Does swash height influence even collective travel?

[curmudgeon]

I'm setting up the VBar.  I am using the recommended servo to swash link lengths with minor length adjustments to level the swash mechanically.  I leveled the swash at high and low using the VBar Pro software.  I have uneven collective travel of about +13.1°/-11.4°.  I understand that I can even out the collective travel electronically by a combination of adjusting the VBar collective range (80-100) and the Pitch Travel channel on my transmitter.

I am wondering if I can even out the collective travel mechanically by adjusting the swash height.

Can I even out the collective travel by lowering the swash by shortening the 3 cyclic links?

[Chris Sexton]

I would first check the difference with a mechanical pitch gauge. I found my RC Logger to get a little off when going from positive to negative pitch without re zeroing in the center.  Even then, it is slowly becoming less and less accurate, and yes I have re-calibrated it several times.

But as for getting the travels the same. VBar actually expects you to use pitch servo travel to get the same negative number. This is the same as when in the BeastX you have to adjust the positive throw and the negative throw. BeastX lets you do it with software, VBar wants you to use pitch travel.  Even the MSH Brain has you use Pitch travel to even them out.

Lowering the swash might help, but if the real issue is the controller not knowing how far to move the servo without the TX aiding, then lowering the swash might not help.

[RichL]

I'm setting up the VBar.  I am using the recommended servo to swash link lengths with minor length adjustments to level the swash mechanically.  I leveled the swash at high and low using the VBar Pro software.  I have uneven collective travel of about +13.1°/-11.4°.  I understand that I can even out the collective travel electronically by a combination of adjusting the VBar collective range (80-100) and the Pitch Travel channel on my transmitter.

I am wondering if I can even out the collective travel mechanically by adjusting the swash height.

Can I even out the collective travel by lowering the swash by shortening the 3 cyclic links?

I would do as you proposed and mechanically even out your pitch numbers by lowering your swash.


Rich

[curmudgeon]

I posted the same question in the VStabi forum.  http://www.vstabi.info/forum/read.php?26,94854,94858#msg-94858

According to Rainer, adjusting the height of the swash will not even out the collective range.

MrMel recommended that I increase the VStabi collective range (I currently have it at 81) so that the low collective will be my goal of -12.5°, and then decrease the high Travel on the transmitter to bring down the +14.1° down to +12.5°.

[Chris Sexton]

yeah that is what I thought.  I am pretty sure I have tried to lower swash to even it out before.

Do as Mr Mel says, he knows :0

[RichL]

Built a new E7 this weekend for a friend used the mechanical method to equalize the pitch.  I'm sure the method Chris recommended will work as well.

Rich

[steffgiguere]

You can fix the collective differences in the radio.

[RichH]

I had similar differences in pitch using the stock lengths.  I initially used my radio endpoints to even the pitch, but eventually lowered the swash to get even pitch with even (100) endpoints. Lowering the swash does resolve this.


Rich

[stevehof]

It seems to me that with a FBL head, if the servo arms are exactly 90 degrees to the mainshaft at zero pitch, you should have equal +/- pitch. Can anyone give me a scenario where this would not be true? Assuming a perfect setup like this is possible all the time...

[scotty82]

With a few helis I have had the horns at 90 deg with 0 deg pitch. The pitch range has been out by 1 to 1.5 deg and I have lowered or raised the swash to fix this.

The height of the swash would alter the geometry slightly to the blade grips. I use a RC logger pitch gauge now and get very fussy with the setup.

A good mechanical setup will improve your FBL gyro performance.

[stevehof]

If the swash moves the same distance up and down from zero with full servo travel, I don't see how the height can affect geometry. I submit that most of these small pitch range errors are due to one or more servo horn being 2 to 4 degrees off 90....??

[Kevin Dalrymple]

It will not be true if your servos are not at 90 degrees at the same time the blade grips are at 90. Or if the awash is not level or at 90 degrees to the swash. My rule is when the pitch is at zero every thing has to be at zero or 90 degrees. Yes you can use the radio or change it in the FBL, but it is not as good as a properly set up mechanical FBL system. With a proper set up you should be able to repeat your measurements. But as Chris pointed out the digital gages are not as accurate as people think.

One thing I think people get hung up on are the numbers. The feel of the Heli is what is important. The Heli needs to flip and roll in both directions the same speed. It also maters when doing upright and inverted climb outs. They should feel the same.

One way to see if you set up is right is to fly it and do a upright and inverted climb out and see if the Heli climbs at the same speed. If it dose not feel like it dose then lower the swash two turns and try it again. Just lower the links going to the swash and not the one going to the head.

One last important thing about swash positioning is you need to have room  to have it travel with out crashing or binding in either direction.

[steffgiguere]

This statement is good for sure with V-Bar, could be different using other FBL systems.

Lowering the swash does not resolve the problem, you have to do it in the radio. Trust me I've programmed close to 50 V-Bar and lowering or raising the swash never worked, you can even read this on the vstabi forum. The only way to fix this is through the radio.

[curmudgeon]

I still do not understand why one ends up with uneven collective range even with an optimal setup with servo arms centered at mid-stick and using digital servos.  Is this a VBar firmware issue?

[stevehof]

I still do not understand why one ends up with uneven collective range even with an optimal setup with servo arms centered at mid-stick and using digital servos.  Is this a VBar firmware issue?

If you end up with an uneven pitch range, then it's NOT an optimal setup mechanically and/or electronically. It is not a Vbar issue. However, servo resolution and spline count and maybe some other factors make an optimal solution in some cases impossible. When you think about it, one or two degrees is a pretty small increment to try to manage.