More time on the NuVinci

Having resolved install issues akin to making a square peg fit in a round hole, the NuVinci equipped city beater has been logging miles running around town.

But first, one thing I recommend is to mate the NuVinci to a bike with the correct style dropouts.  I’m not happy with the result of trying to juggle different sprocket sizes and chain links to achieve the right chain tension.  Until a 7/32 link is invented, I’ll have to be content with occasionally dirtying my fingers to remount a chain.

Aside from that, there’s been much to like about the Nuvinci and only a few demerits.  I don’t think there’s a quieter ride this side of a fixie; the supplied freewheel makes no noise on over-run and the Nuvinci itself is completely silent.  So silent, in fact, that I can hear the bottom bracket bearings popping and a little grinding in the head bearings, leading to the realization that my city beater may simply be beat.

With 36t front and a 17t rear sprocket the gearing range is just about perfect, in fact I’ve only rarely gotten up to top ratio but find the low ratio to be fine for dumping torque to the rear wheel.  The gripshift type Cruise Controller is a clever piece of work only let down by chintzy cable tension adjusters.  They don’t seem to keep adjustment very well and I find myself fiddling with them to wring out the play in the mechanism.  A little rubber glue on the threads might be all it needs.  CruiseController action is smooth and proportional to controller input though shifting effort is proportional to pedal force so smoothly changing the ratio while accelerating requires a bit more effort to twist the CruiseController than a typical gripshifter.

A harder problem to address in the Nuvinci’s considerable weight.  A bit of weight is lost by jettisoning the derailleurs and extra sprockets but throwing the bike over the shoulder is significantly harder not just due to some extra weight, but also because it’s all in the rear wheel and hence harder to balance.  It does feel like a bit of an anchor, to be honest.  The other effect of a heavier rear wheel comes in when riding over bumps.  If I felt the beater’s seat was a little thin before, it’s certainly inadequate now.  The additional energy of a heavy rear wheel shot upwards by a bump is absorbed by the rider’s nether regions in an occasionally painful manner.  This effect is readily apparent while navigating Baltimore’s patchy streets and riding up and down curbs.  If your bike doesn’t have rear suspension, I would suggest a shock absorbing seat stem or at least a plush seat.

Luckily, the way the NuVinci is packaged in the velomobile design minimizes the NuVinci’s drawbacks and plays to its strengths.  I’d still recommend it for a regular bike especially if you like your ride to have clean lines but still want adjustable gearing.

About Suhas Malghan

Inspired by the kinetic, this blog documents the design and development of environmentally sustainable machines and the overarching issue of humane design practices in general; machines that work for humanity as well on the move as they do sitting still.
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2 Responses to More time on the NuVinci

  1. jsmithson says:

    You can resolve the chain tension issues with a chain tensioner. Shimano makes a good one (hard to find in the US) as do others.

    http://harriscyclery.net/itemdetails.cfm?ID=2817

  2. smalghan says:

    Hey thanks for the tip. I’ve seen a couple of tensioners that mount to the chainstay lately that look like they would work. By that time I’d already removed the NuVinci to use on the velomobile but they definitely would have been a good addition.

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