Shear Pin

[paul330]

I am still trying to get approval from the UK LAA for my installation.    They have a slight issue with the large offset on the roll servo to bellcrank fitting in the event of a servo jam.  Presumably they are worried that enough force can be appied to the servo to break the pin without distorting the fitting.

Can you tell me what the shear pin break torque is for the SV42 servo?  Then I should be able to design a test to prove the system.

 

[davemgill]

Paul,

It is 100 in/lb (see page 6-10 of the EFIS-D10A install guide). I've just done a similar test for the LAA on the RV-9. I had to apply 150lb along the push rod and check for any deformation of the attach plate and hardware (which there was none).

Regards
David

 

[paul330]

Thanks Dave

If you have already done a test, I wonder why they are still querying my installation?

Anyway, I make 100/2.6 x 1.5 a pull of 58lb on the outer hole.

 

[davemgill]

They wanted to test on the inner hole (1" from pivot centre). Presumably as someone might connect it that way. I can't remember which RV you have but if it is not a 9 then the push rod attachment to the bell crank direct rather than through an attach plate.

I think you should be using 1.5" for the outer hole. The 2.6" figure you quote is from the movement.

Flight test report and final paperwork was posted yesterday so hopefully should get fully approved soon.

 

[davemgill]

Paul,

I have just learnt that the LAA have approved my Dynon Pitch and Roll installation in my RV-9

Regards
David

 

[paul330]

Thanks Dave.  Hopefully I should hear soon that mine is approved without further tests. I have a -10 and thought the bellcrank attachment was identical. In any case, you were right about the arm length. Actually, I have to say that looking at the fitting on the bellcrank and imagining putting 150lb pull on it does make me wince a bit!  

Happy New Year!

Paul