Sunday, May 31, 2015

Bikes for transport, electrified xtracycles

I've written about bikes before. I first introduced my xtracycle here, the ebike and associated thinking here, and talked about cycling with two kids here.

As I introduced last post, if we want to lessen the destruction we cause to the biosphere, it can be hard to identify where to best focus. Here is the priority list (as I see it):
  1. drive less or (preferably) not at all
  2. eat less industrially-produced meat, fish and dairy
  3. use less energy and buy GreenPower
  4. buy less stuff
In terms of reducing environmental damage, I think these are the Big Four. It's also great to buy organic, go to farmers' markets, do gardening, and play acoustic guitar (we try and do all these) but if you drive across town to pick up your organic veg in your Pajero, it's of questionable benefit (in my opinion). To my mind, this is similar to the (well-intentioned) person with a drawer full of washable nappies, and a disposable nappy on their child.
This is the reason I haven't written much about the garden. We put a fair bit of effort in, but it seems to me in many ways the less important part of what we are striving for -- though that could be seen as my prejudice as an engineer! I'd love to hear people's thoughts/criticisms of this idea. I do plan to write about it though.

We have a car (a small SUV in fact!), and are exploring how little we can drive it (it has been about a fortnight since we drove). I'm keen to see whether we can share a car with some like-minded people nearby but we're yet to organise that. A difficulty is that my youngest child is under 3, and so we have many years of car seats ahead of us.

In terms of thinking about efficiency, 1 L of petrol is equivalent to about 10 kWh. That is extraordinary, and shows just how much energy a car is using (and just how energy-dense petrol is). This is a big reason I love bicycles.

I recently made some changes to our bikes. The xtracycle was on a bike that was really too big for my wife and I hoped that putting it on a smaller bike would let her use it more effectively. Also, we sometimes took the kids places quite far away (or up a decent hill) that was hard to pull the trailer. I hoped that combining the xtracycle with the ebike would solve all these problems.

The xtracycle, now with electric assist front wheel and disc brakes.
I also took the opportunity to alter the platform on the back (using some found material) and bring the child seat forward. This greatly helps the dynamics of riding it, as the kids' weight is now in front of the rear axle. I've also mounted the battery for the ebike beneath the rear tray. I'm yet to finish installing a front rack on the bike.


The bike rides well. It carries a rider and two passengers (front passenger sits on platform and holds rear-facing handlebars, rear child sits in the plastic seat). It has a huge luggage capacity. It is fast, and can easily be ridden at 25 - 30 km/h on the flat when fully loaded. Handling is greatly improved with the children's weight further forward. Because the rear wheel is now 26" instead of 27", the weight is also marginally lower, which also improves handling. At some point, I might consider replacing the rear wheel with a strong 20" or 24" wheel.
In its previous  configuration (here) I carried a child and about 100 kg of luggage on it. It's quite amazing how much weight it can bear!

The problem is that it is still relatively hard to ride with a child in the rear seat, and my wife is still uncomfortable. It requires a lot of upper-body strength to balance -- particularly when the rider is getting on/off with two kids on the back. I do think a smaller rear wheel would help this, but we may consider a bakfiets (or similar dutch bike) instead. Not sure at this point. Also, our oldest child is nearly at the point where he could ride a tag-along (he can ride his own bike 5 kms, so could probably do 15 km on a tag-along).


We use this bike a lot. It's good for two kids, and great for cargo. Also, there have been many times that the ebike has allowed us to leave the car at home. I believe that, if electric vehicles are the future, it will be electric assisted bikes for most people -- electric cars will remain too expensive for most.


  1. Hi Angus,

    Nice setup with the e-bike. That is quite a fast speed on the flat even for a non power assisted bike. 100kg of load is very impressive. Out of interest, what sort of range can you get the bike in its current incarnation? I'm assuming that you run a lithium ion battery? What sort of longevity have you had out of the controller?

    I'm thinking of an electric go kart here, but have totally run out of time to experiment this year, but have a petrol powered go-kart which can be easily adapted.



  2. Hi Angus,

    Forgot to add: Yes, electric cars as they look now make very little economic sense.



  3. Hi Chris,

    I am yet to really test its range -- I've only had the bike set up like this for about a month, and most of our trips have been 10 - 15 km.

    The first ebike battery held 14 Ah at 36 V or 0.5 kWh and had a range of about 50 km on the flat (depending on how strong the rider is). I estimate that capacity has halved now, due to use of the battery and taking the ebike up some big hills with a child trailer on the back (totally drained the battery and I think that was quite destructive).

    The new battery holds almost 1 kWh (ie. double the old), so I think it should get about 100 km range on the flat. I'm hopeful that the better range will mean lower depth-of-discharge and a longer life for the battery. The first battery lasted just over 3 years before we replaced it, and I guesstimate it still has a useful capacity of 0.25 kWh.

    Cheers, Angus

  4. Hi Chris,

    I've been thinking more about this over the last few days and have done some research. I have since found out that to build a 1 kWh Li-ion battery uses nearly 500 kWh of energy. This is complete madness. I'll have to think about this more, but to be honest I can't see how such a battery is a good choice.

    Cheers, Angus

  5. Hi Angus, what an amazingly useful person you are! I am assuming you live in a flattish part of Adelaide? I live in an all-hills area of Launceston (most of it is), but the most sensible decision we ever made was buying a house 20 mins walk from the centre of town, so we walk most places, teenagers can walk to town, walk or bus to school, and my only driving is generally to child-related activities which I combine with other errands normally, and also generally car-pool. My most high-tech walking-related gadget is a nana-shopping trolley for the farmers' market!

    However it is only in the last year that I have been fanatical about walking - before that I would drive the five minutes it took to get to town. In fact, some neighbours are still aghast that I would walk all that way!

    I am all for home gardening. Remember 48hrs of groceries on the shelves? Without a garden we are all very vulnerable. And when I look at the huge amount of preserved food in my house from the garden, I imagine all those hundreds of thousands of miles that same food would have to have travelled if I had bought it..

  6. Hi Angus,

    Thanks for the info on the bike and batteries. I use Lead Acid batteries here in a Gel solution so that the hydrogen and oxygen recombine more efficiently. However the second law of thermodynamics points to the fact that the batteries will cease to operate sooner or later. The info on the lithium batteries is frightening. A lot of off grid households are switching over to the too. They do tend to run smaller batteries with deeper discharges so I waiting to hear how they work in the real world. Most of the people seem very confident in those batteries though. The thing I notice with lithium batteries is that the voltage doesn't seem to drop as they get depleted and I'm not sure whether that is a good thing or not. Get the batteries here down to 50% full and you'll know about it! :-)!

    But then I know of one or two people that use Nickel iron batteries which have very long lifespans - at least 3 to 4 times the batteries here.

    Nice work with the e-bike. What watts is the motor rated at?

    Cheers. Chris

  7. Hi Jo,

    Bicycles are fantastic if travelling on the flat or "slightly hilly" ground when you need to go some way or carry a lot of weight. How big the hills can be is largely determined by training ;-) But if you can walk places, that is good too. My wife and I make the effort to walk too -- it's pleasing to just continuously walk from the kitchen to the shop and back -- no messing around with helmets, bike locks, etc. It's meditative too.

    I agree regarding gardening, preserving and resilience. It's important to remember that resilience and a light ecological footprint are not the same thing though: in fact, there's a tension between them. (To highlight this tension, consider the "preppers" in the USA building fully stocked bunkers, etc.)

    Cheers, Angus

  8. Hi Chris,

    I like the idea of Nickel-Iron batteries. I'd consider those if we were going to get stationary batteries, though your Lead-Acid ones sound good too with an expected long life. It's interesting (from the article I linked) that LA batteries have about 1/3 the embodied energy of lithium ion batteries. Very telling. To me, that suggests some serious hidden subsidies for lithium ion! Interesting what you say about voltage drop too.

    The ebike has a 200 W motor. That doesn't sound like much, but it is a lot. A moderately fit rider can sustain about 200W, whereas 400W is more like an olympic athlete. In other words, the ebike turns a moderately fit cyclist into a super-cyclist! ;-)
    Also, I was thinking about that 500 kWh embodied energy in our battery. That sounds like a lot and it is -- but it is only about one tank of fuel in the car. It the ebike replaces 450 kms in the car, it's a net benefit. (Of course, that's only for trips we wouldn't have made on the ordinary bike, which is even better). I guesstimate the previous ebike battery did at least 5000 kms, 1/2 of which would otherwise have been in the car.

    Cheers, Angus


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