Dave Moulton

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Riding a bike: Science or Natural Instinct?  

I recently came across this article about scientist Matthew Cook working on a project to design a computer that could steer a bicycle.

I quote from the piece:

The problem is more difficult than you might think, we may be able to ride bicycles, but, as Cook notes, “We do not have great insight into how we ride a bicycle.”

Really! I will tell you. We do it instinctively, (With a little practice.)

The same instinct we use to walk and run.  When man stumbled upon the bicycle, he built a mechanical device that is a simple extension of the human body.

Scientists find it hard to accept “Instinct” as a reason, because they can’t prove it, either by demonstration or mathematically. How many times have I watched nature programs on TV and heard the quote, “Scientists do not know how the salmon or the turtle swims thousands of miles through the ocean to find its way back to its place of birth.”

Or how birds migrate huge distances with the change of seasons. How do they know it is time, and how do they find their way?” The answer of course is instinct. Some inbuilt intelligence passed on from generation to generation, throughout evolution.

I said earlier that man “Stumbled” upon the bicycle. He did just that, there was no single inventor.

The fore runner of the bicycle was the Hobby Horse, generally attributed to a German, but the French and English were building similar two-wheeled devices about the same time.

Even the Hobby Horse was not an original invention. For thousands of year’s children’s toys, models of animals, were made with wheels for feet.

Before the automobile the main form of transportation was the horse. It was natural children would play with pretend horses. The name “Hobby Horse,” is a clue. It was an adult size toy horse.

Later when cranks were attached to the front wheel, it became a bicycle. We no longer had a toy, but now a bona-fide form of transport, whereby people could travel under their own power. Moving greater distances, and with less effort than walking or running.

To explain my thinking that humankind rides a bike and balances instinctively, let me pose this question.

How does a running man change direction? He leans to the left or right.

Not only man, but every other animal on earth.

Try this simple experiment. Stand in one spot and lean to the left. When you reach the point when you are about to fall, you will instinctively step to the left, thus bringing your feet back directly under your body to bring it upright once more. This is how all animals turn while running at speed.  They lean to the left or right, causing them to step to the left of right.

Also Newton’s Law of Physics states an object moving in a straight line will continue to do so until forces from a different direction cause it the change direction. If a running man were to try to turn by stepping left or right without leaning he would probably trip over his own feet as the law of physics would be forcing his body to continue straight. The lean, and the pull of gravity as he falls that way counters the forces causing him to continue straight.

A bicycle becomes a mechanical extension of the human body because the wheels simply replace our feet on the ground.  If we fall to the left, we instinctively steer to the left to bring the wheels directly under our body mass, just as surely as if we were walking or running and fell to the left or right, we would instinctively step in the direction we were falling.

Furthermore, we instinctively lean in the direction we wish to turn, this time with the added bonus that a bicycle will steer itself in the direction of the lean. Actually three forces come into play:

1.)    A spinning wheel or disc will turn in the direction it leans. Roll a coin on a flat surface it will roll in ever decreasing circles until it falls, as it turns in the direction it is falling.

2.)    Because the steering axis is angled forward, and the front fork is raked or offset forward, there is  a greater portion of the wheel ahead of the steering axis. The wheel’s own weight will cause it to turn in the direction it leans.

3.)    On a racing bicycle, a handlebar stem or extension is used, placing the bars ahead of the steering axis. The weight of the handlebars will cause the front wheel to turn in the direction the bike leans. It will even do this if you lean a bike while stationary.

Riding a bicycle slowly is a simple balancing act as we constantly steer to the left and right to stay upright. No different in principal, than balancing a broom on the palm of our hand. The fact that we are slightly higher above the ground than we would be on our feet, works to our advantage. It is actually easier to balance a long handle broom with a heavy head, than a short handle lightweight broom.

As we gather speed and momentum, it becomes easier to balance and ride a straight line, as laws of physical motion take over. And when we wish to turn, we instinctively lean in that direction without thought, and with the same ease we would do so if we were running.

Finally, I leave you with these observations, and to me further proof that a cyclist leaning into a corner is an instinctive move. The cyclist will lean into a corner but keep his head vertical to the road surface. (See top picture.) Probably a vision thing to keep the eyes focused, and done instinctively. See also the picture of the Cheetah. The head is vertical, and the eyes horizontal, focused. 

Also the cyclist’s inside knee pointed out. Is this too instinctive as if the rider was stepping in that direction? Motorcyclsts do it to the point their knee almost touches the ground. And yet it would seem unnatural not to do it.


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In Search of Diamonds

In 1969 in my native England, I had just moved from a large industrial city to the relative peace and tranquility of rural Worcestershire. The move was prompted by a desire to improve the quality of life for my family that included my wife and two small children. This unspoiled West Country area was mainly agricultural and there was very little industry, but I found work with a farmer maintaining and repairing his farm equipment.

Part of the farm included an old abandoned WWII Airfield. The runways were still in place although grass and weeds now grew in the cracks between the concrete. Also in place were the many buildings used during the war. Built with brick with corrugated asbestos roofs, these buildings once served as workshops, offices, and living quarters. One of the buildings was now my repair shop, while others served as parking garages for the tractors and other farm equipment. Some were used for storage but many were empty and lay derelict.

When I first arrived I explored throughout a labyrinth of empty rooms and passageways. Wild blackberry bushes grew around the outside in some cases as high as the buildings. Shutting out light, branches reached in through broken glass in rusting cast-iron window frames, giving this place an eerie atmosphere. I wandered into one room and a startled rat, which in turn startled me as it ran across the floor and leapt through an open window. It was hard to imagine this place as it once was, a hotbed of activity during the war some twenty-five or more years before.

One warm and sunny spring morning I was outside when something caught my eye. Sunlight reflected on something and it sparkled brightly in the brickwork that formed the corner of an empty building. The walls of the buildings were only a single brick wide and a thin layer of cement had been applied to the outside to keep out moisture. With the years of neglect and weathering most of this cement had fallen from the walls. The object reflecting light was lodged in a crack between a remaining piece of cement and the brickwork.

I was intrigued enough to investigate further but a blackberry bush prevented me from getting any closer than eight feet away. I found a heavy wooden plank and laid it across the brambles. Stepping carefully, bouncing on the plank to crush the thorny branches, I reached the corner and looked directly into the crack in the wall.

I could not believe what I was seeing. I closed my eyes tight then opened them wide again. I peered inside the crack with one eye, closing the other against the bright sunlight. My eye was only inches away and I could see the object was a diamond ring. Gold with three large diamonds in a beautiful ornate setting. I reached to retrieve it but stopped immediately as I sized up the situation. At the slightest touch this heavy piece of cement would fall and the ring would be lost in the brambles.

I walked back along the wooden plank and removed it from the bush. I ran inside the building and hitched a tractor to a heavy-duty brush mower. This piece of equipment would clear this blackberry bush in very short order. It was really a two-man job to attach this mower but my adrenaline pumping provided the strength needed.

As I struggled to attach first the drive shaft then the hydraulic lifting arms, I wondered how the ring had got there. Had it been there since the war? Maybe a thief hid it, hoping to retrieve it later. Someone on a bombing mission, not sure if they would return would not want a stolen ring to be found in their personal effects later. Or maybe a woman whose fiancé had been killed came here after the war and left the ring there in some personal ritual of closure.

I suddenly realized the mower was attached and I was standing daydreaming. I leapt into the tractor seat, started the engine and roared out from the building. I swung around the corner and put the tractor in reverse. I lowered the mower, engaged the drive and backed slowly to the wall.

The mower cut a swath through the bush about five feet wide at one pass. I was careful not to hit the wall for fear of dislodging the piece of cement. I pulled forward, then drove the tractor back inside and ran to get hand tools to finish the job. I found a pair of pruning shears, some heavy leather gloves and a rake. I finished clearing the area around the corner of the building, removed the gloves and prepared to retrieve the ring.

My heart was pounding so fast I had to stop and take some deep breaths. Placing my left hand to catch the ring as it fell, I reached up with my right hand to remove the piece of cement. I barely touched it and the ring disappeared in a flash. It was nothing more than a drop of rainwater suspended between the brick and cement.

I stood there feeling very foolish, nature had played a trick on me and I had fallen for it. There was no mistaking, I did see a fine gold and diamond ring. I saw thee large diamonds in a beautiful setting but it was nothing more than a trick of sunlight on a drop of water.

Over the years since this incident I have come to realize a valuable lesson here. So often in my life I pursued something I perceived to be of great value. Some material thing, or maybe a career or relationship. After a great deal of effort on my part in pursuing these goals, I found they too were illusions. Lke sunlight on a drop of rainwater.


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The New Normal

Italian cyclist Giuseppe Martano. 1934 TDF

Life is a constant change, new ideas, and new technology. People hate change, they fight against it, but it is futile. Change will come for better or worse. In time we accept change, (Often we have no choice.) and a new “Normal” is established.

In the mid-1970s I wrote a series of articles on frame design for the British “Cycling” magazine. There was no Internet back then, no email, and no comments section where you could debate any ideas put forward. However, one older gentleman took the trouble to write and mail me a long hand-written letter, explaining my theories on “Trail” were wrong, and he enclosed a photocopy of an article from ‘Cycling’ dated 1946 to prove it.

Back in the 1930s, 1940s, and even into the 1950s, there was a thinking that trail was a bad thing.

It was thought that it made the steering of the bike sluggish.

Front forks had a rake (Offset.) of 3 to 3.5 inches. (76mm. to 90mm.) See the photo at the top, from the 1934 Tour de F rance, and the drawing, left.

I can even see where this idea gained traction.

At first glance it seems logical that the steering axis should reach the ground at the exact point the wheel makes contact and therefore turns at that point. Or it would make sense if a cyclist steered his bike by turning the handlebars, and the frame remained upright.

However, we steer a bicycle by leaning in the direction we wish to turn, and the steering axis ahead of the wheel’s point of contact, is one of the forces causing the wheel to turn in the direction of the lean. (See drawing below right.)

As far back as the late 1950s, early 1960s, I had realized that trail was a good thing, as had almost every other framebuilder. It provides a caster action, and gives the bike stability when going straight, and certain ‘self-steering’ characteristics into the corners.

Trail is the distance the wheel "Trails" behind the steering axis

However, trail goes hand in hand with the head angle. Steeper angles are more sensitive, and need less trail to achieve the same self-steering qualities. As many framebuilders in the 1970s were building frames with 75 and even 76 degree head angles, their trail would have been a lot less than mine.

Also, as my seat angles were steeper the rider’s weight was more forward, which also affected the ‘feel’ of the steering. The point I am making, you cannot simply say fork rake should be this much, and trail should be this, without taking into account the whole frame’s geometry.

My last article, where I explained the thinking behind my design philosophy, and the comments that followed, reminded me of the old gentleman that took the time to write me in the mid-1970s. He was quoting from an article written 30 years earlier in the mid-1940s.

It made me realize there were more changes made in the 30 years that were the 60s, 70s, and 80s. than there were in the previous 60 or more years. Changes in actual frame geometry that is. Angles, tube lengths, and fork offset, etc. Closer wheel clearances, shorter wheelbases, and higher bottom brackets too.

Some changes brought about by economic factors, others by framebuilders trying the make something better. It once again made me realize how fortunate I was to have been around in that period. Those times will never happen again. There was so much experimentation going on amongst so many individual craftsmen. There will never be that many individual craftsmen at the same time again. 

We have also seen many changes in the last 30 or more years since the 1980s. The whole appearance of the bicycle has changed. We’ve seen clipless pedals, index shifting, leading to 11 gears. Thread-less headsets. Oversize tubes and carbon fiber have changed to look of the frame, along with sloping top tubes and tee-shirt sizing.

But actual frame geometry has not changed that much, 73/73 angles came out in the 1960s. My road bike fork rake was 35mm. I don’t think other steel framebuilders were too far away from that. Probably around 38mm. was an average. It seems to me fork rakes increased when carbon forks became the norm. But you will have to ask others in the know to confirm that.   


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My Design Philosophy Explained

I look at frame specs of all the major bicycle manufactures today, and they all follow each other within certain parameters. Of course the UCI (The governing body of the sport of cycle racing.) lays out certain rules and regulations pertaining to the design of a racing bicycle. However, within these UCI rules there is a pretty wide scope for any individual to do something a little different.

Most take the safe approach and follow what their competitors are doing. It has always been that way, framebuilders do whatever is easiest for them, and bike riders make do with whatever is available. When I got into cycling in the early 1950s, the standard frame of the day was 73 head and 71 seat angle.

Sitting back that far was totally unsuited to my short stature of 5’ 6” (167 cm.) I got into framebuilding trying to build a better frame for myself. I found as soon as I made an effort, I would slide forward onto the tip of the saddle. This was not only extremely uncomfortable, it had the effect of my saddle being too low. The answer seemed simple to me. Make the top tube shorter, and the seat angle steeper, thus moving the saddle forward to where my backside wanted it to be.

Why were seat angles so shallow in the 1950s and before that? It was a throwback to the “Ordinary,” the high-wheeler that was the forerunner of the chain driven bicycle. In 1950 the chain driven bike was only 65 years old. There were still people around that had actually ridden the old high-wheeler.

By the 1960s the parallel angle frame came into vogue. By making the seat and head tube the same angle, the same size top tube could be used over several sizes, tubes could be pre-mitered, and simple frame assembly jigs could be used, thus speeding up production.

First came the 72/72 degree frame, followed a short time later by 73/73 degree angles. The reason being, people were not ready to jump from a 71 seat angle to a 73. 72 parallel was a good compromise. When people found that worked, it was an easier sell to the 73 degree parallel. 73 degrees was a better head angle anyway. That had been established as far back as the 1930s, and is still the standard today, for a road frame.

In the 1970s most Italian builders, and many English builders switched to 73 degree seat with a 75 degree head angle. No one was going back to a 71 seat angle, but having that 2 degree difference in the angle, and with the two tubes getting further away from each other as the frame got taller, was an advantage for the framebuilder. The top tube automatically became longer for the larger frames.

The selling point was, ‘Steeper head angle makes a livelier handling bike.’ It did indeed. Lively to the point of being dangerous for an inexperienced rider. I did not follow this trend, but instead made the top tube shorter. For example a 54 cm. frame (C to T) had a 54 cm. (C to C.) top tube.

A 55 cm. frame had a 54.5 cm. top tube, and a 56 cm. frame had a 55 cm. top tube, and so on. As the seat tube increased by one centimeter, the top tube only increased by half a centimeter.

This simple formula meant that by increasing the handlebar stem length to compensate for the decreasing top tube. It meant the front part of the handlebars was always in the same position directly above the front hub and the point where the tire contacts the road.  This was the case throughout the range of sizes. (See top of page drawing.)

When sprinting out of the saddle, there is always a certain amount of “Throwing” the bike from side to side. If the rider’s weight is directly above the tire’s point if contact, the wheel will remain straight. If the rider’s weight is ahead or behind this point of contact, any sideways movement could translate into the front wheel steering this way and that. I found with this set up, the 73 degree head angle can feel just as lively in a sprint, as the steeper angle, but without the “Squirrely” feel of the steeper bike.

Except for my very smallest size frames, 51 cm. and below. Which had a 72 degree head angle, and 38 mm. fork rake, all other sizes had a 73 degree head angle with 35mm. fork rake. This ensured the same handling characteristics for all sizes.

Above: A small 19" (49 cm.) frame, built in England in 1977. the differance in seat and head tube angles can clearly be seen. However, for a rider of small stature the riding position is more balanced than it would be if the frame were built with a shallower seat angle and a longer top tube.  

The seat angle varied from 76 degrees for the smallest frames, gradually decreasing, 75, 74, to 73 degrees for the largest sizes. This was often a hard sell to a market that had always heard 73 degree seat angles.  

What I had, (And still have today.) is a “Niche” following. I gradually built a network of bike dealers, who once they, or their employees had ridden my bikes, they were sold. It was then an easy sale to their customers, because they truly believed in the product. The proof can also be seen in the number of “Original” owners on my Registry website.

Will my ideas ever become “Mainstream.” I very much doubt it. Frames today either pop out of a mold, or they are welded steel or aluminum. There are no restrictions what-so-ever on angles or tube lengths, but most stick to the tried and safe 73/73. Any slight variation on this I feel is not done to improve handling or ride qualities, but rather to keep a balanced look throughout the range of sizes.  

Large corporations have to sell a lot of product to survive, and you can’t sell a lot of product in a “Niche” market.


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Measuring Frames

Growing up in England, and taking up the sport of cycling there, later building frames, there was only one way  to measure a bike frame and that was from the center of the bottom bracket to the top of the seat lug. It never occurred to me there was another way.

Italians measure frames from the center of the bottom bracket to the center of the top tube. However, I had very little exposure to Italian frames, there were few in the UK, I had no reason to measure one.

When I came to the US I continued measuring center to top as I had always done. One change I did make when I resumed building my own frames, I did switch from inches to centimeters. In England I had always built frames in half an inch increments. For example, 21”, 21.5”, 22” 22.5” etc.

I noticed Americans always spoke of frame sizes in Centimeters, so I switched. I always thought it strange that in a country so entrenched in Imperial measurement in every other walk of life, people would readily accept the metric system with regard to bicycles.

I continued to build frames and still no one ever questioned my method measuring, I was well into the 1980s and I gradually discovered I was in the minority, and almost everyone measured center to center. But now it was too late to change. I had hundreds of frames out there, it would have been chaotic to switch. I had no alternative but continue as I had always done.

If there is one instance in my life where I could go back and do things differently, I would have measured center to center when I started building frames again in California. It would have been no big deal. But no one told me, I didn’t know.

Working for Masi I never had to measure a frame. They had a series of “Jig Frames.” Frames built by Faliero Masi himself when he first opened his shop in California. One in every size. I would simply choose one in the size needed and use it the set the frame jig. This ensured that every Masi frame was built exactly to Masi’s design.

Also at the back of my mind I seem to remember the Masi frames were measured center to top anyway. Faliero Masi was always a bit of a rebel amongst Italian framebuilders, he used Reynolds 531 tubing for example.

Measuring center to top is not the wrong way, it is simply a different way. Where it become an issue is when frames are bought and sold. A seller lists it measured center to top, and the buyer assumes it is center to center, or vice versa. The buyer ends up with a frame the wrong size.

All frames I built were measured center to top and stamped that way under the bottom bracket. If you are buying one of my frames, and the seller doesn’t clearly state what size is stamped on the frame, ask. The center to center measurement is simply 2 cm. less than what is stamped. For example, a frame stamped 56 cm. will measure 54 center to center.  


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