Undercarriage Adjustments

This blog covers those small jobs that ensure smooth operation and to allow greasing at the service points.

Overview
Final assembly of the undercarriage and linkages to allow greasing.

Installation
The first task was to disassemble the trailing link to allow the final adjustments to be undertaken.

Next operation ask was to reduce clearance in the linkage arms, this was achieved by super gluing two brass washers to the face of the cylinder link after dressing the both working faces to remove machining marks. The brass washers were then filed until they would insert into the mounting bracket firmly. Once correct, the arm was removed, labyrinth grooves added to allow grease to be distributed to working faces.

Hole marked A is used for cylinder attachment  was re-reamed 6 mm od and a suitable bolt installed with a nylock nut,

Note: Labyrinth grooves were added after it was found that grease would not pass between the faces when fully tightened.

The next issue discovered was that the grease nipples on the main pivots were hard to access and it was decided to rotate both pivots 30 degrees, this required removing all AN3 bolts plus the brass retainers. 

While removed, labyrinths were added to the retainers allowing grease to pass between the mating faces.

With all the preparation complete the links were reassembled for a final time. 

Each bolt was carefully adjusted to provide a zero clearance but not more with the goal to place the faces in contact under light pressure.

Three different locking methods were used, at the main pivot, an aluminium locking tab was employed at the knuckle, a castellated nut was installed. The later was selected because there is a possibility of relative movement between the two items and this is generally accepted as the reason to use mechanical locking method such as a split pin.

At the rod end secured to the leg, the pivot bolt was drilled to allow lockwire to be fitted after final adjustments are completed. The factory has released an instruction to over this task and should be followed.

Note: A Titanium bolt was used providing a plain shank for the rod end to operate on, this was covered in a previous blog. 

Comment
The gear manufacturer supplies nylon washers to pack the wing pivot that provides a bearing surface but at assembly, it was found that a number of additional washers were required. All pivots are fitted with dry lube bushes, secured with commercial bolts that create clearances between the shaft and the pivots. Hence there is a need to ensure both bearing faces are in full contact without over tightening bolts. 

Dry running is the proven option, but the clearances must be minimal after assembly.

The work outlined in this blog is a conclusion of fitting greaseable points.

Yes, old school but remember, it fitting not assembly.