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Solar-powered recumbent trike

December 21, 2024 — BarryK

Page created May 17, 2023
Updated December 21, 2024 

This has been a slow project, over 12 months. I bought a "320" frame TrikExplor basic recumbent tadpole trike, and proceeded to modify it over succeeding months. The main structural change was the front wheels were brought closer together, with coil suspension, making it a full-suspension trike. A motor and LFP battery were added, with electrical control systems and a solar panel.

As to motivation, these were the main reasons:

  1. The original trike was 910mm wide; however, the maximum legal width in Western Australia is 800mm. Besides, I wanted it to fit through my front door, so as to keep inside.
  2. Want full-suspension, for a comfortable ride on corrugated gravel roads common in rural Australia. The original trike only had rear suspension.
  3. Love the idea of touring the countryside, not just in the comfort of a reclining "lounge chair" ride, but having solar assistance for the motor. The promise is, on relatively flat terrain, ride all day, with only token input to the pedals.

They are the main ideals, but of course many compromises along the way. Hardly knowing anything about bicycle design and maintenance was also a challenge; especially design of the steering geometry. The solar panel has a nominal rating of 200W, less than I would have liked. The motor is 250W, again a legal requirement, and also less than I would have liked.

Over the approximate 12 months, I posted progress to my blog. Due to the highly experimental nature of what I was doing, there were some attempts that got aborted; design of the front suspension for example, went through a couple of iterations. Here are the blog posts, in reverse-chronological order...

The early days

This is the "genesis" post:

Did lots of online research, posted interesting information about trike design and riding:

I puchased a "320" frame trike, with rear suspension:

img1

There are some oddities about the design, and in retrospect I would have chosen some other trike. Also, I think a steel frame would be more amenable to a DIY project.

Embarking on the project, the front suspension was a major undertaking. I had to learn about caster, camber, toe-in and toe-out,  Ackerman, etc. The first attempt at a front suspension was not very good; that got aborted. Ended up with a steel framed front suspension, and it was difficult to match it to the weird 320 frame.

Front suspension design

Originally was very ambitious, wanted a leaning front-suspension trike. Ended up deciding the leaning part is too complicated. Anyway, here are posts from that time period:

I continued looking around online, on the lookout for other designs and ideas. For example:

Kept on playing with suspension designs:

...that last post is close to the design finally settled on.

Axles and knuckles

Construction of the axles, or more encompassing, what are known as the "knuckles", proved to be a major challenge, as I did not use any of the original knuckle mechanism:

img2

Matching the knuckle to coil-suspension swing-arms went through some design iterations. There was also an aborted first attempt at the swing-arms:

At this time, I was still thinking of it being a leaning trike. Designed the suspension framework accordingly:

...actually, retained that potential for a leaning trike in the "mark-2" and "mark-3" swing-arm designs, except locked it in place and not used.

Suspension and steering

As already mentioned, the mechanical design and geometry of the suspension and steering was a major learning exercise. Some posts:

Here is the "mark-2" front suspension:

...that used wood for the swing-arms and framework. Didn't like it, decided to go for an all-steel design, which is "Mark-3", the final design.

  

A digression; what do recumbent trikes weigh?

I was working on the steering geometry, learning and trying to get it to a final build:

...getting there.

The final design

Now onto mark-3 design, all-steel, with the weird attachment to the trike alloy frame:

More reasons why I did not like that 320 trike:

...apart from those complaints, which can be fixed or worked-around, the quality is good, and it is strongly constructed.

For the mark-3 steering linkage, I ended up with a compromise, mostly because just wanted to get something built:

Photo of mark-3, upside-down:

img3

Assembling the trike

From there on, progressed to assembling the trike.

...almost there.

 

A digression, this is something that you seriously need to consider when riding a trike:

Another major structural change was at the rear of the trike. The luggage rack and pannier frame were bolted directly onto the rear fork. Simple from the manufacturer's point of view; however, I wanted them to be above the shock absorber:

...even closer to almost there.

  

Here is another digression. One wonders how stable a trike will be with solar panel on top, when there are strong side winds. Well, there are people riding two-wheel ebikes with solar panels, and surprisingly stable:

Progressing to the electrical systems...

Electrical design

Now getting onto the electrical design. I wanted more safety than you normally get in an ebike, and designed an electrical junction box with three circuit-breakers and various other switches. As mentioned in an earlier post, have used a LFP (LiFePo4) battery as it is safer than the usual NMC Lithium type. Electrical design posts:

img4

...that junction-box is mounted under the seat, within easy reach.

 

Another digression, useful information about LFP batteries:

...I wonder how much longer LFP will be considered as the safest choice? There is sodium-ion on the horizon.

The assembled trike

Having constructed the frame for the solar panel, what remained was to put the solar panel on top, then wire it to the MPPT controller:

Finally, taking the trike outside for its first test:

img5

A further note about the solar panel: the above posts show rather low power output, but I expect to be getting closer to the 200W rating; probably about 150 - 170 watts when sun is high in the sky and the BMS working as expected.

...ready for adventures!

Conclusions

The project is not finished. The very nature of such an experimental project is, once built, the mind is full of ideas for an improved "next project". Don't know if I will ever do a complete rebuild; for now, want to use what exists, and hopefully go on multi-day countryside touring.

I will mention one thing that I would change if do a rebuild; bringing the front wheels closer together has the downside that it restricts the turning radius. Turn too sharply and there is the risk of the wheel touching the rider's foot. This is a 20-inch wheel, and I think with 16-inch wheels could manager sharper turn without touching the foot.

One more thing; the rear wheel is 20-inch, and I don't like the derailleur gear mechanism being so low to the ground. Would prefer at least a 24-inch wheel.

Yet another: might build my own lithium battery, with a BMS that has same +ve and -ve wires for charging and discharging. This has some advantages, including simplified charging and discharging simultaneously.

My blog will have more posts as I outfit the trike for this proposed country touring, so please do monitor:

https://bkhome.org/news/tag_light.html

https://bkhome.org/news/tag_nomad.html

I have also started a YouTube channel. Nothing much there yet:

https://www.youtube.com/@meanderinglight

Hope this page has inspired you!    

Tags: nomad