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Cozy MKIV - Chapter 23 - The Last? of The Oaf Stories

or: What's up with the engine mount?

Start Date: July 2, 2000

Fourth (and hopefully last) in our Oaf's Saga:

So our Oafish hero has worked on Chapter 23 (Engine Installation) on and off since February, 1999. He had previously purchased an engine (O-360-A2A) from AeroSport Power, and an engine mount from one of the mount vendors. He had worked his way through the engine mounting, the firewall installation, most of the cowling installation, the airbox/heat ducts and most of the miscellaneous cables and tubes that venture through the firewall and attach to the engine somewhere. As far as our Oaf's dim bulb of a brain could tell, things had gone basically OK, but there had been a few nagging issues.......

  1. When first rigging up the cowling around the engine and trying to achieve the correct distance between the cowl and the ring gear on the engine, the Oaf had a heck of a time trying to get the 1.5" distance - when the cowl lined up with the fuselage/spar/wings, the distance was more like 2.5" - 2.75". "Hmmm", says the Oaf's tiny cerebral cortex, "that's interesting".
  2. After fitting the aluminum baffling to the engine and reinstalling the cowls, our Oaf noticed that even though he had left 1" extra material on the top of all the baffles (to be trimmed to height later [cleverly, he had thought to himself]) the top cowl was STILL more than 1.5" away from the top of the baffles, and it seemed pretty consistant from front to back. "Hmmm", says the Oaf's tiny cerebral cortex, "that's interesting - I'll have to add a 1" riser to the top of the baffles". So he did.
  3. After fabricating the airbox for the recommended air filter, our Oaf test attaches the airbox to the Ellison throttle body, climbs under the aircraft to look at clearances for the lower cowling, and notices that there is no dang way on earth that the airbox is NOT going to interfere with the lower cowl - there's no possible way to fit it. "Hmmm", says the Oaf's tiny cerebral cortex, "that's interesting - guess I'll have to modify the lower cowl somewhat".
  4. While the cowls had fit reasonably well around the engine before the Oaf had mounted the exhaust pipes, as soon as he mounted them he could no longer get the lower cowling to come close to fitting (not to mention that he had to cut 1" off the bottom of the rear baffle just to get the cowling close enough to the pipes to notice that they were interfering). "Hmmm", says the Oaf's tiny cerebral cortex, "that's interesting - I'll have to hack away a substantial portion of the lower cowling (which he hadn't done yet)".
  5. Other, smaller issues with positioning of components......... "Hmmm", says the Oaf's tiny cerebral cortex, "that's interesting".

Now the Oaf, being the dufus that we've all come to know (if not love) was having a terrible time integrating all this information into a coherent picture. Since these issues had cropped up intermittently over a long span of time, he didn't have the brain power to associate them with one another - to him they seemed this fog of disconnected bits (sort of like what the World Wide Web seems to the Oaf's father). He hypothesized about each one, guessing that some sort of tolerance stackup had reached out and bit him in each instance (not the Oaf's instance, because the Oaf doesn't even know where he might find his instance, but the problem instances) and that maybe he just needed to be more careful (given his previous experiences, this was not an altogether idiotic hypothesis).

One day, while once more trying to get the lower cowling to fit (and while staring at an incipient interference issue with the engine mount and the oil cooler mount on the firewall), it struck our Oaf like a bolt from the blue - "Hey" (he thought to himself; no, wait - he said it out loud, to no one in particular, since there was no one else in his enchanted garage) "Hey - maybe the engine mount is wrong. Can such a thing be?". He rummaged around in his pile of old drawings, found the engine mount specification drawing, and began to take measurements. He found this a difficult task, as the drawings did not have all defining dimensions on them, but with a bit of hard work, he was able to determine the relationship between the dynafocal donut mount points and the firewall bolt mount points.

"GOOD GRAVY, MAN!" (or words to that general effect) our Oaf thought to himself, as he determined that the dynafocal mount points were approximately 1.25" to 1.5" TOO LOW. This explained EVERY LAST ONE OF THE POSITIONAL ISSUES MENTIONED ABOVE! It wasn't our beloved Oaf's fault (this time) - there's actually some other Oaf out there screwing up too! And our Oaf pays for it!

At any rate, our Oaf contacted the mount manufacturer, who quickly accepted responsibility and promised to replace the mount with a better one (gratis, of course). The manufacturer also said that they now sub-contract thejigging and welding of the mount to a vendor that has made substantially more engine mounts than the previous one did, and that this problem should not occur again.

So, THIS Oaf's story (the story, not the Oaf) actually has a recognizable moral to it (unlike those other stories, which seem less than optimally useful without one).

Do a dimensional check on ALL of your purchased parts - verify that they do, in fact, meet the dimensional specifications on the drawings. In the words of our illustrious ex-president, "Trust, but verify".

End Date: September 2, 2000


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Copyright 2000, 2001 All Rights Reserved, Marc J. Zeitlin
email: marc_zeitlin@alum.mit.edu