Alex Wetmore is always busy with something…

The current fad in road bicycles is to move to 110mm BCD “compact doubles”. Compared to a 130 or 135mm BCD this lets you run slightly smaller chainrings. A typical 130mm BCD double has 53/39 chainrings, where a typical compact double has 50/34 chainrings. I’ve talked about this many times on the BOB and RBW lists, but a conversation yesterday with Jan Heine reminded me of it and I thought it would make a good blog entry.

I’ve been experimenting with compact doubles on and off for 5 or 6 years. I started with a 110mm double (this was a fairly common crank in the 80s). My first bike setup like this had 50/34 chainrings with a 12-25 7sp cassette. Just looking at those numbers this sounds like a pretty reasonable setup: a high gear of 112″ and a low gear of 36″. Indeed the range worked well for me.

The problem with this setup is that my normal gears lived in the crossover range of the drivetrain. This meant that I was always shifting between the chainrings. Even worse when shifting chainrings I also had to shift many cogs on the rear due to the large difference in chainring sizes. This becomes more obvious when you chart out the full gearing:

From riding singlespeed I know that my normal cruising gears are in the 60-70 gear range. 70″ is the right gearing to go about 18mph at about 85rpm, a comfortable cadence. When you look at this gearing chart you can see that this gear is near the end of the cassette. So if I’m out the outer chainring and come to even a moderate hill I’m quickly dropping down into the 34t chainring. Likewise if I’m on the small ring and crest the hill I instantly need to shift into the outer chainring. Worse was that I ran this combination on a short chainstay bike (a Miyata 912 with 39.5cm chainstays) so using the 34t ring with the 2 smallest cogs or the 50t ring with the two largest cogs was noisy and inefficient. After about two weeks with this setup I changed the bike back to a triple.

This gearing is suited for someone, but it is someone who normally rides an 80″ to 90″ gear, not a cyclist who normally rides a 60-70″ gear. Even a 53/39 double would be better here because at least I could do most of the riding on the 39, just changing chainrings for long flat sections or downhills.

A couple of years ago I started experimenting with compact doubles again. This time I chose cranks with an even smaller BCD: 94mm and 86mm. 94mm BCD was commonly used on mountain bikes in a 94/58mm BCD triple. The smallest ring for 94mm BCD is 29t, but those are hard to find. 30t and 31t are a little easier, and 32t is very common. You can get large rings up to about 48t pretty easily. 86mm BCD was used on touring triples in the 70s and 80s where all three rings were mounted to the same BCD with extra long bolts. These cranks were made by SR and Stronglight. A typical setup would be 48/38/28 or 50/45/28. 28t is the smallest ring made.

Another change was putting on wider range cassettes. All of my bikes now have 8sp or 9sp cassettes. That one extra gear makes a noticable increase in cassette range. Here is what a 94mm double with 46/31 chainrings and a 12-28 8sp cassette looks like:

Look at what has changed. My cruising gear is now in the center of the cassette with the 46t chainring. The gear range on the 46t chainring extends down to 44t, low enough to let me climb most hills. The smaller large chainring also let me get a smaller small chainring with good shifting and that now goes low enough for almost any hill when unloaded. I did give up a little on the high end, but I almost never use gears over 100″ so this is not a problem.

This setup works great. I can do 95% of my ride in the 46t chainring, only shifting the rear cassette. I shift the front only for long hills. On my normal 10 mile commute this means that I’m only in the small ring once,where I’d drop into it 8 or 9 times with the 50/34 setup.

The hard part about getting real compact doubles is finding the cranks. If you want to experiment with this your best bet is finding a 86mm triple crank. The Trek touring and triple bikes sold in the early to mid 80s often came with the 50/45/28 cranks. These are reasonably easy to find on the used market and are nice production bikes which ride well. You may be able to find the entire bike used at a garage sale or swap meet for the price of a new crank. To make a compact double just remove the 50t large ring and replace the chainring bolts with double bolts instead of triple. You’ll also be able to put in a shorter bottom bracket (I think 107mm or 110mm is what I used) and you’ll end up with a lower Q-factor. Try this out with the 13-28 6sp freewheel that the bike probably came with and I think you’ll be a convert.

If you are lucky enough to have a Ritchey Logic Compact Triple then these cranks also make great compact doubles. They are extremely well made,the silver ones have a nice finish,and the cranks have no built in spacers for the granny ring, so they easily convert to running as a double. The hard part is setting up the bottom bracket. As a triple these cranks want a 107 or 110mm bottom bracket. When you remove the inner chainring you need to get even shorter. The shortest commonly made bottom bracket is 103mm and these are not easily found anymore (Shimano sold one for the 8sp Dura/Ace cranks). This is still not quite short enough.

I removed the fixed right shoulder from a Dura/Ace 103mm bottom bracket so that I can slide the bottom bracket about 3mm to the left. This gives me a much better chainline when running as a double. These bottom brackets use a removable right “cup” so I can move my modified cup to another bottom bracket unit when this one fails (I have a few spares). If you like this setup then the best alternative is to buy a Phil Wood BB. They’ll make whatever length you can dream of and list a 102mm that should work well in this application since Phil Wood BBs already have an adjustable chainline.

The TA Carmina is also available in a 94mm BCD double. This is a nice crank, but looks very modern and costs over $300.

Leave the 110mm doubles to the racers who actually cruise all day in 85″ gears. Most recreational cyclists will find a 48/38/26 triple to be better than a 52/42/30 triple and likewise they’ll probably find something like a 46/30 double to be better than a 50/34 double. Try it and I think you’ll like it. If enough people try it and like it maybe we can get a special run of 94mm BCD double cranks from Kogswell or Rivendell.

alex

These days I seem to like brewing beer more than drinking beer. Right now in the basement I have the following on tap:

• A pale ale (fairly hoppy, actually a blend of three other beers that I made)
• A really fine Porter
• A nice Weizen
• Two kegs of Barleywine (what was I thinking, this is strong stuff and probably will last me two-three years)
• A keg of Oat Wine (this is a Barleywine that is primarily made with Oats)
• Some Ginger Mead
• A way too sweet ale (sort of a clone of Mac and Jacks’ African Amber but it was the first beer on our new system and efficiency was way higher than expected so it is too sweet. Oh, plus, we had less hops than we thought we did).

That is 8 corny kegs. I only own 8 corny kegs (and one or two of these probably really belong to my friend Peter).. Too much shouldn’t be a problem, but I need some empty kegs so I can try making something new (perhaps an Oatmeal Stout with the rest of the malted oats).

Yeah, there are much more reasonable things to complain about like the fact that Bush has 3 years and 1 day left in office, but this is more fun to think about.

I hope everyone is having a great Jan. I’ve been busy at work and haven’t done too much interesting at home so the blog has been taking a break. It should wake up in a month or two once we start on the kitchen remodel and I do some work on one of my woodworking projects and one or two bike projects.

alex

P.S. Here is some math because I am bored. A corny keg is 5 gallons or 640oz. The beer glasses that I use these days are only about 7oz (half a bottle’s worth) or about 90 glasses. If I have ten glasses a week that means a full keg should last about nine weeks. Not all of my kegs are full, but at this rate I might have 8-12 months worth of beer on hand. Overboard? I probably just need to have another party or two.

At the last party the ginger mead was a big hit and it is almost gone, so I need to make more of that too. Easy and good.

A few days after Christmas I bought a sewing machine and started teaching myself how to sew. This was my second project, a small saddlebag. It is made from Cordura and I scaled down the design from http://www.geocities.com/lazyf62/saddlebag/sdlbag.html.

I’m pretty happy with how it turned out. It is the right size for a day ride without my panniers, but small enough that I can use it and panniers at the same time. The volume is somewhere around 300-350 cubic inches. There are no pockets (I originally made a side pocket, but it was really only large enough to hold my keys so I removed it).

I didn’t get a chance to make the straps for going through the saddlebag loops, so for now it is ziptied to a Carradice Bagman QR to hold the bag to my bike. That should be fixed shortly. This will also pull the top closer to the saddle and make the bottom flat as it should be.

I copied the drawstring closure from the current Carradice bags as shown below. I used some lightweight cloth called “supplex” for that.

I learned a lot from this project (as you’d expect from the first time doing anything):

• Cordura is tough stuff to sew through. At the uppercorners I was going throughfour layers of cordura and two layers of nylon webbing. The stiffness of cordura also made it hard to line everything up to do all of the seams. If I were making this bag again I’d use a lighter pack cloth and just add the heavier weight stuff where I need it.
• Matching your thread to your cloth makes it easy to hide sewing mistakes.
• Seam rippers are very helpful for undoing mistakes.
• I need to move the upper buckles to the top of the lid. They don’t provide enough compression when the bag is empty or nearly empty.
• I cut the lid too short, it should be at least an inch longer. I might sew on an extension.
• The “Baggins Little Joe” has it’s flat interior pocket design for a reason. On a small bag like this that maximizes capacity without being too complicated. I’ll probably copy those pockets if I make another one.
• I didn’t make the holes for the supporting straps large enough for leather straps to fit. My holes are slots about 3/4″ by 3/16″. The Rivendell Baggins bags use a round 3/4″ hole and that is probably a more appropriate size.

Anyway, it was a fun and I think successful project. I look forward to making another one in (perhaps a little larger) in the future. For anyone else thinking about sewing bags this is a good first project because there is a fair amount going on (but not so much to overwhelm you) and it uses a very small amount of cloth. I bought all of the the cloth from the remnants section of Seattle Fabricsfor under $10 and have enough left over to make another bag that is about 50% larger.

alex

I’ve had the last two weeks off. It has been very relaxing and I ended up doing very different stuff with my time than expected.

Accomplished:

• I built most of the radiator cover for our guest bedroom. This one is more or less a prototype since I’m using pine and I don’t know if that will hold up to the heat or warp and twist. I’ll have to put up some photos soon. I got some hints from this other radiator cover, including how to do mission/arts and crafts style vertical slats. The front and top are done, I just need to make some sides.
• I got a sewing machine and taught myself how to do basic sewing. The big projects coming up are making an underquilt for my Hennessey Hammockand a seat cushion for the living room bench seat. So far I’ve made a little case for my digital camera and I’ve done about 2/3rds of the work on a Carradice-style saddlebag for my bikes. I have no interest in making clothing but I think that making more custom bags will be handy and cool. I was going to include some photos of my projects so far, but my camera battery just died so I’ll do it later.
• I went snowboarding on New Years Eve with my friend Kathy. We didn’t really have snow last year, so this was my first trip in a very long time. The snow was pretty good and I got a good number of runs in. My knee didn’t bother me at all!
• Today (New Years) I went for a fun bike ride with a lot of cool people on interesting bikes.
• Lots of hanging out with Christine and other friends.
• Lots of catching up on sleep. Normally I don’t sleep more than 8 hours a night, but on this vacation that has grown to around 10. It is going to take a while to get used to my old sleep schedule and waking up at 6am.

I had high hopes for more projects around the house but did very few of them (on the other hand I didn’t think I’d be teaching myself to sew over the holiday). Hopefully sometime this winter I’ll get around to putting new lights in our living room (ripping out the last track lighting in the house), building the new storage rack in our basement, and perhaps putting in a basement sink.

I hope everyone else was able to take some good vacation time and spend some time with family.

alex