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Sunday
Mar042007

Attention Grabber

Checking out my favorite Bike Blogs this morning I noticed Fritz over at Cyclicious had some early pictures from the NAHBS, including this attention grabber. It is Craig Calfee's personal bike.

I was immediately reminded of the famous “Birdcage” Maserati sports car from the early 1960s. The car’s chassis being made up of hundreds of small diameter aluminum tubes.

It was rumored that one of the design tools used was a small bird placed inside the chassis. Wherever the bird managed to escape, they welded in another tube.

I understand this frame is a continuing work in progress, and I wondered if Craig had considered this design concept; maybe substituting a small mouse in place of a bird.

The frame could then be dubbed the “Mousecage Calfee.”

Friday
Mar022007

Against the Wind

"You know it’s windy outside when you look out of your window and birds are walking."

The weather was a stormy here in Charleston, SC last night, with the wind waking me up several times.

I was reminded of such a night in England back in the mid 1970s; I commuted on my bike, 29 miles each way to my frameshop just outside of Worcester. It was nine-thirty at night, raining heavily and with gale force winds blowing. The bad news was that the wind would be directly in my face on the ride home.

I was extremely tired after a very long day and while changing into my cycling clothes, I contemplated the ride ahead of me. Seated on a chair, I bent over to tie my shoes, and fell asleep. I woke suddenly when I almost fell over. I got my bike, staggered outside and locked up the shop. Succumbing to the realization that I had no choice but to ride home; I would make the best of it.

A mile into the ride I was not only wide-awake, but was riding into the wind as if it wasn’t there. I had somehow found super-human strength and was on one of those epic rides that happen just a few times in a life. Finding occasional respite in some sheltered areas, but mostly on roads across open farm land, I battled against the wind.

Meeting every strengthening gust with matching effort, uttering curses at the wind as if it were some demonic monster; never submitting or allowing it to beat me. Finally arriving home, wanting more, and only slightly slower than my normal time.

Years later, living in Southern California, it was a mid afternoon and I had to go on a long business trip by car. I was very tired and knew that I would be asleep at the wheel in a very few miles.

I remembered my epic ride home that stormy night back in the 1970s and how exercise woke me up. I got my bike out and rode about three or four miles as hard as I could. I turned around and didn’t ease up until I arrived back home again.

I showered, changed and took off on my trip. Once again, the physical effort had done the trick. Got my adrenaline going and woke me up.

Do you have a story of an epic ride against the wind?

Tuesday
Feb272007

Abandon or Repair?

Here is a quote from an email I received after my recent post about a severely damaged Masi frame sold on eBay.

“I am certain other readers of your blog would be interested in you expounding a little more on where you consider the break to occur between abandon and repair, and the salient factors you would consider.”

Probably the best way for me to answer this question is to explain what is involved in repairing a lugged steel frame, and how I would approach it.

The easiest tubes to replace are the top and down tubes. I would cut the damaged tube with a hacksaw a few inches from the lug. Heat the lug uniformly, and to do this I would often use two oxy-acetylene torches, one in each hand on either side of the lug.

With one torch heating first one side then the other, one side will cool as you move to the opposite side. If you don’t have the luxury of two torches, then a simple hearth made out of fire bricks, to hold the heat, is called for.

[Left: Brazing Hearth. Picture from Mercian Cycles.]

If you don’t heat the joint uniformly you risk breaking the lug. With everything at uniform heat, (Orange red for brass, dark red for silver.) you can simply grab the short piece of tube with pliers, twist, and it will slide right out.

Some framebuilders pin the lugs to ensure they don’t move during brazing, so you need to look to see if there is a pin sticking through inside the tube. If there is, reach in and grab it with a pair of needle nose pliers, heat the spot on the outside where the pin is, and pull the pin through inside to remove. Then you can go ahead and remove the piece of damaged tube.

After the frame has cooled, the inside of the lug can be cleaned up using a carbide burr in a hand held grinder. With a tube removed the frame is very flexible and will easily spring apart to allow the replacement tube to be inserted.

The most difficult tube to replace is the seat tube. It is a simple matter to hacksaw the damaged tube out and remove the lower piece from the bottom bracket. However, removing the piece of tube from the seat lug is a completely different story.


To heat this area uniformly you are going to melt the joint where the seatstays are attached to the seat lug, and in all probability, the seat lug will move or come off the top tube.

Some repair shops have a set up where they can machine out the piece of seat tube using a reamer or correct size milling cutter. This way no heat is used in the removal of the old tube, but you still need to exercise caution in re-brazing the joint. Care is needed so you don’t melt other parts of the joint.

The way I approached this repair, was to replace the seat tube complete with a new seat lug. This way I could cut out the damaged tube, and hacksaw the seat lug on either side of each seatstay.

Next I would heat and detach the rear brake bridge on one side only, and spread the seatstays apart by inserting a six inch piece of wood between them. Then the cut pieces of seat lug still attached to the top of each seat stay could be removed by heating from the inside without melting the entire seat stay cap.

The final piece of seat lug had to be removed from the top tube by heating uniformly and then pulling it off with pliers. After cooling and clean-up, it is a relatively easy matter to put the new seat tube in place, along with the new seat lug, and re-braze everything in the normal way.

It is rare to have to replace a chainstay or a seatstay, but these would be cut out with a hacksaw and the remaining pieces removed by heat. It is often easier to replace a both seat stays, even if only one is damaged, rather than try to match one new one to an existing seatstay.

Slightly bent seatstays can be safely straightened, (Providing they are not kinked.) as can front fork blades. These are much thicker that the main frame tubes.

I would only repair my own frames, and did this as a service rather than as a money making proposition; most other framebuilders are the same. A big consideration is not so much, can a frame be repaired, but can you find a reputable framebuilder to do the work, and what will be the cost?

I fail to see where buying a damaged frame on eBay or anywhere else is a worthwhile proposition. With used steel frames still plentiful and at reasonable prices, in most cases the only reason to repair a frame would be one of extreme sentimental value.

The frame pictured at the top is my own Fuso frame damaged in my accident last December. The frame cost me $260, and if I can find another for close to that price it would clearly be less than the cost of a repair and re-paint. On the other hand, it may be difficult to find another in this size (52 cm.) so I may have to consider having it repaired.

Saturday
Feb242007

Bike Blog Block

Sitting at the keyboard
Staring at the screen,
A case of bike blog writer’s block
The worst I’ve ever seen.

The bicycle so simple
You push one pedal down,
The other one comes up again
And the wheels go round and round.

Have I reached the limit?
Is there any more to say?
Will it all come back again
If I wait another day?

I go on to Bike Forums
To try to find ideas
But they’re asking “If I shave my legs,
Will my wife think I’m queer?”

I struggle to find answers
To questions quite inane,
Like, "Do you still commute to work
If it looks like rain."

And on the vintage forum
Someone’s asking for advice,
On dating a Bottechia
I say, “Why not if she’s nice.”

I wonder if I write a blog
A post nobody finds,
Then did I really write it?
Is it only in my mind?

I know by now you’re asking
Has he really lost his marbles?
The longer I go on with this
The message becomes garbled.

Writing about nothing
And even make it rhyme,
Is really not that difficult
All it takes is time.

But to write exclusively about
A subject like a bike,
And try to keep it interesting
The stuff that people like.

Is really not that easy
And like my Momma said,
There will always be days like these
When there’s nothing in my head.

If by chance you are still reading
Maybe I’ve entertained,
I’ve made something out of nothing
And my posting’s not in vain.


Please check back again, after this it can only get better.




Wednesday
Feb212007

Bottom Bracket Height

Let me explain the difference between bottom bracket drop, and bottom bracket height. Bottom bracket drop is the measurement from the bicycle’s wheel center, to the center of the bottom bracket. Once a frame is built this measurement is fixed and never varies, therefore it is the most accurate.

However, bottom bracket height is easier to visualize and so is widely used. It is the measurement from the center of the bottom bracket to any level surface that the bicycle is sitting. This measurement can change because fatter tires will raise the bottom bracket height.

On the spec sheet for my Fuso frames, [PDF file.] I listed both bottom bracket height 10 5/8 inches, and 2 ¾ drop. If you add the two measurements together it is 13 3/8 inches, the radius of an average size wheel. (26 ¾ inch dia.)

The argument usually put forward for a low bottom bracket is that it lowers the center of gravity and therefore improves stability. I do not subscribe to this theory because center of gravity is not really an issue on a bicycle, and raising or lowering it has little effect on stability.

On a three or four-wheel vehicle a low center of gravity is important because when cornering at speed the centrifugal forces generated can cause the vehicle to tip over. However, a two wheeled vehicle leans into a corner, and the centrifugal forces actually push the bike down onto the road, which assists traction.

You seldom hear of a bicycle or motorcycle tipping over or falling outwards on a corner; if the rider goes down it is because they leaned too far and the bike slid out from under them. Alternatively, they fell because of road conditions like water, ice or loose gravel, but once again the bike slides out from under the rider, and it is loss of traction not center of gravity that is the issue.

If C of G were an issue, a bicycle would be a lot more difficult to ride; the bicycle can weigh less than twenty pounds and the rider a hundred pounds and above. The center of mass is somewhere in the center of the rider’s body some four feet or more above the ground; proof of this is the racing tricycle. These fascinating machines, rarely seen in the US, are very unstable on corners and it takes a great deal of skill to corner at speed and not tip over.

Picture from the [UK Tricycle Association website.]

This is why I maintain raising or lowering the bottom bracket on a bicycle has little effect on its stability, the center of mass is still very high.

The advantages of a high bottom bracket are obvious on an MTB or a cyclo-cross bike going over rough terrain. Pedal clearance on a road bike when cornering is another, but with clipless pedals this is less of an issue that it was in the 1980s.

The disadvantage of a high bottom bracket is that it makes it difficult to reach the road with your foot when you come to a stop.

Raising the bottom bracket even a little, shortens the chainstays and the down tube on the frame; conversely, lowering it will lengthen them. This is because the wheel center remains constant and so do the rear dropouts. The front fork remains the same, so does the bottom head-lug of the frame.

If these points of the frame remain constant, raising or lowering the bottom bracket shortens or lengthens the lower tubes in the frame, it also raises or lowers the top tube and therefore lengthens or shortens the head tube.

If I raised the bottom bracket on a criterium frame, it was not just to achieve more ground clearance; it was to make a more rigid and responsive frame. The head tube became longer, but as this is the least stressed tube in a frame, it had little affect. On the other hand, the down tube and chainstays are the highest stressed tubes in a frame and shortening these is a definite advantage.

If I lowered the bottom bracket on a touring frame, it was to lengthen the tubes to make a more comfortable ride. It had nothing to do with stability.

With any design aspect it is best not to go to extremes, the 10 5/8 inch (27 cm.) bottom bracket height or 2 ¾ (7 cm.) drop was where I built most of my frames, and is still a good average.