The Ah-Ha! Moment. It's what keeps you coming back for more. It even almost compensates for all those hours you spent thinking inside the box. It even almost counteracts the inevitable feelings of inadequacy and block-headedness that burst into technicolor clarity when you realize that if you had just noticed it four hours ago you could have spent those hours more profitably slaying the next mechanical dragon on the seemingly endless list of "to-dos".
I had one of those today after working for hours and achieving little. Truthfully, I almost gave up. My neighbor Andre wandered in at one point. He has 6 decades of experience working on the whole spectrum of cars and motorcycles--new, old, cheap, expensive, foreign, domestic, stolen, you name it--that came through his shop in New York City. His conclusion was the same as mine: "you haven't properly diagnosed the problem yet. Don't start messing with it until you know what's wrong!" And then he left to exercise one of his Porsche 911s leaving me to to figure out why I was assuming something was right when it was really wrong.
The original suspicion was that the brake linings on the rear shoes were not sufficiently thick to make strong contact with the drum linings. Dan Allen came to the rescue (again!) by furnishing shoes with thicker linings that I could use to replace the originals. After installing the new shoes, and with the adjustments contracted to the maximum, it was clear that the linings on the new shoes were too thick to fit inside the drums--aargggh!
So now I was back to refitting the old shoes and linings--and discovering that the shoes no longer fit inside the drums!
Changing chairs did it. Because my "MaxJax" lift stops at 48 inches, I do a lot of the work under and around The Alfatross sitting on an old roll-around office chair. After frittering away more hours than I am willing to admit trying to figure out why the right rear wheel brake drum stubbornly refused to fit over the newly-installed brake shoes, I changed to a taller chair. Suddenly, from this new perspective, I could see that the shoes were not aligned concentrically with the axle. But what was causing it? It went together before, why not now? I racked my brain to figure out what changed. The rebuilt wheel cylinders?
No! Not the recently rebuilt wheel cylinders! The "Ah-Ha" moment occurred when it occurred to me that the two "pistons" in the adjuster mechanism might not be identical--that I might have assumed they were because the difference might not be obvious. If that were the case, the shoes might be too far apart to fit inside the drums.
The Alfatross' front brakes are brilliant, but the rear ones have been problematic ever since I first installed them more than a year ago. Drum brakes look simple, and they are--the ones on The Alfatross are an elegant solution to several engineering problems at the same time. Because the brake shoes have to be centered inside their drums, a good drum brake design must let them "float".
The Alfatross' rear brake shoes are not "anchored" in any way. The drums themselves are steel where they mate with the shoes, but that thin band is encased in finned cast aluminum to dissipate the heat generated by friction. They also have to be adjustable to compensate for wear, and it was the adjustment mechanism that spoiled my day. I was deceived by its apparent simplicity. To compensate for reduced lining thickness due to wear, the shoes can be moved closer to the drum linings by turning a screw on the backing plate. Inside the adjustment mechanism, the screw has a faceted, tapered point that engages the flat sides of two cleverly-designed pins encapsulated inside a machined steel housing bolted to the backing plate opposite the wheel cylinder.
I disassembled the adjustment mechanisms on both rear wheels, extracted the "pistons"--and the "Ah-Ha!" moment occurred! They were different!
So now I have made sure there is one of each different kind of "piston" in each adjustment mechanism--and realized that this may have been my problem all along!
But I won't know for sure until I get The Alfatross on the road again, which means finishing re-making the brake lines, checking the master cylinder, installing the new exhaust system and replacing the rear suspension springs with the new ones from Hypercoil.
Gonna be a long, hot summer!
I had one of those today after working for hours and achieving little. Truthfully, I almost gave up. My neighbor Andre wandered in at one point. He has 6 decades of experience working on the whole spectrum of cars and motorcycles--new, old, cheap, expensive, foreign, domestic, stolen, you name it--that came through his shop in New York City. His conclusion was the same as mine: "you haven't properly diagnosed the problem yet. Don't start messing with it until you know what's wrong!" And then he left to exercise one of his Porsche 911s leaving me to to figure out why I was assuming something was right when it was really wrong.
 |
| The lining on the new shoes (upper) is both different in composition and a lot thicker than the lining on the original shoes. |
So now I was back to refitting the old shoes and linings--and discovering that the shoes no longer fit inside the drums!
Changing chairs did it. Because my "MaxJax" lift stops at 48 inches, I do a lot of the work under and around The Alfatross sitting on an old roll-around office chair. After frittering away more hours than I am willing to admit trying to figure out why the right rear wheel brake drum stubbornly refused to fit over the newly-installed brake shoes, I changed to a taller chair. Suddenly, from this new perspective, I could see that the shoes were not aligned concentrically with the axle. But what was causing it? It went together before, why not now? I racked my brain to figure out what changed. The rebuilt wheel cylinders?
No! Not the recently rebuilt wheel cylinders! The "Ah-Ha" moment occurred when it occurred to me that the two "pistons" in the adjuster mechanism might not be identical--that I might have assumed they were because the difference might not be obvious. If that were the case, the shoes might be too far apart to fit inside the drums.
 |
| The revelation: something is wrong with the brake adjustment mechanism--but what could it be? The mechanism has only 4 parts: the housing, two "pistons, and a screw. |
 |
| The housing for the adjustment mechanism, bolted to the backing plate. Note the grooves in the housing to receive the steel tabs at the ends of the brake shoes. |
The Alfatross' front brakes are brilliant, but the rear ones have been problematic ever since I first installed them more than a year ago. Drum brakes look simple, and they are--the ones on The Alfatross are an elegant solution to several engineering problems at the same time. Because the brake shoes have to be centered inside their drums, a good drum brake design must let them "float".
 |
| To adjust for wear on the brake shoes, the "pistons" are moved apart by turning a tapered, faceted screw on the back side of the backing plate. The screw forces the two "pistons" apart equally, moving the shoes equally closer to the brake drums. |
 |
| I don't know how to describe the shape of the rear brake adjustment "pistons" so just try to imagine steel pistons with a perpendicular cut at one end with an angled slot milled down the middle. At the other end of the "pistons" two of them are cut at 45 degrees parallel to the slots and two are cut at 45 degrees perpendicular to the slots! |
 |
| See what I mean? It's easy to think they are all alike! |
I disassembled the adjustment mechanisms on both rear wheels, extracted the "pistons"--and the "Ah-Ha!" moment occurred! They were different!
So now I have made sure there is one of each different kind of "piston" in each adjustment mechanism--and realized that this may have been my problem all along!
But I won't know for sure until I get The Alfatross on the road again, which means finishing re-making the brake lines, checking the master cylinder, installing the new exhaust system and replacing the rear suspension springs with the new ones from Hypercoil.
Gonna be a long, hot summer!
