Rudder Pedal Hanger Bolt Adjustment

//Rudder Pedal Hanger Bolt Adjustment

Rudder Pedal Hanger Bolt Adjustment

The rudder pedal hangers are prone to being assembled in a manner that the two bearings on each hanger are not properly installed for the necessary bearing action.

The half inch bolt that is used to attach the hangers to the fuselage frame also provides the attachment and support for the brake rod bellcrank which is mounted on the outboard side.

The brake bellcrank is designed to rotate on a brass bushing that is held tightly in position by the 1/2 in mounting bolt.

The problem starts when a bellcrank is installed that has the brass bushing frozen in the center hole of the bell crank.  Sometimes a hole has been drilled in the bellcrank and the bushing, then a zerk fitting is installed in the hole, which really freezes the two together.

 Even with a proper bushing, the 1/2 in bolt has a head with a large slot, and it takes a bit of creativity in holding that head while the nut on the other end is sufficiently tightened. So sometimes it is just left too loose.

When the bushing is frozen, and the 1/2 inch bolt is tightened up on installation, the brake bellcrank won’t turn.   Then the solution often is to loosen the nut on the bolt until the bellcrank turns freely.  Now the bellcrank turns by rotating the frozen brass bushing on the bolt, rather than the bellcrank rotating on the bushing.

The fit between the bushing and the bolt is not a close one, so the bellcrank is somewhat wobbly on the bolt and the bolt begins to wear.  There is an oil hole on the bellcrank that feeds oil  to the outside diameter of the bushing, but there is no way for it to get between the inside diameter of the bushing and the bolt.

The only good news is that with the zerk fitting modification, grease can be applied to the poor fit between the frozen bushing and the bolt.

A second and troublesome condition brought about is as follows:  With the mounting bolt loose so the bellcrank will turn,  the inner races on the pedal hanger bearings are not captured, and the pedal hanger rotates with the inner bearing race turning on the 1/2 in bolt, rather than the bearing doing it’s job.  The fit between the bolt and the inner race is not a close one, so now the pedal hanger is wobbly, and the race starts to wear the bolt.  The two greased precision bearings soon stop working at all and the internal race does not rotate with respect to the outside race. You might as well have a steel plug with a sloppy center hole instead of a bearing.  Got it?

This is an easy thing to check.  Take hold of the pedal hanger and wiggle it back and forth inboard to outboard.  It should be absolutely solid.  If you feel any movement or slop, then the attach bolt is not set up correctly.

Another good check is to put an open end 7/8 in wrench on the nut which is on the outboard side of the 1/2 in mounting bolt.  You will have to straddle the cotter pin which holds the nut.  Is it there?

Now  by rotating the nut with the wrench, you should be moving the front pedal hanger along with the rear one.

If the nut and bolt turns at all without moving the pedal , then you’ve got the “loose bolt virus“.

You need to check all four bolts. If  any  of them will turn without the pedal moving, or if there is any side to side play on the hanger, then you need to tighten the nuts. 

The two bearings in the fuselage frame should be pressed in so that  the hanger just slips between them.  Then it doesn’t take much tightening of the nut for the mounting ears and the hanger to capture the inner race on each of the two bearings.  If there is too much of a gap so that tightening the nut would deform the mounting ears, then the bearings have to be pressed in further, or washers have to be added to take up the gap.

At the same time as the internal races on the hanger bearings are being properly captured, the brass bushing in the brake rod bellcrank is also being captured. Then the bolt, the two internal races and the brass bushing are all solidly connected together and won’t turn independently.

Now, if the brake bellcrank won’t turn freely, you have a bushing problem. you have to remove the nut and the bellcrank.  Remove the zerk fitting if there is one.

If you have to use that bellcrank, it will now have a 1/4 inch oil hole. You could  shorten the threaded end  of the zerk so that when it is reinstalled it doesn’t reach the bushing.

Remove the brass bushing. You may have to press it out if it is frozen. Inspect the internal bore of the bellcrank. Clean it up until a new brass bushing will turn freely inside. Make sure that the oil hole in the bellcrank is clear.  If the oil hole isn’t on top on the rear brake bellcrank, so the oil will run down when you apply it, then you have the wrong part dash number installed on that side.  If the one on the other side is also wrong, you can switch them around and be back in business. Or make that $100 telephone call.

Now reinstall the bellcrank and tighten and cotter pin the nut. Again you have to hold the slotted end of the bolt to properly tighten the nut.

The hanger sideplay and wobble should be gone, and those eight expensive bearings and  four brass bushings will be back in action doing what they are supposed to do. If there is still some side play, the bearings  may be worn and should be replaced.  Another $100 phone call!

 This same principle of tightening the through bolt of a bearing until the center race is captured and held tight against the mounting ears,  is true for all other bearings.

Take hold of the trailing edge of your aileron and move it up and down briskly an inch or two. If you feel slop and hear a clatter, you can be pretty sure that some of the through bolts in the several bearings that are in series in those control links are not properly set up.

Usually these bearings require one or more thin washers on one or both sides of the inner race to take up the gap caused by the mounting ears being too far apart.

 Go through each of the bearings, add the washers, properly tighten the bolt, and all that slop will go away.

The same is true of the elevator and the rudder bearings.

By |2016-11-13T09:34:10+00:00August 22nd, 1999|Flying-Wire|Comments Off on Rudder Pedal Hanger Bolt Adjustment

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