Bell Crank ! .. everytime .. I have seen the difference in setup and interactions ...

 

And what differences have you seen?

 

Less interaction in the head and setup is better, giving you a better flying heli ..

 

Yes I agree with the above . But I think the modern FBL unit reacts instantly with torque compensation, thrust and various wind conditions so small discrepancies in mechanical and electronic settings have very little effect. My view is that if for instance you were to do a full vertical climb out the FBL unit assists in keeping it absolutely vertical provided the manoeuvre was started level. This was never the case with the fly-bar system no matter how well it was set up as spinning rotors produce unwanted side thrust proportional to increased pitch angle. I believe in the fly-bar days this was ironed out (tweaked) in the travel adjust end points on various swash servos.
Moving on to the original question. Direct to swash has now permitted us to purchase high speed high voltage high torque high priced servos over the 60 Kg mark just to hold and direct the swash now!

 

If you fly a model that has had the interactions tuned out , you would notice a very big difference. No matter how good the FBl unit ... Direct to swash has a lot of interactions and some other geometry problems, A bell crank setup also has this but to a much lesser degree.. generally speaking it's pretty simple to have almost no interactions in a bell crank system once dialed out. And even then there is less to dial out than with a direct to swash setup. A direct to swash setup even with interactions dialed out tends to still have more interactions that cant be dialed out than a bell crank system that has not even had the interactions dialed out yet.. Nothing wrong with direct to swash, not saying there is.. but when one flys a model that has had the interactions dialed out it's quite a different beast in my personal experience, so much better.. in saying all that even with a bellcrank systems it comes down the the brand of heli as to how good it's going to be, same go's for direct to swash i guess, comes back to the old you get what you pay for.

Ease of setup / Performance?

This area is kinda like the debate between electric/nitro, flybarless/flybared, etc.Everyone has a different opinion. For sure the servo direct to swash is supposed to be easier to setup due to the less parts involved, but being easier - I don't know. What I have found is that most of the direct to swash setups have servo arrangement involved where the exact center of the servo is difficult to see and get to to adjust, whereas the bellcrank setup has the servos conveniently located where the center can be accurately and easily set.I don't mean to say that the setup can't be done accurately on direct to swash setups; I just don't find it a whole lot easier.The direct to swash requires more powerful servos because there isn't the mechanical advantage of the bellcrank style. That requires stronger servo arms, and can lead to more damage to the servos in the event of a crash.There is argument that the more complex bellcrank system isn't as accurate as the direct to swash system. I think Nick Maxwell pretty well demonstrated that bellcrank setups can be competitive if done right. As long as there is no slop in a bellcrank setup, it should be just as quick and accurate as a direct to swash setup - it's just that there is more room for slop due to the complexity of a bellcrank setup.Anyway, those are my thoughts.

At the end of the day we are splitting hairs, all heli's can be setup to fly well..

 

Nothing todo with geometry but .. less parts on d.t.s. for me to fix after I crash

 

My brain hurts reading all the input. My contribution is that I have had many models that are either bell crank or direct swash and it was alway hard to feel which set up was more advantageous as they were all different models. However, I had a vision 90 that was released as a bell crank and then after 3 months of hard flying, a direct swash upgrade was introduced. I instantly felt that the model was more crisp in aileron movements. These days I still fly both and can confirm no real advantage between them.


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Direct and ball are both non linear setups. It means not "perfect". Actually they create mechnically negative expo. To counteract we can add positive expo on transmitter level. Does it help? Not really because all non linearity is compensated by FBL guro. Actually non linearity does not matter at all in FBL setup!

I can not get why many pilots tend to prefer zero expo. Expo really helps. Not only on cyclics but also in collective.

I can not imagine flying without expo. It is doable but why to make your life more difficult?

Percentage of expo is different story and strongly depend on peersonal "taste" and preference.

General principle is so simple. I want more precission at middle stick and maximum throw at stick extremal positoins.

What really matters are:
- servo resolution, centering precision, speed, strenght
- mechanically dependent limits of throw
- cyclic ring parameter we set at gyro programming
- predefined gyro expo - not all pilots realize it exists and can be programmed
- dead band setting
- other gyro settings - it is easy to set it up not correctly
- radio resolution and latency
- signal stabillity provided by receiver - can depend on temperature?
- implementation of multi channel in digital radio protocol - all channels should move simultaneously, keep in mind digital radio transmision is serial not paralell...
- correct and precision phasing
- last but not least RPM is really crucial for flight characteristics - higher is not always better żđďde

My general recommendation is not to be affraid to play with gyro settings. They can make huge difference e.g. piro performance can be horrible in some cases.

There is no rocket science but experience is helpful.

Keep in mind that if you want to fly like Alan Szabo settings from kit manual will not work.

I can be totally wrong but this theory works for me just fine so I am going to stick to it. Anyway it is open for criticism.