Thanks, Pax! I was originally looking at Oshcut before I discovered PTL. I believe PTL laser miters tubes for several different frame builders, so they’re familiar with working with thin wall 4130 tubing. The laser’s chuck needs around 6" of grip length on the tube - butted tubes may be difficult but this method is great for straight gauge tubing.
I used Weldmold 880 for all the joints, and it felt like I was welding a dirty casting. The butt joints were particularly difficult for me. I’m in awe of how clean and consistent the 3DP welds are on the Neuhaus frames. Nick has his process dialed.
I had not seen the earlier posts on you kinematics software. Great bit of work. I can’t count the hundreds of hours I have spent in Linkage moving pivots a mm at a time trying to get the curves to look the way I envision them.
Great work! I really like the use of the printed parts and laser mitering to speed up the process. Glad it’s riding well. It looks like there is very little if any fork rake. I suppose with the little wheels this results in similar trail numbers to a big wheel bike?
I want to build a similar mini cargo bike, but I am thinking of using a suspension fork (our roads here are super bombed out in some places) to compensate for the small wheels. Looks like you have some wide tires on that should smooth things out.
Reviving the thread! I just wrapped up a new 24" mini-velo cargo bike and will be dropping the frame off at powder coating tomorrow.
This frame is primarily an exploration/continuation of my previous 20" cargo bike. Having ridden that bike for the past few months, I’m excited to try a few new things this time around:
Larger wheel size
Integrated front/rear dynamo light mounts and internal wire routing
Bosses for Abus frame lock
Two forks (high/low offset) to compare handling with and without loads
Steeper seat tube, dropper port, and slightly reduced reach + increased stack. My saddle is currently slammed as far forward as possible and I still find my position a little uncomfortable.
Drivetrain: I’ll be re-using a Microshift Advent X setup from another bike (11-48T cassette) with a 36T front chainring. This should give me similar effective gearing to my current 20" setup with a slightly wider range on the low end. (numbers based on 2" tires for 29/24" config and 2.4" for 20" config)
Hi/Lo Offset Fork: I’m investigating a large (around 104mm) and small (around 54mm) mechanical trail by using two different forks. I’m excited to test how sensitive I am to this geometrical change and compare it against my original 20” design which has around 77mm of mechanical trail.
Man that looks sweet. Keen to hear ya thoughts on the forks! Based on my experience the large offset/low trail option should be noticeable better with a front load but I’ve never done a back to back test.
Fun projects for my university’s energy conversion class!
Dynamo Light
Dynamo light in a pill-shaped housing with a single CREE XM-L2 power LED and LEDiL EVA lens. The dynamo uses a full-bridge rectifier to convert the AC output of my Shimano hub dynamo into DC that is either sent to a supercapacitor charging circuit or buck-boost regulator set to 5.5V output. The supercapacitor and regulator outputs run to an ideal diode controller which sends the higher (voltage) of the two signals to the LED driver.
To my surprise, the light works pretty well! It has minimal flickering at low speeds, likely due to the large smoothing capacitor connected near the rectifier output. However, there are a few things I’d like to change for the next version (hopefully with more time to work on it!)
Revise supercapacitor charging circuit and/or move to lipo/li-ion battery. I had a few weeks for the design/build of the light and didn’t do breadboard testing of different supercap charging circuits/currents. I sized the circuit based on the supercap IC (made by TI) datasheet for a ~30 second charge time, but in practice, the supercap charges slower and discharges faster than I anticipated. I need to do a lot more work/research here to come up with an efficient circuit.
The LED driver is driven by one current setting resistor. I want to redesign the current set circuit component to allow for brightness/current changes based on wheel speed and user input.
Move to 3-element LED. The single XM-L2 LED is good for urban illumination and okay for nighttime rides without streetlights. I want to try a 3-up LED next, similar to the Sinewave Beacon.
This one was a lot easier than the Dynamo light (I didn’t have the motivation for another intensive project, lol). I was originally going to make the charger housing a 28T chainring but couldn’t find stock in the right size… I settled for a jockey wheel instead. The charger works well but has faint, but audible, coil whine.
