Problem... how do you bring home a bike from the bike shop when all you have is a bike to ride?
It is my goal to be able to do all of my errands by bicycle. Unfortunately, one errand that I couldn’t do by bike is to pick up another bicycle at the bike shop, that is until now. In order to to solve this problem, I have created a bike tow rack. This rack enables one bicycle to be able to tow another.
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Step 1: Take Measurements
The first task was to measure where the bicycle being towed was to be be positioned. I put the second bike up on blocks and used a bike stand to hold it in place while I measured.
Step 2: Repurpose a Chair
I found an old broken chair that someone was throwing out and I cut it up and reused the steel tubing to create this bicycle two rack. When used as a chair, this steel tubing was strong enough to support a person. Since the bike I am towing weights about 35 pounds, it is easily strong enough for this task.
Step 3: Tack Weld the Assembly
Here is the first layout of the bike rack as tacked together on the welding table. It actually took several revisions to get the placement of all of the elements correct.
Step 4: Fit the Rack on the Bike
It is critical that the vertical bar of the rack and the tire of the bike being towed are far enough back that they don’t not interfere with the heel of the person pedaling the front bike. In the first attempts, the front bar was too far forward,and the tire of the trailing bike was too far back.
I have not provided specific dimensions, but I will offer the guideline that the front vertical bar and the tire of the bike being towed can only be slightly in front of the rear axle. This exact position will dependent on the specific geometry of the two bikes, and maybe the size of the shoes that the person pedaling the bike wears.
Step 5: Creating Mounting Hooks
I continued to cut apart the frame of the chair using the seat frame for the top mounting hook, and tire support. I also bent the chair hinges to create the rack hooks.
Step 6: Further Rack Assembly
The first task of the rack is that it needs to hold the tire of the bike being towed off the ground. It also needs to stop the tire from rolling forward in the event of an emergency stop, and it needs to stop the bike being towed from falling back.
Further, the front tire of the bike being towed needs to be held in such a way that it does not interfere with its forks, which need to be able to rotate on the front axle freely to allow the bike being towed to go over bumps. Here shown is the top hook, tacked in place.
Step 7: Adjusting the Rack Welds
In this image, the rack is tacked together with a slightly different dimension than shown earlier. In the course of this assembly, I broke apart each of the tack welds and reassembled them at least three times.
Step 8: Attaching the Towed Bike to the Rack
There was a great deal of discussion about how to hold the bike being towed on the rack. In the end I just used a bungee cord wrapped around the front tire. Maybe in time I will develop a more sophisticated attachment method. I have left the top bar long to allow for a future hook that will attach around the rear of the tire.
Step 9: Uses for Bike Tow Rack
Here are images of the rack both on and off the bike. Almost everyone who has seen this design has had suggestions about what could be done.
One topic I will look at in the future is optimizing the way this frame clamps on the bike rack. Currently this rack is being held on the bike with the use of three pipe clamps. This is secure, but not elegant. Also, as discussed above, I may develop a better way to hold the bike being towed on the rack.
In practice, this is a very useful rack. In addition to being able to tow bikes with it, I have also carried large cardboard boxes that I would not have been able to tie on top of the rack.
One question I have been asked is, how do you ride with an asymmetric load. The answer is that the bike that I am towing weights only about 30 pounds, and I weigh over 200 pounds. While riding, I can easily compensate for this load on one side of the bike.
The best use I have heard for this rack is as a tool for a bike rental company. If one of their bikes breaks down, they can bike to their customer with a new bike in tow, and then use the rack to tow the broken bike back to the shop!