Tuesday, June 21, 2016

Another Monster Emerges: Damson Retro-Direct 2-speed

Back before derailleur drivetrains became popular, internally-geared hubs ruled the bicycle world. And back before those, mostly everyone rode single speed or fixed gear.

However, very shortly before internal gear hubs became the staple of commuter bicycles, a few builders experimented with a "retro-direct" drivetrain. Such a bike would have two different-sized freewheels threaded onto the rear hub and the rider would pedal forward for one gear ratio and backward for the other. Both gears would drive the bike forward. The way the chain was laced around, whenever one gear was driven, the other would freewheel backward.

1920 Hirondelle Retro-direct, image courtesy of commons.wikimedia.org

Perhaps the most well-known retro-direct bicycle was the Manufrance Hirondelle Retro-Direct, made for decades but still not very well-known in the grand scheme of things. Most of the riding would be done pedaling forward in the cruising gear, while the less-used hill climbing gear was the backward one. Despite still being the cheaper way to get multiple gears, the backward-pedaling bikes quickly fell out of favor because with multi-speed planetary rear hubs (such as the Sturmey-Archer) and bottom brackets (in the case of Sunbeam), the rider never had to power the bike while pedaling backward. Who would want to do that, anyway?

That is, unless you just wanted to have some fun. Enter, "Damn, son! Where'd you find that?" my new 1977 Takara 10-speed, turned 2-speed retro-direct. As you can figure out by tracing the path of the chain, since I built this bike for fun and not practicality, most of the riding is done pedaling backward in high gear, while the hill climbing and acceleration is done by pedaling forward. There is also some practical reasoning to this, as I figured if there was ever a time I had to quickly jump on the pedals to get away from something, I'd probably pedal forward and in those cases, I would probably also like to be rewarded with ample forward motion.

To assemble this, I had to "lengthen" the threading on the hub to fit two freewheels. Through some research, I was told that a standard bottom bracket cup would have the same threading as a freewheel. I used some old alloy wheels that had steel hubs, as I thought steel hubs would have tougher threads, and used the left side adjustable cup from a Giant-made 1980 Schwinn to extend the thread. I used a pie plate and the bottom bracket lock ring as spacers on the hub and threaded my larger gear halfway on. I locked that with the aforementioned lock ring. After, I threaded the bottom bracket cup into the freewheel and tightened that the best I could. I faced the cup side inward (see photos) because it seemed weaker - I figured that the side of the hub might at least support it a bit, along with it being tightly encased inside the larger sprocket that was locked onto the hub. Lastly, I threaded the smaller gear onto the protruding bb cup and tightened it down against the larger freewheel. Both freewheels spun nicely and independently of each other.

I stumbled upon Josh Bechtel's design and really liked the clean look that his retro-direct bike had without the idler pulley. I thought since he used two different freewheels and two of the same size chain rings, I could use the two chainrings that came on my bike along with two similarly-sized freewheels (in my case, 17-18 teeth pictured above). I tried that, and I can't exactly remember why, but the drivetrain was binding up. Also, the chainstay was super in the way. I couldn't really figure out how to rectify it and my brain was hurting so I threw that idea out the window and decided to go back to the more common way.

So I settled on using the 52 tooth chain ring and 16 and 22t Dicta (Sunlite) freewheels. I was told Dicta freewheels are the only kind that do not have a lip outside the thread, allowing the hub threading to be "extended" past it. The low gear isn't as low as I'd like it to be even though I bought the largest and smallest freewheels available. I made the mistake of buying a 14t freewheel for high gear which ended up being of the metric BMX size. The diameter of the threaded area was much smaller.

Predictably, I had some problems with chain stay clearance. Since this was a very low-end frame with nice, thick-walled, hi-tensile steel, I eyeballed it where the chain was rubbing the frame and bashed it in with a hammer and punch (below the old shifter cable braze-on in the photo), then ground it smooth. It wasn't pretty but it was whatever. It still rubs but not nearly as badly as before. To make the idler pulley, I used part of the old derailleur that came with the bike and attached by drilling a hole straight through the chain stay. I had to re-position the pulley further toward the rear (hence the extra hole) to bring the chain line outward a bit; as horrible as the chain line is right now, it's the best that it can be on this bike. I then made more adjustments by giving the derailleur an S-curve inwards.

As a side note, the bike also cannot roll backward because doing so pulls both ends of the chain that come away from the chain ring. Also, people who build backward pedaling bikes tend to weld the pedal axles to the cranks to avoid having them come loose but so far, mine has proven so rusty "down there" that the pedals have stayed put.

Well, how does it ride? It actually rides great. Because it lost the old steel wheels and most of its original drivetrain, it's fairly lightweight to my standards. Two gears are usually enough, although it gives me a relatively narrow range of comfortable cruising speeds. The mustache bars, which I originally bought for appearance, actually work very well with this setup because when I pedal backward, I end up pushing against the bars which would be far less comfortable on drops.

And the saddle. It was cheap and I bought it to try on a different bike a few months ago. It was too narrow and too rounded in the middle to sit on comfortably before but since most of the time on this bike is spent pedaling backward, the weight of my bum ends up getting pushed up so that the saddle is no longer uncomfortable. The brakes are quite good, the original center-pulls having been swapped out for less-finicky side pulls from a KHS Gran Sport (where I also got the wheels). They are assisted by the brake cable braze-ons as well as the fact that I actually used leftover scraps of shifter cable housing which is less compressible. The bike is legitimately fun and nice to ride. There's nothing glaringly wrong with it, aside from the chain rubbing, and it has not failed in any way. I cruised around all day on it for a few days and would not at all be opposed to riding it to and from work more than every once in a while. Not too bad. This thing is a riot!

Since this bike gathered a fair amount of attention while I was riding it, I figured I might as well make it pop a little bit more to those who may care. I used a white chain and also changed the lettering on the down tube from "Takara" to what it is now. I thought this particular phrase could also be mistaken for a brand name at first glance (cue "what in the world is a Damson bike and what is going on with the chain") and possibly prompt interested parties to look it up and arrive at this page. I'm not sure how it will actually work out, but it does make it more unique in the end.

So, enough blabbering for now; it's time to go for another ride. I don't think there will be many, if any, further updates on this bike in the near future since it was done for fun on a low budget. It's good enough as it is. I'll probably just keep riding it and letting other people make sense of it. If anyone who is interested happens to be in the Ann Arbor area, drop me a line and we can go for a ride. More so, build your own! Mine was easy and yielded fun results. Ask me if you need tips. Either way, you gotta try it!

EDIT Feb. 16, 2017: Today, I installed a 24 tooth freewheel in place of the 22 to make the low gear lower, and re-routed the chain so that forward pedaling gave the high gear ratio. Often times, I found myself pedaling backward down hill, looking like one of those schmucks who turns their legs backward whenever they are coasting. Accelerating while pedaling backwards gives the more silly appearance that I was going for. As an added bonus, the chain no longer rubs the stay.

The 24t freewheel, not made by Dicta, was of terrible quality. it came apart as I was installing it so I took the chance to properly assemble it with thin grease (it was dry to begin with). Getting all 94 balls back in was not as time-consuming as I had anticipated.