| 28 |
Since coming back from Australia, have edited some existing (main, transponder, comms, autopilot) and and created some new (GPS, SmartASS) circuit diagrams without explicitly logging that work. Today checking in the trailer for the strobe and analogue fuel gauge connexions, also look at the vacuum pump kit and note that the instrument adaptors for the 3/8" hose are 1/4" NPT. That is OK for the DI but the Italian horizon needs 7/16" x 20 parallel threads. The AN840-6D I modified for it back in 2003 will be fine for one port, I just need to turn up another similar with a shorter nose to avoid damaging the gauze in the other port. Pity I didn't note the changewheel setup at the time, but maybe I can do without screwcutting and just cut the thread with the die. Fortunately the recommended plumbing layout takes the vacuum gauge off the DI ports, so the branch adaptors supplied should be OK for that (providing that when installing the second one, the side takeoff does not foul the first one!). Dig out all the switches acquired from various sources and try to decide which ones to use where. Best 2 for the stick-top PTT are one from LAS Aerospace Aerospace specials table at LAA Rally, and an old one from BT surplus. The latter wins as it is smaller, has good tactile feedback, and does not require so much pressure to hold on. A disadvantage is that it has small solder terminals, but I can secure the wires to the body of the switch with a tie-wrap so that they are supported very close to the solder joints. None of the rocker switches seem small enough & easy to mount for use on the stick-top. The 2 front-runners for a stick-top trim switch are a paddle from Farnell and a miniature toggle from Maplin. I prefer the latter mainly on the grounds of easier mounting and slightly smaller size, although the paddle has a very nice action. They will require protection against inadvertent operation. Measure up each of the 2 preferred designs for preparing drawings, to see how they might be fitted on a stick grip. Check strobe fixings and connexions. Note that power leads are recommended to be 14AWG - should have enough 12AWG in stock. |
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| 29 |
Thinking about the other switches, decide that ones which are normally on all the time (trim disconnect) should have a green LED and those which are only on at certain times (fuel pump, wing leveller, strobes) should have a blue or red LED. The ones from Parts For Aircraft are much more robust, with metal shells and panel nuts, than the ones from Maplin which are all plastic, but the former only have a choice of green or red. I think the fuel pump switch should be beside the fuel gauges. There isn't room on the present layout for the wing-leveller disconnect beside the control head, but it would be OK beside the GPS (from which the wing-leveller derives its course). The trim disconnect should be beside the trim rocker and indicator, but not too close to the rocker to cause inadvertent operation. The P2 PTT could be at the RH side of the radio panel, under the transponder. The strobe switch could be on the switch panel beside the master switches. Modify the main circuit to show the earth connexions for the LED-equipped switches. For the master switches, paralleling the contacts may be easiest done by using a terminal strip with stacked ring terminals rather than trying to crimp 2 wires into each terminal. Check the branch adaptors on the DI - they do foul because the holes are too close together. However, the pressure port is removable with 3 small screws, leaving the coarse filter in place, and so that connector can be assembled to the port off the instrument. Get the 4-way terminal blocks out of the trailer to see how terminals might stack up on them. Not really practical as the screws are 3mm and the only yellow (10-12AWG) crimps I can use for that would be drilled-out male blades, which won't stack more than 2 high. I need 4 for the leads from the master switches and 3 to go to the fuse blocks, a total of 7. Instead, there are plenty of M6 & M8 yellow ring terminals in stock. If I can make or get an insulated stud to stack 7 of them on, that would be a good answer. After some internet searching, find a "battery junction post" on eBay supplied from USA. It's a 3/8" stud and I have 10 off 10mm yellow ring terminals in stock that would fit it, so order it. |
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