Rob's Red Bike

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My Retro-Direct Bicycle

This is my favorite bicycle, and my primary means of transportation. Because I’m highly original, I call it “The Red Bike”. It’s a retro-direct.

RedBike.jpg

What?

Retro-Direct is a gearing scheme for bicycles that enjoyed brief commercial popularity in the early 1900s. It provides a two-speed bicycle, which was very impressive before that meddlesome Mr. Campagnolo worked the kinks out of his crazy “derailleur” scheme. If you pedal normally, the bike goes forward, just like a single speed. But if you pedal backward, the bike still goes forward, like a different single speed.

DriveTrain.jpg

The mechanism is really quite simple. At the rear there are two independent freewheels. Whichever way you pedal, power is transferred directly to one of these, which propels the bicycle. The chain then takes a circuitous route back around in order to make a circle, spinning the other freewheel backward as it goes.

Why?

Retro-Directs have not been made commercially in almost a century, so producing one today requires some amount of effort. Why would you want to do this? Well, if you have to ask, you probably should not. Perhaps obviously, I like tinkering with bicycles, and like stuff that’s a bit weird and different for its own sake. That is certainly the reason I decided I had to build a retro-direct a few years ago when I first saw a picture of a historical one. However, since then I’ve come to greatly enjoy the system on it’s own merits:

  • Two speeds is about right for charging about town on short trips. Getting across town, I can go faster than a single speed will allow, but I’m not going to get up to the top gears of my road bike.
  • You never think about shifting or what gear to be in; both are constantly, instantly available, and picking which way to pedal quickly becomes instinctual.
  • There are no cables, levers, or cams, and nothing to (mis)adjust. Were it a commercial product, it ought to be as reliable as a single speed, and indeed, it mostly just runs great.
  • I’ve hacked it together out of parts made for other purposes, and my mechanical engineering experience consists chiefly of... well, this bike. So to describe its actual reliability as straight-forwardly as possible: it periodically self-destructs in more or less dramatic fashion. After that I have to spend some time wandering around hardware stores and bike shops figuring out what I can cobble together that won’t fail the same way again. Oddly, some people don’t consider this an advantage. However, I ride every day and fairly aggressively, and these failures have all happened in the midst of hard sprints. More reasonable riders and/or superior machinists may well expect better results.

Gearing

The historical retro-directs had a forward gear that was about the same as you’d want on a single-speed, and a backpedaling gear that was quite low so you could ride up hills that would force riders of lesser bicycles to walk. There are no big hills on my commuting and errand-running orbits, and I like to go fast. So my target is to pedal backwards in a typical single-speed gear for acceleration and moderate climbing, and pedal forward in a gear that's higher, but not too high to maintain the speed I can get up to in the lower backward-pedalling gear.

For the current setup, that’s a 53 tooth chainring. The backward-pedal driven freewheel is a 22 tooth, the forward-pedal driven one is a 16, so the ratios are 2.4:1 and 3.3:1 respectively, or for the gear-inch inclined, 65 and 89.