Yesterday I succeeded in getting the Savannah’s cabin top panel ready to go back on so I can now go ahead and complete the work on its windscreen whenever I want to. But today I again concentrated on 28AAD, my French Weedhopper, because I really want to get it entirely finished before the winter.
So today I re-timed the engine, connected up all the rest of the wiring and also connected the throttle and choke, the cables of both of which had been cut when MYRO was originally recovered. I’d only bought one new cable and outer, the latter of which I used to replace the lost piece off the choke cable, so luckily there was enough cable left on both for them to still be long enough to connect up. In fact I even had to shorten the choke cable a bit, although I had to trim the outer on the throttle.
But the important thing was that at the end, both of them worked smoothly as they should do and I was especially pleased to see that the ‘dedoubleur’, parts of which I’d made myself from aluminium tube and bar, worked fine and looked OK too. I’ll do some pics tomorrow probably, when I’ve re-routed a couple of things to tidy them up a bit.
Re-timing the engine was a little bit tricky. All of the ‘how-tos’ that you can find on the internet tell you that you need a dial gauge to accurately set the crankshaft to 18° before TDC, but I don’t have one and would prefer to avoid having to buy one. Victor suggested setting the crank to TDC, which is quite easy, and then rotating it by hand a given number of teeth on the starter ring calculated by counting the total on its circumference.
Unfortunately, this isn’t possible because you have to remove the starter ring to get at the ignition spark trigger units that you have to adjust, so I made up my own variation just using a sheet of paper.
First using my navigation protractor, I drew vertical and horizontal axes on it that intersected and then I drew a line at 18° before TDC that also passed through the intersection. Here’s a picture showing what I mean.
Then I took the sheet of paper out to the engine, which I’d already set at TDC, and put a small felt tip mark on the top edge of the flywheel and another opposite it on the crankcase. Then I placed the sheet of paper over the back of the engine such that the vertical axis that I’d drawn on it was dead over the two marks.
Then came the tricky bit. What I then had to do was adjust the paper keeping the vertical axis over the previous two points until the point where the axes intersected was exactly in the centre of the flywheel. This wasn’t as difficult as it sounds because placing the paper onto the end of the crankshaft and running your (dirty) finger around it makes a circular imprint on the paper and it doesn’t take much to get the point of intersection exactly in the centre of the circle.
Then it was a simple matter to use a small sharp screwdriver to place a mark on the rim of the crankcase where the 18° line intersected it. And that was it. All I then had to do was make that mark easily visible with another dab of felt tip and that showed exactly how far back the the mark I’d previously placed on the top of the flywheel had to be rotated.
Then all I had to do was adjust the ignition spark trigger units so they both lined up with the marks on the flywheel and adjust the gaps between them and the tiny pegs that are present on the flywheel surface (0.016-0.020″, 0.4-0.5mm). Obviously I won’t know how successful my method has been until I come to start and run the engine, but let’s just say that I’m quietly confident as the distance between TDC and 18° before TDC on the flywheel circumference is surprisingly large meaning that errors in measurement should be fairly small 😉
So what’s now left to do? Well, not a lot really. The main breakthrough will come on Tuesday, or more likely Wednesday, when the aluminium tube arrives that I ordered from ULM Technologie. That will enable me to finish off the doors. In the meantime, I’ll be able to finish off running the fuel system, part of which I managed to do today before finally calling it a day at gone 7.00 pm. And tomorrow I should also be able to do the small repairs that are needed to the EGT gauge connections and get the wiring for those and the CHT gauge in. It really is now getting very close indeed!