My Srimok 90E

[5exi]

Please excuse my ignorance, I am just learning the hobby and trying my hardest to understand everything I read.

I have tried to google, but it is difficult to search for this specifically.

What is mechanical mixing with respect to the tail?

I can understand it on the swash (due to phasing etc), but not on the tail. Do you mean the mixing between throttle and rudder? Or something else?

Cheers,
Andrew

Look at this it may help

Modern RC Helicopter Gyros and Tail Setups ? What You Need to Know.

[gorber]

It was an interesting read, but I still don't know what mechanical mixing is wrt the tail.

[5exi]

It was an interesting read, but I still don't know what mechanical mixing is wrt the tail.

Try this then

[Britflyer]

Its not actually mechanical mixing that they are referring, like CCPM or phase mixing etc.

It is the mechanical ratio of the tail servo rotation to tail pitch slider movement. For a given rotation of the servo you can change the 'mechanical mixing/ratio' to the tail pitch slider by changing the length of the ball out on the servo horn.

If the ball is to far out you have to much mechanical movement (gain) in the system, which leads to low (electrical) gyro gains to stop the tail wagging.

If the ball is to far in you don't have enough mechanical movement (gain), and even with high gyro gains the tail hold etc will never be as good as it could be.

The key to getting the best out of a tail is a balance of mechanical and electrical gain of the system.

Ways to effect mechanical gain:
Ball length on tail servo horn
Length of Tail Blades
Tail Blade RPM speed
And models with a bellcrank tail system you can play with the ratio on the bellcrank

Quicker tail servos have a similar effect to increasing the tail servo horn length plus other benefits.


Paul

[gorber]

Its not actually mechanical mixing that they are referring, like CCPM or phase mixing etc.

It is the mechanical ratio of the tail servo rotation to tail pitch slider movement. For a given rotation of the servo you can change the 'mechanical mixing/ratio' to the tail pitch slider by changing the length of the ball out on the servo horn.

If the ball is to far out you have to much mechanical movement (gain) in the system, which leads to low (electrical) gyro gains to stop the tail wagging.

If the ball is to far in you don't have enough mechanical movement (gain), and even with high gyro gains the tail hold etc will never be as good as it could be.

The key to getting the best out of a tail is a balance of mechanical and electrical gain of the system.

Ways to effect mechanical gain:
Ball length on tail servo horn
Length of Tail Blades
Tail Blade RPM speed
And models with a bellcrank tail system you can play with the ratio on the bellcrank

Quicker tail servos have a similar effect to increasing the tail servo horn length plus other benefits.


Paul

Thanks, I see now. I thought I was missing something.

It is interesting to consider mechanical gain also. It isn't something I have paid much attention to when building heli's, they have just worked by adjusting the gyro gain accordingly.

Cheers,

Andrew

[Britflyer]

Thanks, I see now. I Thought I was missing something.

It is interesting to consider mechanical gain also, it isn't something I have paid much attention to when building heli's, they have just worked by adjusting the gyro gain accordingly.

Cheers,

Andrew

Agreed. We all generally rely on the heli manufacturer get the 'fixed' aspects of the mechanical gain correct, tail gear ratio, tail pitch slider lengths etc. It is hard to change those normally.

The aspects we can change easily are tail servo horn length, and tail blade size/shape.

I think these days most helis are ok, but 'back in the day' some manufacturers would get the 'fixed' elements of the mechanical gain all screwed up, leaving us to fix it for them by changing the things we could!!

So next time you ask your heli buddy what gain is he running on his gyro, think about even though you have the same gyro, the following need to be considered, are the tail ratios the same, tail blade length, head speed, tail servo horn length, same shape tail blades, tail servo speed ....... you get the idea, lots of variables that all have different effects on how well your tail performs!!

And thats before you start considering the best mounting methods/locations for a gyro to minimise vibration and therefore increase gyro gain!

Its also important to know that different gyros need different amounts of mechanical gain in the system to work well. For instance I spent 18 months flying the JR 490T and that gyro needed a short servo arm with high servo throws to get full travel on the slider and the tail to work well, yet in the very same model/setup when I changed to CSM they much prefer a longer servo arm with less servo throw to get full travel.

So what works mechanically for one gyro won't allows work with another.

Some gyros are very tolerant of a range of mechanical setups, the GY401 for example, and that is one of the reasons why it is still so popular for the masses, it just works whatever the setup!!



Paul

[gorber]

Agreed. We all generally rely on the heli manufacturer get the 'fixed' aspects of the mechanical gain correct, tail gear ratio, tail pitch slider lengths etc. It is hard to change those normally.

The aspects we can change easily are tail servo horn length, and tail blade size/shape.

I think these days most helis are ok, but 'back in the day' some manufacturers would get the 'fixed' elements of the mechanical gain all screwed up, leaving us to fix it for them by changing the things we could!!

So next time you ask your heli buddy what gain is he running on his gyro, think about even though you have the same gyro, the following need to be considered, are the tail ratios the same, tail blade length, head speed, tail servo horn length, same shape tail blades, tail servo speed ....... you get the idea, lots of variables that all have different effects on how well your tail performs!!

And thats before you start considering the best mounting methods/locations for a gyro to minimise vibration and therefore increase gyro gain!


Paul

So are there advantages to adjusting the balance between mechanical and electronic gain? Could it make for less stress on the tail servo for example? Or even just a better performing tail?

[Britflyer]

Depends how much you want to play and are you happy with your tail as it is?

I find most people just leave there tails as is, if it is working ok.

Personally I have been flying CSM 720s for ages, eversince they were prototypes. So I know how the gyro works and what it likes mechanical wise. Therefore I play with the mechanical side of things to get the best out of the complete system.

Its quite an easy experiment to try moving the ball in a hole on the servo arm and upping the gain (remember you will need to reset your gyro travel so you still get full travel on the tail slider!)...... and seeing if it feels better.

If you can tell the difference then it was worth it. If you can't tell the difference, then you haven't really lost anything.

I've not found it to effect servo life etc. So it is purely tail performance that you are trying to maximise by playing with the setup.


Cheers

Paul

[Jamin_00]

I admit to being lazy when it comes to tail set up and relying on the gyro to cover up my set up of the tail.

Think I will redo the tail's on my machines the correct way and see what difference that actually makes.

Thanks for the informative replys

[5exi]

My feeling is Srimok are over geared on the tail anyway that's why 95mm blades work better well on mine they do.

But as it's being said different set up's give different results

[Jamin_00]

That is one thing I will try myself

[marcosp]

Hi guys, since you are talking tail and gyros. Did you guys set the throw limits all the way to each side on the FAIFA? Seems to be a LOT on the anti-torque side. I was thinking of limiting throw to that side a bit.

[Jamin_00]

I agree it is a lot on that side and I did set full throws both sides however I don't think when I move the ball in one hole that I won't get full that side anyway.

[5exi]

Hi guys, since you are talking tail and gyros. Did you guys set the throw limits all the way to each side on the FAIFA? Seems to be a LOT on the anti-torque side. I was thinking of limiting throw to that side a bit.

Yes ideally you should limit your tail pitch limits to be equal both on both sides as you'll end up with different pirouette speeds if you don't.

Most new gyro's allow for this in there set up screens so you can match speeds, but it's best to find your max pitch and set on both sides equally

[J-S-Q]

Yes ideally you should limit your tail pitch limits to be equal both on both sides as you'll end up with different pirouette speeds if you don't.

Most new gyro's allow for this in there set up screens so you can match speeds, but it's best to find your max pitch and set on both sides equally

But surely you'd need unequal amounts of pitch on each side anyway due to the torque of the main rotor?