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afgarcia

Member
The control system of drift combined with the brakes have a weakness in my opinion.
Indeed, when braking, all efforts to support are transmitted by cable to drift, it does not seem to me very mechanical.
To counter this, I machined a gear, I cut it in half and put each piece on the axes of the pedals. A through screw on each half-sprocket is securely on the shaft.
As the support efforts are offset by gables.
I also manufactures a tensioner cables seen with this system must be able to adjust the cables.

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seven or eight thousand flying aircraft have provided a vast quantity of empirical proof of the validity of the factory design.
 
I think he's trying to improve brake authority when the pedals are less than full throw. Maybe decreasing the counterforce of your opposite foot. Either way, it now has a cable tension that needs to be setup for the rudder.
 
:rolleyes:Vous avez une solution ? un probl?me qui n'existe pas. In addition, in aviation we like to use gravity to our advantage. The bolts holding your block shoud be facing down with washers and nuts at the bottom. Salutations
 
Simplicate and Add Lightness

This is an interesting approach, but it looks to me like a solution in search of a problem, and one that increases rather than decreases the probability of system failure.

In addition to those drawbacks already pointed out, I have two specific concerns:

* With the addition of these gears, the torque tube support block and bracket nearest them most likely will be exposed to stresses beyond those for which they were designed. And since this is an aluminum airframe, those stresses could drastically increase the rate of fatigue accumulation and decrease the effective service life.

* The addition of these gear sectors makes the rudder control circuit structurally indeterminate. That is, it is not possible to analyze all of the stresses in the system without knowing both the end-to-end system geometry _and_ the elastic properties of all of the parts of the system. And even then it is complicated problem with a lot of uncertainty.

Basically, I like the execution, but as others have pointed out it increases the probability of control jamming, introduces increased stresses into parts not designed for them, and introduces new uncertainty as to the distribution and magnitude of stresses throughout the system.

Furthermore, it violates two guiding principles of aeronautic design and engineering:

"KISS: Keep It Simple S[illy]"

"Simplicate and Add Lightness."

Thanks, Bob K.
 
Nice machine work! I'd check the piston initial travel in the master cylinders, to make sure they are actually pushing brake fluid. You may have a small area of no fluid displacement.
Tom
 
I could maybe see this if you only had one leg. But then, the end results could be had with two pulleys and a piece of cable.
 
Many good reasons not to do this. Are you changing to adjustable cable ends and adding idler pulleys? If you get slack in your cables, you cannot take it out with foot pressure like I can. If you have a preset tension on cables, snap bushings will wear faster and produce more friction drag during normal use. Those gears will have to be welded and plastic supports/surrounding structure replaced.

Brakes...I use them for run up, taxiing, turning off of the runway. My pads have worn less than 1/16" in over 100 hours. When I use them, they work great. When combined with rudder at 15 kts and above they both work well. Would I prefer steerable nose gear? Yes. Would I want the extra weight up front? No way.

Stick to the plans for most items and you will fly sooner, cheaper and safer. Maybe run your ideas by us before spending too much time and money on them.
 
It's interesting that when most people get a mod criticized that someone pipes in with "go for it" or "that's why it's called experimental"...... This poor guy is getting reamed out - wrong side of the Atlantic?

I agree it's not the best thought out mod - but then I normally speak up against all of the unnecessarily complicated things that guys do with their aeroplanes. I do, however, think there is a place for a well-designed mod to make the rudder a close-loop.
 
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I'm with Paul

I don't think this mod is for me but I support the idea that WE as experimenters can CAREFULLY evaluate an idea and experiment in the search for a better mouse trap. Otherwise, we can all just go out get a Cessna and be done with it. That being said I do not modify structure or control

I doubt anyone on here knows this fellow or his credentials. For all I know he could be a controls system expert for Airbus. In which case I would take a closer look. He is certainly more mechanically oriented than me if he can make those parts.

Be careful and build a better airplane.
 
I read all your comments and they interest me. I still think it is important to differentiate between the two efforts is the pressure on the pedals and the rudder.

The purpose of this assembly is to cancel the force exerted on the rudder when it slows down and you press both pedals at the same time. Thus, the rudder hinges that efforts will suffer due to the effects of the flight but did not suffer the stresses due to the force exerted on the pedals. It also removes all efforts on the cables and the axes of the pins during braking, thus increasing their life.

You can press all his strength on the pedals without breaking anything and I'm not sure with the original installation can not break anything, especially at the ball of the rudder.

This mechanism is extremely simple and there is very little chance that a problem.
 
Okay, I follow you. I can see how relieving excess stress on the cable and rudder assembly is a good thing. Although, I bet you will skid the tires before anything breaks. I hope so anyway.
 
afgarcia said:
...The purpose of this assembly is to cancel the force exerted on the rudder when it slows down and you press both pedals at the same time. Thus, the rudder hinges that efforts will suffer due to the effects of the flight but did not suffer the stresses due to the force exerted on the pedals. It also removes all efforts on the cables and the axes of the pins during braking, thus increasing their life.
Click to expand...

The trouble is that you are putting all of that both-pedal load through nylon blocks and a flimsy little bracket that are designed only for very light longitudinal loads, and not the large moment couple your arrangement applies.

afgarcia said:
You can press all his strength on the pedals without breaking anything and I'm not sure with the original installation can not break anything, especially at the ball of the rudder.
Click to expand...

In my experience, Vans typically designs their control systems for input loads on a par with those specified in 14CFR Part 23, which are similar if not identical to those in JAR22. So I would have a pretty high degree of confidence that the rudder system as designed will easily handle simultaneous inputs of 150 lbs force on the right and left rudder pedals. And having designed control systems using rod ends of the type and size used at the bottom of the rudder, I am also pretty certain that that part of the system will easily handle Part 23 input loads.

My suggestion would be to disconnect the rudder cables and apply simultaneous force to both rudder pedals while watching what happens to the nylon blocks and the brackets they're bolted to. I think that you will see scary looking deflections long before you get to 150 lbs per pedal.

Thanks, Bob K.
 
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