Shaft Drive bikes

Well, Monday I encountered my first shaft drive bicycle. If you haven't at least heard of such a thing, I'd be surprised. Along with "automatic shifting" bikes that crop up every few years, the "chainless" bicycle in one form or another periodically gets trotted out as the biggest "new thing" to hit the bicycling world ever.

Okay, so that makes me sound like a luddite, or in the bicycle world a "retrogrouch", I suppose. But the fact is that both of the above ideas have been tried many times in the past, with varying degrees of success, yet the chain drive bicycle with gears operated by the rider still remains dominant. I've got some ideas why, and we'll get to those shortly. First though, some pictures:

To the left here is the business end of the bike... showing the drive train. Notice the total absence of a chain. The first thing that struck me (after "what's wrong with this picture") was how tidy it all looks. Let's face it, chains tend to be dirty, and a chain type drive train, especially on a derailleur system, looks kind of cluttered compared to this. And that in a nutshell is one of the primary selling features of shaft drive bikes... it's tidy. Read the ads, and that's what they focus on... how it does away with all the messy aspects of a chain drive. And I can't argue with that... it is a tidier setup.


To the right you can see a closer view of the front end of the system. Where you would customarily have a chain ring or multiple chain rings attached to the crank, here you have an enclosed gear box, containing what I believe is a set of bevel gears... two cogs at 90 degrees to each other, with the meshing, toothed faces angled to 45 degrees, so they convert the rotary motion of the pedals and cranks in one plane into the rotation of the drive shaft in another plane. And you can see, there is no chain or toothed chain ring to make a mess of your pants leg.


And here is the rear of the system. Obviously that is the back end of the drive shaft, and inside that housing by the axle is another set of bevel gears that convert the rotation of the shaft back into rotation in line with the wheel and cranks. It's hard to see in this picture, but the whole system basically connects to a Shimano Nexus 7 speed internally geared hub, a fairly standard bit of bicycle hardware, and very reliable and pretty efficient. And again, no messy chain or exposed sprockets back here either.


So if it's so clean and tidy, what's not to like about it? Well, first off, it's kind of heavy... heavier than a single chainring, sprocket, and chain would be, driving the exact same Shimano hub. How much heavier? Well, I don't know exactly, not having the specs, but it's probably not a huge weight penalty, and honestly, I don't stress that much over a little weight on a bike, especially if it's not a competition style bike.

A much bigger issue for me is the proprietary, or "single source" nature of some of the vital parts. I give this manufacturer bonus points for incorporating the Shimano hub, instead of using something of their own proprietary design, but the drive shafte and gear boxes and cranks ARE proprietary. Why is that a problem? Well, an awful lot of companies that come up with "innovations" in the bicycle industry don't survive, and if this company were to go out of business, you'd be hard pressed to find replacement parts. For that matter, even with the company in business, you're not going to be able to walk into your local bike shop and expect them to have the parts on hand. I'm sure the manufacturer does have provision for shops to order parts, but that's not always as easy or quick as getting more standardized parts, such as chains, cassettes, and chain rings, which are all pretty well standardized in the industry. (Okay, so there are in some cases multiple "standards", but availability of spare parts is rarely a problem.)

And finally, one thing you don't see the manufacturer touting as a virtue of this system is its efficiency. There's a good reason for this... it's not that efficient. Way back when I was in graduate school for technical theatre production, we had a couple of classes in physics and machinery for the stage, and one of the things I learned there was that for efficiency and reliability, it's hard to beat plain ol' roller chain and sprockets, of which a bicycle drive train is a prime example. In terms of energy lost in the process of transmitting power from point A to point B, few other transmissions are as efficient.

So while there are certainly some benefits to the system, all in all, I'd rather have a chain drive bike, with perhaps a good chain guard or fully enclosed "chain case" to keep me clean. That way I can walk into any bike shop and get replacement parts or have it serviced without any concerns about the shop never having worked on one before. And I'll have a lighter, more efficient bike to boot.

The maker of this particular bike is a company called Dynamic Bicycles. Look for them on the web at:

http://www.dynamicbicycles.com/