450 Storm 450 rotor head issues

[Rico]

hi there, I have some problems with my main shaft is bending in like 45 degrees after 5 to 7 flights on 3s 11,1 V 2200mha lipo bat's.
I looked online and read this :

The biggest culprit is the main rotor that is a clone of the T-Rex 450 SE, with a thin (3mm) feathering shaft. Given enough RPM, the blades will shake violently due to a physical effect called "aero elastic flutter", which is possible when the dampening is not enough. This becomes more likely as the rubber dampers get worn out.

Doing some math, the Storm comes with a 3800KV motor and a 13T pinion. For a 150T main gear, the rotor may reach way beyond 3400 RPM, but the old rotor design is limited to about 3100 RPM.

Another component associated with this failure is the cyclic bottom plate (http://www.helipal.com/stgc-040-metal-main-bearing-support-bottom.html). If this part gets cracked, warped or simply loose, lots of vibes will occur.

I've witnessed these vibes a lot of times, bending shafts included, so I call them the "Storm Vibes of Death".

Why the Storm 450 is supplied with such a combination of motor, pinion and rotor is beyond me.


Is that really possible, or not.

and how do I calculate on how big my fettering shaft has to be, or is it good with a 4 mm shaft instead of a 3 mm shaft ???

all help is welcome

 

[Dirk]

Wow, 45 degrees? Will it not be worth it to replace the entire head with an Align head?
The feathering shaft works perfectly on the Align.

 

[Rico]

yah I have been thinking about that, but thy are vary expensive, so I thought that I could get a striped aligen and just move all the electric to that one, but I want to hear if I can get a good rotor head for normal money, or doo something else to make it work hehe

But thank you for your replay Dirk

 

[Tony]

As stated in your first post, the old rotor head is limited to an RPM of about 3100. What I would do is calculate your KV at full battery to find out what your motor is spinning. If you are using a 3800kv motor, you would do ([3800*12.6]*.85) and that will give you your motor rpm at 85% efficiency. Then, you will take your main gear and divide that by the pinion to get your drive ratio. Once you get that number, divide your kv by the gear ratio to get your head speed. After you have that number, that is going to be your 100% throttle head speed. Then, you will want to do the calculations to figure out how to get a head speed of 3000 rpm and set that as your 100% throttle. So say you reach that at about 80% throttle. So from now on, you will change your throttle curves to a MAX of 80. HOpe this helps.

 

[Rico]

than you Tony, that help me a lot, so after my calculations I have to go all the way down to 70% throttle, then the rotor head is at 2906 rpm / min, isn't that a bit too low, I cant do any 3D with that, or can I ???

those 12.6 you times up with the 3800 kv, what number is that ???

my main gear is 150 T and my pion is 13 T, so if I change my 13 T pion out with a 11 T pion, then I can get up to 90 % throttle and I would get 3161 rpm / min.
and I took it all apart yester day, and I saw that my support was bend, I am thinking about making a new one in 4 or 5 mm stainless steel, there isn't much support in the original plate. and I order a new rotor head with a 4 mm feathering shaft, so that should help a lot on all those bend shafts, I hope hehe

 

[Lee]

A 3800KV motor with 13T pinion on a heli of this quality, will shake the thing apart. As you have found out, the main shaft is not strong enough for that headspeed. 11T pinion should do the job of calming things down and reducing the stress on your heli.
Good luck.

 

[Tony]

than you Tony, that help me a lot, so after my calculations I have to go all the way down to 70% throttle, then the rotor head is at 2906 rpm / min, isn't that a bit too low, I cant do any 3D with that, or can I ???

those 12.6 you times up with the 3800 kv, what number is that ???

my main gear is 150 T and my pion is 13 T, so if I change my 13 T pion out with a 11 T pion, then I can get up to 90 % throttle and I would get 3161 rpm / min.
and I took it all apart yester day, and I saw that my support was bend, I am thinking about making a new one in 4 or 5 mm stainless steel, there isn't much support in the original plate. and I order a new rotor head with a 4 mm feathering shaft, so that should help a lot on all those bend shafts, I hope hehe

Yeah, you can do 3D with that head speed, but you will need a little better collective management.

The 12.6 is the max voltage for a 3s battery. They are stated to be an 11.1 volt battery, but when charged, they are at 12.6. You always set your head speed with the highest voltage.

Lee may be on to something with what he stated. Lets compare the two setups at 100% throttle.

With teh 13T pinion your head is spinning a MAX of 4149rpm.

With the 11T pinion, you lower your head speed down to 3512rpm. Then, lets say this is a VERY efficient motor, and set the efficiency to 90%, you are at 3160 which is PERFECT for this head.

Not to mention, with the smaller pinion, you will be putting more torque to the head to keep it spinning at the correct rpm and less likely to bog down on hard maneuvers.

Do what Lee said, set your Tx back to 100% and put an 11T pinion on that thing. It will be perfect.

 

[Rico]

sweet thank you Lee and Tony, I put up an order for a new rotor head, with a 4 mm feathering shaft, so thy might as well send a 11 T pion in that order