My trainer and a 1991 Miata have exactly the wrong thing in common

Won't you join me for a brief journey into industrial design?

You may recall that I bought a "new" trainer a couple months ago: a CycleOps Hammer H2 from the "garage sale" section at REI. In every way it's been an improvement, save for the ~10% power discrepancy, but that's been solvable by just using the on-bike PM's.

It even turns out to be relatively future-proof, with end-caps for easy conversion to 12mm thru-axle support, and even an available XDR freehub conversion.

But what it is not, evidently, is an exercise in good industrial design.

Yesterday I jumped on the trainer for just a short recovery ride and was instantly greeted to neat-o grinding noises. And that's when my afternoon turned into a pile of tools and mild panic.

Distinctly NOT what a quick recovery session should look like

A quick inspection of the outer shell revealed that I was going to need some non-standard bike tools, namely some big Torx bits and FOR SOME UNGODLY REASON a 1/8" allen key: exactly the sort of tool every cyclist with a set of metric hex tools has lying around. Fortunately I found mine before rounding off any of the bolts with the so-close 3mm NORMAL bit. Anyway...

I had a sense that things had gone poorly inside the unit when I saw the molten plastic through the side:

That's not licorice gum

But what I did find inside surprised me. Of all the things in the world from which to draw design inspiration, I would never have expected to see a resemblance to a 1991 Mazda Miata's crank nose, and yet:

Woodruff keys and all. Did we learn nothing the first time with this design?Anyway, this is almost exactly how I first found it, and you might notice that something is missing. Something, say, to hold that pulley and woodruff key in place.

Something like a bolt. Maybe this bolt, melted into the plastic housing:

And along with that melty bolt, a rather tidy shaved detente for that pulley. Notice what else isn't there? Thread locker. Like maybe this thread locker, that they thought to apply liberally to all of the external housing bolts:

So let's fix that and put things back together nice & tidy, shall we?

And once that was done, a quick clean out of all that burnt up plastic:

So the good news is there doesn't appear to have been any significant damage. Once again I seem to have gotten lucky in both timing and the availability of tools on-hand. Had this happened in a race, for instance, I either would have kept riding until it detonated or have lost 45 minutes to the repair.

The less-than-great news is that this piece is clearly under-designed. The bolts for the plastic housing are beefier than this critical bolt that literally attaches the flywheel to the drive-unit. While torque applied to the trainer should, in theory, run in the same rotational direction that tightens the bolt, if it DOES come loose, even slightly, its impact into the housing will cause it to instantly back out completely, which is clearly exactly what happened.

The housing actually created a phillips head driver of molten plastic to facilitate removing the bolt.

After getting it all back together, I hopped on and knocked out a short ride, but now my power meter wouldn't pair, and wouldn't ya know this was the first time the unit reported power numbers that jibed with what my heart-rate suggested. I look forward to re-doing my power test on the trainer now that it's actaually assembled correctly.