Introduction: Modern Penny Farthing
My name is Brooke and I am a third year Aerospace Engineering student at Confederation College. For my final project I decided to make a modern Penny Farthing Bicycle.
Step 1: Materials and Tools
List of Materials:
- Aluminum sheet
- Bicycle seat
- Aluminum piping
- Aluminum solid shaft
- Aluminum plate
- Adult size bicycle (for donated parts)
- HAAS GR510 CNC router
- Conventional Milling Machine
- Conventional Lathe
- MIG welder (aluminum)
- ARC welder
- Band saw
- Radial Arm Drill Press
- Drill Press
- Indexing head
- C clamps
- Hex set
- Wrench set
- Socket set
Step 2: Wheels
One of the biggest challenges during this project, was the wheels. Penny farthing’s wheel sizes usually vary from 40 in to 60 in. In this day in age, a wheel of this diameter isn’t typically easy to find. Many ideas were suggested such as machining out the rim and making individual spokes that would be bolted to the rim, or routing out a wheel design and including the rim and spokes as one piece. For this project, routing out the rim and spokes as one piece was best suited due to time efficiency. Before anything can be machined, a design is in need. For this project, the spoke design was inspired by a picture of a trick bike wheel. A cad drawing was then created using CATIA. Part of the concept behind this design was to make a lightweight bicycle. Originally the idea of using carbon fibre as the sole material for this project was a great desire, but not realistic within the time span given. Therefore aluminum was used. A CNC program was then generated using CATIA. Within the program, a 3/8“end mill was used to rout out the entire pattern of the wheel. Later a finish pass was made using a 5/16” end mill to achieve the inner radii. In regards to setup, a scrap piece of wood (roughly the same size) was clamped underneath the material to the table. This procedure accommodated for cutter clearance. Seven strap clamps were used to fasten the material to the table. The overuse of clamps was needed to keep the material secure because if any movement happened during machining, it would’ve thrown off the alignment of the wheel.
After the machining process of the pattern was complete, three scrap blocks of wood were screwed to the wood, sandwiching the material between them. This procedure prevented the material from moving during the machining process of the rim. The machining of the small wheel took a total of 68 minutes and the large wheel took 4.5 hours.
Step 3: Hubs
The composition of the hubs had a great deal involved. Especially with no experience in building a bicycle, it was hard to comprehend and make sense of the mechanisms that were involved. Before the axel component will be discussed, caps are needed to be made. First, two rough cut circular pieces of aluminum were used. To assure both were equal in diameter, a turning operation was needed. Once the correct diameter was achieved, an 8 hole pattern 45° apart was produced through the material using an indexing head. To assure the holes were perfectly aligned on both sides of the caps, a radial arm drill press was used.
The same process was then applied to the small hub caps but differed in size. Luckily, the donated bicycle parts came into great use during this process. For the large wheel, with a few adjustments the axel which housed the pedals on the donated bike was used as the axel for the XL wheel. The theory behind this design was to have the bearings sit directly on the axel, therefore it needed to be turned down to size for a silky fit.
The next thing to consider was how the axel was going to stay stationary inside the hubs. An idea then came to mind. Welding two pins that would sit in slots which would be clamped on either side to assure the axel stays stationary. First step was to cut the slots. Similar to a horse shoe design, a hole would be drilled then two relief cuts would be made to catch the outer diameter of the hole to create the horse shoe shape.
Once the slots were finished, the pins needed to be welded to the axel. During this process, it was very crucial that the pins needed to be perfectly aligned and not to mention straight because it could easily throw off the whole alignment of the bike. To hold the pins in place, the axel and pin were both clamped in the vise then tack welded in place. The same process was applied to the other pin but placed 180° adjacent to the first pin.
After the axel component was built it was time to assemble the hub entirely. As mentioned earlier, the axel’s pins sat in the slots. Then sandwiching the two caps onto the axel and bolting them together gave the final touches to the assembly.
Step 4: Body
The body took very little design and planning. Looking back at the history of the Penny Farthing, the shape of the body would generally hug the radius of the wheel then flare out to accommodate the smaller wheel. To achieve this shape, a jig was made by laying out the dimensions of the wheel on a table and drawing the radius in representation of the large wheel. Another arc was then drawn about 1 ¾” larger than the original radius to show roughly where the bottom of the body would lie in regards to the wheel and rubber thickness. For the small wheel, since the body wasn’t going to hug its radius, an outline of the wheel was drawn and the center was marked for reference of where the body would end.
The composition of the jig was made from a scrap piece of flat bar that was spot welded to the table following the arc drawn earlier. During the welding procedure, a hand was needed to gently push the flat bar gradually to achieve the arc desired. The type of welding used for this operation was arc welding with a 7018 welding rod.
Now here comes the fun part, the bending of the body. In regards to setup, C clamps were used to clamp both the interior of the tubing to the table as well as the exterior of the tubing to the table. To prevent the tubing from rolling, a scrap piece of angle iron was clamped on top of the material.
Once everything was clamped, it was time to bend. As mentioned before a hand is in need for this procedure. While one is heating the material, the second is slowly pulling the material in towards the jig. To keep the material from warping, c clamps are used periodically throughout the process to clamp the material to the jig to assure rigidity. During this process, one may notice that the material is cracking. This is due to high heat while pulling the material too quick. To fix this problem, reduce the heat and gently push the material.
After the arc is finished, cut the body to size using a hand saw then make saddle cuts on either end to accommodate for the connecting pipe which will be stationary to the forks. To achieve the saddle mark the center of the pipe and draw a semi-circle within the marks. The connector was made from the same material used for the body and was faced on the engine lathe to achieve a nicer finish.
To assure the body was perfectly centered to the connector, shims and ¼” thick welding coupons were used to accommodate the height difference. C clamps were then used to hold the body down to the table as well as the connecting piece in place during the welding procedure. This operation was then mimicked on the other end, but changing the orientation of the connector vertically instead of horizontally.
Step 5: Forks
The forks were a lot more difficult than anticipated. In the planning stage, both front and back forks had a horse shoe shape at the end that would be anchored by a bolt on either side which would sandwich the hubs. However this plan wouldn’t have been able to work with the larger forks due to extensive weight at this critical area. In regards to setup with the small forks, lay out both wheels on the table to be perfectly level. Then, take the body and put it at the desired height above the wheels. After the body and wheels are aligned, measure the top of the connecting bar to the middle of the back wheel. Then take an aluminum flat bar ¼ in thick and cut it to the desired length. For a sleek unified look, rounded the edges to follow the diameter of the connector pipe and then gradually taper down to hug the bolt size of the back hub.
The design is only laid out on one piece because the pieces will be clamped together during machining to assure they are identical. To achieve the gradual angle for the taper, add parallels underneath specified pieces. Some tweaks and adjustments may be needed but once the angle is achieved, clamp into vise and start machining.
After the angles are achieved, the clamped pieces are brought over to the drill press to drill a 5/8” diameter hole through the material to accommodate the bolt for the hub. To get the horseshoe shape, make two relief cuts to catch the outer edge of the hole using a band saw.
After the design of the forks was complete, it was time to fasten them to the body. Before welding them to the body, the pieces needed to be aligned and level which wasn’t too difficult to achieve due to the constant measurements throughout the whole process. To keep the pieces perfectly spaced to accommodate the wheel, cut a small piece of material that is leftover from the forks to size, and place it perpendicular between the two pieces.
Then clamp the horse shoe end and the connector end to the table to prevent from warping during the welding process. For the larger forks, the same tapered design was kept but instead of horseshoed end, a pocket was made to accommodate the fitting of the bearings for the front hub. In regards to the axel and bearings, layout where they would lie on the fork when assembled. Once everything was dimensioned and layed out, the pieces were clamped together and brought to the milling machine. Now this is where things differ from the small fork process. The clamped pieces are placed flat in the vise for the process of the pocket to be done. When doing this operation, make sure the pieces are clamped tightly and that a counterweight is placed on top. The purpose of the counterweight is to prevent the material from propping up when the force of the cutter is applied. Once everything is clamped and machined, continue on with the process mentioned before in regards to the machining of the angles. After the desired shape of the forks are complete, they can either be fasted by bolts and screws or welded to the connecting piece, depending on the maker’s preference. Welding definitely has more strength but be aware that once welded, the pieces are assembled for good.
Step 6: Neck
As mentioned before, during this project lots of material was donated. The composition of the neck was mostly built from donated parts, which made things not necessarily easier but time effective as well. To begin this process, a 1¼” pipe was welded to the connecting piece that was fastened to the larger forks mentioned earlier. The completion of these two entities welded together, will be known as the neck piece. Once finished, the neck piece is brought over to the lathe for turning and threading operations.
The material was turned down to size which would accommodate the inner diameter of the bearings. A shoulder was then created allowing the bearing to sit upon. Donated parts such as the fork sleeve, was cut from the donated forks and turned down on the lathe to a diameter that would allow a pressed fit into the neck. This operation was crucial because the mechanisms of the neck depended on the threads whose sole purpose was to secure the bearings together.
The sleeve on the figure shown is in reference to the assembly of the neck. Keep in mind the distance of the threads may differ depending on the height preference of the handle bars.
Step 7: Seat Rest
The seat rest was probably the easiest part to this project. It required very little preparation but the end result finalized the project. Before starting, take reference of where the seat should lie in regards to the bike. When Penny Farthing’s were made back in the day, the seat would generally sit bordering the center of the large wheel. When this historic design is taken into consideration, realizations are made. For example having the seat so close to the center probably resulted the bicycle to being accident prone. To modernize this design and prevent the same accident from happening, the seat would be placed 2/3 of the overall length. This would allow the weight of the user to be more directed to the back wheel instead of the front wheel and prevent them from going over the handle bars. To start, a 1 1/8” aluminum round stock was turned down to specified diameter. This allowed for the seat clamp to fit perfectly onto the seat rest. One recommendation for the assembly of this component would be to somehow sit on the bike to show where the seat would lie in reference to the pedals as well as the user’s height.
The shaft was then cut to a 60° angle which would accommodate the arc of the body as well as the leg distance to the pedals. To fasten the shaft to the body, MIG welding process was used.
After the seat stem is mounted, give yourself a pat on the back because the bicycle is complete!
In regards to aesthetics, I have spray painted each component separately.