Tuesday, November 12, 2013

'N Sync

Most of us have forgotten this, but there was a 'boy band' in the mid-90's named 'N Sync. They never amounted to much, but I remember them because they came around for their brief period of notoriety right around the time young Co-pilot Egg was starting to take an interest in things like that. One of the members, Justin Timberlake, went on to have an equally lackluster career as a Hollywood actor.

All in all, they left me cold.

Which has to be one of the most labored segues ever to appear on these pages.

I may or may not have mentioned this before, but one of the reasons that I was reluctant to remove the carburetor when I was working on my soon-to-be-unveiled project was that I would then have to re-sync the carbs.

In saying this, I realize that some of you have no idea what that means, while others, who may have tinkered with motorcycles at one time or another, are nodding along and thinking, "Yeah. That sucks."

They don't know the half of it.  Syncing airplane carburetors is a hundred times worse in the summer, and a thousand times worse in the winter. Yet there I was: needing it done and 33 degrees showing on the in-car thermometer.

The reason for synchronizing the carburetors is that one carb is managing the fuel to half of the cylinders while the other is responsible for the remainder of the cylinders. If the carbs aren't delivering the same amount of fuel to their respective cylinders, the power pulses being delivered to the common crankshaft will vary in intensity.  This sets up a lot of stress and vibration, two of the worst enemies of engine and airframe longevity.

The process for syncing the carbs involves inserting a balancing device into the process. This device is inserted between the tube that runs from one carb to the other. It can be a simple mechanical device that is really nothing more than two pressure gauges, or it can be a fancy electronic thing that, as it turns out, works far, far better than the mechanical device.

I own one of the mechanical devices.

Kyle, official Syncopation Composer for The Jackson Two, has one of the electronic models.

Synching the carbs, just like moving a sofa to the fourteenth floor of a hi-rise condo, is a two-person job. And, just as with the sofa, the owner gets to do the nasty part. With the sofa, that means walking up fourteen flights of stairs backwards. With carb syncing, it means standing behind the propeller of a running engine, enjoying a buffeting wind chill factor of roughly -25 F while the helper, in this case Kyle, sits in the relatively warm airplane diddling with the screen settings on the Skyview.  No, really, I have photographic evidence of that!

Now, to be honest, this would be my first time syncing my carbs; Kyle's Dad did it for me last November.  It turns out that there is a bit of a learning curve, similar to, say.... learning to set up a tent for the first time when you reach the last base camp prior to the final push to the summit in a Mt. Everest climb, just as a winter storm hits.  Really: it was JUST LIKE THAT!

Having bought the mechanical gauges, I wanted to try to use those rather than the fancy device those spoiled modern kids are using. That was a waste of time. The carbs were so out of sync that the needles bounced around so fast that they were nothing but a blur. No meaningful information was to be had. I suppose they smooth out once the carbs get closer to being synchronized, and we could have done that by not skipping the first step in the process (which is to set the idle stops on each carb to be more or less identical), but it was easier to just ditch the mechanical gauges and hook up the electronic thingy.

Which, when activated, sent its display so far off of the scale that no amount of diddling on the adjustment nut would bring it back towards the center.

We shut down the engine and set the idle stops.

With the engine running again and the indicator now responding to changes made to the adjustment nut, I was able to get the display centered. It wasn't easy - standing behind the blast of cold air pummeling me with hurricane force wind made it very difficult to see what was going on. That, along with the vibration of the engine, made it very difficult to make adjustments to the little nut. Eventually, though, I got it centered.

But not before I decided that I needed to protect the exposed skin on my neck. I hunted around the hangar until I found an old, ratty beach towel and MaGyvered* myself a scarf out of it.

Hey!  That's not my Dynon screen!  Someone's been fiddling with it!

The centered indication lasted right up until I tightened up the jam nut to hold the adjustment nut.  Doing that threw it way off the scale again and I had to start over. I tried the same thing three or four times with the same result. Eventually I figured out that I had to keep the jam nut tight and make adjustments using a two-stage process of slightly loosening the jam nut and tightening the adjustment nut back up against it, watching the indicator the entire time.

If I thought it was tough managing one little wrench in all of that wind, I had no idea what it was going to be like to have to coordinate two of them.

It's done now, and for that I am thankful, but I don't think I will ever attempt to do that job in the winter months ever again.

And I will be buying the electronic tool, too.

UPDATE: It is also possible, as I have been informed by a reliable source, to smooth out the bouncing needles by partially (by which he meant "nearly completely") closing the ON/OFF air valves on each of the two hoses. That still seems overly finicky and since the majority of the cost of the thing was in the hoses, which worked just fine with the electronic version, I won't be losing much if I buy one of the electronic ones.

* MacGyver is an American action-adventure television series that ran for seven seasons from 1985 to 1992. Resourceful and possessed of an encyclopedic knowledge of the physical sciences, MacGyver solves complex problems with everyday materials he finds at hand, along with his ever-present duct tape and Swiss Army knife.

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