Taking a Brake

The RV-12 hose/line replacement kits are flying (heh!) out of the collaborative effort between Steve from AircraftSpecialty and Tom from TS Flightlines - you probably still remember the replacement fuel lines I installed just a week or two ago, and here they are back again with a kit to replace the aluminum brake lines that run from a fitting up in the belly of the plane down to the brake calipers on the wheels.

The standard aluminum tube lines don't suffer from the onerous five year life limit that the fuel lines did. In fact, chances are that these lines would last the life of the airplane.  That said, there is a chance that they won't - through vibration and wear against the tie wraps that hold them, or from metal fatigue/work hardening near the fittings, they could eventually become brittle. That alone may or may not be a compelling enough reason to replace them, but for builders that want to install the optional wheel pants, not having to work around the loop in the aluminum line that gets added at fabrication time to provide a little "slack" in the line to move the caliper out of the way when working on a wheel (this loop itself could also get brittle or damaged with time) is a boon.

The replacement lines are far more robust and easy to work with because they are made of the same type of strong, flexible hose as the fuel lines, although these lines have an outer abrasion-resistant cover rather than the fire sleeve that encases the fuel lines. They also have the same high quality fittings as the fuel lines, and as with the fuel lines, they have been pressure tested to ensure their integrity.

You will note that one hose is longer than the other. The kit components that I received were, just as with the fuel lines, intended to test lines sized based on anecdotal measurements. Sometime back in the early days of the RV-12, conventional wisdom stated that the left side hose needed to be 34" long, while the right side should be an inch shorter. That seemed as good a place as any to start testing, although no one could definitively state the reasoning behind the need for differing lengths on what to all intents and purposes is a symmetrical airplane.

I decided to test two methods for replacing the lines.  While it seemed that it would theoretically be possible to do the replacement using only the access provided by the inspection ports located under each of the pass-through blocks up in the belly of the plane, it seemed that access to the fittings up in there would be much easier if I drilled out the rivets that hold in the panels that close the gap around the landing gear legs as they exit the sides of the fuselage.

I laid out the tools that I thought I would need.

  - Drill with #30 bit (Method #1 only)

  - LP4-3 rivets (Method #1 only)

  - Modified center punch (Method #1 only)

  - Phillips head screwdriver

  - 9/16" stubby open end wrench. Stubby wrenches are essential, and are thankfully dirt cheap at Harbor Freight, Home of Approximately Sized Wrenches. This one is approximately 9/16".

  - Side cutters.

  - Two AN caps sized to fit the fittings currently installed on the plane.  I think they're AN-3, but as with the gender of cats, I have no idea how to tell for sure.

  - Eight 12 - 14" long tie wraps (not shown)

For Method #1, which is the removal of the panel, the first step is patently obvious: drill out the rivets.

During the build, I found that the easiest way to drill out a blind rivet is to punch the mandrel out with a modified center punch. Harbor Freight has a $5 punch that is perfect for modification, primarily due to its most important quality: five bucks.

The grinding wheel meets yet another Harbor Freight tool.

Grinding the tip down allows it to fit into the hole of the rivet and make direct contact with the mandrel.

In many cases, a couple of "pops" with the center punch will push out the mandrel. Sometimes it won't.  It doesn't matter - the next step is to drill the head off of the rivet with a #30 bit. This is much, much easier than drilling out a solid rivet because the hole in the rivet will hold the bit where it needs to be. After just a few seconds of light drilling, the "cap" of the rivet will typically come right off, leaving either an open hole, or the remains of the mandrel if the first attempts with the punch didn't remove it.  With the cap gone, another punch at the remaining mandrel should pop it loose.

These are rivets with the caps gone but mandrels that resisted the punch still in place:

A couple more tries with the punch popped them loose.

Step Two of Method #1 is the same as Step One of Method #2: remove the inspection plate.

The fitting on the left is the one that will be removed, but DON'T DO IT YET.

There are a couple of things to do first that will serve to keep brake fluid from dripping all over your hands, paint, and hangar floor.

You're going to want to be able to move the brake line fitting away from the pass-through once you loosen the fitting in order to cap the fitting on the mount. This will keep brake fluid from draining out.

To allow the line to move enough to get the fitting out of the way, you have to first use the side cutters to cut away the tie wraps that hold it in place.

Now the fitting can be removed and the cap put in place.  This is far, far easier with the side panel removed, but it can be done even with the panel in place. With the panel in the way, it required quite a bit of digital dexterity (which I lack) to get the cap on, resulting in a lot more brake fluid coursing its way down my arm.  This also made the cap very slippery and visibility of the operation nearly nil.

So, it's your choice, but if I were doing it over again, I think I would opt to remove the panels on both sides.

The fitting at the caliper can also be removed.  Brake fluid will drain out of the line, so it is advisable to have a towel ready.

The line will be easy to remove from the airplane, although the loop might have to be opened a little to get it past the gear leg.

Remove and retain the plastic tubes used to protect the line from wear induced by the tie wraps.

Attach the new line to the caliper.

Slide the plastic tubes onto the new line.

This next step is an area where I stray from the by-the-book approach. Rather than introduce a line full of air into the system, which would then require a full purging of the brake system (which seems to invariably introduce a little air into the system), I pre-fill the new line with brake fluid before attaching the fitting at the pass-through block.

Do this at your own risk!! It has worked flawlessly for me, but it is a non-standard practice.

Just as the brake fluid starts coming out of the hose at the top fitting, I screw in finger tight onto the fitting. Again, this was far more difficult on the side that I was working exclusively through the inspection port.

With the fitting finger tight, I pumped just a little more brake fluid in, then tightened the fitting.

Repeat on the other side.

Tie wrap the brake line to the landing gear leg. I used four tie wraps rather than the two that were on there originally to better control the path of the line.

This is the right side, which was the shorter hose. This length looks just about right, although it would still create a potential problem for fitting wheel pants. I discussed that with Steve - he had heard the same from another builder. He is working on a solution that will provide a differently angled fitting that will remove the need for the semi-loop in the line.

He is also going to shorten the left side hose. The extra inch was clearly not needed or desired.

Here you can see how a different fitting would help keep the line right up against the gear leg, allowing it to exit the smallish opening in the side of a wheel fairing.

Because of the non-standard process of keeping the lines full of fluid while installing them, I pay particular attention to testing the brakes for firmness - they were perfectly fine.  I have flown the plane for roughly three hours since the installation of the lines and tested the relatively hard braking used in a short field landing with no symptoms of sponginess at all.


Disclaimers:

  - Products described were provided from the vendor at a substantial discount. 
  - Methods and processes described in this posting are experimental in nature and are not to be taken or construed as technical direction. Use your own judgment.

Carb Syncing from the GOOD seat

Rule #1 when it comes to the recent phenomenon of Black Friday, the day when sadists and masochists unite in an orgy of tribal commercialism is "Don't leave the house." Fortunately, the corollary to Rule #1 is "Unless it is to go to an uncrowded place."  This loophole leaves me open to accepting requests of the nature "I'll buy lunch if you fly down and help me sync my carbs," which refers to a mechanical calibration of the two carburetors on a Rotax 912 engine, not a dietary effort.

As loyal readers will recall, I recently sync'd my own carbs with the assistance of Kyle, presumably no relation to Colonel Andrew Lewis, who will be making a cameo appearance here shortly.  Even without the offer of lunch, I would absolutely have jumped at the offer - a day locked in the house, while far more appealing than being trampled by hoards of hungry shoppers, held no real attraction in and of itself. 

Plus, flying.  Right? Who's gonna say no to that!  Not this guy!!

And one more thing: I would have to GOOD seat this time. Because I'm here to tell ya, standing in the frigid blizzard of prop blast is no great shakes, although it does serve as a convenient reminder as to why I consistently decline invitations to climb Everest.

The trip down to Jackson was routine, the saying of which is a pre-excuse for this inexcusably boring, low-resolution video:

I have to say it: THIS is the way to do a carb sync. That standing out in the prop blast thing is crazy. In fact, I'm going to move my annual re-syncing to July or August.

It sure is a great feeling to finally see that LED in the middle light up!

The morning light really made my new paint look great, so I availed myself of the opportunity to get some pictures with better backgrounds than the row of hangar doors across from mine.

And then... lunch. I found this place on Yelp.com before I ever left the house.

They have an extensive and eclectic menu:

But again, I knew what I was going to have before even setting a foot out the door.

Jambalaya:



It was very good, although Andouille sausage would have been better, albeit probably impossible to find locally. The fresh shrimp more than made up for that, though.  One of the shrimp still had a tail on it, which reminded me of a recent epiphany I had. Back when I was a young 'un, my grandmother would make home made cherry pies. She would tell us to be careful because she might have missed removing a cherry pit, but if we found one, she would give the lucky discoverer a dime.

I don't remember what thought process got me on that subject, but as I look back on it today I realize that someone found a pit every single time. It took me 40+ years to realize that she was leaving one in there on purpose.

Kyle went for a 1/2 pound mushroom & Swiss burger which also looked fabulous, but brought forth no childhood memories, at least none that he chose to share:



The place wasn't very crowded, what with it being early in the day, so I took a little walkabout to see what the rest of it looked like. First stop was the bar, which was mildly depressing in the same way that the bars at Put-in-Bay are: since I only ever fly there and don't overnight, I never get to partake.

Which made this really frustrating:

After lunch, we had a little historical tour of downtown Jackson. Quite a bit has happened there.

Kyle needed to borrow some scales for re-weighing his plane post-paint (something I need to do, too), so we stopped by a friend's race shop. I wandered around looking at old stuff sitting out in the scrap yard. I really like this old drill press:

From the alliterative manufacturer Manning, Maxwell & Moore. A company name like that makes me feel like like I should be wearing a fedora and griping about Prohibition.

More or less on impulse, we decided to fly over to Parkersburg to visit Rick Gray, the guy that most inspired me to buy my RV-6, and then eventually to build the RV-12.  Rick is very well known in the RV world, to a large degree because of the incredibly high quality work he does with building airplanes. He built a couple of airplanes that were so good that they were awarded Lindy awards at Oshkosh, a feat that very, very few builders accomplish.  He also gave Co-pilot Egg her first ride in an RV-6, back when I was trying to convince her to let go of her emotional attachment to its predecessor, our Socata Tampico.

I like going to Parkersburg because I like flying along the Ohio River, checking out the barges and such.

And here we are, parked in front of the coolest hangar ever.

This is what the tools of a busy builder look like: there's no time to be constantly swapping dies for every different squeeze like I did.

This is Rick's personal plane. It's a Pitts S-1S. The '1' means single seat, and the second 'S' means that it has a symmetrical airfoil. This is as opposed to the S-1C that I always wanted, which has a flat-ish bottom wing and only two ailerons versus the four on the S-1S.

Rick explained the name of his plane. Some of you will remember a couple of years ago when Rick was involved in an accident involving an RV-10. The engine pretty much exploded, leaving Rick and another pilot gliding over the hilly, wooded terrain of southeast Ohio. Rick had to crawl through burning fuel to get away from the crashed airplane and the ensuing years of recovery left him, not surprisingly, with a fear of flying. His doctor recommended a "get back in the saddle" therapy, which led to:

It's good to see him back to doing what he loves.

That bottle lists the twenty-seven (27!!!) planes that he has owned/built.

Kyle and I, at least one of whom is never going to build a trophy-winning airplane (Kyle might have a chance), got a kick out of holding a Grand Champion Lindy:

This is simply amazing:

I told Rick he could look at my plane, but that he would have to stay 50' away. Rick and I have very different mindsets when it comes to airplane building: he is a maximizer, I am at satisficer.  As long as its safe and airworthy, "good enough" is good enough for me. Well, within reason, at least. I actually laughed out loud at a manager once when he told me in a performance review that people didn't like working for me because I was "a perfectionist." I was able to laugh because I knew quite well that the "people" he was talking about was a mediocre female developer with whom he was having an inappropriate relationship.

So, the first thing Rick sees when he puts on his judging hat is an edge of the top cowl where I sanded a little too much fiberglass off, leaving what I would describe as an "Oh, well, it'll fly fine" sized gap.

"Who fit the cowls?"

"That would be me," I replied somewhat sheepishly. "But that's why I told you to stay fifty feet away."

"Oh, I would have seen that from fifty feet," he countered.

"Sure," I replied, "but I would have been fifty feet away on the other side and wound't have been able to hear you!"

Joking aside, he did have some good advice on fixing an area of the avionics cover that I damaged when trying to remove the canopy after it got hung up on a "ballooning" edge of edge skin on the avionics cover.

Rick needed to get back to work and I had the ticking clock of early-Winter sunset to worry about, so Kyle and I made our way back to Jackson where I quickly refueled and headed home.

And courtesy of Rick, I now have a new "passenger" that will ride with me in the -12 every time I fly it.

Oh, if you're still waiting for the cameo appearance of Colonel Lewis, go back to the historical tour of downtown Jackson and try again.