| 19 |
Position the TS01/TS02 flange assembly against the rear fuselage bulkhead with the TST template in place. There's nothing to ensure the bracket is mounted vertical, so set the digital level on the torque tube as a datum and then place it on the bulkhead at 90 degrees to that and draw lines on each side for guides. Re-position the TS01/TS02 assembly and clamp it lightly in place with a couple of long-reach G-cramps. Adjust position to get bellcrank on centreline with both flange feet flat on the bulkhead and parallel to the marked lines. Tighten G-cramps and drill through mounting holes 4.8mm, putting an AN3-5A bolt in each hole after drilling to preserve alignment. Build up the damper assembly. Decide that it will probably be easier to attach the trim servo link before fixing the assembly to the bulkhead. Get out servo, cut a 34mm length off the stainless studding and screw the plastic fork-ends onto it. The clevis pin will not pass through the small hole at the end of TS03 bellcrank so open it up with a 3.1mm and then 3.2mm drill bit. Assemble the pin with washers and insert the split-pin. Bending over the ends of the split-pin is definitely easier with full access than it would be in-situ. Try to test servo with a 12V lead-acid battery (recovered from an alarm unit) but it just barely moves. Try another similar battery and all is well - the first one was showing over 12V open-circuit but dropped to about 0.3V on-load so has obviously developed a huge internal resistance. Note that the hole in the bulkhead for the TS05 link rod is not yet made. Check the bulkhead template in the manual annex and find I can take the measurements for the hole off that. It is an oval about 24mm wide with the centres of the semi-circular ends about 35mm apart. The bottom centre is about 20mm above the bottom edge of the ply insert. Mark up the hole centres and start to drill through with a 25mm Forstner bit, but it's too old and blunt to make much impression on the layup. Drill pilot holes through and then use a 25mm grit-edge holesaw from the aft side for better drill chuck clearance. Drill another 25mm hole between the first 2 and clean up the sides of the oval with a TC grit file. Connect the servo to the link rod, insert split-pin and bend. Strip the wires from the servo and solder them onto the 5-pin XLR free plug with double heatshrink covering as support: pin 1, white; pin 2 white; pin 3 blue/white; pin 4 green/white; pin 5 orange/white. Mount the whole assembly to the bulkhead but the port flange is not properly aligned. Apparently the nut on the AN4-15A bolt was not tight enough to maintain correct alignment when I first set it up, and I was so focussed on the vertical alignment that I didn't notice it was skewed in the other plane. It needs to be slightly further outboard to be orthogonal to the bulkhead and to give better clearance for the end of the clevis pin. Strip one end of the 5-core cable and solder it to the 5-pin XLR chassis socket to the same pin/colour arrangement, again with double heatshrink for strain relief. The servo wires are so short that positioning the socket may be tricky. Connect the rocker switch & LED indicator to the remote end of the 5-core cable with a chocolate-block connector and try it out - all seems fine. Take the assembly off the bulkhead and ease the port holes slightly outboard. Re-assemble and alignment is much better. |
1388.7 |
| 26 |
Re-wire test rig with the Matronics Governor Mk III in circuit. Leaving the trimpot as found, servo movement seems quite slow. Wind the trimpot up to fastest setting and that gives an end-to-end travel time of 26 sec. Wind it back to slowest setting and servo does not move at all. Hold the trim switch on while winding up the trimpot and it starts to move after a few turns. Wind it slightly further to be sure it's in the working range and full travel now takes 56 sec. Disconnect the Governor and restore original wiring; travel time is now about 20 sec. Loosen the trim damper assembly so I can see where TS04A shaft is in relation to the slot in the bracket. Run the servo to the "in" end and position the servo so TS04A is at the top of the slot. Clamp the servo lightly to the bulkhead with a plastic-faced clamp. Run the servo to the other end of its travel and check the clearance between TS04A and the end of the slot. More room at that end, so adjust the servo position slightly down. Run the servo through its travel a few times, checking slot end clearance for TS04A and tweaking servo position until it is square and well-aligned with the bellcrank while achieving correct clearance at end of travel. Drill through the servo mounting holes 4.2mm, putting an 8-32 screw in each hole after it is made to maintain alignment while drilling remainder. It's now clear there is enough room to mount the XLR chassis-mount socket on the bulkhead between the servo and the bellcrank support flanges. Drill through with a 20mm grit-edged holesaw and fettle with TC files to fit the shape of the socket. Find a couple of M3 x 12mm countersunk Pozidriv screws for securing it and drill through for them. Degrease the screws and nuts then fit them, applying Loctite 243 threadlock. Think about a route forward for the 5-core cable and decide that it will go on the port side, and the radio aerial cable will go on the starboard side. Will need to make up some BID clips for it using a 3mm or 1/8" former. Think about using anchor nuts for mounting the servo but decide it'll be just as easy to put BID patches on the aft side of the bulkhead to secure the stiffnuts. Fit the servo mounting screws, washers and nuts. Check the servo travel again to make sure TS04A does not hit the ends of its slot. Tighten up the damper assembly again. Can find no advice at this stage on how tight it should be, so just get the threads of TS04A fully engaged in the locking insert. With the load of the damper, full servo travel now takes 22 sec. Measure the cone angle of CS17A as 45 degrees. Snip off a small piece of thin soft aluminium sheet and shape the end to 45 degrees. Check that it can be used to gauge the depth that CS17A is inserted into CS17 while setting the tailplane deflection angles. Do some checking of the wire labelling database and enter the servo cable as the first cable, labelled 6001. (The battery to engine block strap was already entered to test the file as wire 1001.) |
1391.3 |
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