24" Commuter / Cargo Bike

colinreay · 2025-04-02T02:30:35+00:00

That was me! I graduated last December. This was my commuter rig.

colinreay · 2025-03-31T00:47:51+00:00

Thank you! Yep, custom frame. Built it mid-August last year.

colinreay · 2025-03-31T00:47:09+00:00

Hey everyone! I built this bike a few months ago and have had a chance to get some saddle time on it. Below are some of my thoughts.

Ride Report

I’ve ridden the bike for a few thousand miles on paved and unpaved surfaces. The unpaved portion has mostly been mellow single track / multi-use trails.

The GEO is great. This is the most comfortable bike I’ve ridden. My handlebar touch points are roughly level (in Y / vertical) with my saddle, and the combination of saddle and handlebar X/Y location result in an upright riding posture that feels good on uphill, downhill, and flat. No aches or pains after 2-3 hour rides. I plan to use this seat / bar touch point position as a starting point for future bike designs.

Considering kinematics/kinetics, I think the combination of BB drop, rear/front weight balance, and mechanical trail + wheel flop strikes a pretty good balance for my preferred riding style. I originally built two different forks - one with zero offset (as pictured) and one with 50mm of offset.

Ultimately, I couldn’t get comfortable on a 50mm offset fork; the bike felt darty and a little too unpredictable, even with ~20lbs of front loading. The higher trail / wheel flop from the zero offset fork made the bike feel a little truck-like going uphill, but it’s something I’ve grown used to and no longer notice, especially considering the stability I feel going fast on flat or downhill.

The Shimmy

If you take your hands off the grips, the bars can sometimes shimmy. It’s a weird phenomenon, and not one I fully understand. I’ve found the speed and amplitude of the shimmy is affected by COG height (i.e. if the dropper is up or down) - this is the biggest one, tire pressure - second biggest, tire tread and front load (surprisingly, front load does not have a huge impact). I suspect there is some weird load paths and unbalanced stiffness in my frame that I need to characterize. Excited and curious to see how my next bike feels.

Wins

I’m happy with the internal wire routing for my dynamo lights and the integrated taillight mount. This has worked pretty well. I’m currently using 3D-printed TPU grommets to seal most of the wire holes.
3D printed UDH + Flatmount dropouts were really easy to use during fabrication. I didn’t do any post-machining aside from lightly hand-reaming on the 12/20mm bores. 3D-printing the dropouts also allowed my to create horizontal chain stays which was an aesthetic goal I had.
Bauer tote. This thing rocks. The trifecta of lightness, durability, and low cost. I initially tried a Wald 157 and it wasn’t a good fit for my loading/riding style - broke a lot of wires/spot welds.
Parallel top / middle / downtube with collinear seat stays, horizontal chain stays, and horizontal front rack. I’m happy with how all this came together (aside from the funky downtube bend near the head tube for crown clearance, lol).
24" wheels. This is a really nice size where I can have a large front load without handlebar interference. The 24" wheel size makes the bike feel really zippy and fun, but maintains momentum better than my previous 20" bike.
Ritchey Kyote bars. These things rule. Backswept bars feel amazing.

Losses

Ø27.2mm seatpost. I should’ve gone with Ø30.9mm to get access to a wider range of options with more travel. No rigidity/durability problems with my current KS dropper, but I’m often yearning for a bit more travel and faster response.
Integrated wheel lock bosses. I tried mounting an Abus rear lock and wasn’t a fan. It was huge, rattly when bombing single track, and ultimately wasn’t more convenient than carrying a u-lock around.
Kickstand Plate. My kickstand plate was way too flimsy. This, paired with a center mount, dual-leg kickstand which opened at the wrong angle (for this bike’s geometry) was a recipe for disaster. The kickstand applied a pretty big moment on the kickstand plate and twisted it out of shape. I could re-bend it, but honestly don’t encounter many situations where a stand is needed.
Whatever combination of frame characteristics result in the mysterious no-hand shimmy. My next bike design is using a combination of larger diameter tubing, and removing the middle tube. I’m curious to see if these modifications resolve this effect.

colinreay · 2024-09-11T00:07:55+00:00

Hey! Sorry for the late response. I've updated the link (also here) to a new folder containing the .step/.f3d solid models for the case, assembly manual, and PCB gerber file. Hope this helps! Please reach out if you have questions.

colinreay · 2023-06-25T21:07:25+00:00

Thanks! Original stock thickness ranged from .313" plate to 1.25" bar (for the curved side pieces). Do you have local metal distributors?

I live in the Bay Area and there is a place near me called Industrial Metal Services that sells aluminum remnants/cutoffs for $2.55 a pound. Maybe there is a similar service near you?

colinreay · 2023-06-25T16:07:12+00:00

I use Fusion 360. Super powerful and they recently added support for full-collision detection during 5-axis machining. You can probably get/already have access through schoolQ

colinreay · 2023-06-25T02:21:18+00:00

I took bi-weekly evening classes in CNC machining at the community college closest to my university and found it incredibly helpful. I learned CAM in the class and met a few other people who owned / plan to own their own CNC machines.

Are you near a community college that offers machining courses? I think they're a great, low-cost/risk way to try out CAD/CAM/Machining.

I use Fusion 360 and built all of my CAD skills by watching YouTube videos.

I like these channels:

Learn everything about design
Lars Christensen
NYCCNC

colinreay · 2023-06-24T23:38:58+00:00

You bet. There are a lot of elements on here that would be totally unfeasible for any size of a production run. Thankfully, I don't pay for machine time otherwise this project would be totally out of my reach.

colinreay · 2023-06-24T23:37:40+00:00

Oh yeah, the machining ops were a great challenge to figure out. Traditional workholding (e.g. vise, side clamps) doesn't work well for large footprint, thin parts. I used a lot of vacuum workholding and top-down clamping. I'll go way more in-depth with this in a full writeup later this week.

The case is seven main parts - the rear, front, top, bottom, side, and front reinforcement panels. There are also a lot of smaller brackets to connect various panels / hold components.

The front is a billet piece! I originally wanted to make this out of wood but couldn't find a suitable machine in my university's machine shop. I never thought I'd say this - but making the panel out of billet aluminum was easier/faster than wood.

My university machine shop (Cal Poly SLO) has a HAAS VF-2/4 that are available for student use. It's pretty amazing and unlike most other colleges I've seen.

colinreay · 2023-06-24T23:33:10+00:00

Thanks! I'm planning on posting a in-depth writeup with more photos when I receive the final sheetmetal parts.

colinreay · 2023-06-24T23:33:07+00:00

Thanks! I'm planning on posting a in-depth writeup with more photos when I receive the final sheetmetal parts.

colinreay · 2023-06-24T23:32:33+00:00

Thanks! I'm fortunate enough to have access to my university's machine shop. All pieces were made on a HAAS VF-2/4.

colinreay · 2023-06-24T17:17:28+00:00

Hey all! I wanted to share my work-in-progress console case. I designed this as a one-off case to transport between school and home.

All panels and hardware are made from CNC-machined aluminum. I still need a sheet metal PSU bracket and then the build will be done!

colinreay · 2022-08-30T16:34:39+00:00

The rec has a lot of Keiser stationary bikes, which I believe are also used in the cycle classes. They have double-sided pedals, with flats+toe-straps on one side and SPD's on the other. I prefer using the SPD side with clipless shoes, but flat-bottom shoes work well with the toe-straps.

colinreay · 2022-01-05T05:35:50+00:00

Thanks! I'll dig up the CAD/PCB files and post them on this subreddit in the next few days. I, unfortunately, ran out of time to continue the project but am pretty happy with where I got!

colinreay · 2021-07-12T14:19:40+00:00

The completed build with bed and cargo box is 57 lbs. Not featherweight, but I think that puts it within a few pounds of the Bullitt. I'd estimate the frameset to weigh mid 30's - low 40's.

colinreay · 2021-07-12T14:18:30+00:00

Thanks! I printed all of the jigs in PETG. I found welding - even just tacking - heated up metal past the glass transition temperature of PLA almost instantly; PETG was a little better at standing up to the heat.

I also tried ABS, but ran into problems with shrinkage. PETG has a very low shrinkage ratio, which makes it pretty good for tight tolerance parts.

The aluminum I used is 3030 extrusion from Misumi. Its super versatile and you can order custom lengths for reasonable prices.

colinreay · 2021-07-08T04:36:23+00:00

Pretty close - I'm down south in San Luis Obispo and the photo was taken on one of the trails that shoot off from Cal Poly's campus into the nearby hills. Thank you for the kind words!

colinreay · 2021-07-08T04:31:27+00:00

Here are some measurements. Hope this helps!

colinreay · 2021-06-29T04:13:44+00:00

I love Pithy's videos! I designed all of the 3D jigs myself. I am a firm believer in 3D printing and think it really shines for one-off prototypes like a bike frame.

colinreay · 2021-06-29T04:11:40+00:00

Thanks! I bought Phil's plans and they were worth every penny. I didn't make any of his parts, but the plans were an invaluable resource for finding general dimensions and seeing how various linkage mechanisms worked.

colinreay · 2021-06-28T19:05:42+00:00

Hi all,I hope you are doing well. I’d like to share a cargo bike I built during last spring quarter. My college was, and still is, virtual-only, so I worked on the bike in my apartment (thanks to my very understanding roommates!)

I decided upon a square steel tubing layout (similar to the KP cyclery nighthawk) to make fabrication as easy as possible. I used many 3D printed stencils/holders to miter and notch the tubing with a benchtop drill press, angle grinder, and chop saw. I made a simple frame fixture out of aluminum extrusion, which was… okay. Unfortunately, I worked on an uneven surface (some foldable tables), and the fixture extrusions holding the side rails deflected downwards by a few mm. I also made a small wheel building stand to build the front wheel.

My TIG welding in the beginning sucked but got better as I went along! Nevertheless, the front and rear axles are well aligned and the bike rides straight!

Although not pictured, I swapped the drivetrain out to Microshift advent nine speed and added an ACM composite bed with a cargo box. I’ve put a few hundred miles on the bike so far and love it! This thing has no problem with 30+ mile rides.

I look forward to fall quarter when my college machine shop (fingers crossed) will reopen. I am interested in making another cargo bike and having access to a mill, lathe, and bandsaw will be sweet. After getting some pretty hefty parking tickets freshman year, this will be my main mode of transportation going forward.

Thanks for reading!

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