.
10-28-2007, 02:27 AM
I just flew a 4 bladed head Trex today without flybar and no electronics stabilizer. It was flyable but had some strange tendencies. If you fly it slow and smooth, it was fine but when you give it aggressive moves, it seemed uncontrollable.
10-28-2007, 07:42 AM
Yea, I wasn't really thinking about attempting it without electronic stabilization. The 450's are skittish (for my skill level) enough already. I don't need to really push the envelope. Two more gyros isn't a big deal. (except for the monetary payout)
I'm just wondering why, if your going to remove most of the flybar assembly, why would one leave the Bell-Hiller arms? The only thing I can see is, with a direct connection to the grips, a lot more load will be applied to the servos and links. But is it too much?
Oh, I should mention too, if I were to do this, it would only be used as scale flight and/or mild, mostly positive G aerobatics. (loops, rolls, stall turns) I'm not into the 3D thing.
10-28-2007, 10:25 AM
the mixing arms reduce the movement and give more power to the servos.
10-28-2007, 11:14 AM
Yes, agreed. So far, there appears to be no other reasons, so....
That leads me to more thought about this, and probably on my way to answering my own question. Since the mixing arms reduce travel and increase power to the grips, it's a simple matter of moving my servo arm ball link in towards center, to achieve a similar travel/power result to the grips. Taking some measurements, I've determined the mixing arms generate an advantage ratio of 2.375:1 If I move my ball link in to it's inner most position from where it's at now, I get a 2.083:1 change in ratio, so the payoff is nearly identical. This appears very doable. So the only other function the arms serve, is to mix in the flybar inputs, and since that'd be removed, it makes the mixing arms unnecessary as well.
The only bad thing is, I'd have to flip my ball links to the outside, since the barrel of the horn would conflict with the connectors. This would put the geometry of the connector further out of alignment to the swashplate, unless I can come up with a way to mount the servos deeper into the frame. (can be done easy enough, it's just a lot harder to get thtem out later for maintenance) I imagine my phasing would be off as well, but that's easily addressed in the Cyclock.
10-28-2007, 11:27 AM
the mixing arms reduce the movement and give more power to the servos.
This may seem the case but the mixer arms are not needed. Think about when you give a collective input, there's no mechanical advantage there to give more power to the servos? Most people leave the mixer arms there to keep the swashplate in phase or it makes it easier to convert a flybar head to flybarless.
10-28-2007, 11:49 AM
it helps keep the links in a more straight up orientation. But on mine its cuz the links don't reach without them.
11-14-2007, 05:34 AM
Just converted my Venture30CP to flybarless out of sheer boredom (it is quite stormy here these days, so no real flying anytime soon)...
No electronics, just plain mechanical conversion...
I removed the complete flybar-assy but had to leave the washout-links, which was necessary to keep the swashplate in sync with the head. Without washout-block, there's no way to keep the swash-plate in the correct position to the rotorhead, resulting in massive phasing. I even had to connect one of those washout-levers with the headblock itself, or else the washout-block could have slided too far down on the main-rotor-shaft and disengaging from the locking-pin.
Additionally, I had to turn the blade-grips around, so the linkage is now leading-edge control. Since Collective was handled over the flybar-linkages before, which worked as a see-saw, inverting the input, no changes in direction of collective input had to be done. I did not do this due any stress-related thought: The linkages would've binded on the washout-block if they were trailing-edge-control.
Test hover so far was unspectacular in the way of the modification. Since I only guessed cyclic and collective throws, I went way too low on the cyclic, though collective is pretty much spot-on. I reduced the swash-mixing for collective fomr 60% to 40%, cyclic is down from 60 to currently at 30% but needs to go up as said before, I expect somewhere at 40% as well...
Spectacular though was the fact the tail left me after about 1min of hover: First of all, the belt became loose, disengaging the tail-rotor, second the battery was dead due to my dumbness. I only discharged it last time, hasn't been charged since. Add a little cool temperature et voilą, only half the servos would move... I could've slapped myself pretty hard...
What i do expect from this little experiment (the flybarless, not the dead battery... ;) ):
- More cyclic. The Venture30 is quite lame on that point. It doesn't lack power, it lacks roll- and nick-rate due to quite limited flybar-movement...
- More power. Mikado stated that without flybar, there can be a power-increase of up to 15%. Well, the Venture already has enough power, so I'll gladly invest that excess into rollrate... ;) On a side-note: RPM was higher than last time, though first of all weather is somewhat different and I did not measure, so it could be pure placebo.
- Coolness-factor. On a first glance, the head looks much cleaner, though you couldn't put a finger on what's exactly different. And that *damn* flybar isn't anymore always in the way of whatever you're attempting to do... :)
- Something exciting to do.
I'll post back when I had time to dial this one in...
11-15-2007, 12:40 PM
Hey guys, i saw a few asking for photos of flybarless trex450's Check this link http://runryder.com/helicopter/t382810p1/
That is my recent conversion you can read all about it there.
11-16-2007, 07:43 PM
YES! Great! That's exactly what I wanted to see. (though, I'd definitely use a set of gyros) Some thoughts:
Probably wasn't neccesary to extend the blade grip ball-links, but since you did, what do you think about using some of the extra anodized fuselage spacers that came in the parts bag, to give it a more refined appearance?
I like the way you came up with to secure the washout base to the head. Clever. I probably would have not thought of that one.
Your right on with the placement of weight. Forward CG is always more stable. I'd have to find a solution to make that look a bit more refined. Soon, manufacturers will be making blades specifically this way for the ever-growing flybarless crowd, and we won't have to deal with that mod ourselves.
Lastly, you made a great setup for quick change between flybar and flybarless heads. merely pulling the jesus bolt and popping off the four swashplate links and your off. Slide on the other washout base and head, reconnect the links and bolt and your back in business. COOL!!
As my skills continue to grow, I'm definitely looking forward to making this changeover. Like you, I want to use stock parts so I can easily replace anything damaged or worn. Turns out, the linkage rod set (http://www.helidirect.com/product_info.php?cPath=110&products_id=1600) for the Trex 600 happened to have a pair of perfect length rods to make up my swash to grip links. (though you also need a set of ball link ends for a 600, since the rods are 2mm, instead of 1.2mm) Actually, I like the thicker rods. I'm less concerned about them bending under compression loads which are bound to occur.
One step closer. ;)
11-23-2007, 09:09 AM
Some flights performed, I'm sober now... ;)
HInt for those that want to try with theirs:
Measure cyclic and collective pitch *before* doing anything.
That allows you to simply adjust your swash-mix after the mechanical modification to the same values you had before. That solves a lot of guesswork with a high ass-puker-factor...
Guess how I know... ;)
My conclusions of the conversion:
It still flies like a heli... *surprise*
Though I have to say you will now significantly feel the effect of lift generated by forward movement (in fact, any laterla direction). Accelerate slightly forward and if you leave the heli on its own, it'll stop itself after about 5m to fly backwards and go even further back than it was before. So it's like giving an input to start a movement, let the heli accelerate and than push further to keep the heli going. To stop moving, be gently and move the stick just a little bit aft from where you're at (neutral does no more mean no roll-rate in cyclic when moving... ;) ), let it decelerate, then back off further to keep it slowing down...
It is now definitely much more "scale"... Needs to get some used to though, but it's definitely fun 'cause its different... :)
I do have now approx 10° collective as well as cyclic (before 10° pitch, around 7° cyclic), but I had to increase expo from none up to 25%
And there is now an insane rollrate achievable. Yes, I talk about a Venture30... ;)
More power I'd guess too, but problem is there, that we have temperatures around freezing and the last RPM's I took was when we had comfortable 20°C outside, so I do not really have a base to compare the current readings with.
It was interesting, but not overwhelming...
I think this one is for sale anyway and if it doesn't go any soon, it'll be back to normal for training-flights...
Hope I was able to give some insights...
02-11-2008, 10:52 PM
Just an update from my original question and discussions. I have finally committed to changing to flybarless, and attempt it the way I originally discussed. First pic:
Flipped the grips for leading edge control. (not sure if this makes a difference other than keeping the swash commands the same, but everyone is doing it so.......) No mixer arms, just direct connection to the grips using linkage rods from a Trex 600. Modification to the washout base include pressing out the brass bushing, and pressing it back in the opposite side. I filed off the bushing on the short side, and drilled the guide holes out to accept 2mm screws. I cut off the long part of the washout arms, and filed them down to look nice. (with the exemption they aren't completely blue) I pulled the pins from the main rotor housing (after significant heating and elbow grease) and tapped the holes for 2mm screws. With M2x14mm screws, I attached the washout base to the main rotor housing. Alright, second pic:
It doesn't show well, but the ball joints have been swung to the outside, and moved to the inner-most holes of the servo arms. In addition, I mounted the servos deeper into the fuselage with spacers and are well supported by the bottoms going through the opposite frame side. This realigned the linkage rods to as close to vertical as possible.
Alright, now the iffy stuff. I just got a set of the cheaper Align carbon blades on. From what I read, Radix is the way to go, but pricey. I wonder if they are really all that necessary, since I don't plan on hard 3D. (evident by the scale body in the pics) Also, I'm going to give a set of Telebee gyros a try for my pitch and roll. Maybe this is a mistake, but I can't imagine a high-dollar, programmable gyro is required for those two axis, like it is for yaw. So anyhow, you can guess it hasn't flown yet. Just waiting for some decent weather.
Looking forward to the "first" flight, but nervous as heck as to how well this is gonna go. ;)
02-11-2008, 11:55 PM
First, nice job on the mods.
I've tried both leading edge and trailing edge on the grips and leading control is more predictable where trailing edge is a little twichy.
Without gyros on cyclic, it will be flyable but will be a little sensitive on the stick. Also the model will feel like its not trim right when just hovering, it will drift one way and when you correct it, it will drift the other way. These issues can be tone down by adding weights to the blades.
Becarefull when going forward flight. Going too fast and you'll will see it do some unintended moves. Don't even try to do loops and rows without gyros or added weights to the blades.
If you plan on adding gyros for the cyclic, you also need a ccpm mixer.
Good luck on your first flight!
07-26-2008, 10:46 AM
Well, a ways back when, I tried to hover the 450 flybarless with the Telebee gyros, but was having issues, namely, a severe tendency to shake out of control just as it was lifting off. I believed it was due to the body and a few other things, so I went back to the flybar to work things out. (and mainly to gain additional proficiency) Over time I became happy with my abilities (evident by me always taking bigger risks) up to the point where my recent last crash, I decided it'd be a good time to revisit flybarless once again.
So I again rigged up the gyros and changed the head, and found that the very same condition still exists. Just at liftoff, the heli will begin to oscillate which rapid progresses to a violent shake if I don't set it down immediately. (looks just like ground resonance, and perhaps is) I just didn't have the guts to go any higher to see if it would come out of it, and risk ripping itself apart. I messed with the gyro gains to no avail.
I finally decided to try unplugging the gyros and go at it without them. Surprise-surprise, I could hover again. (though, not nearly as steadfast as with a flybar) So it appears the problem is related to the gyros. My thinking is, it seems the reaction time is behind the curve, and that sets up the rapidly increasing oscillation. As it sets now, the gyros are mounted right and left of the motor. I wonder if mounting them closer to the rotor plane (above the tailboom base or in front of the swash) would do anything to make things work. Perhaps the cheapy Telebees aren't capable of handling this function, and all the fancy settings of the CSM SL720 gyros are really necessary.
Maybe I should just press on teaching myself unassisted flybarless, and forget about gyros all together.
BTW, the 450 with scale body looks so cool (finally) flying without all that extra crap spinning around. :YeaBaby:
07-26-2008, 08:09 PM
Your cyclic gyro gain is way too high!
If u set it too high, the heli will start to oscillate (similar to high gain in tail gyro to the tail)
07-26-2008, 09:29 PM
Nah, I tried setting them all the way to minimum, and it still happens. It's odd, with the gyros, I can get it light on the skids, and rock and pitch with stable results, but the moment I lift off slightly, it all goes to heck in less than a second.
07-28-2008, 08:09 AM
Folks, there is a flybarless SK 360 in market and it is nerve shocking..... besides, direct link between swash and blade holder will overload the servo, better keep the mixing arm
07-28-2008, 02:26 PM
..... besides, direct link between swash and blade holder will overload the servo, better keep the mixing arm
As far as flybarless goes, I disagree, but will agree it adds slightly more load to the servos.
Though the linkage passes through the mixing arms, the connection is still directly connected. The advantage ratio by passing through the mixing arms (when connected to the outer most holes in the servo horn) is 2.375mm of servo ballink travel for every 1mm of grip ballink travel. With the direct connection as I have it, (the ballink in the inner most hole of the servo horn) the advantage ratio is 2.083mm servo ballink travel for every 1mm grip ballink travel, thus it does apply slightly more pressure on the servo, (about 15% more) but certainly isn't overloading it.
Now, if I didn't move to the inner most holes on the servo, then I'd agree with you, the servo would become overloaded, but then I'd also have to have my endpoints turned down so low that I'd loose a ton of resolution in the servo. Therefore, making it necessary to do so for both reasons.