Let's start this off right for my fellow Americans and remember the reason for the season:
It's not about celebrating the government, the military industrial complex, voting, the liberal world order, american exceptionalism, proxy wars, bacon, cheap gas, the CIA, illegal fireworks, legal fireworks, baseball, hot dogs, school teachers, flipping off the british royal family, V8s, cold beer, the police, monster trucks, or even apple pie. It's about the right to self determination, and often in ways that make state officials nervous.
Now, as you may recall from my previous blog post (a mere half a year ago) I made a mountain balance bike for my boy. He has enjoyed it and used it well, but recently it became apparent despite his protests that he was ready for pedals. (Yep, it's another bike post)
The original McDurdle
I had built this bike with the conversion to a pedal bike in mind. This is why I went to the extra trouble (and it was a lot of trouble) of re-lacing the rim to a hub with provision for a freewheel sprocket. In order to convert the bike to a pedal bike, I needed to weld in a bottom bracket shell. The bottom bracket is where the crankset (axle, crank arms, sprocket) mounts. Before I could do that, I needed to cut away some material in the frame to make room for the bottom bracket shell. Lacking precision machining equipment (don't let my angle grinder hear that) I needed to get a little creative if I wanted the bottom bracket to go in perpendicular to the other frame tubes. Cue the 3D printer.
Pilot hole drill jig
Bottom Bracket holding jig
In the flesh
I planned to cut the material out of the frame using a hole saw roughly the same size as the bottom bracket shell, but if you've ever used a hole saw, you are probably thinking I'm insane. Everybody knows hole saws were invented by the prince of darkness, Satan himself, as a way to injure tradesmen. If everything isn't perfectly square when using a hole saw, a tooth will catch and twist the user's arms into a pretzel, or smack them in the head with the drill, in the case of overhead use. I've come to learn however, that hole saws can indeed be used to cut all sorts of irregular work pieces, so long as the workpiece and the hole saw are held rigidly in relation to one another. An example of this would be a milling machine, lathe, or even a tube notcher being used to notch tubes for a roll cage. In my case, I figured if I could drill a pilot hole squarely through the frame, I could then use that pilot hole to guide the hole saw and keep it relatively ridgidly aligned with the frame. That's a word salad that is better explained by the pictures below:
Jig clamped in place with a drill bit inserted
Holes drilled, pilot rod in place
Hole saw with pilot rod in place
Cut in progress
Finished cut
Fine tuning the cut to fit the BB shell
As you can see, the cut came out decent. I did need to modify it slightly with a die grinder but it was much better than if I had free-handed it with my angle grinder. Satan still got his laughs in though, at one point during the cut a tooth caught and twisted my arm around so quickly that I sprained my wrist. Nothing too serious, but I did miss my weekly mountain bike ride because of it.
Now it was the other jig's time to shine. I pressed the BB shell firmly into the jig and mounted it up. With everything held securely in place it only took a few minutes of welding, and this was now a pedal bike. Or was it?
Even before I had welded the BB shell in, I could tell that there would be a clearance issue with the chainring and the chainstay. This is not an uncommon problem in mountain bikes, and there are many ways of making clearance. I went with a simple notch, which I then patched with a scrap of steel. There's not a lot of clearance, but it works.
And with that, the drivetrain went on. Unfortunately the chain rubs slightly on the seat stay, so that will require some correction. All in all, it works pretty well though, and I was pleased that it only took one night minus the jig design and printing.
Best of all, the next morning I showed the kid and despite not being that confident that he could ride a bike, he picked it up in about 5 minutes.
But wait, there's more! Just as more pistons in an engine or brake calipers on your car is more gooder, more pistons in your mountain bike brakes is more gooder. And I decided I needed more gooder. The brakes on my mountain bike aren't bad, per se, but they sure could be more gooder, especially when I do big descents like at a bike park. Good brakes have a couple advantages. First, better stopping.
Second, less hand and arm fatigue which means less falling off the mountain. And third, more street (trail?) cred with the bros. I mean who still rides with two piston brakes anymore??
Just calipers. Most of the time bikers swap out the whole system, but I'm cheap.
The contents of one box
Count them pistons
Old vs New
Four pistons of power!
So that's it. I've been working on bikes again. Somewhere in there, I rebuilt my rear shock. That might have been neat to see, but it also might have been unbearably boring. Thinking about writing that just made me tired, it would basically be an instruction manual.
Now lest you get discouraged and feel this has become a bike blog, I do have a little secret to share: I've gone green.
