Retro-Direct Idea: Pedal forwards in 39/18. Go forwards. Pedal backwards in 39/16. Go forwards. No derailleurs or gear changes. 1 chain. Freewheel whenever you want.
Last produced: 1903 by Hirondelle
Purpose: To make a bicycle that is excessively complex and only works some of the time (although this one is 98%) =P
Reason I made a new thread was because there were very few resources available when I was building this bike involving any details. This way, it will be searchable through the goog and such. Just move it to “post ur bikes” or “jackass” otherwise. I left the explanation a little dumbed down. I’m also predicting right now that this will be the next “trendy mobile”.
This bike is assembled off of my old Sekai 400 (rusted) frameset. I ended up stripping the fixed side of the hub trackstanding on a hill.
There is nothing special about this bicycle in the assembly. I “built” the rear hub myself using parts of cassettes and bottom brackets as well as other hardware.
There is another fellow who has just posted pictures of this design, literally using the EXACT same setup as me. I am not claiming that he copied my design as I don’t think there was any way he could have. But I am stating that I certainly did not copy him as my design had been conceptualized roughly 10 months ago.
This bicycle has taken nearly 6 months to get working properly. I am now able to successfully commute around town with literally zero flaws in the drivetrain. The drivetrain has been assembled and dis-assembled completely no less than 20 times to get the smoothness and reliability of a normal bicycle.
This is a closeup of the drivetrain. On the rear hub it is worth noting that the 18t freewheel is on the inside section of the cluster while the 16t freewheel is outboard on the cluster.
The chain when pedaling forward and starting from the top of the crank heading backwards will go directly over the 18t freewheel as it would normally. From here, it will wrap around heading directly to the chain tensioner. Chain tension is very key to the successful operation of this bicycle. The Kore tensioner is set at maximum tension and oriented in such a position in which it can be no tighter relative to leaving slight flex aftward, as well as spring tension. It is also worth noting that I have seen significant reliability issues with wether the chain loops through the tensioner from above or below. You’ll note that I have the chain coming up from the bottom of the chain tensioner and passing back over the top. I would be happy to explain the physics behind this if necessary for your own information. The chain then heads directly back to the BOTTOM of the 16t freewheel at the cluster and loops back over the top. From here it will pass THROUGH the Kore chain tensioner (using it as a chain aligner at the same time (If any of you were around during version 1 of this bicycle you’ll recall I was after a separate piece to accomplish this, but was unable to find a piece that would accomplish it in a successful manner. This has been the solution)) the chain rub here must be carefully adjusted. Too much pressure on the chain and you will regularly snag your chain tensioner providing a “catastrophic” hangup of the drivetrain. Too little and the chain will regularly derail at varying points on the drivetrain. You can also notice that I have experimented with many different positions of chain routing (marks on the chainstay) including running it outboard of everything. It will not work.
The chain continues through the tensioner to the bottom of the crankset completing the loop.
Tips: I have the rear axle completely respaced VERY far to the left to allow for the accommodation of the “cluster” (two independent freewheels and associated spacers). There is also almost no axle left as the rear spacing is now in the vicinity of 150mm! This factor also limits this build to steel framesets in my opinion. I also recommend starting with the wheel as far back in the dropouts as possible (against the stops). This is advised because it gives you a consistent variable when trying to adjust the chain size, and consistent positioning when adjusting chain alignment. I also highly recommend using a Sram or quick link capable chain as you WILL need to re-route the chain several times to experiment with positions relative to your frameset. Version 1 used a 9 speed chain with limited success and this current version is using an 8 speed chain (exaclty 3 1000ths wider) with great success.
To do this project correctly, some advanced bicycle knowledge is necessary, specifically understand hubs and respacing and disassembling them.
This bike is otherwise assembled with spare parts as more of a proof of concept than anything else. If you have questions about how to work it out, ask away as there were almost no resources available to me when I was assembling this bicycle.
You’ll notice that while there are a few other RD bikes on the web, many of them use cut chainstays rewelded for clearance and more primitive tensioning mechanisms. My build was intended to directly avoid using any crazy ideas. A build in your garage out of spare parts type of approach.
the gearing is currently 39/18 forwards, and 39/16 backwards allowing me to successfully accelerate away from people/cars while pedaling backwards “mindfucking” them. I’ve also used a 52t ring with poor success and a 46t ring with decent success.