Lightweight, folding, airplane-travel-compliant, EU-compliant, long-distance ebike that can be easily pedaled

J A G

10 mW
Joined
Aug 15, 2019
Messages
23
Hi all. I've gained a lot of useful information from this forum, so now that I'm actually starting my build, I thought I'd document my build to possibly help others in the future.

My motivation to build an ebike is that I'm moving to France next year (or so) and would like to explore the countryside. There is a good train network, but it doesn't go everywhere. For example, if you want to see the WW2 sites at Normandy, the train can take you to the general area, but there are lots of little museums and monuments that are really too far apart to walk. I'd rather avoid the expense of a car. Many people use small gas-powered scooters or motorbikes, but I would really rather have an electric vehicle, and I've discovered that there is an extensive network of bike trails around Europe that I could access if I keep my bike within EU rules. I'm imagining pedaling though fields of lavender or grapes with a pannier bag full of bread, cheese, and wine.

I don't have a big budget, as I've been saving my pennies for this adventure. I'm shooting for <$600, including the bike.

A folding bike can be taken on any train in France as ordinary luggage without special arrangement. I'm small and not very strong, so I want to keep it lightweight. That led me to the Vilano Urbana folding bike, which is 22 lbs with 20" wheels. I can save a few pounds by changing out the heavy (steel) seatpost and seat for an aluminum one. It has coaster brakes and is fixed speed, which I like, because I haven't ridden a bike since I was a kid, and so kid bikes are my comfort zone. So there's my donor bike.

20190720_194937small.jpg
20190720_194919small.jpg

It cost $200 shipped from Florida.

I will need a rear rack for the battery and that bread/cheese/wine, and couldn't find a lightweight cheap one that would fit my 20" wheels, so I bought some aluminum U-channel at Home Depot ($8) and made one:

rack.jpg

In order to avoid losing the rear coaster brake, I went with a front hub motor. I've read this is not a good idea for all ebikes because forks are not designed to take high torque, but because EU regulations limit the motor to 250W and the speed to 25kph, and the fork of my bike is steel, it should be okay.

I ordered a cheap Chinese motor from ebay ($109 shipped) https://www.ebay.com/itm/36V-250W-3...var=462985163234&_trksid=p2057872.m2749.l2649. It appears to be the same as the MXUS XF07, although it was not sold as such. To satisfy the EU regulations, it is 250W, although I've read that they are often capable of higher power, and labeled 250W to satisfy the EU. I went with a geared motor, because it is lighter and better for pedaling if your battery is dead. The freewheel spins nicely, although it has drag in the opposite direction.

The motor created two problems for me. One is that even though the motor is supposed to fit a 100mm dropout, and the bike front dropout is supposed to be 100mm, the motor has various bumps that require it to actually have a wider fork. And the bike's fork is actually 95mm. So upon consulting the internet about spreading a steel fork, I went for it. I wrapped a dish towel around several pieces of wood and tapped them into the fork to spread it out. And it worked, just barely. Here is the motor in the fork. You can see how close it is to each side of the fork, which is spread to about 110mm

fork.jpg

The other problem is that the hub motor has 36 holes and my rims have 28. So I did some internet research and found this: https://www.sheldonbrown.com/mismatch/index.htm. I did all the math three times (protip: Excel's trigonometric functions assume that your angles are in radians. Go figure) and came up with spoke lengths. Then I realized how expensive custom-length spokes are. There is an ebay seller who would made Sapim Strongs that are thicker at the hub end, because the holes are larger) for $2 each plus shipping. Finally I found references on regular bike forums to Dan's Comp as a cheap source of spokes. They sold me the custom-length single-butted stainless spokes for 50 cents each. They only had silver, so I ordered non-butted silver spokes for the rear wheel at 25 cents each and still came out ahead. And once I started to take off the old spokes, I realized that the supplied spokes were a bit short, so that the threads were showing, so it's good that I replaced them. Dan's Comp only does business through email, and they are a bit slow to respond, but sent me exactly what I needed, all neatly labeled in envelopes. And once I finally got the order put in, the spokes arrived in a few days.

That lead me to the fun of my first bike wheel lacing. I did the rear wheel first, since I could follow the pattern of the old spokes. Then I did the hub motor. Apparently my math was fine, because it all fit beautifully. I had to modify the instructions because the screws on the motor didn't permit outbound lacing for some holes. I don't have a truing stand, so I just used the bike upside down, and they don't appear to wobble or bounce when I spin them.

lacing.jpg

I ordered a Brainpower controller and S866 display combo from Aliexpress ($31)https://www.aliexpress.com/item/33004354051.html?spm=a2g0s.9042311.0.0.27424c4dLPUZdW that will allow me to set voltage, max current, and max speed. EU regulations require PAS rather than throttle, but the controller will allow me to install a thumb throttle and turn it off when I'm in Europe and back on in the US. I haven't had a chance to test it yet, as I'm still working on the battery.

Speaking of the battery... you can't take a regular ebike battery on a plane. Too much risk of nasty battery fire. TSA says that you can have as many batteries as you want, as long as each is less than 100 WH. But the international air association limits you to 20 batteries under 100 WH each, so many airlines place the limit there. So I found this thread: https://endless-sphere.com/forums/viewtopic.php?t=72138&start=40 in which cells are snapped into spring holders that are beefed up with copper bus bars. I am making a 20Ah battery (10s 6p), so I'm making the 6p packs out of these spring holders and will shrink-wrap each one, which will be 3.6V x 3.4ah x 6 = 73Wh. Banana plugs connect the 10 packs together once the bike and I are safely in France. I'm going to build an aluminum box that they all will slide into, and that attaches to the side of my rear rack.

I ordered 60 18650 cells from Liitokala (https://www.aliexpress.com/item/32807032859.html?spm=a2g0s.9042311.0.0.27424c4dM8E8KA) for $140. I also ordered a Lii-500 tester ($20), which puts 4 cells at a time through a cycle of charging, then discharging at 250 mA to test actual discharge mAh, then charging again. They are almost done (it takes a full day for 4 cells) and they are averaging the advertised 3400mAh, although a few are down around 3200mAh. I am planning on arranging them so that each pack has approximately the same Ah, so that weaker cells in a pack are charged by their stronger parallel neighbors. If you do it the other way, with the 6 parallel cells matched, the discharge will stop before the stronger packs are empty. That means the weak packs would wear out faster than the strong ones, and make the imbalance worse.

Because the clip in battery packs don't come in a 6-cell variety, I epoxied a 4-cell and 2-cell together. Then I slightly flattened a 12g copper wire to keep it from rolling, and soldered it on to create the parallel bars on each side. Then I added 14g wire (my BMS is 15A max, so my system shouldn't go over that) and the sensor wires. I then added gold-plated copper banana plugs. The plugs have holes in the side so that I could wrap the wires around securely and fill in the little cup with solder. Then I wrapped the exposed wires in stretchy electrical tape.

battery case.jpg

I was a bit concerned that the snap-in connections would be a point of high resistance and therefore high temperature. So I rigged up a single cell with a phone charger circuit board to see with my FLIR camera if there was a lot of heat at those snap-in points. This is ~0.7A draw off a single cell to a phone, which is 0.2C. That's not much, although if my motor actually operates at 250W, it will draw 0.35C, which is not too far off. Happily, I'm not seeing any hot spots anywhere, and the battery is only a few degrees warmer than the surroundings, even after giving it a few minutes to reach thermal equilibrium. The last picture is a pre-made battery charging pack, and the circuit board and USB plug are clearly getting a lot hotter. I am looking forward to testing the whole pack with the motor, but the throttle still hasn't arrived, and I'm still working on testing the batteries.

battery flir.jpg

That's all I have for now. I will update as I can.
 
Thanks for posting this...

Have you considered bringing a Vruzend kit with you (to assemble a battery pack), and then ordering loose cells to be shipped to France?
 
Just FYI - that rack is going to fail quickly. If you can't sit on it with 180ish pounds while it's not moving, it won't stand up to 10-20 pounds while dealing with potholes and curbs.
 
If you do need to redo the rack, to prevent side to side wiggle and whatnot that can fracture the aluminum, you can look at this rack I built here:
https://endless-sphere.com/forums/viewtopic.php?f=3&t=85317&p=1247409
which is steel, but could be made in aluminum instead.
It would've been built with an X across the top instead of H's, but Bill needed it this way for some reaosn
 
spinningmagnets said:
Have you considered bringing a Vruzend kit with you (to assemble a battery pack), and then ordering loose cells to be shipped to France?

In order to avoid hefty import and value added taxes, I have to buy in the US and carry it with me. I couldn't even mail it to myself from the US without doing a huge amount of paperwork to avoid taxes.

billvon said:
Just FYI - that rack is going to fail quickly. If you can't sit on it with 180ish pounds while it's not moving, it won't stand up to 10-20 pounds while dealing with potholes and curbs.

The weak points are the front struts, which are attached by aluminum rivets. I can add another rivet on each side to strengthen it. I also used JB weld on the inside to strengthen the four corners of the top, and can add some of that to the struts. When I took the wheels apart, I realized that the rims are pretty weak -- single-wall aluminum and daylight visible through the seam. So if I come to a curb or unavoidable pothole, I'll stop and walk it over. So the rack will not get a lot of stress.

amberwolf said:
If you do need to redo the rack, to prevent side to side wiggle and whatnot that can fracture the aluminum, you can look at this rack I built here:
viewtopic.php?f=3&t=85317&p=1247409
which is steel, but could be made in aluminum instead.
It would've been built with an X across the top instead of H's, but Bill needed it this way for some reaosn

Thanks for the link. I originally intended to use aluminum brazing rods to put it together, but then I realized that this particular alloy does not allow for that, at least not in the presence of oxygen. Apparently magnesium in the alloy forms oxides on the surface preventing anything from sticking. If mine looks like it is not going to be durable, I can order different aluminum alloy online and go with a design more like yours. I have plenty of time to test it before my trip.
 
Welcome to the forum

I have a different version of that bike to that I built for similar reasons, though I eventually dropped the weight concerns as I don't fly with it.
I found 3 modifications were needed right away.

The pedals. Mine broke the first time I had to get across a road in a hurry, and put some weight on them. I replaced those with a quick release that makes the bike fold smaller, too.

The Seat. It's a real pain in the arse. I solved it by getting an adult sized seat.

The Tires. While they are light, they are too skinny to absorb any bump. I was getting rim damage riding on a well maintained smooth road. They also were not comfortable to ride on. I solved this the first time by going to a 20"x2.125" rear tire. This transformed the bike into something pleasant to ride. I'm now on a 20"x2.50" tire, and it's even better, but that may be too big for your needs.


As for the rack, I tried to build a rack out of that same type of aluminum once. It gets stress cracks too easy. But also you may find a seatpost rack is the best answer for folding the bike. I found I can fold mine smaller if I remove the seatpost entirely and lay it in between the wheels Being able to remove the rack too also helps. If you attach the seatpost rack to a bag, you could use it as your carry-on bag with the batteries removed.
 
J A G said:
Thanks for the link. I originally intended to use aluminum brazing rods to put it together, but then I realized that this particular alloy does not allow for that, at least not in the presence of oxygen. Apparently magnesium in the alloy forms oxides on the surface preventing anything from sticking. If mine looks like it is not going to be durable, I can order different aluminum alloy online and go with a design more like yours. I have plenty of time to test it before my trip.
Unfortunately even a welded rack of the shape yours is will still wiggle side to side with a load on it as you pedal, or lean the bike, etc. That's the main problem, and is what fatigues the struts and the points where it connects to the bike frame. That's where most racks break. (Iv'e broken more than my fair share over the decades).

Any rack design that can't wiggle side to side will survive longer than one that can.

They don't usually move in other directions, but if the vertical supports can bow outward (or inward, etc) then there can be fatigue from that, too, and if the bowing allows a load to continue pushing down during an impact, for instance, it can bow it out permanently or even collapse (steel or aluminum).

But usually it's the dropout rack supports that fail, right there at teh dropout.
 
Drunkskunk said:
Welcome to the forum

I have a different version of that bike to that I built for similar reasons, though I eventually dropped the weight concerns as I don't fly with it.
I found 3 modifications were needed right away.

The pedals. Mine broke the first time I had to get across a road in a hurry, and put some weight on them. I replaced those with a quick release that makes the bike fold smaller, too.

The Seat. It's a real pain in the arse. I solved it by getting an adult sized seat.

The Tires. While they are light, they are too skinny to absorb any bump. I was getting rim damage riding on a well maintained smooth road. They also were not comfortable to ride on. I solved this the first time by going to a 20"x2.125" rear tire. This transformed the bike into something pleasant to ride. I'm now on a 20"x2.50" tire, and it's even better, but that may be too big for your needs.

As for the rack, I tried to build a rack out of that same type of aluminum once. It gets stress cracks too easy. But also you may find a seatpost rack is the best answer for folding the bike. I found I can fold mine smaller if I remove the seatpost entirely and lay it in between the wheels Being able to remove the rack too also helps. If you attach the seatpost rack to a bag, you could use it as your carry-on bag with the batteries removed.

Thanks for the welcome. I've already ordered a new seat, and will watch out for the pedals. I've looked into better wheels, but they would add more to the cost than I'd like, so I'm planning to at least test it as is. I'm small and hopefully that will make my weight on the pedals and wheels more manageable. Maybe I can run the tires slightly deflated to get more cushioning.

amberwolf said:
Unfortunately even a welded rack of the shape yours is will still wiggle side to side with a load on it as you pedal, or lean the bike, etc. That's the main problem, and is what fatigues the struts and the points where it connects to the bike frame. That's where most racks break. (Iv'e broken more than my fair share over the decades).

Any rack design that can't wiggle side to side will survive longer than one that can.

They don't usually move in other directions, but if the vertical supports can bow outward (or inward, etc) then there can be fatigue from that, too, and if the bowing allows a load to continue pushing down during an impact, for instance, it can bow it out permanently or even collapse (steel or aluminum).

But usually it's the dropout rack supports that fail, right there at teh dropout.

I hadn't considered that, but it totally makes sense. I need to think about that some more.

spinningmagnets said:
If you speak French, you might consider joining the French electric bike forum...

http://cyclurba.fr/forum

Thanks! I'm better at reading than either writing or speaking, but I can at least lurk.
 
I think what you're trying to build is kinda cool. I always liked the idea of a minivelo type bike over a scooter/etc.
Best wishes with the build!
 
neptronix said:
I think what you're trying to build is kinda cool. I always liked the idea of a minivelo type bike over a scooter/etc.
Best wishes with the build!

Thanks! So far I'm having a blast!
 
Update on the build, specifically the rack. Several people here mentioned that racks like mine have a tendency to fail at the joint where it is attached near the hub. The idea is that weight on the top torques the rack from side to side, leading to metal fatigue and eventual failure at the point of attachment. So I made two modifications. One is the addition of triangles to reduce side-to-side movement. This is the same general principle used by amberwolf, although because I'm retrofitting, mine is not as sturdy. The other is the addition of cross-linked polyethylene (PEX) strips across the part that is susceptible to failure. The idea is that the additional layer makes that part stronger, and also if the aluminum does break, there is a flexible piece that will not -- kinda like fiberglass, where there is a combination of flexibility and rigidity. PEX is used for water lines, as it can expand without breaking if the water inside freezes. I have a lot left over from plumbing a house I'm working on. I cut strips from the largest diameter I had (3/4"). It's still a bit curved, but not so much that it won't work.

Added triangles:
trianges.jpg

PEX inside the U-channel, with rivets to attach, and holes to attach to bike
pex2.jpg

Reverse side of U-channel where PEX is attached:
pex1.jpg

On the bike:
rack attached.jpg
 
amberwolf said:
That will probalby help, if it doesn't fix it entirely. :)

Should be interesting to see the results over time.

I hope so. It certainly feels a lot more durable. I'll try to remember to update either way.

My latest:

I didn't want to use one of the standard brake-lever-style motor cut-outs. I'm adding a front caliper brake, and I will have a lever for that. But I decided that it was a good idea to have some sort of motor cut-out, as the PAS continues to run the motor a few seconds after pedaling stops. So I bought a small button that shorts when pressed, and drilled a hole for it on my thumb throttle. I will have to turn the throttle off from the controller when I'm in France, but I can leave it attached to the bike. So if I want to cut the motor, I just press the red button.

The button:
button.jpg

The thumb throttle:
throttle.jpg

My melding of the two:
throttle button.jpg
 
J A G said:
I didn't want to use one of the standard brake-lever-style motor cut-outs. I'm adding a front caliper brake, and I will have a lever for that.
There are a few sensors designed specifically to avoid changing the lever out.

One is called the HWBS, hidden wire brake sensor, and it goes on the cable itself, at either brake or lever end, and detects the cable movement to engage. It does require 5v power, unlike most ebrake switches, so if your ebrake wire on the controller doesnt' provide that, you have to tap the throttle or otehr 5v line for it. Otherwise it works the same, grounding the ebrake signal wire when active.

There's also the Tripwire setup, sold by Grin Tech http://ebikes.ca , and a number of DIY versions of that sort of thing around the forum over the years.

Other DIY stuff includes microswitches on the brake arms, etc. All sorts of ways of doing it automagically. ;)



FWIW, they also have throttles with a button built in. SOme of the buttons are prewired to go in series with the throttle power line, to disable throttle (easily rewired), and some are not wired to anything yet, with both wires going out to the cable bundle to use for whatever you want. Most of these also have a voltmeter of some type, but some are just the throttle and button.
 
amberwolf said:
There are a few sensors designed specifically to avoid changing the lever out.

One is called the HWBS, hidden wire brake sensor, and it goes on the cable itself, at either brake or lever end, and detects the cable movement to engage. It does require 5v power, unlike most ebrake switches, so if your ebrake wire on the controller doesnt' provide that, you have to tap the throttle or otehr 5v line for it. Otherwise it works the same, grounding the ebrake signal wire when active.

There's also the Tripwire setup, sold by Grin Tech http://ebikes.ca , and a number of DIY versions of that sort of thing around the forum over the years.

Other DIY stuff includes microswitches on the brake arms, etc. All sorts of ways of doing it automagically. ;)



FWIW, they also have throttles with a button built in. SOme of the buttons are prewired to go in series with the throttle power line, to disable throttle (easily rewired), and some are not wired to anything yet, with both wires going out to the cable bundle to use for whatever you want. Most of these also have a voltmeter of some type, but some are just the throttle and button.

Yeah, my controller has both brake options -- the three wire one that is powered, and the two-wire one that just shorts. I was going for cheap, as my throttle was ~$3 and the button about a dollar. But I like the idea of engineering the cut-off onto the regular brake. I might try to build something when the brake handle arrives.
 
The switch (to avoid sparking) finally came in, so I'm done with the battery. I went with a flat, aluminum-sided pack design, in order to keep the batteries from heating up. I'm working on a way to attach it with magnets, but in the meantime I strapped it on the rack with velcro straps to take my first ride.

I also added a cut-off switch on the brake handle. I flattened a piece of copper wire that contacts a steel spring when I brake. It works really well.

Battery in progress
battery in progress.jpg

Finished battery
battery.jpg

Brake-mounted motor cut-out
brake cut off.jpg
 
Here is the finished bike, folded and unfolded. I tried to run down the battery in order to test the charger, and after 24 hours of running at top speed and no load (bike upside-down) it had drained half way. If I give it full power going up hill with my weight on it, which should drain the battery much faster, the front wheel spins out. I suspect this is a problem of having the motor on the front, rather than the back with more weight. But I think it will give me a lot of distance at lower power, and on steep hills, I can overcome the skidding of the front wheel by pedaling to give all-wheel drive.

bike finished.jpg
 
Nice build mate! Just on a sidenote... Did you ever take a big lithium battery on an airplane? Its strictly regulated (and rightfully so!) Please let us know if you succeed in flying with the bike (in the air, not on the road :lol: )
 
dvdspelert said:
Nice build mate! Just on a sidenote... Did you ever take a big lithium battery on an airplane? Its strictly regulated (and rightfully so!) Please let us know if you succeed in flying with the bike (in the air, not on the road :lol: )

Thanks! I haven't flown with it yet, but when I disassemble it into 10 packs of 6 cells each, then I'm well within the strict regulations, so it should be okay. Each pack is 73 watt-hours, and the limit is 100 watt-hours per battery. FAA / TSA regulations do not limit the number of <100WH batteries you can carry, although EU regulations limit you to 20 batteries, and a few small airlines (like Ryan air) have lower limits.

I haven't done it yet, but I'm going to shrink-wrap each of the 10 packs, and laser-print labels that have the specs on them, so that they look more professional.
 
Back
Top