Lesson in humility: failed headset crown race press

Part of doing-it-yourself is failing to do it yourself. It's not a bad thing unless you refuse to learn from it. Up until now, I had made it a point to only post my successfuly hacks/tweaks/mods/etc to this blog. However, today's post is abouta well-planned diy tool that didn't work. Let's try to learn something from it.

While doing my annual bike tune-up, I realized that part of my headset was installed incorrectly. I designed and built this tool in an attempt to fix that.

First, a bit of terminology.

A press is simply a tool that works by pressing things together, in contrast to a jack which pushes things apart. There are lots of kinds of presses: simple ones use a screw, complicated ones use pneumatic or hydraulic pressure.

A bearing is a mechanical component that acts to reduce the friction between two parts which move relative to one another. A ball bearing is a bearing which uses balls to accomplish this (though many other types exist: the brass bushings on cantilever brakes are an example of non-ball bearings).

And now some bike terminology.

The fork is the fork-shaped piece of a bike which straddles the front wheel (n.b. the things on the back are called the stays, and are NOT a fork). The steer tube is the tube which extends up from the fork to the stem, which connects to the handlebars. The fork crown connects the steer tube to the two tines of the fork.

The headset is a pair of bearings which connect the fork to the rest of the frame, allowing you to steer without much friction. Those two bearings in the headset are cup-and-cone style bearings. These types of bearings are popular in older bikes, but are being gradually replaced with cartridge bearings. This is unfortunate, since cup-and-cone bearings can be adjusted for a prolonged life, while cartridge bearings must eventually be thrown out and replaced. Nonetheless, because the main force on headset bearings are thrust forces (parallel to the axis of rotation), and because of the size of the bearings, cup-and-cone style bearings remain the standard for headsets.

A cup-and-cone bearing consists of three pieces: two races, and a set of balls. Sometimes, those balls are held in a ring formation by an unnecessary, though helpful piece of metal or plastic called the retainer. One of the two races is concave (the cup), and the other is convex (the cone). The fork crown race is the cone which is seated on the steer tube just above the crown, on what is called the crown race seat.

The crown race is press-fit onto the crown race seat, which is to say that the crown race seat is slightly larger in diameter (1.185") than the internal diameter of the crown race (1.180"). This minor difference in diameter (only 0.005 inches) is enough to make it hard to install, though once installed, it may as well be a piece of the steer tube.

So, as I was stripping my bike down for its annual paint job, I noticed that the crown race was incorrectly seated, and I decided to remedy it. It only took a few seconds for me to decide that I wouldn't be able to press it on by hand, and so I went forth building a tool.

I tried two variations on the same design. The first attempt failed: as I tightened the drive bolt, it worked well until the steel bar bent, and then the plastic snapped, and ultem shrapnel ricocheted off of my luckily-closed eyelids. Although a failure, it worked for a while; the race was halfway pressed onto the race seat. I was encouraged to try again, using a heavier construction that hopefully wouldn't snap, crackle and pop.

I have annotated the picture on the left.




I used my lathe to turn a piece a ultem plastic (a metal replacement, similar to delrin) into a race guide. The race guide had a 1.125" hole bored through the center of it, so it could slide along the length of the steer tube, and had a larger recess bored at one end of that hole to snugly fit the crown race.




I then drilled and tapped two holes on either end of the race guide, and used bolts to fasten the race guide to a bar of steel placed between the two tines of the fork. A third bolt--the drive bolt--past through the center of that steel bar against an ultem plunger, which pressed against the other side of the fork.

Again, I have annotated the picture on the left.






I wrapped some fabric around the new paint on the fork, and began torquing the drive bolt. Just like the first time, it began working. In fact, this second attempt put the race close to the right position.

But alas, it too failed.




The failure was very similar to the first time. First, the steel bars bent. And again, since it seemed so close to being complete, I chanced tightening even further. Unlike my first attempt, however, the plastic never broke. Instead, the press tore the head off of one of the hanger bolts.

Disheartened, I decided I would need to try a different technique. But what? I couldn't easily make this design larger, since I was already working with the largest plastic stock I had available. I read and re-read Sheldon Brown's advice, until it came to me.

Duh! I have a lathe.

I chucked the crown race, and took a few (i.e. added) a few thousandths to the race's internal diameter. The race still had to be pressed onto its seat, but I could do that under hand power using the race guide I had already built.

So, as I mentioned earlier, there is a lesson hiding in here somewhere. I'll try to be thorough it down, but please let me know if I elide anything:

Lesson 1: Keep it simple, stupid (KISS). This is the prime directive of engineering. By elaborating the design, I added too many points of potential failure.

Lesson 2: Determine which problem constraints are true constraints, and which are only constraints in name / by convention. The crown race should be tight on the crown race seat so that the steer tube doesn't rattle within the bearing. But does it need to be press fit? There will be no motion between crown race and steer tube, so long as the bearings are doing their job. By increasing the internal diameter, I allowed easier installation, but without sacrificing holding power.

Lesson 3: Wear eye protection.

Spring bike maintenance

Spring is finally here, even in the frigid New York City, and time has come for my annual bike tune-up. Sure, I could take it to a bike shop, but then I'd miss out on all the greasy hands, the hundreds of little cuts on my hands, the OCD adjustments that a bike offers, and the feeling of triumph of riding the optimized bike.

Now, I admit that my hand was forced into doing a tune-up. Work has kept me busy enough that I just put off the repairs, one weekend after another. It was a mechanical failure that got my focused.

Daya, Chris and I were at Ben's surprise birthday party at a brewery on the ground floor of the Empire State Building. Eventually, we got sick of paying $7 / pint, and decided to go back to Brooklyn. Our destination was a bar called "Alligator Lounge," serving $5 drafts and a free pizza with every drink (no, really). We set up a race: Daya and Chris took the subway, I rode my bike.

I took 5th Ave down to Union Square Park, and got onto Broadway. I kept flying south until I hit Grand St, realized I went too far, and backtracked to Kenmare. I took the Williamsburg Bridge, landed in ... Williamsburg, and then started looking for the bar. People on the streets tried to give helpful directions, but each pointed me in the wrong direction. Finally, when the alligator lounge was in sight, I started pedaling from a read light, and then ...

My chain fell off.

This is rare, but not unheard of. I have my bike rigged with only 1 chainring up front, and no front deraileur. Thus, as the rear deraileur shifts from side to side, there is a slight chance (say, once in 200 miles) that my chain will fall off.

But not this time.

As I started to put my chain back on, I noticed that my chainring had inexplicably bent itself beyond repair. My bike could be pushed, but not ridden, and I was still miles from home. Knowing that I had lost the race, but that I should have won, I pushed my bike the last few blocks. Daya and Chris were there, smug with their victory. This was the first time I had lost a Subway-versus-bicycle race, and I was not happy.

But I digress; this post is about my spring bike tune-up.

I replaced my broken 48T chainring with a new 53T chainring. This has upped my ratio significantly, but still in my comfort zone. I also replaced the chain, and put on a new 8-speed 11-28 cassette (same as before). I put on new brake shoes, bought new cycling shoes and installed new cleats.

But that's the less interesting part of the tune-up. I also did some work on my headset, and I repainted. Each of those is a big enough task to warrant their own posts. So, those posts come next over the next few hours. Stay tuned.

Shout-out to Dennis Ferron

Dennis recently linked to me from his blog, and I wanted to say thanks, and to point out a particularly cool post. Ferron's Guaranteed No Mess No Mixups Method for Swapping Rims without Relacing is something that I wished I had happened upon years ago.

The problem: you have a new rim, and you want to build a wheel. This task is typically a pain, though some people enjoy doing it.

The special circumstance: you already have an old wheel built.

The critical observation: in addition to re-using the spokes and hub from the old wheel, you can preserve the information stored in the old wheel's lacing.

The method: put the two wheels side by side. Transfer one spoke at a time from the old wheel to the new (in careful order), and you save your self a lot of hassel.

Well done Dennis.

On a congestion tax for cars entering lower Manhattan

NYC is currently considering congestion pricing for automobiles entering "lower" Manhattan, by which they mean Manhattan below 60th St. This tax would not apply to bicycles, pedestrians, or public transportation. As you may have guessed, I am totally in favor of this; it's a plain and simple example of polluter-pays.

The benefits of this plan include:

1. Taxation is applied directly to those who choose to pollute. It is not based upon income level.
2. It will act as a deterrent, discouraging people from driving when they don't need to. As a result, emissions will be reduced.
3. As a corollary to [2], it will encourage public transportation ridership. With a higher percent of the population on public transportation, there will be a greater push for improved services.
   
4. It will make the streets of Manhattan safer, since there will be fewer cars to run over pedestrians and cyclists.

Opponents of the plan claim:

1. That this is a regressive tax, since it taxes those who can't afford to live in lower Manhattan. This is false. Of the people who don't live in lower Manhattan, but who wish to enter, the lower-to-middle class are more likely to take public transportation, walk or bike, while the middle-to-upper class are more likely to drive or take a taxi, car-service or limo. Furthermore, many of the lower-to-middle class who live outside of lower Manhattan also work outside of lower Manhattan.
   
2. Councilman Lew Fidler claims that this tax will "segregate communities," (Park Slope Courier, 8 Feb 2008). This is sort of false, since the communities are already divided. I live in Brooklyn, and I don't think of lower Manhattan as my neighborhood. Hell, walk 10 blocks in any direction, and I don't think of it as my neighborhood.
   
3. That these commuters need to drive to work. This is false. We have extensive, 24-hour public transportation in this city, tons of bike lanes and paths, and unlike some places I have lived, every street has a sidewalk.
   

I would also note that Lew Fidler's alternative plan calls for hydrogen fueling stations (Park Slop Courier, 8 Feb 2008). The keen-eyed reader will note that this simply displaces pollution to the point of hydrogen isolation, and is in effect moving the pollution to places with lower property values. I think that's regressive.

On a similar note, London is doing right. A recent report says that London's congestion tax will be expanded, charging roughly $50 for gas guzzlers, and $0 for low-emission vehicles. This is on top of their plan for a billion dollar bike path.

Why I think bamboo bikes fix the wrong problem

I've been seeing a lot of posts all over the interweb about wooden and bamboo bikes. Hey, that seems clever! Solves the world's problems! Right? I'm not so sure.

So, I agree it would be a great world if everyone who wanted a bike had one. And, I agree that bikes are better for developing nations (and all nations) than cars, since they provide mobility and portability with few/no recurring costs. They even have nice side effects, like physical fitness and zero pollution.

What I don't buy is whether a bamboo bike is any more accessible to the developing world than a steel bike. Here is why I think that.

My criticisms could apply to any bamboo bike, but for argument sake I'll pick one. Let's pick on Bamboo Bike Project, a joint venture between the Earth Institute at Columbia University and Calfee Design.

First of all, let me thank them for trying to do good in a world where so many don't do squat. My criticism is to encourage you to seek a more realistic design, not to discourage you.

My first observation is that the bike is not made entirely out of bamboo. All of the components are normal components (and note that componentry is generally more than 50% of the cost of a complete bike). Suspend your disbelief and assume we can get all of the sundry components to put a bike together; let's focus on the frame itself.

On the bamboo frame, the following pieces cannot be made out of bamboo:

1. The head tube, since it must support the bearings in the headset,
2. the bottom bracket shell, since it must support the bearings in the bottom bracket, and
   
3. the dropouts, since they must support the wheel.
   

The photo gallery confirms all of these constraints. One could presumably make these pieces from scap, if one had a machine shop. But machine tools are expensive (a cheap milling machine costs $525, a cheap bike costs $50), so let's assume that we don't have one.

The only other solution is to scavenge them from metal bike frames, and then bonded to the bamboo frame. So where do those parts come from? In this case, those parts must be taken off of broken bike frames. In this case, we do accomplish reuse of a small fraction of trash frames.

However, I think we could accomplish more by attempting to repair those bike frames. The cheapest, most common bike frames are made of steel, and improvised welders are not too difficult. Also, Sheldon Brown gives instructions to repairing bent frames via cold setting.

What could be done to improve this design? I have no concrete points here, only general guidelines:

1. Consider the context in which these will be built. Does it ever make sense to saw off 99% of a bike frame and replace it with bamboo?
2. Focus on the consummables. Assume that bike frames are pretty easy, and instead figure out a cheap hack to replace burst tubes or tires, rusty chains, broken cables and worn brake shoes. In other words, follow the 80-20 rule for bike repair.
3. Make the bike more useful. I see that they added a large rack on the rear for carrying cargo or additional passengers. That's golden! Pursue this further, design bike trailers, or figure out how to use a stationary bike as a motor to drive tools, feed generators, or purify water.
   

Meet me at Manhattan Critical Mass

25 Jan, 7pm, Union Square North

Freegan Events Calendar

Here's a calendar of upcoming Freegan events in NYC.















Highlights include:

• Trash (read dumpster diving) tour, 21 Jan, 9:30pm on 38th st & 3rd ave
• As well as weekly bike co-op hours on Wednesdays 6pm-, and Saturdays, 2pm-
  

Easy handlebar camera mount

This is fun. It's made out of two (2x) 5/16 bolts with washers, (1x) 1/4-20 bolt for the camera mount, and (a length of) 1/4" aluminum key stock. All of these parts were found on the streets of Brooklyn.

I use this to take time lapse videos of bike rides, such as:

• Prospect Heights to Roosevelt Island [google video] and the route [mapmyride],
• Prospect Heights to Union Square [google video] and the route [mapmyride],
• Stuyvesant Square to Prospect Heights [google video] and the route [mapmyride], and
• Prospect Heights to Freegan Bike Co-op in Bed-Stuy [google video] and the route [mapmyride].

Wind-proof toes

After you've patched those innertubes one time too many, you realize that you already have enough old innertubes repurposed as bungee chords. You need another way to reuse them.

At the same time, realize that winters in New York are really, really cold (I'm a Virginia native) and really windy. Although you can usually put ten layers on your hands, chest, arms, fact, whatever, it's pretty difficult to layer things onto your feet.

Enter the Wind-proof toes. Take one old innertube, and cut in in half, discarding the valve. Use one half for each shoe. The toe portion is about two 6-in lenghts of innertube, slit lengthwise.

Sew it together with normal needle and thread, or use a leather needle if you have one handy.