Post-019
Mar. 21st, 2022

Bike upgrades part 3: fixing the seat and handlebars.

Brown? It's brown? Since when did I like the color brown? 

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So this post has a few stories in it, but it started — when I walked into D-Lab one evening and noticed a specific and interesting scene unfolding in the main shop area. I found shop manager Jack Whipple, and a few others friends including John and maybe Quang (I forget, writing this a few weeks later), surrounded by around 20 pairs of bicycle handlebars just lying on the floor. The most curious thing about them though was they were small, like 16 inches wide small. Much smaller than normal handlebars. This made me imagine them on my bike.

The ones that really caught my eye were these two handlebars with brown handle rubber wrappings on and they looked super retro and cool. So I thought it would be pretty fun to replace the handlebars on my bike with these ones and try to make a short video along the way because I hadn't made a video in a while and I was kinda missing it.

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Here's a picture of the handlebars to start. There are two main problems with this. The first is that they're continuous vs. my bike has "foldable" handles since it's a foldable bike. That also means each handle is a separate piece, there's no one continuous bar going through the setup. The second problem is that we couldn't find one of these "re-used" handlebars with the nice brown wrappings on both sides, so we had to cannibalize two of them.

We decided the greatest chance of success was likely attaching these handlebars to the ends of our current handlebars. But to do this we needed to make some modifications. We tried to get the current black handles off the metal ends of the bike's current handlebar setup but this didn't work after repeated attempts of blowing air, peeling glue, etc etc, so we decided the best thing to do was to cut the ends off :)! 

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Angle grinder... straight against the metal, the black handles fell right off even if the cutting disk was significantly worn down (change blades kids). Now we were left with these two random sticks sticking out the front of the bike. Also took the brakes off while we were at it (the handle part). 

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Here's "Wiggles" the stabilizer and "Hubble" the camera. Both keeping a 6K watch on the bike as we complete the modification steps. 

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The next step was to prep the handlebars, we wanted to make them a reasonable width so we cut them right before the little bumpy part that usually is used inside the clamping mounts of typical bike handlebar holders. The concept here was to slide the new handlebars (after we cut them) over the old ones. Since these tubes were a bit thicker, we thought we might get lucky.

There was also this little decorative end-piece that was on the bottom of both sides of one of the handlebar sets, but not on the other. Presumably they had fallen off. So we moved one from the half of the handlebar we weren't using to the half we were. 

Now there was of course only about a one in a million chance that this new handlebar was going to smoothly fit over the last one, of course it did not. So we needed a new plan and we started by taking off the old handlebar "studs" from the bike.

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We went downstairs to the lathe and popped the old handlebar "studs" on to turn down their outer diameters by a little bit. The tubes they were made out of were hollow but pretty thick so if we took off just enough material for the new handlebars to slide onto the old tube, we determined it would still be structural enough to be a handlebar. We marked out how much of the tube needed to actually stick into the bike for it to still mount using the original spring-locking mechanism the bike comes with, and we turned the tube down until it fit inside the new handlebars. 

Because we wanted to be able to disassemble this new setup easily, we turned the diameter to a close slip fit and slid the two tubes together. 

Of course, Hubble and Wiggles joined us for this adventure.

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Because this whole thing was only a slip fit, we had to attach these things together somehow. The new bar was also a larger diameter and the brake could no longer slide on and clamp mount to the bar. We decided to use a bolt to hold the whole assembly together but this involved removing the brake mount from the brake handle itself as well as the bowden cable that actuates the disk brakes (we'll put them back on later).

We lined it up, stuck this whole assembly on the drill press, drilled through, and bolted. Now note that if we just bolt on the brake mount as we showed above, when we apply the brake hard the brake mount might just turn so the brake won't actually be actuated because of the fact that we're only using one bolt. In this case, by drilling the hole such that when the whole assembly is bolted together and mounted on the bike itself, the brake mount sits flush against a part of the bike frame that acts as a hard-stop and prevents it from rotating when the brakes are applied. This will become clearer in later pictures.

We also had to rotate one of the brakes around 90deg so it didn't interfere with the other. We tested this out, personally I was fine with the small decrease in comfort. 

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We then re-assemble the brakes and slotted the handlebars back in and voila! We had a new pair of handlebars. And that's where the build video we made stops but we still had a problem. 

The handlebars are brown. The seat? Is black. 


This is a tragedy. 

This cannot stand. No way. 

I want to deeply apologize for this truly first world problem I've outlined here, but I wanted the design to be consistent. This, and it was really bothering me that last time when we "fixed the seat" we also removed the ability for the bike to fold. Nono, we can do better than this.

So the plan was a two part plan. First we would exchange the seat we got with the same exact model in brown, and then we'd design a CNC'ed part that was very similar to the previous seat (the plastic one before we changed it) but out of 6061-T6 Aluminum. We spent an evening measuring the new seat we designed from last time, the old seat, the alignment pins on the bike (which there is one for the old seat), and just kinda CAD'ed something up. There's only a few notable parts of the design to share. The rest was pretty straightforward based on the original seat.

 

  • We measured the alignment pin with a caliper and added like 0.5mm of diametral clearance to the respective alignment hole on the newly designed seat. 

  • We thinned the overall geometry to one inch aluminum tubes and added a bracing bar under the seat itself.

  • We measured the diameter of the tube that the seat currently clamps onto and matched that diameter on a feature the seat will mount to on the new part.

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So usually I'd put in the CAD and the machining plan for this but we did something with this part we usually never do for personal projects. I was going to CNC it myself but I didn't want to waste this much stock in-case the setup was wrong, and I was already sending out a CNC order for something else so we outsourced it. Since the shop I usually send to has a pretty good metal recycling policy, I didn't mind so much and it wasn't super expensive either.

There was also an alternative design made of welded steel tube which would have given me the chance to learn to weld. But steel rusts pretty easily and stainless is harder to weld. Something I might've tried had this been summer or winter break and we had a little more time. 

Regardless, here's the part. It only took like a week to show up which was super fast considering I told them "I don't need this for like a month, just whatever is cheapest." The strength of the Aluminum was already going to be higher than the plastic and the tolerances didn't need to be super tight. We went with the standard surface finish, and it matches the handlebars and head lamp well so we won't change it from what it already was when it showed up. 

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So we disassembled the old seat and we actually also cleaned the bike. A few months of Boston winter was enough to form some small cakes of salt on the frame. Look at how gross the towels are, ewwwwww! There was a lot of dirt on the frame so we cleaned before mounting the new seat.

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Here's the new frame component on the bike, you can see the hole that is used to line up the alignment pin. The pin prevents the whole seat from rotating. It is taking a lot of force, but we think it's a safe assumption that it was design with the loads of a rider in mind since that's what prevented the plastic seat from rotating as well. Note all the torsional load of this seat is on one pin, not great but it'll do (we're neglecting friction here so maybe it's not that bad).

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So the question became how to mount this thing. We were initially going to drill holes and bolt but that seemed difficult because there was no good way to get this on a drill press and the hand drill would've been a little sketchy (do-able, but sketchy). Walking around the D-Lab store room we found some large diameter pipe clamps. Since the old seat was also a similar clamp kind of mount, we thought we could try these. 

The clamp mounts fit around the Aluminum bike frame as well as the seat. We tightened down as far as they would go and then did a good shake test on the seat to see if it would come off. It seemed to support weight well. We then attached the new brown seat to the top, and sat on the seat and leaned back and forth to make sure it was stable enough. It was, so we decided we were done pending a ride test on the road (update: it passed). Now it's picture time! 

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Here are some fun pictures of the bike! They were taken on an iPhone 11 but we pulled highlights all the way up and decreased saturation so that gave us this funky "white-washed" look to the colors.

We also made this fun video from all the footage taken with the camera. Hope you enjoyed this three-part series of the bike and the video above! That's it for the bike upgrades so see you next time for the next project! 

#bike #upgrades #film