Monday, May 30, 2011

Getting a grip...

What was it I said yesterday? Oh, yeah:

By saying that, of course, I have doomed myself to a prolonged struggle to find the parts...

Remember that? Truer words have often been spoken, but not all that often. I had a plan, though. It's not like I just went off the cuff, assuming that Radio Shack would have the stereo jack or would even be open on a Sunday. I was fairly confident that Wal-mart would be open and that I'd be able to find some bike grips there, so I didn't do much by way of research on that aspect. A perusal of showed that the part number extracted from the Van's plans was, in fact, valid, and that they were open until 8pm. Shiny! Off we went, first stop Wal-mart.

That was its usual treat, winding through aisles crowded with shoppers apparently unaware of their size and the effect it has on others trying to get down the aisles. As coincidence would have it, I stood impatiently waiting behind a slovenly group of five teenagers who were also in search of bike grips, apparently not happy with the ones that were on the bike when they stole it. It didn't seem a difficult decision; there were precisely two choices available. Anyway, there the were, and there I waited.

Done with Wal-mart and on to a nice dinner at Joey Chang's with the co-owner (of my fleet of airplanes and palatial mansion, not the restaurant) before crossing the street to the Radio Shack. The one that was open until 8pm.

Which was closed. So much for - they had closed at 5pm. You just can't trust anything you read on the internet.

I wasn't in any great hurry, anyway. The stereo jack could wait. Still.... keep your web site up to date, Radio Shack!

I tried again this morning at a different Radio Shack. They were open, but this particular store is a perfect example of how things have changed in Radio Shack's market. There was a time when the guy at Radio Shack wouldn't have had to look up the part in the computer to see if they had any in stock, nor would I have had to help him find it on the shelf. Radio Shack today is basically a Subway-sized Best Buy. They're quite capable of selling you a cell phone or a pack of AAA batteries, but beyond that they know little about their own stock.

After watching the employee flail around looking for the stereo jack in the cabling aisle for a few minutes, I suggested that it would more likely be found in the drawers where they keep electronic parts, such as they have electronic parts at all these days. I remember the day when the entire back half of the store was comprised of walls full of resistors, diodes, capacitors, integrated circuits, switches, etc. Now it's all scrunched into a few drawers that seldom see the light of day. Back then, no purchase of components occurred without the employee asking you what you were building. This guy refused to display any personality at all, assuming that he had any to show in the first place. He seemed almost aggressively bored with the entire interaction.

I didn't even ask about the 47k ohm resistors - I just went and found them myself.

I suppose this is the way things are now. We can buy electronic gadgets for less than $20 that would have been unattainable even with the combined billions in wealth of every petty dictator of an oil-rich kleptocracy in the world, or the U.S. Congress, assuming there's much of a distinction to still be found between the two. There's just no point in home experimentation or do-it-yourself electronics experiments anymore. Why dabble with building an AM radio that will cost $75 or $80 once you gather up the components when you can get thousands of stations through your cell phone via satellite?

Still, they're the only game in town and we inhabit the times we live in, like it or not.

I started with the bike grips. The first thing to be done is to remove the end caps. They will need to be drilled to accept the little push-to-talk (PTT) micro-switches that I will someday use to key the microphone in order to talk to the control tower.

The caps came off easily enough, but I could see that they were going to be problematic. Rather than a hollow "cylinder" inside that the switch could fit up into, they had a central spine with rings centered around it. There was going to be no way to fit the switches up inside there. I just cut the spines off. I'll do some duct-tape engineering later to see if I can figure out a way to get the caps to stay on the sticks. If not, it will be no big deal to try a different set of grips. That could end up being another lengthy search; there's no way to see the inside of the caps while the grips are in a package or visible only as a .jpg on a web site.

It also looked like the grip themselves were going to be too long. That was easy to fix with the band saw.

It turned out that I would need to take the control sticks and the grips back home for installation. It's a very tight fit and I'd need to use some dishwashing detergent and water for lubrication. I jumped back to the building of the stereo jack for awhile. The first thing I had to do was match up the little terminals on the stereo jack with the wiring diagram.

The resistors needed to then be soldered onto the stereo jack. I've become quite adept at using tape in lieu of another pair of hands.

To keep the wires/resistors from coming into contact with each other, and also to provide some strain relief for what will surely someday become a troublesome connection (hard wire soldered to a terminal is not consider good practice in the vibration-rich environment of an airplane), I added a couple of pieces of heat shrink.

In an attempt, probably futile, to keep undue bending from occurring on the rigidly soldered wires/terminals, I encased the whole enchilada in another piece of shrink wrap. Thank goodness this part is optional; with this measure of prophylactic protection and foresight, failure is inevitable.

Once the grips were on (and make no mistake - it was a tremendous battle dishwasher detergent notwithstanding), it was time to pull the PTT wires through the control sticks. Millions of pixels have been spilled in documenting the unimaginable difficulty in performing this reportedly impossible task. You see, the stick is anything but straight and not nearly as hollow as you'd expect. And worst of all, there's a ninety degree bend in it just before an obstruction - getting the wire past that is all but impossible. Dozens of solutions to the dilemma have been tried and documented, but all admit to the same sad, immutable fact: it's a pain in the ass.

The solution that seemed best to try first involves pushing a string through and then using the string to pull the wire through. Of course, you can't push up on a rope, and you can't push a string around a ninety degree turn. The best suggestion I have come across described using vacuum to pull the string through. Now if there are two things I have handy in the hangar, they are 1) a vacuum, and 2) string.

The posting I read on the topic said that it would work best to tie a cotton ball on the end of the string to provide some surface area for the vacuum to work against. Now, if there's one thing that I don't have in the hangar, it's cotton balls. I tried a different approach; I tied a little washer on the end.

I started with a goodly length of string, fed the washer down in the top of the control stick, and stuck the bottom of the stick into the hose of my running shop-vac. It sucked that string in so fast that I barely caught it before the loose end got sucked into the top of the stick. It's good that I caught it when I did - had it gotten down in there I would never have gotten it out. Why? Well, note that none of the string has yet come out the bottom.

I figured that the washer was getting stuck against an obstruction down in the tube somewhere and that the strength of the vacuum was sufficient to still keep pulling the string down into the tube despite the fact the the washer was stopped. This convinced me that I didn't need the washer at all; the strength of the airflow was sufficient to pull the string on its own.

I also decided that I'd just pull string off of the spool rather than limit myself to just the length that I had cut. The first few times I tried it, I had no trouble getting string to pull into the tube. In fact, I had trouble providing enough slack on the string because it was going in so fast. Still nothing came out the other end, though.

I reached another decision: the string was getting trapped either at the ninety degree bend or just behind the obstruction soon thereafter. Or both. I decided to feed the string in from the bottom instead. By watching down inside the tube (and, not inconsequentially, exposing my bald(ing) spot to the camera) I was able to see precisely what was happening. The airflow was so strong that it was causing "waves" in the string, much like a flag waving in the wind, and the waves were sticking to the rough interior of the tube. The string would just bunch up in there once a wave had gotten caught.

I found that if I kept some tension on the string as I let it go into the tube and watched inside the tube to make sure string kept to the straight and narrow, eventually enough string would go in that a loop would pop out the other end.

Once the string was through, it was just a matter of using it to pull the wire through. That wasn't as easy as you'd imagine. The first risk was accidentally pulling the wire through from the bottom since that's the way the string had been pulled. That won't work since the PTT switch would then be at the bottom of the stick rather than the top. The other is that the area where the wire is taped to the string will get caught as it tries to navigate the ninety degree turn. Two bad things can happen if your response to this is to just tug harder on the string. First, the string could separate from the wire and you'd have to start all over. The second, and far worse, would be for the little gold pin on the end of the wire to break off.

I got lucky: it was the former that happened to me, not the latter.

Eventually I got both sticks done.

At this point it was well over ninety degrees (what was it with "ninety degrees" giving me problems today??) in the hangar and I was ready to quit, but the next step was to temporarily install the control sticks in the plane. That seems a momentous event, somehow, and what better day for that than Memorial Day and besides, it seemed easy enough.

All I'd have to was add a couple 4.5" tie wraps to hold the wires in place. How easy!

Right. You know exactly what that means.

I have no 4.5" tie wraps. I have a bag of 50 4" tie wraps, but they were too short. I also have six 6" wraps that are probably intended for something else. I'll burn that bridge when I get to it - I went ahead and used them.

With that done, I thought about just heading home, but all I'd need to do to get the sticks in now would be to retrieve a couple of bushings and bolts from the parts bags and put it all together. Piece of cake!

Right. You know exactly what that means.

The bolts would not fit into the bushings.

Hey, it's just a temporary installation anyway, so who needs bushings? It should be easy to just use the bolts.

Right. You know exactly what that means.

The control stick wouldn't fit into the control rod.

That was pretty much it for my patience. I made it fit.

So, there they are! Control sticks in my airplane, even if it is just temporary!

1 comment:

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