Compact Bamboo Long-John Cargo E-bike

[karlInSanDiego]

Much thanks to James at the Bamboo Bicycle Club. Here are some shots of my finished Compact Bamboo Long-John Cargo E-Bike. I designed it on SketchUp. It's inspired by a German Muli design. It has a 1000W mid-drive Bafang motor, 2 used 491Wh e-scooter batteries, located in a homemade battery box in the basket base. I learned to weave for this project, and the reed is rattan, so grass like the bamboo frame. It has 9 speeds on a cassette and a 3 speed Sturmey Archer CS-RK3 internal gear hub. I built the wheels using Alienation BMX rims, with 305mm front and 406mm rear. It's running Magura MT5e brakes with 180mm MDR-C rotors and sport pads. Front fork is a SR-Suntour SF18 XCM JR-AIR-SL Lo 20 with air adjustment and lockout. It has a SRAM 20th Anniversery XO rear deraileur from 2007 and SRAM X9 trigger takeoffs from even earlier, which I chose because of their visible gear indicator windows. I added an EggRider v2 display which allows easy motor tuning via bluetooth and includes a range indicator. Saddle is Brooks Cambium C17 Special. Front light is Busch + Müller IQ-XS high beam and the high/low switch integrates with the Magura brake lever. Seat post is a carbon fiber knockoff of the Ergon suspension post. Headset is Viscoset steering damper.

Some bikes deliver a pizza. This bike delivers the pizza oven.

Sized to fit on the trains in San Diego

Design and Build

Used fork cut and welded to steel tubing to form custom steerer

 

[ZeroEm]

Enjoy the Bamboo builds. Does the frame end up as light as a metal frame or lighter?

 

[AdR]

Love it.

 

[2old]

WOW!

 

[PaPaSteve]

A + craftsmanship
Clearly someone who has built other things

 

[karlInSanDiego]

ZeroEm - I'd say bamboo is probably the same or heavier than most comparable shaped frames. When you have no experience doing successive builds or destructive testing, you tend to overbuild your lugs. Same problem if you built your first carbon fiber frame by hand without molds and intimate knowledge of layup from a recipe of where to increase layers and add reinforcement.

The Bamboo Bicycle Club does sell kits with pre-made lugs, and I imagine that allows for less unnecessary overbuilding.

Many first time cargo bike builders who try to wing it with steel can't source lightweight bike tubing or find it's really difficult to weld. Many pros braze. Using square steel tubing from a metal supply shop must really be hella heavy.

 

[ZeroEm]

I'm attracted to Bamboo. It's an interesting material. When a nice build like this comes along, start to think about it. Like the look of it. Must be the color.

 

[amberwolf]

Using square steel tubing from a metal supply shop must really be hella heavy.

Depending on the tubing, it certainly could be. The SB Cruiser trike uses a main "keel" / downtube of ~2" square tubing (with smaller tubing inside it at the highest stress point just in front of the cargo-seatbox), with >1/16" wall thickness (but less than 1/8", I think), and just that part is hefty. The rest of it is made mostly of 1" generic steel (retail fixtures/signage), relatively thinwall, but it's all still pretty heavy. If I could afford the few thousand dollars for it, I'd get good cromoly tubing to build it from...but it would still be square cross section for most of the frame for various design and usage reasons.

 

[karlInSanDiego]

Yeah, if you ever cut through a double or triple butted steel triangle and see how scary thin it is, it makes you appreciate the skill needed to build steel frames.

 

[99t4]

Curious how the steering mechanism works. Can you explain?

 

[karlInSanDiego]

Curious how the steering mechanism works. Can you explain?

I was really concerned that remote steering involved critical geometry consideration, but I was overthinking it.

For my build I sourced a local used fork in ebay, and sectioned and MIG welded a length of new steel tubing between the upper and lower portions of the steerer. I cut off the fork legs and welded on an extention at the bottom using a failed hood hinge from a 1948 Chevy truck. That extention sticks out the bottom of the main steerer bamboo pole, 90 degrees to right by around 5 or 6 inches from the center. It's suspended in the hollowed out steerer pole by a standard bicycle headset mounted in aluminum inserts spread much farther apart that any normal headtube. Aligning those two separate head tubes perfectly in line was accomplished by splitting the steerer pole in three vertical strips, temporarily gluing the head tubes to angle iron and bonding two of the three strips, and then removing the angle iron after if set and finally glued in remains strip + a filler strip. In bamboo building speak, it's laminated or engineered.

Back to how it works, you fabricate a remote steering rod that connects to that 90 degree extention on one end, and to a fork arm on the other end. The distance of each of those connections from their pivoting axis should be approximately the same for each. This results in a steering movement at the bars translating to an equivalent movement of the fork in that direction. The remote steering rod can, and will include at least one angle, and it's attached with adjustable ro ends to fine tune alignment. The steering rod actually floats freely, but gravity holds it vertically. If you grab it and swing it to the left or right, the distance between the rod ends remains constant, so there is no change in steering angle.

I assumed at first that if the actual fork head tube angle was different than the handlebar steerer tube, that the steering would not be linear or symmetrical. But actually, it is both. Really simple, time tested remote steering. You can increase or decrease the steering ratio by moving how far out your rod end attaches to your 90 degree extention, and you see some builders leave themselves extra length and a few options for where to attach it.

Remember that steering on a moving bike and keeping it upright is a series of hundreds of micro inputs to control and correct the lean. So you need to retain a tight ratio, but not overly tight. Building a bike with a sloppy, slow ratio would create the need for a tiring exaggerated handlebar movement. But making it overly tight, makes the bike twitchy and difficult to steer straight. This combines with rake and trail and headtube angle to result in the bike's handling. Mine feels a bit foreign to use despite a fairly relaxed head tube angle. So it may be that I need to tighten the ratio.

 

[amberwolf]

For my long cargo bike CrazyBike2, I made the remote steering slightly adjustable at first, and eventually settled on nearly 1:1; been quite a while now but IIRC it was just a bit less handlebar turn for a bit more steerer rotation.

The main thing I found necessary is having no slop in any of the joints or the rod itself, or else it would be "wiggly"--even a tiny bit of joint slop (so little I couldn't directly feel it playing with the joint) would make steering unstable. So after making various DIY versions of the tie rod, I went to a local outlet for McMaster-Carr (IIRC) and bought a pair of rose-heim joints for the rod ends, bolts, washers, nuts, and spacer tubes for the bolts to give an exact fit in the rod end bushings, and used some 1/2" (or thicker?) threaded rod from Lowes (or HD) to install the joints on...fixed all the slop and made steering nice and easy.

OVerall RS took a bit of getting used to, but after a fairly short time it was as natural as any other bike...and I kinda miss it (since CB2 has been out of action for some years).

I intended to do remote steering the same way for the SB Cruiser trike (and still would like to) but didn't have the parts to do it at first, and went with a long tiller, and it's worked well enough for several years that way...so probably wait till v2 of SBC to do RS (since SBC is my primary transportation).

 

[lkcl]

Enjoy the Bamboo builds. Does the frame end up as light as a metal frame or lighter?

hell yes! it's basically fibreglass techniques but with different materials. Calfee Design uses carbon fibre tubes. i did some test pipes with kevlar (aramid) cloth and they're astonishingly light and strong. at 200 mm long with only 3 wraps round a 21.5mm PVC pipe i can barely get any bend.

i'm designing a 200kg Category L7e Hybrid EV using the same "nodes-plus-pipes-plus-cloth-plus-resin", except using FR4 (fire resistant resin), kevlar cloth (also fire-resistant) and hemp hessian. 21.5mm PVC pipes for heavy-duty connections and 12mm bamboo where it doesn't matter so much. nodes are 3D printed to "hold" the pipes in place whilst the kevlar/hessian is wrapped and the resin hardens.

this is basically a really good proven technique, it's just not commonly known.