How to plug the crank oil galleys after ball removal and cleaning

[BogusSVO]

How to plug the crank oil galleys



I have spoken out about removing the oil galleys balls in the crank.


So once the balls are out


So all the crud can be removed.


After you have gotten most of the crud out, spray with brake cleaner.

Then use a small brush to scrub the galley.
Then spray some more brake cleaner, and blow out with compressed air.


Next have a new tap, and some sleeve retaining loc-tite

6 bolt cranks use a 5/16 x 18 tap and set screw (3/8 long)
7bolt cranks use a ¼ x 20 tap and set screw (1/2 long)

Caution must be used when tapping the crank so you do not snap the tap off in the crank.


Again spray with brake clean and blow out with compressed air.
Apply the green sleeve retaining loc-tite and screw in the set screw.

After tighten the set screws, take a blunted center punch and peen a few spots around the set screw.


This will deform the threads in both the crank and set screw so it cannot vibrate out.
Now you have a crank that you do not have to worry about the crud becoming loose and being carried into the bearings.

 

[paul j]

Will this procedure alter the balance of the crank?

 

[CutlassJim]

How do you clean it a second time? Or will it at that point have 10 jillion miles on it and be trash anyway?

 

[misterfixit]

That set screw is cracked and mishapen. could you not have made less of a mess of that?

Staking is a common retension method in the aircraft business, and is perfectly acceptable if done correctly.

Rich

 

[toybreaker]

^^^ this

The crank in those pics looks like it still needs some love.

I always removed the balls, prepped the crank for the screws, cleaned the crank, installed the set screws (sans locking agent) then did all the machine work, including any balance work.

After all crank work was done, the set screws were removed, and a final cleaning was then performed.

[edit]Doing it like this prevented any machining swarf/polishing abrasive that entered the crank galleys diring machining/ transport to be flushed before sealing things up.[/edit]

After the final cleaning, some thread locker was applied and the set screws were than installed and staked.


To ensure that the crank could be serviced in the future, I always tried to get the screws to a position where they are underflush with the crank surface

That way, the staking proccess will not deform (or even fracture) the screw.

A quick hit with a carbide will remove the defrmation of the staking proccess, allowing the plug to be removed in the future.


quality set screws (in various lengths) are available from many machinery supply shops, or you can go aviation grade (always my choice /ubbthreads/images/graemlins/smile.gif )



I always strove for return serviceability!

My philosophy was to make it easy on the next guy, as many times, I was the next guy. /ubbthreads/images/graemlins/wink.gif

 

[BogusSVO]

The pics are from several different cranks, Most of the time The set screw do no protrude like the one in the pic, this crank had the balls set shallow.

For the change in balance, I doubt the difference in the weight of 4 set screws and the 4 balls is .3g so it has the smallest effect if not balanced afterwards, the factory balance is commonly off more than that.