Thread: Discussion Request to any machinist
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Old Oct 12, 2012, 09:43 AM
SCALEFAN is offline
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Fly allot, Crash allot, next?
United States, CA, Corona
Joined Feb 2006
7,378 Posts
Racer (Clay) hit the nail right on the head.

The real weakness with EFlight retracts is not the trunion, it is where the shaft connects with a small gear inside the transmission. If you unscrew the two screws holding the silver cover you will expose the transmission.

Here is what happens:

On the stock EFlight, a hard landing will bend the arms of the trunion and then the gear will wobble. When you strenghten the trunion, the stress is completely passed on to the connection of the shaft and transmission, the shaft will easily snap off the tiny gear. This cannot be fixed and the whole retract will be trash.

I have experimented with this, have modified both sizes of EFlight retracts with Tam's upgrade, all with the same end result. All the EFlight retracts are made the same.

The fix is not a stronger trunion, but nobody believed me when I said this before and Tam wasted his time with the upgrade.Only the best pilots will realize the benefit of the trunion improvement. (pays your money and takes your chances)

PS: You also can cause the shaft failure by jamming up the retract, or trying to free a jam up with your hand.

PPS: Before splitting the aluminum case for an EFlight retract mark the exact position of the curcut board, on the bottom, held between both sides. Sometimes the factory glue doesn't hold and the board can slide forward and back. This will render the retract useless until you keep loosening the sides of the retract while trying to find the exact position of the board. This board has contacts that determine the lock to lock position of the mechanism. The retract will act dead if this board is installed in the wrong position. This usually happens when installing the Tamjets upgraded trunion.

Originally Posted by racer1 View Post
Making a stronger trunion will probably make a different failure point.

Since you are exceeding the weight limits of your gear.

Even Robarts that handle that kind of weight are not that expensive.
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Last edited by SCALEFAN; Oct 12, 2012 at 11:57 AM.
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