Solution For Iffy Bendix?

[fiveboy]

As I have written, my bendix has been working then not working. It hangs up while engaged and is not easy to get to release or come back down as it should. I have taken it out and cleaned it and done alight lube with silicon spray and its ok for a while then not....

So the other day I took it down again, thinking either I get this thing working reliably or its getting replaced. Since AC says they almost never have to replace them Im thinking maybe its me?

I took that puppy down and it is sticking in the upper throw (when extended). I cleaned it really well and it was still sticking. So I soaked it in penetrant spray (loosens nuts and bolts) and worked it repeatedly in the area it was hanging up - better.

Then I notice that on the shaft where the bendix rests when extended, there were ridges and sort of wear marks.... so I gently filed them away. Problem gone! No matter how hard I throw that thing into full position and/or twist it up as though under a real load.... it drops back down now.

We shall see!

(If you got em light em.... candles that is!)

[Timchick]

Did you throw some grease on the shaft? It sounds like the ridges got there from no grease being there.

[fiveboy]

I didnt because the whole thing is all lubey slippery now. I just left the penetrating oil all over. I have read conflicting versions of how to lube these things. Some say run them dry, some say use white lithium grease and some say just light silicon.....

[Harry_S.]

I've used coppercoat. A light coating on the risers when it's extended and on the upper shaft when it's at rest.

I've only greased it maybe three times in 11 years with no problems in that regard. Of course I don't fly in the rain and the machine is completely covered when hangared.


Cheers :)

[Chuck Roberg]

Had the same problem in a students Sparrow Hawk. Found out the shaft was slightly out of round and the gear would hang up on it.

He disassembled the bendex. Put the center shaft in a drill press and ran some light grit sand paper up and down on the shaft. Reassembled it and it's been working fine since.

[fiveboy]

Chuck, what you described may actually be what I discovered as well. Ill be reassembling everything in the next few days..... and then well run that bendix a while and see if its not healed.