Solving the geometry of the flap linkage and Ray Allen POS 12 sensor.

[claycookiemonster]

If this was obvious to everyone else, or was solved in a thread I never found, apologies.

I struggled with the apparently infinite ways to arrange the Ray Allen POS 12 flap sensor linkage and it's attachment to the flap arm. I looked at all the photos and read as many build sagas as I could find.

We finally fixed the sensor to the bulkhead in a position as near as we could get to the "average" position of all the installations we'd seen here. But then, finding the exact place to attach the end of the small linkage from the Ray Allen sensor was equally frustrating. Even with one end fixed, it seemed impossible to find where to put the other end to give a relatively linear travel to the sensor and achieve something nearing full travel of the sensor.

In the end, here's what worked for me:
Create the smallish fixture you'll attach to the flap arm from a piece of scrap. While most photos show a single Adel clamp holding it to the arm, I used two to eliminate any temptation to rotate. I also clamped my proto-fitting INSIDE the Adel clamp. Initially, make the proto-fitting overly large. Mine was about 3" long along the flap arm and extended about 2" above the arm. Leave it square.

Make a small length of coat hanger with 90 degree bends at each end. Mine ended up to be 2 1/2 inches long.

Now fully retract the flap arm, and fully retract the sensor arm. Put one end of the coat hanger in the hole of the flap sensor and swing a radius from that point across the proto-fitting so that it leaves a scratch. Now, fully extend the flaps and fully extend the flap sensor and repeat the radius swing, scratching a second line on the metal. Where those two radius's intersect is where you drill the hole to receive the flap end of the small linkage that connects the two. Trim the excess from the 3"X2" piece of metal.

I used RC control linkage parts to make the small linkage that connects the sensor to the flap arm.

 

[Jpm757]

I have installed several of these, you do not have to achieve full travel in either direction, this can be adjusted when you setup your flap indicator in your EFIS.
When installing the POS-12, be very careful not to overextend the arm, as this will ruin the unit.

 

[Mike S]

I used RC control linkage parts to make the small linkage that connects the sensor to the flap arm.

be very careful not to overextend the arm, as this will ruin the unit.

Since you are already using R/C hardware, you can use a "servo saver" setup from an R/C car to prevent damage to the sensor.

I had to do this in my current aircraft----works just fine.

https://www.towerhobbies.com/produc...MInpbB9-DXgQMVgAqtBh2Y7gvcEAQYAiABEgK6K_D_BwE

 

[planenutz]

That Servo-Saver is a nice idea. Clever.

Instead of making my linking arms rigid I used model aeroplane pushrod steel (like a 1mm dia welding rod) to make a "V" shapped link that acts as a semi-rigid connection between the flap tube and the sensor. It means there is a little bit of spring in the system so that if it gets out of calibration the link will bend without damaging the sensor.

 

[Webb]

Please show how you secured the wiring for the sensor and the flap actuator.

 

[fixnflyguy]

On my -4

I mounted mine (on a -4) in the center tunnel with a little bent up angle and connected it to the idler arm that drives the flap weldment. I also used the R/C wire and servo saver z bend . In hind sight I probably wouldn't install an indicator for the flaps simply because I never look at it. Unless its pitch black dark (I seldom fly at night), I just look outside and watch them. I have my control buttons on the stick wo there is no reaching for a toggle. The indicator is pretty accurate, and I have one for my aileron and elevator trim also.

 

[Tony Kirk]

Clay, It appears that the bearing block bolt is not tight.
.

 

[claycookiemonster]

Work in progress...

As soon as the wiring is secured, I'll show you how I did it. Also, thanks re: the untightened bolt.

 

[Kolg]

If this was obvious to everyone else, or was solved in a thread I never found, apologies.

I struggled with the apparently infinite ways to arrange the Ray Allen POS 12 flap sensor linkage and it's attachment to the flap arm. I looked at all the photos and read as many build sagas as I could find…...

Thanks for the great idea. It eliminates the trial and error. I’m going to do the same.

 

[PhatRV]

As soon as the wiring is secured, I'll show you how I did it. Also, thanks re: the untightened bolt.

If you still have the access to the flap bolts, replace them with the drill head and safety wire them permanently when it's time to close the floor. That way you never have to worry about them working loose or forget to tighten them at a later time.

 

[nohoflyer]

Is this the best solution for seeing flap position with electric flaps? What is the alternative or is there no one?

 

[ljpappas]

POS-12

Don't forget that Ray Allen does not recommend the sensor be fitted so it reaches the extreme ends of its travel. If it does, the PC board inside the sensor can crack rendering it useless. Don't ask me how I know.

POS-12 should be fitted so there is a slight amount of travel left at each end when the flaps are fully extended or retracted. I used 1/8 of an inch at each end and it works as designed.

 

[Ex172Owner]

Alternate flap sensor position sensor installation

See attached photo. This works very well for me. The plate with multiple holes allowed me to select the right hole by trial and fit to ensure the sensor's travel didn't bottom out. I was then able to calibrate the flap positions to the G3X. The cockpit side panel keeps the seatbelt from interfering with the arm.

 

[wirejock]

Position sensor

Is this the best solution for seeing flap position with electric flaps? What is the alternative or is there no one?

The alternative is the PH Aviation Flap motor.
It has built in position sense.
Minor change to the mounting hardware.

 

[rv8ch]

Is this the best solution for seeing flap position with electric flaps? What is the alternative or is there no one?

Can't recall who it was, but many years ago one of the RV-8 builders on the forum here said something like "it's really easy to see the flap position with your eyes from the cockpit." And he was right, I just look out the window to see the flap position.

During the phase of flight that you use flaps, your head is outside the cockpit anyway. I also have 3 commonly used positions - no flaps, about half flaps, and full flaps. I eyeball the half flaps position - full up and full down you can both see and hear with the flap motor.

There may be a case for some kind of electronic indicator that flaps are deployed for your AoA indicator.