In the Pedersen design, since there are two independent fixation points for the fork, the head tube does not bear flexional moment, and therefore it is half the length of a head tube for a standard bicycle. In the very early original Pedersen designs there were no head tube at all. Just a hinge to support the upper part of the fork. See for example this original Dursley-Pedersen below.
Here is again the original head tube slaughtered from the Condor donor bike. Its length is about 15 cm. I started by disassembling both upper and lower head tube bearing races. They will be reused along with the complete head tube set in my new frame.
I cut to length, nearly by half. The problem is that the top and down tube are brazed to the head tube using lugs. To utilize the lower part of the original tube I will have to cut out the lug for the down tube.
Here the cut head tube can be seen mounted in the lathe. To turn it perfectly centered I had to prepare a wooden plug to fix the counterpoint.
Here it is before...
... and here it is afterwards. It took some time to center the workpiece accurately, but it was worth the effort, as I did nicely shave out the complete lug and old brazing material. Many of you could ask why did I not use the torch to melt the old brazing joint instead of taking the trouble to turn the piece into the lathe. The reason is that I am using just a propane torch and a brazing alloy with a solidus temperature of about 600 C. The brazing alloy used by the original manufacturer was probably with a much higher Copper content and a higher melting point. When I slaughtered the donor frame I tried to melt some joints with the propane torch, without success. An oxy-acetylene torch would be needed, which I do not possess.
Notice that in the right there is still the original brazed ring at the point where the bearing race is fixed. Since I did cut the original head tube, I have lost the ring in the left, ergo the upper ring. I will have to manufacture a new ring out of the remains of the head tube to braze it in place later. I was having a rather oriental mood that day, as you can see from the original japanese tea pot and tea cup that can be seen in the picture.
Once the main tube was under control, I turned my attention to the pieces I will braze in place for the fixation point of this head tube to the frame. I started from the other half that was recycled from the original head tube. I filed the lugs out to get it clean and cut the tube open longitudinally in the back. The whole idea is that I need another tube of slightly larger diameter that will be brazed as a lug on top of the head tube. As the recycled tube for the lug is of the same diameter as the head tube, I cut the tube in the back and forced it open carefully so that it perfectly fitted the head tube. After that I have to manufacture the rear part of the assembly that will provide the fixation point.
I took the trouble of carving the badge of my bicycle brand in the jacket piece that will contain the head tube. As my very special mark I selected a three-leafed shamrock. Nothing to do with Ireland, if you ask. It is a symbol that has some tradition in my family, as my grandfather used this mark long ago for livestock branding at his farm.
It took some time to carve such a design, but it was worth the effort. In the first blog I promised that this was about "rolling scupltures". Well, not yet rolling, but sculpture it is.
To manufacture the rear part of the head tube support I formed 2 plates 2 mm thick and brazed them together. I carved one finger each side with a puzzle-like shaped for a perfect fit with the front part.
Front view...
rear view...
Perfect fitting. Notice the upper ring still missing.
Machining the upper ring.
Assembled and fluxed. This is going to be the most complicated brazing joint so far. It is very bulky and therefore, it is difficult to apply heat evenly. It consists of many pieces and with large contacting surfaces that require very accurate heat application so that the filler alloy will flow properly.
It went well after all. I would not describe it as a surgical procedure, but solid it is, without a shade of doubt. This is how it looked immediately after brazing and without any cleaning yet.
After cleaning... Note the upper ring, nicely brazed back in place again. Note the jig-saw puzzle shapes nicely fitting.
I drilled the hole for the shackle, as I was impacient to see the whole assembly. This is how it looked. I tried and filled the shamrock with brazing alloy, but the result did not impress me. The contrast between steel and Cu-Ag-Zn filler material was not very sharp. I will better cut the shamrock again out of copper sheet and braze it in place in the carved recess.
Evolution
Sunday, December 12, 2010
Sunday, November 28, 2010
Fork construction continued
The process of fabricating the fork took nearly a month of patience, miting and brazing. Once both blades were ready the lugs were brazed in place, after careful alignment of the wheel axis.
Here are both fork blades put together with the wheel. The lugs are solidly fixed to the fork and I was satisfied with the resistance of the whole assembly. Note the radial lacing of the front wheel spokes. Anyway, this is a topic for a future post.
The next point was to align the fork and prepare to braze both fork blades together. The upper part of both blades was carefully mited to fit together at a precise angle. This is was can be seen in the next picture. The wheel is assembled in place and centered. Both fork blades are hold together with clamps, cleaned and fluxed.
Neat and solid brazing joint.
This is how the bare fork construction looked like. No bracket or stem yet. I put the mudguard in place to measure the bracket position and dimensions.
For the bracket I used a steel plate with a thickness of 2mm, conveniently bent at 90 degrees, that I found at my standard source place for scrap metal. I started from the very basic specifications for the bracket: I need to hold together 4 fork tubes, to support the articulated joint that connects with the frame and to support the caliper brake and mudguard.
Once the functionality of those features is secured, I proceed with cutting bracket with a design-as-you-go approach unleashing the best of my plastic artist's creativity. In the next picture it can be seen how I carved the holder to braze the nut to fix the articulated joint. The slot for assembling the brakes and mudguard is already done.
Here is the nut in place, fluxed and ready for brazing. Note the carvings I did in the bracket. It took some time, but was a rewarding experience.
Here is the bracket aligned, fluxed and ready for brazing. Below you can see my Sievert torch with a 70 g/h nozzle and a 0,4 kg camping-type butane bottle.
The idea to fix the stem was originally just to mite the inner stem tube to match the four tubes of the upper fork blades. I was concerned that this point where the stem is brazed to both blades, would become the weakest point of the whole construction. After some discussion with my work colleage Peter, he came up with the suggestion of a bolt with cylindrical head brazed to the tip of the fork blades that fits the inner diameter of the stem. This contraption was named the "Boldten" piece, and really reinforced the whole stem assembly considerably. Thanks, Peter!
The stem was recycled from the donor bike. It was necessary to cut out the recessed part where the headset lower bearing was fixed, since the new head tube will have shorter length and different positioning. A new ring for fitting the lower headset bearing will be needed.
Careful miting of the stem inner diameter to match the four tubes of both fork blades can be seen in the next picture.
The stem was solidly brazed in place. Note the small holes in the stem. Their purpose is to access the cylindrical head of the "Boldten" piece for brazing. Now it is evident that the stem is attached to the blades fork construction in two points, increasing the rigidity of the whole structure.
Next step was to manufacture the ring that supports the lower bearing of the headset. This was done in my old trusty Unimat 3 from Austria, as shown below.
Coincidentally, the ring needed to be placed over the holes used for brazing the "Boldten" piece, and therefore, no traces of such holes were left after the ring was brazed in place.
Here are both fork blades put together with the wheel. The lugs are solidly fixed to the fork and I was satisfied with the resistance of the whole assembly. Note the radial lacing of the front wheel spokes. Anyway, this is a topic for a future post.
The next point was to align the fork and prepare to braze both fork blades together. The upper part of both blades was carefully mited to fit together at a precise angle. This is was can be seen in the next picture. The wheel is assembled in place and centered. Both fork blades are hold together with clamps, cleaned and fluxed.
Neat and solid brazing joint.
This is how the bare fork construction looked like. No bracket or stem yet. I put the mudguard in place to measure the bracket position and dimensions.
For the bracket I used a steel plate with a thickness of 2mm, conveniently bent at 90 degrees, that I found at my standard source place for scrap metal. I started from the very basic specifications for the bracket: I need to hold together 4 fork tubes, to support the articulated joint that connects with the frame and to support the caliper brake and mudguard.
Once the functionality of those features is secured, I proceed with cutting bracket with a design-as-you-go approach unleashing the best of my plastic artist's creativity. In the next picture it can be seen how I carved the holder to braze the nut to fix the articulated joint. The slot for assembling the brakes and mudguard is already done.
Here is the nut in place, fluxed and ready for brazing. Note the carvings I did in the bracket. It took some time, but was a rewarding experience.
Here is the bracket aligned, fluxed and ready for brazing. Below you can see my Sievert torch with a 70 g/h nozzle and a 0,4 kg camping-type butane bottle.
The idea to fix the stem was originally just to mite the inner stem tube to match the four tubes of the upper fork blades. I was concerned that this point where the stem is brazed to both blades, would become the weakest point of the whole construction. After some discussion with my work colleage Peter, he came up with the suggestion of a bolt with cylindrical head brazed to the tip of the fork blades that fits the inner diameter of the stem. This contraption was named the "Boldten" piece, and really reinforced the whole stem assembly considerably. Thanks, Peter!
The stem was recycled from the donor bike. It was necessary to cut out the recessed part where the headset lower bearing was fixed, since the new head tube will have shorter length and different positioning. A new ring for fitting the lower headset bearing will be needed.
Careful miting of the stem inner diameter to match the four tubes of both fork blades can be seen in the next picture.
The stem was solidly brazed in place. Note the small holes in the stem. Their purpose is to access the cylindrical head of the "Boldten" piece for brazing. Now it is evident that the stem is attached to the blades fork construction in two points, increasing the rigidity of the whole structure.
Next step was to manufacture the ring that supports the lower bearing of the headset. This was done in my old trusty Unimat 3 from Austria, as shown below.
Coincidentally, the ring needed to be placed over the holes used for brazing the "Boldten" piece, and therefore, no traces of such holes were left after the ring was brazed in place.
Sunday, November 21, 2010
Fork construction
The fork is the key element in a Pedersen design, where the paradigm of the diamond frame is really shattered. Instead of the classical fork with two blades hold together to the stem by a bracket, the Pedersen fork consists of a truss construction out of basically four triangles united at the top and reinforced with a central bracket. Instead of a stem supported by bearings in a 10 cm head tube as standard bicycles, the Pedersen fork has two separated fixation points about 35 cm apart, so that the fork is an integral part of the frame structure.
Here is a picture of the Dursley Pedersen factory workers showing the advantages and resistance of a truss construction for the fork. Impressive resistance, and yet lightweight. This picture is a really convincing example of marketing and advertising techniques of the early XXth century.
The construction of the fork and the upper head tube with the frame fixation point is rather complicated and time consuming. It took me more than half of the whole project duration, as I did all tubing miting by hand and using no power tools. Just old fashioned hand filing.
For my fork design I recycled the top stays of the donor bicycle, as you can see in the following picture. This recycled bent tubes were used for the rear fork tubing, along with straight tubing 12mm diameter with 1mm wall thickness for the front tubes. This tubing was of regular quality and I bought it in the nearest hardware store. I did not use for this bike any specialized Columbus tubing, chromoly or anything like that. In the picture below also a prototypical bracket can be seen, along with a recycled lug, the shackle and the lower fixation head.
The first step was to manufacture two fork blades, left and right, with a triangular shape, out of one straight and one bent tube. For the top joint I had to mite the tubing very carefully to an exact match before brazing. The miting can be seen here, and it took much more time than what could be guessed from the picture.
Prepared for brazing, fluxed and ready to go.
A brazing professional would probably describe this as a butcher job rather than a clean joint. However, a solid joint it certainly is.
Here is after cleaning and miting for the upper joint between the two blades. Notice that the miting revealed a very nice layer of brazing filler material at the joining surfaces in the tip. There it is, a sound brazing joint after all.
For the lower side of the triangle I deviced another type of design for joining both tubes, as the lug has to be solidly attached. I turned in the lathe a steel bolt which I brazed to the tip of the rear bent tube. In the tip of the straight tube I filed and shaped the connection to fit the lug. In the picture below, all this can be seen, with the raw brazed joint.
Finally I did mite the steel point at the tip of the bent tube, to meet the straight tube precisely at an angle and prepared the connection for the lug. I did not yet braze the whole assembly with the lug, as I need first to check proper alignment of the wheel within the complete fork.
Here is a picture of the Dursley Pedersen factory workers showing the advantages and resistance of a truss construction for the fork. Impressive resistance, and yet lightweight. This picture is a really convincing example of marketing and advertising techniques of the early XXth century.
The construction of the fork and the upper head tube with the frame fixation point is rather complicated and time consuming. It took me more than half of the whole project duration, as I did all tubing miting by hand and using no power tools. Just old fashioned hand filing.
For my fork design I recycled the top stays of the donor bicycle, as you can see in the following picture. This recycled bent tubes were used for the rear fork tubing, along with straight tubing 12mm diameter with 1mm wall thickness for the front tubes. This tubing was of regular quality and I bought it in the nearest hardware store. I did not use for this bike any specialized Columbus tubing, chromoly or anything like that. In the picture below also a prototypical bracket can be seen, along with a recycled lug, the shackle and the lower fixation head.
The first step was to manufacture two fork blades, left and right, with a triangular shape, out of one straight and one bent tube. For the top joint I had to mite the tubing very carefully to an exact match before brazing. The miting can be seen here, and it took much more time than what could be guessed from the picture.
Prepared for brazing, fluxed and ready to go.
A brazing professional would probably describe this as a butcher job rather than a clean joint. However, a solid joint it certainly is.
Here is after cleaning and miting for the upper joint between the two blades. Notice that the miting revealed a very nice layer of brazing filler material at the joining surfaces in the tip. There it is, a sound brazing joint after all.
For the lower side of the triangle I deviced another type of design for joining both tubes, as the lug has to be solidly attached. I turned in the lathe a steel bolt which I brazed to the tip of the rear bent tube. In the tip of the straight tube I filed and shaped the connection to fit the lug. In the picture below, all this can be seen, with the raw brazed joint.
Finally I did mite the steel point at the tip of the bent tube, to meet the straight tube precisely at an angle and prepared the connection for the lug. I did not yet braze the whole assembly with the lug, as I need first to check proper alignment of the wheel within the complete fork.
Sunday, November 14, 2010
Frame geometry design
In order to design the frame geometry I prepared a very simple spreadsheet, which I show below and explain briefly. Unfortunately, I cannot attach files to this blog. Anyone interested, let me know and I send the spreadsheet.
The input parameters are the following:
- wheel radius:
in my case 342mm as I am using 32 x 622 (700C x 32) wheels. Is not only about the rim radius but about the radius of the outer rolling surface of the tyre. For every other tyre type this information can be found in the following site
http://www.sheldonbrown.com/cyclecomputer-calibration.html
- angle of the chainstays with respect to the horizontal
In the donor bicycle this angle was 8 degrees, but it is possible to modify this angle, say to 6 degrees or less, thus increasing the height of the front bracket center, positioning the pedals higher with respect to the ground and allowing for more clearance of the back stays with the rear wheel
- relative position of the upper node of the frame where the top stays and the down stays are attached together to the head tube.
The selection of this point will largely define your frame geometry, and both the vertical and horizontal coordinate have to keep a certain ratio. By modifying the height of this point the size of the frame can be adjusted to match the desired inseam distance of the prospective cyclist. The vertical coordinate of this point, together with the rake angle and other fork parameters, will define your wheelbase.
- rake angle and fork offset
It is the angle between the steering axis and the horizontal. This is a key parameter of the steering geometry, together with the fork offset. Both these parameters are essential in defining the steering stability and maneuvrability of this bicycle.
Standard bicycles have a rake angle of 73 degrees, along with a curl at the end of the fork in order to position the wheel center a certain perpendicular distance from the steering axis. This distance, called fork offset, is usually about 40 to 45mm in standard bicycles. These two parameters combined, define a certain trail, which is the horizontal distance from where the steering axis intersects the ground to where the front wheel touches the ground. Except exceptional cases the front wheel ground contact point is behind the steering axis intersection with the ground, which is then called positive trail. The trail is directly linked with the steering capabilities of the bicycle. However, for a more detailed analysis of bicycle steering geometry the following article is recommended,
http://www.phys.lsu.edu/faculty/gonzalez/Teaching/Phys7221/vol59no9p51_56.pdf
In the Pedersen design the truss construction of the fork with a central bracket inherently generates a very large fork offset of more than twice as much the standard value of 45 mm. Using this large fork offset in combination with a standard rake angle of 73 degrees would result in a very small or even negative trail which would render the bicycle very unstable or even unridable. That is why for such large fork offsets of a Pedersen fork, rather shallow rake angles of about 65 degrees are needed to get a reasonable positive trail of about 40 to 50mm.
- seat tube angle position
This angle should be chosen so that it allows clearance to the rear wheel and yet get a reasonable position of the anchoring point for the hammock saddle. One important parameter for frame sizing is the inseam distance, which for my purposes I defined from the calculated seat point to the center of the pedals bracket. A feature to calculate the seat position and the inseam distance. included in the spreadsheet. I compared this distance and also the angle to the horizontal with the same parameters in my standard conventional frame bicycle, to get an idea of the ergonomics of my saddle position and size frame. For this specific frame I am constructing, my target is a M size frame with inseam distance adjustable between 640 and 740 mm.
The input parameters are the following:
- wheel radius:
in my case 342mm as I am using 32 x 622 (700C x 32) wheels. Is not only about the rim radius but about the radius of the outer rolling surface of the tyre. For every other tyre type this information can be found in the following site
http://www.sheldonbrown.com/cyclecomputer-calibration.html
- angle of the chainstays with respect to the horizontal
In the donor bicycle this angle was 8 degrees, but it is possible to modify this angle, say to 6 degrees or less, thus increasing the height of the front bracket center, positioning the pedals higher with respect to the ground and allowing for more clearance of the back stays with the rear wheel
- relative position of the upper node of the frame where the top stays and the down stays are attached together to the head tube.
The selection of this point will largely define your frame geometry, and both the vertical and horizontal coordinate have to keep a certain ratio. By modifying the height of this point the size of the frame can be adjusted to match the desired inseam distance of the prospective cyclist. The vertical coordinate of this point, together with the rake angle and other fork parameters, will define your wheelbase.
- rake angle and fork offset
It is the angle between the steering axis and the horizontal. This is a key parameter of the steering geometry, together with the fork offset. Both these parameters are essential in defining the steering stability and maneuvrability of this bicycle.
Standard bicycles have a rake angle of 73 degrees, along with a curl at the end of the fork in order to position the wheel center a certain perpendicular distance from the steering axis. This distance, called fork offset, is usually about 40 to 45mm in standard bicycles. These two parameters combined, define a certain trail, which is the horizontal distance from where the steering axis intersects the ground to where the front wheel touches the ground. Except exceptional cases the front wheel ground contact point is behind the steering axis intersection with the ground, which is then called positive trail. The trail is directly linked with the steering capabilities of the bicycle. However, for a more detailed analysis of bicycle steering geometry the following article is recommended,
http://www.phys.lsu.edu/faculty/gonzalez/Teaching/Phys7221/vol59no9p51_56.pdf
In the Pedersen design the truss construction of the fork with a central bracket inherently generates a very large fork offset of more than twice as much the standard value of 45 mm. Using this large fork offset in combination with a standard rake angle of 73 degrees would result in a very small or even negative trail which would render the bicycle very unstable or even unridable. That is why for such large fork offsets of a Pedersen fork, rather shallow rake angles of about 65 degrees are needed to get a reasonable positive trail of about 40 to 50mm.
- seat tube angle position
This angle should be chosen so that it allows clearance to the rear wheel and yet get a reasonable position of the anchoring point for the hammock saddle. One important parameter for frame sizing is the inseam distance, which for my purposes I defined from the calculated seat point to the center of the pedals bracket. A feature to calculate the seat position and the inseam distance. included in the spreadsheet. I compared this distance and also the angle to the horizontal with the same parameters in my standard conventional frame bicycle, to get an idea of the ergonomics of my saddle position and size frame. For this specific frame I am constructing, my target is a M size frame with inseam distance adjustable between 640 and 740 mm.
Sunday, November 7, 2010
Slaughtering the donor frame
The first thing before starting with the detailed design of the frame geometry was to slaughter the old frame and see which parts I can re-use, so as to design a frame around these parts.
The frame was a classical woman type with these upper bent stays from the rear dropouts to the head tube. Here it is, after disassembly.
The bent stays and the chainstays were cut, as well as the head tube and front dropouts. All these parts will be re-used. Here are the results...
I left the down tube and the seat tube uncut for the moment, as I have the idea of producing a bolted design but I am not yet sure about how to fabricate the coupling points in the existing frame. There will be a lot of time to consider this problem as I am busy with the fork construction.
I measured carefully the distance between the center of the bottom bracket and the point in the rear dropouts where the center of the wheel will be normally fixed. This distance I will take as a fixed parameter in my spreadsheet for frame geometry design.
The frame was a classical woman type with these upper bent stays from the rear dropouts to the head tube. Here it is, after disassembly.
The bent stays and the chainstays were cut, as well as the head tube and front dropouts. All these parts will be re-used. Here are the results...
I left the down tube and the seat tube uncut for the moment, as I have the idea of producing a bolted design but I am not yet sure about how to fabricate the coupling points in the existing frame. There will be a lot of time to consider this problem as I am busy with the fork construction.
I measured carefully the distance between the center of the bottom bracket and the point in the rear dropouts where the center of the wheel will be normally fixed. This distance I will take as a fixed parameter in my spreadsheet for frame geometry design.
Saturday, October 30, 2010
The master himself
After the First World War Dursley Pedersen Cycle Co. closed down. Mikael Pedersen continued his activities in engineering fields other than manufacturing bicycles and his design was soon forgotten.
In 1979 Jesper Solling, a bicycle mechanic in Christiania, near Copenhagen, rediscovered the design and started manufacturing hand-made frames. He manufactured about 6000 of these exquisitely handcrafted frames in the last 30 years, which are true pieces of art.
Here is the story and pictures of the beginnings of Jesper's manufacturing in Christiania.
http://www.pedersenbicycle.dk/more1978.htm
In the following, there is an article about an American woman flying to Copenhagen to pick-up a Pedersen bike she bought over internet, just to find out that it was not in the best condition. What else to do, other than to find the master himself, to set things straight with the frame? Yes, there is people willing to do anything to get a Pedersen. I am not the exception...
http://www.bicycling.com/news/featured-stories/strange-and-not-unpleasant-experience
And finally, here is the master in his workshop, teaching us how to braze a bicycle frame.
Jesper Solling at his workshop (youtube)
In 1979 Jesper Solling, a bicycle mechanic in Christiania, near Copenhagen, rediscovered the design and started manufacturing hand-made frames. He manufactured about 6000 of these exquisitely handcrafted frames in the last 30 years, which are true pieces of art.
Here is the story and pictures of the beginnings of Jesper's manufacturing in Christiania.
http://www.pedersenbicycle.dk/more1978.htm
In the following, there is an article about an American woman flying to Copenhagen to pick-up a Pedersen bike she bought over internet, just to find out that it was not in the best condition. What else to do, other than to find the master himself, to set things straight with the frame? Yes, there is people willing to do anything to get a Pedersen. I am not the exception...
http://www.bicycling.com/news/featured-stories/strange-and-not-unpleasant-experience
And finally, here is the master in his workshop, teaching us how to braze a bicycle frame.
Jesper Solling at his workshop (youtube)
Thursday, October 28, 2010
Donor bike
To look for a donor bike there are few criteria I had to take into account and which I describe in detail in the following.
General layout
I need a donor with a steel frame brazed with lugs, out of round steel tubing. This is essential as I want to cut the old frame and use parts and tubes. Since I will be using brazing to join the parts of my frame, sophisticated alloys of Aluminium, Magnesium and other aerospace materials so favored in modern high-end bikes are out of the question. Standard alloy steel is the way to go.
Frame geometry
The rear part of the donor bicycle's frame will be used complete as a module for my new frame. This includes the pedal bottom bracket and the chainstays. Therefore the shape of this module has to fit my needs. The shape of the rear dropouts is very important, as I would prefer a semi-horizontal rear dropout with wheel disassembly to the front. I want to avoid horizontal dropouts with rear disassembly that require adjusting bolts to tense the chain, which are common in many older bikes.
I do no have a use for long 1 inch tubes such as the top tube, seat tube and down tube, as the Pedersen design is based in thinner and longer 1/2 inch tubes. On the other hand, I need a strong head tube, but much shorter than in a standard bike. I need a frame with a head tube that can be cut to the desired length and recycled. For recycling I will have to turn the head tube in the lathe to cut out the old brazed lug. Therefore, if possible, I have to look for one that is best suited for this operation.
The front fork is the most complicated part in the Pedersen construction, consisting basically in 4 tubes assembled in a truss type of structure. The two tubes in the rear of the fork are bent at a subtle angle of about 15 deg, exactly at the point where the fork bracket is located, about mid span of the fork length. I have observed many woman bicycle frames, which in order to replace the top tube on a standard diamond frame use two long and thin tubes from the rear dropouts to the head tube with a slight bending about mid span when passing near the seat tube.
I think I could recycle such tubes to be reused in the fork, being the dimensions and the bending angle very similar to what I need.
Gears and brakes
I want the bike to be functional in the street and also on the road, for longer several days cycling tours. Thus, a minimum of gear ratios availability is to be secured. At least a range spanning from 3 to 7 meters per pedal revolution is needed, to cover from some modest climbing to flat or slight downhill cruising. Getting pedals radius of 170mm or 175mm will not be an issue.
Brakes will probably not pose a problem, as I would rather go for caliper brakes both in the front and rear and they are commonly available in old bikes. They are simple and reliable and fit for the purpose of this bike.
Accessories
The more accessories I can recycle from the donor, the less I will have to search for later on. The handlebars in a Pedersen are along with the fork and the hammock saddle the most conspicuous features. They have this very particular shape, bent in the "wrong" direction, that provide a confortable wrist position when riding. If I might find an aluminium granny-bike type handlebar, I could mount it upside down in the stem and adjust it to match a Pedersen shape.
An old fashioned leather saddle Brooks-style could be recycled for the hammock saddle, if I can find one.
Finally, if I can get a donor that comes with fenders, rack, dynamo and lights, all these extras are welcome.
Having in mind the complete set of specification as described above, I set to search for a prospective donor. This is what I found in the local dump: an old Swiss Condor woman type bicycle from the late 80s with 28 inches wheels and 6+2 Sachs Huret combined derrailleur with internal hub, caliper brakes and the bent "top tubes". General status is acceptable. The only problem being both original Weinmann 700C rims bent. The rear one is most severely bent, as seen in the picture. However, nothing that some patience cannot bring back to true.
General layout
I need a donor with a steel frame brazed with lugs, out of round steel tubing. This is essential as I want to cut the old frame and use parts and tubes. Since I will be using brazing to join the parts of my frame, sophisticated alloys of Aluminium, Magnesium and other aerospace materials so favored in modern high-end bikes are out of the question. Standard alloy steel is the way to go.
Frame geometry
The rear part of the donor bicycle's frame will be used complete as a module for my new frame. This includes the pedal bottom bracket and the chainstays. Therefore the shape of this module has to fit my needs. The shape of the rear dropouts is very important, as I would prefer a semi-horizontal rear dropout with wheel disassembly to the front. I want to avoid horizontal dropouts with rear disassembly that require adjusting bolts to tense the chain, which are common in many older bikes.
I do no have a use for long 1 inch tubes such as the top tube, seat tube and down tube, as the Pedersen design is based in thinner and longer 1/2 inch tubes. On the other hand, I need a strong head tube, but much shorter than in a standard bike. I need a frame with a head tube that can be cut to the desired length and recycled. For recycling I will have to turn the head tube in the lathe to cut out the old brazed lug. Therefore, if possible, I have to look for one that is best suited for this operation.
The front fork is the most complicated part in the Pedersen construction, consisting basically in 4 tubes assembled in a truss type of structure. The two tubes in the rear of the fork are bent at a subtle angle of about 15 deg, exactly at the point where the fork bracket is located, about mid span of the fork length. I have observed many woman bicycle frames, which in order to replace the top tube on a standard diamond frame use two long and thin tubes from the rear dropouts to the head tube with a slight bending about mid span when passing near the seat tube.
I think I could recycle such tubes to be reused in the fork, being the dimensions and the bending angle very similar to what I need.
Gears and brakes
I want the bike to be functional in the street and also on the road, for longer several days cycling tours. Thus, a minimum of gear ratios availability is to be secured. At least a range spanning from 3 to 7 meters per pedal revolution is needed, to cover from some modest climbing to flat or slight downhill cruising. Getting pedals radius of 170mm or 175mm will not be an issue.
Brakes will probably not pose a problem, as I would rather go for caliper brakes both in the front and rear and they are commonly available in old bikes. They are simple and reliable and fit for the purpose of this bike.
Accessories
The more accessories I can recycle from the donor, the less I will have to search for later on. The handlebars in a Pedersen are along with the fork and the hammock saddle the most conspicuous features. They have this very particular shape, bent in the "wrong" direction, that provide a confortable wrist position when riding. If I might find an aluminium granny-bike type handlebar, I could mount it upside down in the stem and adjust it to match a Pedersen shape.
An old fashioned leather saddle Brooks-style could be recycled for the hammock saddle, if I can find one.
Finally, if I can get a donor that comes with fenders, rack, dynamo and lights, all these extras are welcome.
Having in mind the complete set of specification as described above, I set to search for a prospective donor. This is what I found in the local dump: an old Swiss Condor woman type bicycle from the late 80s with 28 inches wheels and 6+2 Sachs Huret combined derrailleur with internal hub, caliper brakes and the bent "top tubes". General status is acceptable. The only problem being both original Weinmann 700C rims bent. The rear one is most severely bent, as seen in the picture. However, nothing that some patience cannot bring back to true.
Pedersen on a budget
As mentioned before, one of the very reasons for existence of Badenia cycles is challenging the paradigm and stereotypes of bicycle construction.
Therefore, it was for me clearly obvious that the first project of Badenia cycles was going to be a Pedersen bicycle.
What is a Pedersen bicycle anyway?
Well, there are many sites that deal in detail with Pedersen history, design, ergonomics, functionality, etc., etc., as the few examples below
http://www.pedersenbicycles.com/form.htm
http://www.dursley-pedersen.net/index.html
http://www.pedersenbicycle.dk/
In short, Mikael Pedersen was a Danish engineer and inventor who developed this bicycle concept at the turn of the XIXth century. At that point in time, the diamond frame so-called "safety frame", as opposed to the penny-farthing type of frame, which was not considered to be particularly safe, was established as a standard in bicycle construction. The whole Pedersen concept originates at challenging the paradigm of the bicycle saddle. The notion of what a bicycle saddle should look like comes probably from transposing the heritage of equestrian tradition into wheeled vehicles. Pedersen wanted for his bicycle a hammock saddle. His frame concept originates from the necessity of developing a structure around that saddle to provide the two anchor points for such a hammock.
Pedersen manfactured his bikes commercially in England from 1897 to about 1917, vanishing after that the concept into oblivion. Here is an example of an original Dursley Pedersen from 1910.
Project specifications of my recreation of the Pedersen concept
- street bike with 28" wheels
- based on a discarded "donor" bike, probably a woman frame type
- utilizing as much as possible the original components or other recycled components
- silver-brazed frame with lugs
- dismountable, bolted frame construction
- decent amount of gears to render it functional (if possible internal hub gear)
- estimated 200 hours of work (nice winter project)
Therefore, it was for me clearly obvious that the first project of Badenia cycles was going to be a Pedersen bicycle.
What is a Pedersen bicycle anyway?
Well, there are many sites that deal in detail with Pedersen history, design, ergonomics, functionality, etc., etc., as the few examples below
http://www.pedersenbicycles.com/form.htm
http://www.dursley-pedersen.net/index.html
http://www.pedersenbicycle.dk/
In short, Mikael Pedersen was a Danish engineer and inventor who developed this bicycle concept at the turn of the XIXth century. At that point in time, the diamond frame so-called "safety frame", as opposed to the penny-farthing type of frame, which was not considered to be particularly safe, was established as a standard in bicycle construction. The whole Pedersen concept originates at challenging the paradigm of the bicycle saddle. The notion of what a bicycle saddle should look like comes probably from transposing the heritage of equestrian tradition into wheeled vehicles. Pedersen wanted for his bicycle a hammock saddle. His frame concept originates from the necessity of developing a structure around that saddle to provide the two anchor points for such a hammock.
Pedersen manfactured his bikes commercially in England from 1897 to about 1917, vanishing after that the concept into oblivion. Here is an example of an original Dursley Pedersen from 1910.
Project specifications of my recreation of the Pedersen concept
- street bike with 28" wheels
- based on a discarded "donor" bike, probably a woman frame type
- utilizing as much as possible the original components or other recycled components
- silver-brazed frame with lugs
- dismountable, bolted frame construction
- decent amount of gears to render it functional (if possible internal hub gear)
- estimated 200 hours of work (nice winter project)
Wednesday, October 13, 2010
Laying the foundations of Badenia cycles
Motivation
I am an avid cycling enthusiast: commuting to work every day, some short tours or even day tours on the weekends and at least two cycle tours a year, one of them longer than a week.
Owning three bikes, I do myself all mechanical work. Every one of them has its own story, its own role in my cycling life. None of them is an expensive bike and yet I developed kind of a sentimental attachment to each one. I know them intimately after many complete overhauls over the years and after many thousands of kilometers. It would be difficult to decide parting with any one of them.
Being an engineer, and having a strong do-it-yourself approach, I usually have a couple of projects in the pipeline. Some of then reach a certain reasonable level of completion just before entering the misterious status of "on hold". Just a few are ever definitely finished. While visiting my main source of metal and material for my projects, the municipal dumping place, I noticed over the years the large amount of bicycles that are discarded. Among many cheap mass-produced mountain bikes, it is not difficult to spot once and again high quality gems manufactured in the old days, with lugs hand-brazed frames, with top edge classical components like Campagnolo, Weinmann, Shimano, Sachs, Brooks.
On the other hand, a certain fact came to attention as I was reading an article about cycling statistics in Britain. The article analyzed the number of active cyclists and compared with the number of new bicycles sold every year and the number of bicycles scrapped every year to reach the conclusion that a large amount of bicycles have a life cycle that includes being purchased, "owned" and scrapped rather than ridden.
Bicycles became, at least in Europe, USA and other developed countries, more a consumer article than a true means of transport. A standard bicycle shop in Switzerland, for instance, will have on display very expensive models, in general over-engineered for the purpose. Of course, a downhill mountain bike cyclist with serious competition goals will need specialized adjustable full suspension, titanium and magnesium alloy frames as the serious racing bike enthusiast will intend to reduce every gram of weight by using reinforced fibre carbon components and aerodynamically shaped frames and spokes. However, the fact remains that for most of the standard cyclists the bikes are over-engineered for the function that they are targeted to perform. Without exaggeration, I can say I have seen grandmas cycling to the supermarket on nice urban paved roads, basket included, on bikes with full suspension and hydraulic brakes worth 2 or 3 thousand CHF.
Many organizations exist that address the bicycle life cycle issue by recycling
http://www.bicyclerecycling.co.uk/
http://bikerecycle.org/
and it is not only about non-profit organizations; there are also some shops trading in used recycled vintage parts for restoration projects
http://www.recycledcycles.com/
http://oldroads.com/bicycles_for_sale.asp
Things did not change dramatically in the history of the bicycle since the introduction of the so-called "safety frame" in 1880s as opposed to the high wheel bicycle type or penny-farthing. The diamond frame became since then the very paradigm of bicycle construction.
I was always attracted to alternative bicycle concepts that would challenge the paradigm in a true Kuhnian sense (I cannot help it!). Recumbents, tandems, Pedersen, folding frames, rowing propulsion... Such bikes, even if you can find what you are specifically looking for, cannot be bought for reasonable money, as they are hand-made and usually carry a premium tag price for rarity, scarcity or oddity. They are out of reach for a reasonable and price-to-functionality minded engineer. A hand-made Pedersen, for instance, will offer for more than a couple thousand Euros basically the same functionality than a second-hand granny bike for 50CHF. After all, even if the Pedersen concept is charming, such a bike represents the very consumer object that I so deeply reject.
Therefore, and in order to give way to my interests on alternative non-standard bicycle concepts, my interest on workshop activities and to explore my creativity and sensitivity as a plastic artist; I am founding Badenia cycles to create rolling sculptures out of discarded and neglected materials and scrap metals at hand in the local dump.
I am an avid cycling enthusiast: commuting to work every day, some short tours or even day tours on the weekends and at least two cycle tours a year, one of them longer than a week.
Owning three bikes, I do myself all mechanical work. Every one of them has its own story, its own role in my cycling life. None of them is an expensive bike and yet I developed kind of a sentimental attachment to each one. I know them intimately after many complete overhauls over the years and after many thousands of kilometers. It would be difficult to decide parting with any one of them.
Being an engineer, and having a strong do-it-yourself approach, I usually have a couple of projects in the pipeline. Some of then reach a certain reasonable level of completion just before entering the misterious status of "on hold". Just a few are ever definitely finished. While visiting my main source of metal and material for my projects, the municipal dumping place, I noticed over the years the large amount of bicycles that are discarded. Among many cheap mass-produced mountain bikes, it is not difficult to spot once and again high quality gems manufactured in the old days, with lugs hand-brazed frames, with top edge classical components like Campagnolo, Weinmann, Shimano, Sachs, Brooks.
On the other hand, a certain fact came to attention as I was reading an article about cycling statistics in Britain. The article analyzed the number of active cyclists and compared with the number of new bicycles sold every year and the number of bicycles scrapped every year to reach the conclusion that a large amount of bicycles have a life cycle that includes being purchased, "owned" and scrapped rather than ridden.
Bicycles became, at least in Europe, USA and other developed countries, more a consumer article than a true means of transport. A standard bicycle shop in Switzerland, for instance, will have on display very expensive models, in general over-engineered for the purpose. Of course, a downhill mountain bike cyclist with serious competition goals will need specialized adjustable full suspension, titanium and magnesium alloy frames as the serious racing bike enthusiast will intend to reduce every gram of weight by using reinforced fibre carbon components and aerodynamically shaped frames and spokes. However, the fact remains that for most of the standard cyclists the bikes are over-engineered for the function that they are targeted to perform. Without exaggeration, I can say I have seen grandmas cycling to the supermarket on nice urban paved roads, basket included, on bikes with full suspension and hydraulic brakes worth 2 or 3 thousand CHF.
Many organizations exist that address the bicycle life cycle issue by recycling
http://www.bicyclerecycling.co.uk/
http://bikerecycle.org/
and it is not only about non-profit organizations; there are also some shops trading in used recycled vintage parts for restoration projects
http://www.recycledcycles.com/
http://oldroads.com/bicycles_for_sale.asp
Things did not change dramatically in the history of the bicycle since the introduction of the so-called "safety frame" in 1880s as opposed to the high wheel bicycle type or penny-farthing. The diamond frame became since then the very paradigm of bicycle construction.
I was always attracted to alternative bicycle concepts that would challenge the paradigm in a true Kuhnian sense (I cannot help it!). Recumbents, tandems, Pedersen, folding frames, rowing propulsion... Such bikes, even if you can find what you are specifically looking for, cannot be bought for reasonable money, as they are hand-made and usually carry a premium tag price for rarity, scarcity or oddity. They are out of reach for a reasonable and price-to-functionality minded engineer. A hand-made Pedersen, for instance, will offer for more than a couple thousand Euros basically the same functionality than a second-hand granny bike for 50CHF. After all, even if the Pedersen concept is charming, such a bike represents the very consumer object that I so deeply reject.
Therefore, and in order to give way to my interests on alternative non-standard bicycle concepts, my interest on workshop activities and to explore my creativity and sensitivity as a plastic artist; I am founding Badenia cycles to create rolling sculptures out of discarded and neglected materials and scrap metals at hand in the local dump.
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