Busted! Part Deux: Crowded Balls
So, I got the new hub on Monday, swapped out the innards, took it four times around the block, all was well.
At around five today, I decided to squeeze in an hour's ride to nowhere. I rolled out of the driveway, shifted the new hub into 3rd, and was rewarded with a bunch of distressing metal-crunching noises.
I put it back in first, headed back to the driveway, and opened up the hub. Several bits of loose metal fell out. One of the four small flip-out bits (called "pawls") at the non-drive side of the hub was broken into pieces, and the spring and retaining ring that held them all in place were mangled.
I replaced the broken spring, the broken pawl, and the bent retaining ring using parts from the old hub, which I still have. No dice: the hub still makes unpleasant not-working-properly grinding noises in 2nd and 3rd now.
This really kills the average lifespan of DualDrive hubs for me: before today, it was just shy of 1,000 miles, based on two hubs. Now, it's about 650 miles.
I'm just baffled. Doing the swap was fairly straightforward. All the bearings seated properly, I didn't bang on it with a hammer or set it on fire or anything. It worked fine on Monday when I toodled around the block a few times. I might not be a mechanical genius, but I'm an OK wrench and I knew enough to study the way the old hub was put together before I started mucking about with replacing bits of it.
Ian Sims, Greenspeed's CEO, figures that the first two hubs failed because of the caged bearings...sort of like these bearings right here. The eponymously-named bearings bear the weight of the axle, and in a bicycle hub, consist of balls sandwiched between two "races," which are sort of like tracks the balls roll in. "Caged" bearings have the little balls set into stamped metal ring-shaped cages, to hold the balls in place on the races. They make assembly easier, but they're not as strong: fewer balls, because the cages take up space between the balls, means a higher load per individual ball. So they might not hold the axle steady under load, see? The axle, as I toted my trailer up and down mountains for months, was twisting and putting strain on the hub's mechanicals that eventually cracked them. Twice. Short of spending $1,000 for a 14-speed Rohloff hub, the solution is to install what Ian called "crowded balls," meaning bearings without cages. That allows for more individual balls, less stress on each one, a stiffer axle, and longer hub life.
I do feel the need to say "Oh, grow up" now...but only to some of you. You know who you are.
Anyway: replacing the caged balls with crowded seemed like a doable thing to me, so that's what I was thinking about doing when I left for my fifty-foot ride this afternoon. Without, I might add, the trailer. So even though the explanation of the first two hub failures works, because they were both under heavy load for extended periods, today's failure makes no sense: no load, new hub.
It is of course possible that I did something terribly wrong...maybe I missed a small broken chunk of the old hub innards that got stuck inside the hub shell, and it mucked up the new hub's works. Maybe I shouldn't have taken it apart and juggled the pieces while doing a little softshoe and singing I'm Just A Hub-Jugglin' Fool.
But enough of this idle chatter! What to do? Write to Jerome, Greenspeed's U.S. rep again, that's what. And ask for another hub. Again.
One of the great things about Greenspeed is that they're a small company...small as in "nine full time staff members." I cc:'d the CEO, and within half an hour he had cc:'d me a note he'd sent to Jerome, which basically read: I think we need to get this guy a complete rear wheel with a new hub that has crowded balls. Because he shouldn't be allowed to have a cone wrench, in the same way that a monkey shouldn't have a gun.
OK, he might've thought that last bit, but he didn't write it. I remain fairly sure that a complete rear wheel with a new hub that has crowded balls will show up here within the next several days. And that's just fine with me.
On the rare occasions when I actually tell people how much I spent on this thing, I always tell them what comes along with that high price tag: bulletproof support.
Now, I actually set out to write the sort of thoughtful post-trip post I've been threatening to write since the journey ended, but I seem to have written this instead.
So maybe I'll write that other post later.
UPDATE:
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Instead of watching me stumble around trying to explain bearings, you can just read Ian's concise treatment of the whole issue, which he just posted to the IHPVA's [trikes] mailing list.
Of course, if you've read this far, you've already watched me stumble around trying to explain bearings, haven't you?
