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Old 02-14-2018, 10:13 PM   #1 (permalink)
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Default Feb.15, 2018 - Important Tail blade and build update from Luca.

Date 15-02-18 – OXY4 Important information for perfect Tail System Setting
We just finished doing a lot of testing to recreate the tail blade issues with breaking.
We discovered why some users having issues in some of the higher powered oxy 4 set ups.
The issue is not the material or other Oxy 4 mechanical parts.
The issue is from a combination of factors.
I study really carefully the report and I than work in bench and fly test until I find a combination of factor:
POWER / TAIL SET UP / GOV GAIN / TAIL GAIN / TAIL RATIO that can easy destroy tail blade plastic in few fly.
On begin I was worry about tail blade material or injection issue, we test different special material, we changed injection temperatures and injection point, but after the test, the combination of factor can destroy any of my beta tail blade.
Once I find the combination of factors were user can casually have, I work in the solution.
The solution I find work definitely removing the tail failure and increase the tail efficiency of OXY 4.
We test in company bench and in fly with 5 Top Pilot, and the solution work 100%.
The solution I find is pretty simple to made, solution is about set correctly the tail travel end point.
Read the following very carefully to know how to set the tail on the oxy 4 correctly.
BASICALLY TAIL ASSEMBLY:
- Plastic Tail Blade must assembly on tail grip with loose lock, keep in mind the tail blade must pivot in fly for the best timing and rpm recovering, than cannot be lock. Adjust until you feel it lock and open back the screw to assure the tail blade can rotate.
- Plastic Tail Blade are based Nylon Compound, Nylon have dangerous incompatibly with Lock Thread chemical, than my suggest for a perfect screw holding is use Silicone Glue, the one used for water sealing or aquarium application, a little bit on the thread will assure light lock without contamination issue.
GENERAL DISCOVERY AND INFORMATION:
I designed the oxy 4 for very high tail performance. Now after few issue on the tail blades and more testing I definitely found some situation that can destroy the plastic tail blades, or any plastic material.
OXY4 with plastic tail blades and powerful set up, needs a special set up of the tail.
I discovery that looking the data base and the pictures of the broken tail blades. In the beginning I was worry that it was the material. We tried the new material. Doing test flights and bench laboratory test. I found this situation can destroy tail blade also.
If you use plastic tail blades, the tail travel needs to be reduced. In some cases, the tail blade can stall and dangerous bent, compromising the root or breaking.
What we have discovered, is that the travel needs to be reduce 20% down from the max travel binding point. (on left and right).
I have tested this with many FBL, form Spartan, V-bar / Neo, Brain, Ikon, Axon, Micro Beast and combination with many servos 1520 and 760 micro or medium size and in any combination this following formula listed was the correct way with no blade ejecting issues.
BASICALLY TAIL BLADE ASSEMBLY:
- Plastic Tail Blade must assembly on tail grip with loose lock, keep in mind the tail blade must pivot in fly for the best timing and rpm recovering, than cannot be lock. Adjust until you feel it lock and open back the screw to assure the tail blade can rotate.
- Plastic Tail Blade are based Nylon Compound, Nylon have dangerous incompatibly with Lock Thread chemical, than my suggest for a perfect screw holding is use Silicone Glue, the one used for water sealing or aquarium application, a little bit on the thread will assure light lock without contamination issue.
HOW TO CORRECTLY SET THE TAIL LIMIT ON THE OXY 4
1- The tail need set per manual with the servo linkage ball at 7.5 mm from center. Very important. I cannot stress any more that this distance is very important.
2- Install the servo arm on tail servo with the position closest to 90 deg. angle to the servo and do not use any trim to center that servo, this is very important.
3- The servo must be installed and locked on the servo supports, but the supports need to remain a little loose on the boom. Just a little, so the servo can move front and backward when pushed by hands. This help on the next step were need set limit.
4- Set with FBL tail limit left and right to have the same value, (if using the Brain, you need to go into Advance menu to see the number) if use other FBL units it may be easier to see the number. For an example, with neo or v bar the max travel bind should be closer 120... If you use FBL without number, but click (micro beast) just count the number of click, need be the same. Move the servo to get the bind limit with the same travel left and right numbers or click.
5- Once find that position lock the servo on the boom. Then check again the limits. If you need to fine adjust the servo position, adjust the center stick servo position with the threads on the tail push rod. Again, very important left and right limit must be the same number or click. Don't worry about the center position, you will automatically have a 3.5-degree counter couple like I design.
6- Now, before fly. Reduce your Limit.
You must reduce the travel 20% of the number or click you find as limit on left and right. For example. If you have 120 as limit binding. You need to do this formula: 120-20% = 96.
If you have click: 10 click add as limit binding, you need use that same formula, 10-20%=8 than reduce 2.
If you have the Brain you can use click on basic menu or number in the advanced, Just use that number or click and reduce it 20% (formula number limit x 0.8) and set this number per left and right.
If you prefer use Caliper Tool the reduction of travel must be 0.6 mm each side, based on the binding position.
Remember to reduce limit left and right (CCW and CW) for the same amount, distance or click
This new travel is the best efficiency on tail end points for the OXY 4, removing any possibility of a stall situation in case of overload manures with a powerful system set up.
We already tested this new set up number with myself and 5 international top pilots, and the data has been confirmed. The tail works better and the plastic tail blades can work without any issue.
If you need more information. I thinks the video I will be making will explain very clearly the way to do it.
Luca Invernizzi
Lynx Heli Innovations – Oxy Heli
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Last edited by RichKnapp; 02-15-2018 at 12:29 AM..
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Old 02-14-2018, 10:19 PM   #2 (permalink)
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Admin: Can we have this made a "sticky" please.
Thank you much.
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Old 02-14-2018, 11:14 PM   #3 (permalink)
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So is it necessary for us not-so-extreme pilots to run through setup again?
Also regarding tail blade tightness, we want them to hold their position unassisted, not fall under their own weight, correct?

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Old 02-15-2018, 12:02 AM   #4 (permalink)
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Quote:
Originally Posted by rlane4osu View Post
So is it necessary for us not-so-extreme pilots to run through setup again?
Also regarding tail blade tightness, we want them to hold their position unassisted, not fall under their own weight, correct?

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Personally? I would just to play it safe. Power set up he is talking about the servo strength. Plus having it per Luca's recommendation is always a good thing.

Grips? Yes so they barely stay up but fall if you bump heli.
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Old 02-15-2018, 07:17 AM   #5 (permalink)
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Originally Posted by RichKnapp View Post
Personally? I would just to play it safe. Power set up he is talking about the servo strength. Plus having it per Luca's recommendation is always a good thing.

Grips? Yes so they barely stay up but fall if you bump heli.
Okay will do.

On the grips, mine are a little tighter as they won't move without physically rotating them. They aren't locked but I'll try to loosen them a tad. This is a little tricky since you need a little tension on the screw to make everything set. Easier on the mains with the nylocks.

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Old 02-15-2018, 11:27 AM   #6 (permalink)
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Quote:
Originally Posted by rlane4osu View Post
This is a little tricky since you need a little tension on the screw to make everything set. Easier on the mains with the nylocks.

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If you use thread lock (put in threads with a toothpick ) on the grip threads per manual. They won't go anywhere. Will actually hold better than a lock-nut.
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Old 02-15-2018, 11:30 AM   #7 (permalink)
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The toothpick method on the grip side is my go-to. Never had a contamination issue.

Rich, as always thank you!

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Old 02-15-2018, 11:36 AM   #8 (permalink)
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Quote:
Originally Posted by rlane4osu View Post
The toothpick method on the grip side is my go-to. Never had a contamination issue.

Rich, as always thank you!

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Your very welcome.

Yes by putting it in the grip threads and NOT on the bolt. Your not traveling the thread lock through the grip to get to the threads on other side.

Not as quick and easy, BUT a much more clean and safe install.

I even use this method for NON plastic blades. Don't need a blade to lock up to a bolt.
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Old 02-15-2018, 03:00 PM   #9 (permalink)
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Well done write up and now i understand better.
Especially the part about setting up the tail limits. On my vcontrol,
I will probably hit 120 both sides, then minus 20%, so change both sides to 96. Also, Linkage ball 7.5 mm from center.

Also, I can not stress enough about proper tail ratio. I had another heli where I used tail pulley suggested for low head speed. Decided to fly at higher head speed. Guess what happened? Tails blew off. As you can expect, I will be using 24t pulley for my Oxy 4 for 3000-3700 rpm. (NOT the 23T).

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Old 02-16-2018, 10:32 AM   #10 (permalink)
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So I saw a new report of a tail election on the ground after the new setup method. This looks more to me like weak tail blade roots instead of a setup issue. Yes reducing the mechanical stress on the blades might delay it but if this helicopter was designed for that much tail authority, the blades that come with a $375 kit should be able to handle it.

I should say I'm completely pleased with my model but this has me nervous as hell and I think the blades are the weak point.

That being said, are these just a standard 62mm tail that I could buy some zeals for?

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Old 02-16-2018, 11:46 AM   #11 (permalink)
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I saw what was probably the same report, tail blade ejection even after following these instructions.

Here's something to consider... Most of the development and testing seems to have been done in warm countries and or during the warmer season. Many plastics get brittle in cold conditions, could it be that the failures we are seeing are due to embrittlement in cold conditions? This would explain why Luca (flying in Vietnam) hasn't experienced the problem?
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Old 02-16-2018, 11:57 AM   #12 (permalink)
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Looking at the photos of the failed blades, it does look very much like a brittle fracture. In plastic you would normally expect to see some stretching and whitening of the plastic. The bolt hole would normally be considerably elongated before it failed. There is no sign at all of this in the photos I've seen, it's a 'clean' brake with no sign of any deformation.. This looks all the way consistent with a cold/brittle fracture.

The old school fix for this with nylon props was to boil them for several minutes. Nylon is hygroscopic (it absorbs water) and after it 'soaks up' some water is becomes softer and less brittle (at the expense of loosing some strength). The better fix though would be carbon blades as carbon doesnt suffer the same low temperature embrittlement issue.
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Old 02-16-2018, 12:01 PM   #13 (permalink)
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Quote:
Originally Posted by Grumpy_Old_Man View Post
Looking at the photos of the failed blades, it does look very much like a brittle fracture. In plastic you would normally expect to see some stretching and whitening of the plastic. The bolt hole would normally be considerably elongated before it failed. There is no sign at all of this in the photos I've seen, it's a 'clean' brake with no sign of any deformation.. This looks all the way consistent with a cold/brittle fracture.

The old school fix for this with nylon props was to boil them for several minutes. Nylon is hygroscopic (it absorbs water) and after it 'soaks up' some water is becomes softer and less brittle (at the expense of loosing some strength). The better fix though would be carbon blades as carbon doesnt suffer the same low temperature embrittlement issue.
That's funny, I just had this conversation with myself. I asked if the results would have been different if it we're a summer launch. I bet the roots of these blades are either expanding and cracking or stress cracking from rapid temp changes (indoor/outdoor). Might be a result of the thicker blade root.

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Old 02-16-2018, 12:29 PM   #14 (permalink)
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Stand by for some layman's polymer science....

All polymers experience something called 'glass transition temperature' (Tg).
Tg is the point that the plastic is considered to go from the glassy state (below Tg) to a rubbery state (above Tg). In reality Tg isn't absolute transition point, rather Tg is set in the middle of a curve that the plastic gradually goes though between the 'glassy' state and a 'rubbery' state.

By the time Nylon gets down to around 10 DegC it's fully in it's 'glassy' state, so is hard and stiff but brittle (i.e. it lacks toughness).

I'd put money on it that this is a major contributor to this blade failure issue.
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Old 02-16-2018, 02:37 PM   #15 (permalink)
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Not doubting what you are saying - but they're flying in the snow in these videos
https://www.youtube.com/watch?time_c...&v=7cvRDMKDYm0

https://www.youtube.com/watch?time_c...&v=upCm5DSit7g
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Old 02-16-2018, 02:46 PM   #16 (permalink)
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Quote:
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Not doubting what you are saying - but they're flying in the snow in these videos
https://www.youtube.com/watch?time_c...&v=7cvRDMKDYm0

https://www.youtube.com/watch?time_c...&v=upCm5DSit7g
The day we shot the overview video, it was FREEZE ing! Like painful cold out! It was a tad warmer when we did the different headspeed video, and much warmer the day Devin flew the stretched Oxy 4.
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Old 02-16-2018, 03:31 PM   #17 (permalink)
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Put some carbon fiber blades in the kit not crappy plastic ones. Is the next Oxy 5,6,7 going to have fake looking plastic carbon fiber ones also? Luca, do the right thing and upgrade.
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Old 02-16-2018, 08:49 PM   #18 (permalink)
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Quote:
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Put some carbon fiber blades in the kit not crappy plastic ones. Is the next Oxy 5,6,7 going to have fake looking plastic carbon fiber ones also? Luca, do the right thing and upgrade.
Tons of high end heli have plastic blades. And much larger ones to boot. Carbon fiber isn't the end all.

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Old 02-17-2018, 02:26 AM   #19 (permalink)
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The material of the tail rotor blades does not matter, as long as they do not give up in flight.

In my opinion that "science" in adjusting the tail ist not the solution for this problem. Bring us some reliable tail blades. Or why not use these colerful Lynx tail blades? Or don`t they do the job?
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Old 02-17-2018, 03:10 AM   #20 (permalink)
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Quote:
Originally Posted by Grumpy_Old_Man View Post
I saw what was probably the same report, tail blade ejection even after following these instructions.

Here's something to consider... Most of the development and testing seems to have been done in warm countries and or during the warmer season. Many plastics get brittle in cold conditions, could it be that the failures we are seeing are due to embrittlement in cold conditions? This would explain why Luca (flying in Vietnam) hasn't experienced the problem?
Luca seemed to indicate that he has reproduced the problem (presumably in Vietnam) so it would seem possible to have the same failures even in warm conditions. I agree though, the problem may well be exacerbated by colder temperatures.

I do think that there needs to be a more fool proof fix to this. Relying on people following a series of, lets face it, abnormal set up instructions is not a recipe for success or happy customers because, inevitably, they won’t. Having setup literally dozens of heli’s and being confident that the standard processes work well, it would not occur to me that the tail travel needs to be artificially limited to make this thing work.

The use of CF blades may be a solution but that doesn’t stop people from fitting nylon blades in the future (they are cheaper and often more colourful so appeal to many).

Unfortunately, unless this can be attributed to faulty blades, the only proper solution is to change the mechanical geometry and/or the tail ratios available to keep the stresses imparted on the tail blades in line with those of other heli’s on the market.
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