While we are considering cargo bikes

Jon Norstog

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Nov 15, 2025, 3:43:25 PM (6 days ago) Nov 15

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I got a deal on a slightly used Shimano "STEPS" mid-drive electric setup about 6 years ago and built a 2-wheeled tractor-trailer setup. We live in a small house on a large lot in NE Portland and have a monster garden. I use this setup mainly to haul fallen leaves for mulch, but also sometimes large street finds, building materials, etc.

A full load of wet leaves can weigh close to a thousand pounds. The bike can haul it, long as I can get it moving under muscle power. Bicycle trailers present a design problem: connecting to the bicycle. The bicycle has to be able to bank in a turn while the trailer remains level on the road; and the attachment between them works best if it is on their centerlines.

I had some heim ball fittings I picked up in a thrift store, so I used them and built a little tower on the seat stays so the hitch and the high-mount wagon tongue would clear the rear wheel. Solid axle with wheelchair composite "mag" wheels. The trailer is 5 ft x 3 ft. and 19" high, about .85 cu. yd. piled high.

If I had a canoe, I would build a trailer for that and tow it down to the river. A couple kayaks - that could be done.

I have not encountered any handling or stability problems at the speeds I can go - the motor's 20 mph max was set up for 700 C wheels and I'm using 26" wheels. Unloaded I'll ride about 15 mph, maybe 12 with a full load. Storage is pretty EZ. The tractor unit is just a heavier 26" BMX bike and the trailer can stay outdoors under a tarp.

When I build another one I would look for some kind of buggy springs to soften the ride, and maybe a brake on the trailer. I would also use a motor/control setup that had a throttle for getting underway with a heavy load, and a dedicated lighting circuit.

salvage_load_2021 (2).JPG

oak_leaves_2020 (1).JPG

summer_2020 (9).JPG

tho...@kokopedli.com

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Nov 15, 2025, 4:06:29 PM (6 days ago) Nov 15

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I'm fairly sure I have a spare handle-bar-mount throttle I could send you (if you want it and ask for it).
AND
The upgrade I would like if I built anything like this is a tension activated hitch, so that whenever it senses load it turns on a motor in the hub (hubs?) of the trailer, or when it senses load the other direction it turns to regenerative braking...
Beyond my resources to do this, but that's what I think of =)

noMadic Thomas

Jon Norstog

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Nov 15, 2025, 4:15:22 PM (6 days ago) Nov 15

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I was thinking more along the lines of a foot brake to a disc on a live axle, or discs on the rear wheels. So far I have been able to control the whole setup using the tractor's 203 mm discs, and avoiding hard braking going downhill.

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John

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Nov 17, 2025, 4:54:28 PM (4 days ago) Nov 17

to Jon Norstog, tho...@kokopedli.com, frame builder list

I dealt with some similar design considerations when building a heavy-duty 3-wheeled trailer (CARLA clone) for the bike collective here in Providence to serve as a mobile repair station and to be used to carry heavy/bulky loads around (I used it to move a horizontal milling machine 4 miles across town -- total weight of trailer + load was 900 lbs...).

Lots of photos here, which are probably more useful than the text explanations of design decisions below.

Trailer has overrun brakes, similar to the CARLA. Two disc brakes on the trailer rear wheels are engaged when there's compression on the tow bar from braking by the pilot bike.

Originally the trailer had its own power, via a hub motor on the front wheel. The motor control for this kind of setup really needs to be done by a load sensor on the tow bar, and I haven't had the time to build that so we ended up putting a regular front wheel on the trailer and now tow the trailer behind the shop e-bike (donated to us, and refurbished). When the trailer was self-powered it was controlled by a throttle on the pilot bike handlebars, which was tricky -- if you overdid it on the throttle, it would push the trailer too far forward and engage the overrun brakes. Took a lot of operator skill, and this thing gets used by lots of people, so I switched over to an e-bike.

Tow bar originally had a simple ball joint, but it's been tipped a couple of times and I realized I wanted the ball joint to be able to freely rotate about the axis of the tow bar in case of more tipping... Used a square taper BB to accomplish this and it's been working well for a couple years.

I'm pleased with how the tow bar attaches to the pilot bike. Seatpost for the pilot bike is big enough that I made a secondary sleeve out of steel that has the attachment for the ball joint. Very sturdy, adjustable, and doesn't damage/alter the pilot bike at all.

rosy, in Providence

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