Saturday, June 11, 2016

Trailer for E-trike

In this blog entry, I describe the evolution of the uber-light camping trailer for the e-trike. June 11, 2016 by Joseph McCabe, PE.

I have wanted solar transportation for at least a decade. My first attempt was buying the first three wheeled car licensed for the road in Colorado. That licensing challenge was enormous, but the vehicle didn't deserve the effort. The Zapcar was not a good vehicle. I donated it to a worthy non-profit in Denver. The photo shows an actual flexible photovoltiac (PV) module charging the car. Solar electricity stored in the lead acid batteries moved that three wheeler around the neighborhood.

Photo 1: Solar Charging of EV in Colorado

Next, at considerable expense I converted my 2011 Prius to a plug-in-hybrid. This is a Gen3 Toyota Prius; the on-board computer communications haven't been hacked yet to optimize the scenario like they have on the Gen2 and Gen1. But, from a 4 kWh LiFePO4 battery pack, I can get 15 miles distance on all electric. I have been working with my local cooperative utility (that isn't very cooperative on solar yet) to try and get a community solar garden, perhaps later on this year.

Next came the electrification of the recumbent trike written about in this blog entry: 

That trike has a rear wheel drive, which I attached trailers to for towing kayaks and other things. It makes sense to have a wheel behind the seat, that pushes the driver and pulls a trailer. My thoughts wandered when thinking about camping and trailers. I like taking my trike with sporting gear to local state parks, being able to get into the park because bikes are free. We have a local park that has an archery range which I wanted to trike to with gear, and maybe do a little camping too. So the trailer design began. If you do a Google search on "Bicycle Camping Trailers" you will see YouTube videos, some of which were inspirational. I made some cardboard cut out models of possible fold out trailers. Here is a link to a video I made of that cardboard model if interested:  

I sketched many ideas, and made a list of some camping trailer requirements:
  • 100 lbs.
  • Rugged
  • 35" tall (this is so I can sit up in it and because I have 35" PV modules)
  • Aerodynamic, teardrop like
  • PV integrated
  • Replicate-able, can make more if others are interested
  • Small cross sectional area for limited wind loading
  • Roof mounted on cars
  • Trailer mounted
Photo 2: Some of the sketches and designs used to get project moving. Sorry, blurry.

Often I inventory things I already have to investigate building my projects. I have many long pieces of 1-1/2" angle aluminum that is 1/4" thick salvaged from an old solar installation. The PV panels I will use come from the same place. Using some of the ideas out of the sketches in photo 2 I began to work on phase 1 of the project. There are 5 phases, trailer, solar, front fairing, roof rocket and tail. 

Photo 3, 4 &5: Aluminum work.
Cut, bent and bolted the pieces as shown in the images of Photos 3, 4 and 5. Those squares are each one piece of angle aluminum. Turns out I had a box of bolts, nuts and washers that were perfect. Took a day to built to this point. 
Photo 6: Add trailer and flooring.
Another day to figure out how to do the trailer and flooring, using a trailer I had picked up at a garage sale two years earlier, and available plywood. About this time, I had worked out many design ideas, lengths and orientations. I hadn't spent any money, and the project sat for a few days because I needed to address the wall properly. I went out and paid $70 for 1-1/2" aluminum backed insulation. It isn't exactly what I wanted, what I had been designing was a better R-value system with less weight. That will have to wait, this wall material will do what is needed at this time, keep the trailer cooler in the summer and warmer in the winter.

Photo 7, Video 1 and Photo 8: Insulation walls.
You may notice the trailer is on the floor. I attached four legs that fold down to hold the trailer up, just above the wheels. The wheels can be removed, the trailer can be mounted on-top of a car, specific Yakima rack holes were placed in the frame for this purpose. I had a roll of aluminum foil backed tape that I used on all the edges of the cut insulation. At this point, with wheels the trailer weighs 75 lbs.
Photo 9, some of the hand tools used for the build.
One big challenge has been the hitch to the e-trike. I tried many scenarios which didn't work. My current solution is a light weight ball and socket that attaches the trailer to an aluminum bracket attached to the back axle of the e-trike. I attached an accordion door. The top also slides to let air and sunlight into the trailer. The walls are easily stacked inside the trailer during transportation to reduce air resistance. The trailer walls can be installed in about three minutes. 
Photo 10: E-trike attached to trailer with wheels outside trailer. 
I made a video on how I transport the trailer with the walls flat to reduce wind resistance, and how easy it is to put them into place, about 2 minutes if I knew what I was doing. Little longer for the first time like shown in this 3.5 minute video.

The trailer is so light weight that I designed it to be attached to my car rack using standard Yakima hardware.
Photo 11: Trailer mounted on-top of car with standard rack.
The next entry for this blog will be phase 2, the solar energy part. Stay tuned, and don't hesitate to e-mail me with encouragement. Thanks for reading.

Here is the Phase 2 blog entry:


  1. Love your energy and effort and cool bike stuff Joe!

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