A few photos

Cades Cove on a bike camping trip last fall; a back road on an early spring day; and a new frame for Hayduke.

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A Few Changes

In the last year, I have had two significant career changes.  In February of 2011, I was assigned to work on a nearby environmental clean-up project.  I don’t want to be coy about this, but I don’t want to give the impression that I speak for my employer (now former employer), nor is this the appropriate forum to describe the internal workings of the project, since there are several law suits pending.

The project is located about 45 miles from home, so cycling to the site was out of the question, at least on a daily basis, so I did more driving than I have for years.  Fortunately, I only needed be at the site two or three days a week and I mostly worked out of my downtown office.  I eventually got access to an assigned car, and the ride to pick it up was an opportunity to add a few commuting miles.

Somehow this change in routine, along with the mental exercise of tackling work that I was not all that familiar with, took much of my mental energy.  Blogging frequency suffered, as did other volunteer commitments. Even though I spent much of my transportation time thinking about writing, it seldom made it on the page.

The cleanup project was a great professional experience.  I learned a lot and worked with some great folks.  However, I was not that passionate about the work, and it was a temporary assignment.  At its close, I would have to find a new niche and develop new skills to match.

This was not to be, as it turned out, because a new employer offered me a job with significantly increased responsibilities and an opportunity to work on issues that I really care about, and even to have significant impact on those issues locally.  I started the new job just last week.

This job will consume my mental energy to a much greater extent than the last job change.  I have lots of stuff to write about, including a frame building project and a bike camping trip, along with the new challenge of bike commuting to a coat-and-tie kind of job.  But I suspect that the demands of the job will make me scarce in the blogosphere.

One of the original excuses for starting this blog was to pass on the experience of heart valve replacement and recovery.  Almost two years out, I feel fully recovered, although my sternum still feels less than whole sometimes.  Because of injuries and illness, I have not had a good season of training (to the extent that you can call what I do “training”) since the surgery, so I do not yet have a complete before-and-after comparison of speed and endurance.  The best comparison I have so far is the fall century that I completed this year right at seven hours, about six weeks after the orthopedist let me back on the bike.  The last time I did the ride before surgery, I did it in 7 1/2 hours.  The surgery did not make me 25 again as I secretly hoped (I could have done it in five hours or so back then), but there is a definite improvement in performance and energy level.

The broken arm is not yet completely healed.  I have full mobility and good strength, but the latest x-rays show that the bone is not entirely fused.  I need to be somewhat careful with it, so the mountain bike is still off limits, even though there has been an incredible growth in  trails available with connections only about a mile away from my house.  A piece of advice here: don’t break your arm

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An Experiment in Frame Geometry

My utility bike is a 1974 Schwinn Sports Tourer. It has a straight gauge chromo frame with fillet-brazed joints. The frame design could have come out of the Rivendell catalog: low bottom bracket, moderately long chain stays, and 73 degree head and seat tubes.

I bought it off Ebay in 2003 or so. I converted it to a 7-speed internal hub and added fenders and lights and other utilitarian stuff. It has averaged more than 1500 miles per year since then, commuting to work and running errands.

The bike has a few faults. One is that a 35mm tire is a tight fit laterally in the fork – the sides of the tires tend to rub on the fender and/or fork blades if everything is not set just so.

The second fault is that it rides harshly over bumps, even with 35 mm tires. I would ascribe this to the relatively stout straight-gauge tubing used in the frame. My sportier bike,  with steeper angles, shorter chain stays, and narrower tires but built with standard-gauge butted tubing, is much more forgiving. It is unclear from the information out there whether the Schwinn fork is chromo, but the rear triangle is reportedly plain carbon steel.

And the third problem is that the bike cannot be ridden no-hands at any speed because of a serious shimmy.  This shimmy damps out even with light hand contact on the bars, but it is a significant annoyance.

My theory (at least I have not found anybody who states it exactly this way) is that shimmy in bikes, at least in many cases, is a harmonic phenomenon something like a torsion pendulum, with the trail of the fork, which tends to make the bike go in a straight line, acting as the spring. In a torsion pendulum, the frequency of oscillation is determined by the stiffness of the torsion spring and the moment of inertia of the system.

Bikes are a little more complex than the simple torsion pendulum example, because there are two mass/moment of inertia systems influencing the oscillation. The first is the obvious one: front wheel, tire, any luggage on the front — everything that pivots around the steering axis. The second mass and moment of inertia system is not so obvious. Because the head tube moves side to side as the as the fork is turned, all of the mass of the bike that does not pivot around the steering axis pivots instead around the contact point of the rear tire. This means that the frame, rider, rear luggage, back wheel, and any other paraphernalia influence any oscillation, with mass closer to the front of the bike or extending behind the back wheel (and thus farther from the pivot point) having greater moment than weight directly over the back wheel.

In this conceptual model, shimmy occurs when the front (pivoting around the steering axis) moment of inertia/trail system has a similar natural frequency of oscillation as the back (pivoting around the rear tire contact point) moment of inertia/trail system. Since these two systems are so different, it may also be that oscillation will occur when harmonics are similar.

I don’t know a definitive way to test this theory, but if it is a good model, changing weight distribution should affect a shimmy, as should changing fork trail without changing weight distribution. I have had experiences when changing weight distribution seemed to cause or eliminate shimmy, though other times the shimmy seemed to be insensitive to changes. The Schwinn does not have racks or baskets on the front, so I can’t change loads there, but the shimmy does not respond much to a wide range of loads on the back. I have tried added damping by adjusting the headset too tight with no change. The shimmy persists with tires from 28mm to 35mm and different front hubs.

I decided what I needed was a new fork. The fork crown would be wide enough that there would be no problem with the 35mm tires. The blades would be mid-weight chromo to see if the over-bumps-ride ride would improve over the unknown material of the original fork. And I would try a low-trail design, as championed by Jan Heine of Bicycle Quarterly (here, for example).

Here are the results.

Problem 1: Solved. There is now plenty of clearance.

Problem 2: With the new fork, the bike rides only marginally better over bumps (based on subjective observation), even with the greater offset. Maybe a fork built with lighter fork blades would have enough more give to make a difference, but I think that would be inappropriate for a bike that gets this much abuse. Then again, maybe I will try it someday just to see how much difference it does make. Anyway, the bike got a new sprung Brooks saddle to handle some of the jarring, but that does not help my hands.

Problem 3: The finished fork results in about 25mm of trail, which is at the low end of accepted practice. Somewhat to my surprise, the handling did not change all that much. It feels quick and maneuverable at low speeds and it feels a little twitchy at downhill speeds, but it still in the range of what I would call normal.

The bike now has much less tendency to shimmy – reducing the trail seems to have worked in that regard. If the above theory is correct, increasing the trail should have also worked.

And for a bonus, I discovered that brazed-on centerpulls do indeed have a nice solid feel. But this mounting did not make enough difference in braking to make up for the trouble of making the mounting studs.

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A Visit to Portland

Portland is a wonderful place. Everybody knows it is the one of the best (link) cities if not the best city (link) in North America for cycling. The relatively compact development patterns (for a US city) means that distances between trip generators and destinations are small enough to make cycling practical for a lot of people. And there has been a lot of effort expended to create bike-friendly infrastructure.

It’s also one of the best cities for mass transit (link), and includes real trolleys (with real steel rails) in the transit mix.

There is a little bit of a potential conflict here, as I discovered on a recent visit.

My wife and I visited Portland recently, arriving May 19 for a two week visit to various Oregon destinations. I grew up Oregon, and some of my old friends have ended up in Portland, so I was planning to do some visiting, in addition to getting reacquainted with the city.

The first full day there, my wife was suffering from the remnants of a sinus infection and jet lag, so I left her at the hotel (recommended) and took the trolley to walking distance from the nearest bike rental shop . They set me up with a serviceable hybrid, and I took to the streets.

It was a short ride to the river. After rolling along at the riverfront MUP for a while, I got onto the street again. I made a left turn onto a one-way street, looked over my right shoulder to check traffic before getting into the right lane, and Crunch! I was down hard. I failed to notice that there was a trolley track in the street that I just turned onto. I somehow made it to the sidewalk and called 911. It was clear that my left arm was broken.

Surgery to install plates and screws and two nights in Good Samaritan (also recommended if you have the misfortune of needing their services) later, I was back on the street. The rest of the Oregon visit was less active than originally intended, but visits with family and friends (through the pain-med fog) meant that it was far from disappointing.

The hard cast came off July 11, the eighth week after the incident, and I wore a brace and did physical therapy for few weeks. I got permission to get back on the bike after eleven weeks (August 5). I am now in the 16th week of recovery, and things are getting back to normal. The arm still ain’t quite right, but it’s getting there.

I love Portland, and I even love the trolleys.  The bike/trolley conflict is an open issue. For a first step, a little more warning would be nice.  A few more signs like this might have saved me some pain and suffering.  If you visit (or if you live there) just be real aware of where the tracks are.

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Gearing part III: Gear sequence

The third installment of my gear cogitations addresses gearing systems and how to get low-enough gears without too much compromise.   

First, let me opine that the great majority of cyclists do not need gears as high as what comes stock on bikes these days.  In fact, most don’t need more than 100” ( the old-school 52×14, or with modern hardware, 41×11 ).   A 100” gear allows 27 mph at 90 rpm (27” nominal diameter wheel); most of us only hit this speed going downhill, and if the descent is too steep to pedal with this gear, it is more efficient to tuck.  This even goes for low-level competition cyclists.  As a category 3 rider, I once wore myself out pushing a 108” gear on a long downhill in a race, only to be passed and dropped by some of my team mates who had tucked on the descent and were relatively fresh for the subsequent long climb.  As for top speed and sprinting, a little practice gets a rider’s maximum cadence well about the 90 rpm that is sustainable for long periods — Charles Murphy set his paced record of 60 mph in 1899 on a 104” gear (at 198 rpm).  The 130” gear (52×11; 35 mph at 90 rpm) that comes stock on high-end racing bikes is good only for downhill sprints and for developing bad pedaling habits, unless you can keep up with Mark Cavendish.  For touring and town bikes, a high gear of 85” is not unreasonable, though most of will probably want to stick with 95” to 100” on the touring bike.

So here are my criteria for an all-purpose gearing system:

1)  As explained at length in the last post, with my topography, fitness level, and purposes, I like to have a low gear in the low 20’s or even lower.  People who live in flat places or who are strong climbers (and plan to stay that way) can adjust accordingly.

2) A high gear of 100” or a little lower works for me on the road

3) Gear ratios should be spaced closely enough to allow the rider to maintain a cadence within his/her comfort range throughout the gear range (or at least the most-frequently used portion of the gear range).  As a reference, 5% steps are real tight, allowing a cadence that stays between 90 and 95 rpm.  Most of us are happy with steps of 10-15%. 

4) There should be a logical shift sequence that is easily executed.  It used to be common for people to have a gear chart taped to their stems so they knew how to get to the next gear.  While it is not a bad idea to give some thought to how your gears are laid out, they should not require a map.

Figure 1. Hayduke diagram of 3-speed internally-geared hub with 44-tooth chainring and 19-tooth cog. 25% steps between gears; 178% total gear range.

Internally-geared hubs and single-chainring derailleur systems have the simplest  shift sequence.  Three speed hubs have a relatively narrow range and large steps between gears, which is okay for flat areas, and IMO a lot better than single speeds.  I was happy with a 3-speed commuter bike when I lived in flatter places and had a higher level of fitness than I do now. 

Seven speeds have smaller steps and enough range for short trips in hillier areas.  I currently use a Shimano Nexus 7-speed on my commuter/utility bike geared down for the local hills.  High gear is 80″; low gear is 33″.

Figure 2. Hayduke diagram of my Nexus 7-speed internally-geared hub with a 42-tooth chainring and 22-tooth cog. Average 14% steps between gears. 244% total gear range.

The wide-range double “compact” crank seems to be dominating the market.  This setup has a good range for many situations, though it does not go low enough for my purposes.  For me, the fatal flaw with this approach is the shift sequence.  The shift between front rings is big (30% or so), so usually when the rider make this shift,  it is necessary to correct 2 or even 3 cogs on back to get a reasonable-size step.  This shift is right in the meat of the riding range (50” to 80”) so the clumsy big front shift and rear correction happens frequently.  When I tried a similar arrangement, I hated it because the gear I wanted to shift into always seemed to require this awkward sequence of shifts.

Figure 3. Hayduke diagram of typical compact double with 48- and 34-tooth chainrings and 12-27 tooth 9-speed cassette. Gear range 108" to 34" (318%). Three pairs of near-duplicate gears; 13 usable unique gears. 7.8% average step between gears (neglecting duplicates).

The best way I have found to meet the criteria I laid out above is the step-and-a-half triple with granny.  In this arrangement, the step between the big and middle chainrings is about 1.5 times bigger (in percent) than the steps on the freewheel.  For example, a 9-speed 12-27 cassette averages 10% steps between the cogs; 39 and 46 tooth chainrings are about 15% apart (note that since we are confined to integer number of teeth, this frequently needs some trial-and error to find a combination that works best).

Figure 4. Hayduke chart for step-and-a-half-plus-granny gearing system. 20-36-45 chainrings and 12-36 nine-speed cassette. 15" low gear to 101" high gear (675% range). 7.4% average step between gears on middle and large chainrings; 14% maximum step. 24 usable non-duplicate gears.

Of course most riders are not likely to shift sequentially through the gears.  Usually, one would still use the chainrings as high-range low-range (with a double) or high-medium-low ranges (triple).  However, the  shift between chainrings is not as big as in a compact system, so you don’t need to correct as often on the cassette when you change chainrings; when you want the next sequential gear, you only need to correct by one cog.  The shift from the middle to small rings is still a big step, but this shift does not happen as often as the similarly large step between rings on a compact, because it is at the extreme of the gear range.

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Gearing Part II: In praise of low gears

I may have mentioned in previous posts that there is some topography around here.  In town, 6% slopes are routine, 10% climbs are common, and there are even some block-long hills around 20%.  Rural roads are usually a little gentler, since lower road density allows routes that avoid the steepest hills, but there is little flat road and still plenty of 6-10% and steeper climbs. 

I am not as young (or as fit) as I used to be.   I don’t alway ride with the express purpose of causing myself cardio-vascular distress in an effort to recapture my lost youth.  I am formerly (I hope) handicapped by a bad heart valve, and occasionally get injured (the knee is healing up nicely, thanks for asking).

I like long rides.  Jamming up hills out of the saddle works for short trips around town or even relatively short rides in the country, but I don’t have the fitness (or probably the potential, much less the motivation, to develop enough fitness) to use this tactic for rides longer than 25 miles or so.

I like to be comfortable and reasonably safe on my rides, so my bikes will never be as light as a stripped-down racing machine. And on tour, I carry appropriate loads, including camping gear. I also like unpaved roads, though there is a lot more rolling resistance on them than on smooth pavement.

I am a spinner.  I tend to stay around 90 rpm on the flats (such as they are) and I feel best when I also maintain this cadence on climbs.  If I go much under 70 rpm it  feels like a grind, beats up my knees, and tires me quickly.

All of this has led me to install very low gears on my bikes and use them frequently.

 I consider myself a 100 watt cyclist (see this previous post) though I probably average closer to 125 watts these days.  Of course I can push it up higher for short periods or for training rides.  But I might also slow down and enjoy the scenery.  Pacing is important on day-long rides, and on a tour, you have to leave enough energy to set up camp, cook dinner, and do it all again tomorrow, and  35 watts gets you down the road.

So how low is low enough?  This table gives speed and gear as a function of slope and rider power output for a 175 lb. rider on a 25 lb. bike.

  100 Watts 200 Watts
Slope (%) Speed (MPH) Gear at 90 RPM (inches) Speed (MPH) Gear at 90 RPM (inches)
3 7.3 27 12.6 47
4 5.9 22 10.7 40
5 4.9 18 9.2 34
6 4.1 15 7.9 30
7 3.6   7.0 26
8 3.2   6.2 23
9 2.8   5.6 21
10 2.6   5.1 19

The lowest commonly-available low gear is 19 inches (24 tooth front, 34 tooth rear, 27 inch [nominal] wheel).  A fellow 100 watt cyclist runs out of gear (or has to reduce cadence) on a paltry 5% slope even with this gearing that is extremely low by current convention.    Even the 200-watt sportster who wants to maintain a good cadence on a long hill might find the usual 39×27 (39 gear inches)  or “compact” 34×27 (34 gear inches) too high for a mountain ride.   And this chart does not take into account  camping loads or rough surfaces. 

 The lack of low gears in hilly terrain can turn a pleasant rural ramble into a gruelling test of strength and endurance.  While I enjoy a little gruel now and then, it is nice to have options.  It would be difficult to have gears that were too low.

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December in Knoxville

It has been cold, at least for Knoxville.  A little snow and a little ice has turned some recent mornings into a winter wonder-how-I’m-getting-to-work land. 

In addition to the cold rides to work in the morning, weekend rides have seen water bottles icing up.  None of this is a big deal farther north, but this is not something we are used to here.

 

 

 

 

 

 

The Fourth Annual Tour de Lights took place last night, and a good time was had by all.

More photos (some from me) and more details on the Bike Program blog.

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