Around the world on a solar ebike

[wturber]

This is all super-ingenious, and I think easily qualifies as 'out-of-the-box' engineering. I just watched Justin's presentation (video) about ebike motors at the Vancouver bike fair, in which he mentioned mfgr's claims about their motors' rated wattage. I wonder what he'll make of your brazen "250" label! I'll be curious to hear about your experiences with this approach.

Well, it doesn't say "250 watts" It says, "250W". That could be a model number. :^)
BTW, I'm done some pretty decent etching of stainless steel using nail polish masking, vinegar and salt solution and a 12 volt power supply. Not sure if that would work with aluminum though.

The ambiguity of the 250W label has me thinking ... how nifty if a manufacturer like Grin would give their motors model numbers that gave the impression of being for super low wattage while supplying the motor with a removable label with all of the official stuff. For instance, Model No. G250W.HB might imply a 250 watt hub motor but it is actually just a (semi) arbitrary model number. You wouldn't want to do this if you were assembling complete bikes, but as an independent motor supplier?

Speaking of removable labels, this is the one I made for my motor. ( Laser printer, packing tape for outside lamination, and double sticky tape or contact cement to adhere). I can argue this wattage if need be, but the idea is to have something simple that is visible in the unlikely chance that I ever get questioned. So far the local constabulary has shown zero interest in my motor wattage. I think that's the natural result from not going much faster than 25 mph on flat level ground.

[rowbiker]

Some very interesting motor labeling ideas here!

I actually *am* a lawyer (now retired, and recovered), and if some police/prosecutor anywhere in the world brought charges against solarEbiker, I'd simply turn him loose in front of the jury and have him show off his homework. No jury convicts someone they're in awe of.

[solarEbike]

But wait, there's more! Emboldened by my initial successes with designing my own 3D printed parts, I decided to apply my favorite new tool to a couple of design challenges on my long list.

• Where do I mount additional switches to control the trailer tilt motor and to cut power to energy sucking accessories when they're not in use? I need to be able to reach them while riding. Also, it would nice to have an enclosure to house wiring, voltage converters and such.
• Where do I store items I want to access throughout the day--camera, snacks, etc. The panniers are a hassle to open multiple times per day and a traditional handlebar bag is not an option on a recumbent with under seat steering.

I have some space under the seat but the need to maintain handlebar clearance made it virtually impossible to use any off the shelf solutions. Here's what I came up with. I've calling this one the wiring pod.

wiring pod 2.jpg (386.06 KiB) Viewed 1717 times

I started with some CAD (Cardboard Aided Design). Thanks, fechter.

Then did some CAD (Confuser Assisted Doodling). Thanks, AvE.

A few clicks with the mouse and this shows up at my door.

A couple of rattle cans of paint later, here's how it looks from the side.

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With the pannier removed, you can sort of see the hinged rain cover I made for the batteries, motor controller and solar charge controllers. They're all fully potted but there are a lot of exposed JST and XT60 connectors here which will benefit from having most of the water channeled away from them. The rain cover also hides the clutter while still allowing airflow to help shed heat.

wiring pod with LiGos.jpg (388.02 KiB) Viewed 1717 times

The switches are waterproof. There are a couple of extras for future ideas and/or field replacement. The hood above them is to channel away water and provide some physical protection. The round black thing in front is a 12V motorcycle horn.

wiring pod horn.jpg (302.47 KiB) Viewed 1717 times

Inside, the wiring ended up looking more messy than I had imagined. There's an o-ring seal around the door and it's held in place by magnets. The DIN rail mounted spring-loaded terminal blocks are the smallest ones I could find--easy access for troubleshooting and swapping things out in the future.

Cables enter the back through a multi cord grip designed for combiner boxes on commercial PV installations. There are 9 holes and they come "skinned over" so you only use the ones you need. To my surprise, I ended up using all 9 holes. The 1" NPT threads are big enough that I was able to 3D print them on the enclosure.

Watt's Up meter to monitor accessory loads.

Here are back and bottom sides showing how the voltage converters are mounted externally to allow airflow to shed heat. Alarm siren? Yeah, I installed this motorcycle alarm system with a long-range two-way pager, shock and motion sensors mostly so I can keep an eye on the bike when I need to leave it unattended with luggage on the bike (think resupply stops).

There's also a 3s-18650 backup battery pack inside to run the 12V lights if the main batteries run all the way down. It's set to charge off the main batteries to 4.1V/cell and has a transfer switch I can flip over to run the lights.

Finally, on the right side we have the "snack pod" with an integrated camera holster for quick and easy access... because pics or it didn't happen.

[fechter]

The pod looks great. I did something similar on my A2B to hide all the mess of wires.

[wturber]

A few clicks and how much money for the 3D printed parts? That's been my hesitation with such doings. That said, the pieces look great and the ability to get shapes and fits that are exactly what you want (or what you think you want) is great.

[wturber]

Some very interesting motor labeling ideas here!

I actually *am* a lawyer (now retired, and recovered), and if some police/prosecutor anywhere in the world brought charges against solarEbiker, I'd simply turn him loose in front of the jury and have him show off his homework. No jury convicts someone they're in awe of.

If you listen to Justin's explanation of motor watts and then look at the ambiguous nature of many of the laws, I figure the best approach (at least in the U.S.) is to let the police/prosecutor make their case first. They'll probably make some assumptions and assertions and/or fail to have the necessary facts. So I figure that they are very likely to torpedo themselves unless you are operating grossly outside the ambiguous legal boundaries.

Of course, I'm not a lawyer so I could be dead wrong.

[solarEbike]

A few clicks and how much money for the 3D printed parts? That's been my hesitation with such doings. That said, the pieces look great and the ability to get shapes and fits that are exactly what you want (or what you think you want) is great.

Your point is valid. I was being cheeky. "A few clicks with the mouse" was more like 50-100 hours of modeling time--agonizing over every detail knowing that the print was going to be so expensive that I had to get it right on the first try. My total printing costs have now exceeded the price of a decent desktop extrusion printer and filament material to print all these parts. I have no regrets about that, though. Trying to print all these parts myself would have taken much longer and I'm not sure I could get the strength and finish quality I was looking for.

However, I can imagine getting a desktop 3D printer in the future to rapidly prototype parts and refine the design before making the "production" part using a more expensive process. What I really want is something like a Tormach CNC so I can make more stuff like these aluminum brackets for the new trailer suspension. Then again, I was able to make these using a drill press and a band saw so I may need a better justification for more expensive toys. Kickstarter campaign for high-end solar upgrades for ebikes, anyone?

Mmm. Monkey like shiny.

[thundercamel]

Great result on the wiring pod and snack pod! Wiring always surprises me too once I put it all in one place trying to clean it up. I'm usually just to chicken to trim all the wires to length, in case I make any changes later.

[solarEbike]

Wiring always surprises me too once I put it all in one place trying to clean it up. I'm usually just to chicken to trim all the wires to length, in case I make any changes later.

Tell me about it. I was envisioning something more like this masterpiece... or at least something that could be described as "neat and workmanlike." My rat's nest is so unruly I can barely get the door closed. Now that I know where all the conductors terminate, I really ought to go back and trim them down to length.

Uncredited masterpiece. Not my work.

cable-porn.jpg (119.91 KiB) Viewed 1661 times

Also, this was my first time using these wire ferrules. I've read they're much more common in Europe and some other places but not very well known in the US. I would definitely recommend them for any projects using screw or spring clamp terminal blocks.

And as long as I'm calling attention to my failures I might as well share this "oopsie." While I was wiring those terminal blocks, I accidentally connected battery voltage to the CA3 5 volt line. Actual smoke came out. Killed it dead.

[rowbiker]

Ouch ... I hate the kind of smoke that hurts to the tune of triple digits ... not trivial. I'm curious to see if Justin thinks the CA PCP is salvageable or not. Either way it will be a costly glitch in either/both time and money. The worst of it is that you learned nothing from this mistake, since you already knew what would happen under the circumstances.

Ditto on the 'square crimper' for loose wire ends. I used to solder/tin the ends of wires to keep them from splaying/fraying, but these ferrules make it very simple. They'll still suck up solder after crimping if you really need tough connections.

[solarEbike]

This happened back in January. I've already replaced it. Justin's take was that it was beyond repair.

Yes, it stung. I was a lot more careful about labeling and double-checking connections before applying power after that. I suppose the dead CA3 may come in handy for spare parts later on.

[solarEbike]

Yesterday, I took my new trailer design out for its first road test. You won’t believe what happened next!



Learning to fail is a critical step on the road to success. I learned something yesterday. To explain what happened, allow me to recap some highlights from my solar bike trailer failures.

This was one of my first attempts at using a trailer, back in August 2015. I was so impatient to experience the difference between riding with just the 50 watt front fairing and the 200 watts of this rig that I failed to take the time to properly attach the flexible solar panels to the trailer. The rear-most 100 watt solar panel bounced like a trampoline and flexed so much that it failed during my first day of riding. I never found the problem but it was likely a broken connection between two cells somewhere within the laminate.

Aug 2015 trampoline trailer.jpg (90.45 KiB) Viewed 1599 times

As long as you put some cross-bars or a rigid panel under the solar panels, this is the easiest way to add solar charging to any ebike. Just about any bike trailer will do. This could be a weekend project and only requires a few basic tools.

Two years later, I had distilled my ideas and completed this one wheeled trailer. The idea was to pare the trailer down to the minimum required to tow a solar panel behind a bike. The 1" (25mm) aluminum tube attaches to the bike rack using a universal joint so the trailer can tilt and turn with the bike without falling over. I rode about 100 meters, stopped and had to walk the bike back because it was so unstable.

Wet noodle 1.jpg (198.84 KiB) Viewed 1599 times

I don't have a video of that first tide, but here's a demo of the problem.



Theoretically, it's possible to attach a one wheel bike trailer with a u-joint. There are a couple of commercially available trailers that do just that. I've never seen one in action but I assume they handle well. Tout Terrain even makes a kid trailer like this.

Tout-Terrain-Mule-trailer.jpg (97.45 KiB) Viewed 1599 times

I attributed the problem with this design to the flexibility of the thin walled aluminum tube I was using. I assumed it was twisting under the load. My recent experience would seem to indicate that there's more going on here. I solved the problem by changing the boom tube to a larger diameter, moving the wheel further back and replacing the u-joint connection to the bike with a Bob trailer fork which connects to the rear wheel axle. Effectively, it's just a bigger u-joint with a horizontal axis and a vertical axis. This is best photo I have showing how it attaches the trailer to the bike.

This completely solved the handling problem but I didn't fully grasp how each of those changes contributed to the solution. This trailer weighed 27 lbs (12 kg) and had 188 watts of solar panels so about 16 watts per kg. For my current build, my goal is to increase the solar to 248 watts and bring the weight down to around 20 lbs (9 kg) so about 27 watts per kg.

I started over from scratch and re-examined every component for weight saving opportunities.

• The new solar panels are much lighter.
• The red foam/fiberglass support panel is being replaced with a lighter honeycomb/carbon fiber sandwich panel.
• The simple elastomer suspension was inadequate on rough roads so I upgraded it to an adjustable air shock. It's slightly heavier but should ensure that the trailer will survive thousands of miles of rough roads.
• I moved the trailer wheel forward to shorten the boom tube segments. They need to pack down to fit airline luggage constraints.
• The Bob trailer fork is made of heavy steel tubing designed for a trailer plus cargo combined weight that is nearly 4 times the weight of my trailer so it seemed needlessly heavy duty. I went back to the u-joint with the hope that the carbon fiber boom tube would be stiff enough to make this design work.

And here's where we are today. The plywood panel is a temporary stunt double for the solar panel assembly. It matches the weight and center of mass but is about 1/3 of the size of the solar panels.

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Possible culprits for the stability problem:

• The u-joint is too far back from the bike or maybe the bike rack to which the boom is attached has too much flex and sets up the oscillations? I'm leaning toward dropping the u-joint and going back to the Bob trailer fork.
• The trailer's center of mass is too high? I need some room for suspension travel but there's room to lower the the boom. Also, the photos above are a bit deceptive because I hadn't adjusted the shock preload yet.
• The trailer wheel is too close to the center of mass? I can test this with the current rig by mounting the plywood further forward.

[wturber]

just looking at the commercial unit and your design, my gut tells me that the answer is in the downward angle of the commercial trailer't tube where it attaches to the bike. Is it the asymmetry of the U-joint alignment or perhaps the downward angle reduced the mechanical leverage that the trailer can exert on the bike. I dunno, but I suspect that the direct alignment is at the heart of the problem.

[Chalo]

[*]The trailer's center of mass is too high? I need some room for suspension travel but there's room to lower the the boom.

I think that's the main issue. The torsional axis of a one-wheeled trailer is a line between the hitch joint and the tire's contact patch. Mass located away from this line exerts a twisting moment in proportion to its distance from the axis.

When the trailer wheel tilts, it creates a camber thrust in the direction of the tilt, steering the same way a bicycle does when it tilts. This causes it to right itself and then overshoot in the other direction, and you get your death wobble.

It doesn't help that your hitch seems quite elastic in torsion.

I don't think there's any practical way to put rigid PV panels the size you're talking about on a one-wheeled trailer without having an objectionable amount of wobble. I think you'll need a two-wheeled design to fix the problem. Fortunately, those wheels don't have to be substantial and can be very lightweight. You might be able to use racing bike front wheels, if they have cartridge bearings so you can remove the axle and mount them on frame stubs. Or you can get one-sided hubs from a stroller or baby jogger and lace ultralight rims to them.

[thundercamel]

[*]The trailer's center of mass is too high? I need some room for suspension travel but there's room to lower the the boom.

I think that's the main issue. The torsional axis of a one-wheeled trailer is a line between the hitch joint and the tire's contact patch. Mass located away from this line exerts a twisting moment in proportion to its distance from the axis.

When the trailer wheel tilts, it creates a camber thrust in the direction of the tilt, steering the same way a bicycle does when it tilts. This causes it to right itself and then overshoot in the other direction, and you get your death wobble.

It doesn't help that your hitch seems quite elastic in torsion.

I don't think there's any practical way to put rigid PV panels the size you're talking about on a one-wheeled trailer without having an objectionable amount of wobble. I think you'll need a two-wheeled design to fix the problem. Fortunately, those wheels don't have to be substantial and can be very lightweight. You might be able to use racing bike front wheels, if they have cartridge bearings so you can remove the axle and mount them on frame stubs. Or you can get one-sided hubs from a stroller or baby jogger and lace ultralight rims to them.

I agree completely, and Chalo did a better job putting my thoughts into words than I could have. The picture of the cargo trailer shows the center of mass inline with the wheel and hitch. A kids half-a-bike must have a higher center of mass, but also must be very torsionaly rigid from the hitch attachment through the frame.

[Chalo]

A kids half-a-bike must have a higher center of mass, but also must be very torsionaly rigid from the hitch attachment through the frame.

I built myself a pusher trailer around one of those half bikes a few years ago. I went to lengths to adjust, shim, and tighten the U-joint to eliminate all free play. I was never able to persuade it to not shimmy at its full speed of maybe 18 mph (though the lower and farther forward I shifted the load, the more stuff I could put in the pannier baskets without making it unrideable). But generally, the more weight I carried on it, the lower the speed at which it would dance. I think it's key to those things that a kid is a highly damped load that's too floppy to resonate.

[solarEbike]

Endless Sphere to the rescue! I really appreciate all the feedback. You guys rock.

[*]The trailer's center of mass is too high? I need some room for suspension travel but there's room to lower the the boom.

I think that's the main issue. The torsional axis of a one-wheeled trailer is a line between the hitch joint and the tire's contact patch. Mass located away from this line exerts a twisting moment in proportion to its distance from the axis.

Here's the Tout Terrain Streamliner trailer with the torsional axis marked in green and approximate center of mass marked in red. This design made think my approach would work. More photos and great article here.

Here's a close-up of the hitch. I'm wondering if the offset between the two pivot axes plays a role here? If it does, I confess that it's not intuitively obvious to me.

tout-terrain-hitch_3.jpg (86.09 KiB) Viewed 1548 times

Same color scheme here. I've offset the center of mass to include the wheel and fork because the solar panel assembly is only about half the weight of the trailer. Green is the current torsional axis with the u-joint. Blue is where the axis would be if I switched to the Bob trailer fork. The mass of the trailer would be significantly further from the axis but based on my previous experience with this type of hitch I believe the flexing would be eliminated.

Here's the Bob trailer.

It doesn't help that your hitch seems quite elastic in torsion.

I totally agree. This was unexpected and undesirable.

Here's my u-joint. It's an automotive steering joint. It's bonded to the carbon fiber tube with epoxy and held in place by M8 screws going into tapped holes in the u-joint. This assembly feels very solid and has virtually no play. The two pivot axes cross in the center (no offset). I'm tempted to try building a new u-joint from scratch to test if this makes a difference. This would allow me to salvage most of the current design. Or is it a sunken cost fallacy?

u-joint close-up.jpg (76.57 KiB) Viewed 1548 times

For comparison, here's my last trailer build. This trailer is heavier than the new one, it has a lower center of mass and it uses the Bob trailer fork hitch.

This is the same trailer I used in this video where I get it up to 42 mph (67 kph). I've ridden hundreds of miles with this trailer and never had any wobbling issues.

[thundercamel]

That's still my favorite ebike video Torsional rigidity then? Can you have anyone hold your bike upright, and you try to twist the trailer?

[Chalo]

The torsional axis of a one-wheeled trailer is a line between the hitch joint and the tire's contact patch. Mass located away from this line exerts a twisting moment in proportion to its distance from the axis.

Here's the Tout Terrain Streamliner trailer with the torsional axis marked in green and approximate center of mass marked in red. This design made think my approach would work.

I think if you bolted a rigid child-sized mass in that position, you'd have the same kind of problems you're facing.

Here's an image of my pusher trailer when I was first trying it out. This is about the stablest configuration it ever had, with no pannier baskets and everything as close as possible to the torsional axis. It would still wag its tail at full speed. Every change I made from this point forward added mass and made it wobble more and at a lower speed.

[solarEbike]

I think if you bolted a rigid child-sized mass in that position, you'd have the same kind of problems you're facing.

I was thinking the same thing. Must have been an interesting challenge trying to prototype that design without using actual children.

Thanks for posting the photo of your design. Do you have a close-up of the u-joint hitch?

That's still my favorite ebike video

10,000 views on YouTube. I'm blown away. When I first posted it, I didn't expect it to get more than 100 views or so.

Torsional rigidity then? Can you have anyone hold your bike upright, and you try to twist the trailer?

Fixing torsional rigidity seems to be the low hanging fruit here so I'm going to try to address that first. The distance of the mass from the torsional axis certainly plays a role but it's not something I can easily change. The trailer in the video is stiff enough that I could hold just the trailer and lean the bike side to side and they move as one solid unit. If I tried that with this new one, I'm pretty sure the bike would fall over. I knew there would be trouble as soon as I hooked up the new trailer for the first time and tested by swaying the bike side to side and seeing the trailer start wagging like a golden retriever.

So I sketched this out today. I'm reasonably sure I can make this with my tools and skillset out of aluminum stock I have on hand and some skateboard bearings. What do you think, is it worth testing?

[Chalo]

I think you can use plain bearings or plain closely size holes instead of ball bearings. Stiffer that way, and the hitch barely moves anyway. I'll try to remember to take a picture of my hitch next time I'm at work (where it's stored).

[solarEbike]

I think you can use plain bearings or plain closely size holes instead of ball bearings. Stiffer that way, and the hitch barely moves anyway.

That's an interesting idea. It would be easier to fabricate as the 22 mm holes sized to the press fit the bearings were giving me some pause.

I found an even better photo of the Tout Terrain hitch and saw that they're clearly using bearings. Monkey see, monkey do.

[Cephalotus]

I found an even better photo of the Tout Terrain hitch and saw that they're clearly using bearings. Monkey see, monkey do.

I do own a Tout Terrain Mule and for me it works very well. (I don't use it so often for bike touring, mostly I do not need the storage capacity)





I think the hitch is excellent, but I lack own experience with other solutions.

So far I was only transporting the center of the mass inside the mule. I believe the suspension does work better if the trailer has a weight og lets say 20kg instead of 10kg. (on the other hand at more than 30kg the weight Distribution between bike+rider at roughly 100kg vs trailer gets worse).
Imho 20-25kg is ideal for that trailer with a 100kg bike+rider in the front. The Mule itself weights 7kg.

I assume that you could make the design sinfificantly more lightweigt reducing unneded components and using Aluminium ro carbon fibre instead of steel.
I would be most interested in a streamlined Version designed for minimal air resistance and storage capacity at low center. On the bike itself I would just store the battery and a minimum of stuff where you need quick access or with very high weight to volume ratio like the bike lock.

On the Mule the tow bar rises very high and could/would cause more shading on the panels. There should be a better design for a solar trailer. It is so high that there is room for 29" tires and for an extra rear carrier on the bike itself.

TT Mule in combination with solar moduls have been used here: http://www.tour-de-mongolia.com/fahrzeuge-und-technik/

But imho those are rather "alibi" solar generators at 40W each. I very much doubt that they rode with 100% solar. They mounted their small solar panels quite high.

[thundercamel]

10,000 views on YouTube. I'm blown away. When I first posted it, I didn't expect it to get more than 100 views or so.

Torsional rigidity then? Can you have anyone hold your bike upright, and you try to twist the trailer?

Fixing torsional rigidity seems to be the low hanging fruit here so I'm going to try to address that first. The distance of the mass from the torsional axis certainly plays a role but it's not something I can easily change. The trailer in the video is stiff enough that I could hold just the trailer and lean the bike side to side and they move as one solid unit. If I tried that with this new one, I'm pretty sure the bike would fall over. I knew there would be trouble as soon as I hooked up the new trailer for the first time and tested by swaying the bike side to side and seeing the trailer start wagging like a golden retriever.

So I sketched this out today. I'm reasonably sure I can make this with my tools and skillset out of aluminum stock I have on hand and some skateboard bearings. What do you think, is it worth testing?

The real time data overlay is what makes it great!
It's hard to say from here, but I thought your current u-joint was fine, and the twisting was spread though the long sections evenly. I'm pretty sure the offset between the vertical and horizontal hinges in other joints it just to make production easier.

[solarEbike]

It's hard to say from here, but I thought your current u-joint was fine, and the twisting was spread though the long sections evenly. I'm pretty sure the offset between the vertical and horizontal hinges in other joints it just to make production easier.

Good eye. I took another look this morning, wagging the trailer slowly while the bike was supported by the "landing struts". You can see what's happening much more clearly in this video.




The rack is not rigid enough to support a trailer mount like this. I don't think a better u-joint would help. I'm going to go back to the Bob fork. It's basically an exploded u-joint which mounts to the rear axle, a much more rigid connection than what I have now. I'll have to get creative to adapt the vertical pivot mounts to my trailer but I have some thoughts on how to do that. And this solution disconnects at the rear axle much more easily which will come in handy on a long trip.

Bob fork on Grasshopper.jpg (132.64 KiB) Viewed 1461 times

Also, the carbon fiber tube is twisting more than I would have guessed. I knew that most of the fibers were oriented along the length of the tube, which makes it very rigid to resist bending, but I thought there was one layer of cloth with fibers at ±45° to give it torsional rigidity. I just went back to check the specs and there are no 45° fibers in the tube I ordered. Oops. That would explain the twisting. (For comparison, they make carbon fiber drive shafts for race cars and those are made entirely of axially wound fibers at ±45°.)

Fortunately, I know how to fix this. My last trailer used cheap and bendy ABS plastic drain pipe which I wrapped in a single layer of axially wound carbon fiber braid to make it stiffer. It worked like a charm. The braided sleeve slips over the tube and is perfectly seamless. It's relatively easy to work with compared to other composite products like fiberglass/carbon fiber cloth, tape or tow.

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