2014-02-08 - More Single Speed Bike Mods and Test Ride Around Park

AM
Miles: 6.3
Start Time 11:45
Moving Time: 0:37:28
Elevation(Ft): 0
Avg Spd(M): 10.0
Max Spd(M): 17.0
Temp Out: 70
Temp In: 70

PM
Miles: 7.6
Start Time o4:45
Moving Time: 0:48:49
Elevation(Ft): 0
Avg Spd(M): 9.3
Max Spd(M): 18.3
Temp Out: 68
Temp In: 68

This morning I was looking at the bike and lamenting the loose chain. Even with the tensioner maxed out it had a sway back appearance. I started wondering why I could not use the derailleur to tension the chain. After straightening the hanger and derailleur cage I tried several combinations of chain length and derailleur placement with and without the upper idler wheel. I finally found a combination that seemed like it would work. I also engaged the tensioner (like wearing suspenders and a belt?).

I will comment that this derailleur is unlike any modern version that I have seen. I cannot find this beast on the Internet. The more upscale versions I do find use two cables, push/pull, hence the name Shimano "Positron". As far as I know all modern derailleurs use a single cable to pull the cage up to the larger cogs and a spring to return the cage to the smaller cogs. This version must be aligned (or misaligned) in a way that causes it to drop to the next cog down when the cable is slackened one stop because it has no spring to pull the cage down. It also has no stop to limit the amount of rotation the cage can make towards the cassette. Modern derailleurs have a stop with an adjusting screw which allows one to set the upper idler wheel close to the cogs without touching. I am not sure how this one works but it seems to. The lack of spring comes in handy in my application because the cage just floats on the chainline with no tendency to try to shift cogs. It takes up the slack beautifully. It looks like a winner if it holds up.

I rode down the street a few tenths as a test and noticed the tensioner was making lots of noise in it new position on top of the chain. I came back to the house and disengaged it and then my short test ride turned into 6 miles. It is OK because it gives me about 300 extra calories to work with today. I do notice that my legs are definitely getting stronger from riding this bike with no option to ease the effort by shifting.

The bike worked flawlessly. My faith in it is mostly restored after being ready to put it in the dumpster at the first opportunity last night. I will leave the tensioner on the bike in the disengaged position for a few days just in case the derailleur setup falls apart or otherwise fails.

It is a beautiful 70 degree afternoon with temps slated to reach the low 80 next week. It is about time!

As originally set up:

Final configuration?:

Update: 8:20 PM

After a nice nap I went out and rode another 7.6 miles around the park in the last minutes before sunset. It was a pleasant warm evening and the bike worked flawlessly. Finally!