This page is a summary of the Yuba build blog elsewhere on this site.
My first e-bike has now done nearly 8000km, and while most of it is standing up to the rigours well, I was starting to have difficulties with rear wheels going out of true and breaking spokes. The main reason for this is the excessive load on the rear wheel. As well as my weight (102kg but more like 108kg fully kitted out for riding my bike), there is also the weight of the battery, motor in the rear wheel, tool kits and other stuff carried in the rear panniers. The time had come to look at alternatives.
First requirement is that it carries a lot of weight in its standard form. Second requirement, it must be able to carry gear around, as it was to become the new company vehicle. We had been considering an electric car or van, but finances won’t stretch that far at the moment. After reading many articles in Electric Bike Action magazine, and reviews on Electric Bike Review, I started to like the idea of a long tailed cargo bike. Articles on the Pedego stretch, Yuba Spicy Curry, various Felt cargo bikes, the Xtracycle Edgerunner and many one off or custom builds made them look cool as well as functional, and the many uses people were putting them to made my simple requirements look a bit boring.
The trouble is, the few of these bikes that are available in NZ are very expensive, and some didn’t suit my requirements. Many of the custom builds and self builds I read about and saw were based on the Yuba Mundo in its various forms, and I was impressed with its build and how easy it appears to be to work on. The rear wheel is 48 spoke with a 14mm rear axle, so will take a 120kg rider and 50kg of load on the pannier rack quite easily, and it runs on 26 by 2.125 tyres. Two versions are available here in NZ, the Mundo V4 and the Mundo V5. With a thousand dollars difference in price, the extra bits and pieces on the V5 were not worth it to me, and the V4 was looking like a great base bike. Bicycle Junction in Newtown have a great range of cool bikes, ebikes and cargo bikes, and in particular had a Mundo v4 in stock, which they offered to me for a $300 discount, as it was a little shop soiled and marked. Of course it was not an electric bike, the Yuba electric cargo bike option is way out of my price range!.
My original plan was to buy a Bafang 350W mid drive motor direct from China, and use my existing 15AH battery from my first bike. But Bicycle Junction are suppliers of the Lekkie Summit kits, in 300W and 500W versions. While no one has ever looked at the power of my existing bike since I built it 3.5 years ago, I decided that I would also get the lower powered 300W Lekkie kit from Bicycle Junction, which earned me a little more discount. Total cost of bike and motor kit was $3000 less than a high end ready built cargo bike, and $1000-$2000 less than a low end version.
My last e-bike took me months to build, buying many wrong parts and having to fabricate battery carrying stuff and trying many alternative configurations of controls, controllers etc. I brought the Yuba and the kit home about 3 days after I paid for it, and took my first ride on an electric cargo bike about 4 hours later! The bike was legal, safe and usable immediately, but it wasn’t finished!
The first rides highlighted several issues. First of all it needed mudguards, which were fitted almost immediately (see photo above).
Next, the standard Yuba comes with a 38 tooth chain ring which makes it very low geared when used with a 14-28 cluster and a 26 inch wheel. Of course this has been removed and replaced with the Bafang 46 tooth chain ring that comes with the Lekkie kit. Even with electric assistance, this was very obviously too highly geared. So off to Bicycle Junction again (well a virtual visit anyway) and a 42 tooth Lekkie Bling Ring was installed to replace the Bafang 46 tooth.
This was much better, but the lowest gear was still a little high for some of Whitby’s worst hills, so I replaced the Shimano 14-28 freewheel cluster (14,16,18,20,22,24 and 28) with a new Shimano Megarange freewheel cluster (14,16,18,20,22,24 and 34 teeth) that I had in my spares box. I don’t use 1st gear very often anyway, but now when I do it allows me and the motor to breath a little easier on the very steep hills.
Now I was getting to the point where I could begin to appreciate the bike. As with all Bafang mid-drives, gear changing with the motor assistance is a gear and chain crunching experience, which is an unpleasant and expensive sound when riding a bike. Lekkie sell their own version of the gear sensor which is becoming a standard aftermarket add on for mid drives. This simple device fits inline between the gear change control and the derailleur, over the inner cable. When the inner cable moves, hall sensors detect magnets moving inside the unit, and use the same signal that the brake sensors use to stop the motors. When the cable stops moving, the motor kicks in again. Clever electronics in the device and the controller makes the timing of the motor stopping and starting coincide with the gear change perfectly. However the soft start of the motor means that when changing down the gears, there is maybe 1-2 seconds without power, making for some loss of momentum.
Finally, on the performance side at least, I was not happy with the tuning of the motor. Many parameters of the motor controller can be tweaked or tuned (or programmed as most people say, as a programmer using that word for changing a few parameters is a little irritating). All you need is a cable to connect your motor controller to a Windows PC, and some software on the PC, and some extensive research into what you can change and why.
In my case, assistance was only happening at low pedaling cadences, which meant that if I wanted to do my share of the pushing, but still being assisted by the motor, I had to be in a higher gear, pedaling slowly. This was hurting my knees and was very tiring. If I just pedaled slowly the motor would provide all the power, but this is not the point of Pedal Assistance in my opinion. Anyway, I got the cable and amended a few parameters. Not as many as I thought I was going to, as the Lekkie system already has quite a few deviations from the Bafang standard settings A full description of the changes I made are in the blog. If anyone needs assistance changing the settings of their Bafang or Lekkie mid drive motor, get in touch at firstname.lastname@example.org
The handlebars are a bit strange, swept back and wide, which I can’t do anything about yet, but they were also too low and too far forward for comfortable riding for me. The stem is adjustable, and I raised the angle of the stem to raise the handlebars and bring them back a bit. This also helped later fitting the front cargo rack.
So, the bike is now comfortable to ride, the assistance levels are good, and the gears and gear change are sorted. Time to make it useful!
Many expensive add-ons are available for the Mundo, bamboo decks, floor boards, large panniers, seats, handlebars for passengers, child seats, monkey bars for bigger kids, and a bread basket for the front of the bike. None of which quite worked for me. The Mundo has lugs, many lugs, lugs for Africa in fact. There must be 20 to 30 of the things around the bike, all tapped with screws in in most cases. Fitting your own stuff is very easy.
I designed a plywood deck for the top of the rack, with two coffee cup holders in it, varnished it with three coats of marine grade varnish and attached it with the 8 screws into the top of the rack.
I cleaned up the marks and rust on the foot rest frames and applied reflective orange vinyl over the marks, which adds safety features as well as hiding the scuff marks from several months of abuse outside the shop. I also designed some floor boards, and cut them out of Aluminium Composite Material (ACM), covered them in black vinyl and attached them to the frame. The spoke protectors over the rear wheels have been sign written in reflective orange vinyl also, giving a nice finished off look at the rear.
The Bread Basket by Yuba is beautiful but the cost here in NZ is over $200, way out of my price range. Fortunately, my wife happened upon a delivery system based around an aluminium front rack, with a large plastic box and a canvas and PVC folding lid, which was damaged and surplus to requirements. It is designed to fit on a bike with 80mm wide mounting brackets attached to the front of the head tube. The Mundo has mounting lugs for the breadbasket which are behind the head tube in the down tube and top tube, and are 60mm further back, and only 46mm wide. Careful measurements were taken and some extension brackets were designed. My son in the UK took the design, improved it a little, and made some brackets out of 5mm aluminium plate. These fit to the bike, extending the brackets forwards and out to suit the rack fittings. The rack has multiple mounting points, and one set perfectly matches the best position for the rack, and when bolted in it is rigid and secure. The canvas and transparent polythene lid was a bit worse for wear, but it was cleverly attached to the plastic box, so I deconstructed the lid system, replacing everything above the attachment strip with a new cordura type nylon lid, supported by a closed cell foam insert.
Just one project remains, I need to design and make panniers for the rear, that can double up as a mover for desktop computers and a weekly shopping carrier!