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Cargo Bike – my electric Xtracycle


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I made this bike to carry kids and heavy loads around the mountain. In about 4 years it’s done about 8000km of steep mountain riding.

The Xtracycle is excellent for carrying loads or children. Loads need to suit putting in the huge panniers, or balancing on top of the rear deck.

The Xtracycle feels exactly the same to ride as a normal mountain bike – except that it’s often much heavier because of what you’re carrying. Speeding down hills feels perfectly stable and safe.

Frame and Xtracycle

The frame is a steel mountain bike frame from the tip (re-painted), plus an Xtracycle Freeradical kit from Cheeky Transport in Sydney. I would only use a steel frame for an Xtracycle bike. Steel is strong, almost never cracks, rarely strips threads, is easy to modify or repair and in a cargo bike, the little extra weight is almost irrelevant.
The Xtracycle kit was easy to install, though I have had to mess about a bit with the front bolt (the one that holds the front of the Xtracycle frame near the bottom bracket). The Xtracycle is an excellent product. The only problem I’ve had with it was the plywood deck, which turned out to be non-waterproof ply. This started delaminating after its first ride (during the 2011 floods). Xtracycle were very helpful and supplied me with a plastic deck for a small upgrade cost. It seemed they had been sent dodgy decks by their suppliers. You can usually spot waterproof ply straight away by the dark glue lines (I’ve never seen waterproof ply yet without red/black glue). 

I have installed some vertical sticks down inside the Xtracycle panniers, to stop loads pushing the pannier fabric onto the wheels, sprockets or brake disc. This did happen early on, and wore some holes in the fabric. This is a design problem, but easily addressed.

Gears

As I chose to use a rear motor on this bike, I am limited to spin-on rear clusters - I’m quite happy with this. I use a 7-speed 14t – 28t Shimano cluster. These are cheap (costing me about $12 delivered from GreenBikeKit.com), they shift smoothly and have adequate range for my needs. The 2nd hand Shimano rear derailleur and shifter I first installed indexed poorly, perhaps partly due to the long cable run to the rear derailleur. I switched to an SRAM shifter and derailleur (with the greater cable travel) and it’s been excellent ever since.
I have a 3-ring front chainset, but only use the 2 larger sprockets (42 and 32). The smaller sprocket would give speeds too low for the motor (but it’s there if I need to climb without power assistance). The 42 – 14 top gear is fine for me – I'm over the need to pedal faster than this down the hills…

Brakes

I use rim brakes on the front, because I have plenty of front wheels without disc hubs, and no suitable forks with disc caliper mounts. This is fine – partly because I have disc brakes on the rear.
Rear brakes are disc, which I think is essential for the long, steep, braking descents we need to do on the mountain, often heavily loaded. In these conditions rim brakes risk blowing off tyres when the rim gets too hot from braking (dangerous and expensive, luckily only happened to me once), and rim brakes will wear away aluminium rims surprisingly quickly in mountainous conditions (I wore through the the first rear rim on my Dahon in a couple of years). I have a 203mm rotor mounted on the Bafang hub – this is the disc size the Xtracycle frame requires. The Avid BB5 caliper is fine, but doesn’t really brake any better than the generic Chinese calipers I buy from BMSBattery.com or GreenBikeKit.com. Brake pads (Clarkes organic pads from Chainreactioncycles.com) last 600 – 1000km.

Electrics

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For the first ~3000km the Xtracycle was powered by Bafang/8fun SWXH 250w rear hub motors. The first SWXH 250w motor burnt out after about 2600km, which I now understand as being due to the long slow climbs with heavy loads – mostly carrying our 8 year-old boy. See my page on burning out Bafangs.
Now it has a Bafang/8Fun BPM 350w code 12 rear motor, with a “Con91 450w 36V 9 mosfets” controller from Greenbikekit.com. This is a significant improvement.
The BPM is a really nice motor for a cargo bike in the mountains (and anywhere else too). The BPM weighs 4.5kg (bare hub), compared to ~2.75kg for 250w motors. It is labelled 350w, but with the Con91 controller it draws only up to nearly 18A max (250w motors generally draw 15A max). The BPM has excellent torque at low speeds, but runs completely out of spin at about 25.5km/h, making it a little slower on flat roads than a 250w motor. Given its weight, size, modest power and reputation, I expect the BPM motor to last a long time. Unloaded, this bike is slower than my Dahon.
The rear motor gives good traction on steep dirt roads, but I have since made and helped with a couple of front motor Xtracycles which work well on flatter, sealed roads. There is significant extra trouble in dealing with a rear motor when service is necessary of the wheel or motor, especially with a sensored motor which has no plug in the 3 phase cable.
I use a 10Ah Headway Lithium Iron Phosphate battery (from Greenbikekit.com) which goes in a plywood and fibreglass box behind my seat. The controller is zip-tied under the battery box with a jiffy box to hold the bundle of plugs and wires.

Metering

This bike carries my Cycle Analyst, which measures lots of things, including speed, current, power, maxes and minimums, and watt-hours per kilometre. Metering is really helpful when you are starting out using an e-bike, otherwise you have no idea what you have used until the battery switches off.

Extras

I’ve made a front pannier rack for this bike, which works really well. It’s made from 6mm mild steel round bar, so it’s not super light, but it fits the bike and task perfectly (made for the job!).
Check out the steering damper behind the fork crown. This is really helpful, and stops the bike from falling over when standing. It's made from some small bungy cords and an old steel front reflector mount. 
I’ve mounted a foot rest, made of wood, to make travel safer for small passengers. This is bound on with long strips of bike inner-tube rubber, which works very well.

Efficiency

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Using the Cycle Analyst, I routinely measure and occasionally log energy consumption of this bike. Around the mountain (which I remind you always involves steep climbs and some sort of load), this bike uses between 5Wh/km and 18Wh/km, depending on how heavily it is loaded and how much climbing it does. This would yield from 25km to 70km from a full 10Ah battery charge. On normal rolling country with a light load, electricity consumption is around 6Wh/km. My maximum trip average consumption is just over 18Wh/km, bringing my 30kg son from Mt Nebo up to Mt Glorious.
Part of the story with the low energy consumption of this bike on flatter roads is that the motor is doing very little at speeds of 25km/h and up. So on flat roads I tend to be pedalling without assistance much of the time.
Interestingly, switching from the 250w SWXH to the 350w BPM motor did not result in a big increase in energy consumption (I suspect there is a small increase when lightly loaded, but very little). 
Battery box

The battery is carried in a plywood and fibreglass box behind the seat post. Here under the seat it doesn’t work to use a hinged lid (it would run into the seat), so I have a loose lid I lift on and off. Currently it’s held down by a strap of bicycle inner tube, which works fine until the road gets too bumpy and then the lid tends to start jumping off.

How this bike works for us

This is a really useful bike for our family transport. It is essential for transporting our youngest child Luka (currently still under 30kg) for weekly trips to music lessons and often to play dates, school events etc.. This is a pleasure for Luka and me, except on cold nights when I am sweating up the front and Luka is shivering on the back (he gets to warm up a little while walking up the steeper hills). I also occasionally carry our (much heavier) teenage kids shorter distances, which requires them to walk or run up the steep hills.
Between this bike, my electric folding bike and Jasper’s electric folding bike, our family avoids needing a second car. I estimate this is worth over $10,000 per year in direct car costs, plus the savings in time not driving Jasper to and from school, plus the health and pleasure benefits.
The Xtracycle format of cargo bike is less convenient for load carrying than a box bike, and also carries the load higher. However around the mountain, where descents can be up to 80km/h if you don’t brake, the Xtracycle handles extremely comfortably – I doubt a box bike would be so stable at speed (but I haven’t tried it).
For most places I think the 250w SWXH (rear) or SWXK (front) Bafang/8Fun motors would be fine for a cargo bike. However if you have long slow climbs, especially with heavy loads, I think the BPM motor is a major improvement and will be much more economical over time.
Cargo bikes – Xtracycle or box-bike or others – are really important to extending the capabilities of a bike, while keeping it stable and safe. There should be more of them!

Speculation…

The Xtracycle Edgerunner looks like a significant improvement over the old kits, with a lower deck (on a 20” rear wheel) and a stiffer frame. This would go really well with a rear motor and derailleur gears, or a front motor and hub gears (I love 8-speed Alfine hubs). I wonder about putting the battery in a box in front of the headsets.



4 comments:

  1. Hi there, You told us here about your super Electric Cargo Bikes that you are using for your daily tasks. You also told about how you are maintaining this bike in easiest way. I am really happy to saw your blog on this subject. Thanks a lot for that.
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  2. Well done there. I have built a couple of mine own cargo bikes, and love them to bits. I am still working on an ebike version, which is up and running but lacks torque, cast a rueful eye over my efforts. I am looking at the Bafang BMP, I was very interested to see your write up on the bafang.

    If you google "Dorky Thorpy Cargo Bike" thats the non-ebike one. The e-bike has 20" wheels. Which is OK, but means kids drag their feet on the floor! Also limits pannier options.

    E bike: Google: "Dorky Thorpy DIY Long Tail E-Bike"

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    Replies
    1. Thanks for your feedback, and thanks for your blog on making your cargo bike. Well done! I can see it's rough but you did it and it works and that's excellent. I recommend the BPM rear motor as mine has: slow but so strong and reliable. It makes the increasing mass of growing children no problem (and they can always hop off and walk up the really steep hills).

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  3. I really like this post and its information is really very nice and useful for all users.

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