Here's something that will really develop your neuro-plasticity! A bicycle whose front wheel turns right when you turn the handlebars left and visa versa.
Don't ask me why, because I don't have an answer. A friend wanted the bike and knew I could build it, so it fell to me to do so.
Step 1: Tools and Materials
- Oxy/Acetylene Torch or Mig welder
- Dremel moto-tool
- Felt pen
½" thick UHMW
- Donor bicycle
- Extra head tube, fork and handlebar gooseneck
Step 2: Make the Gears
Begin by making the gears that will do the work of changing the steering direction. We're going to make them from UHMW (Ultra High Molecular Weight) plastic. The easiest way I've found is to print the image of the gears, glue it onto the UHMW and cut it out on the bandsaw.
The hardest part is figuring out what the gears should look like and Mathias Wandel over at Woodgears.ca has stepped up with a fantastic solution. He makes a lot of great things from wood and if you haven't seen his YouTube channel, you're really missing some great stuff! The man is an inspiration!
Among his many great creations is an on-line gear template generator. I used the default settings and made both gears 20 teeth. If you have a laser cutter or CNC router, I think the downloadable version will even spit out G-code for a really precise cut. Here's the online gear generator.
Step 3: Make the Gear Mounts
The way this system works is by using two handlebar goosenecks to hold the gears in place. On one of them, cut the handlebar clamping tube off altogether and grind it smooth so it looks like a round tube with an angled nut at the bottom. Remove the bolt and cut the tube an inch or so from the top.
Next, slot the bottom tube with three equal slots. The depth of these slots should be the same as the thickness of your UHMW. This will leave three big teeth sticking up. Align these teeth to the top tube and mark the top tube with a felt pen. Use those marks as a guide and file corresponding landing points into the top tube. They don't have to be deep, but they do have to mesh perfectly. 1/16" is plenty, less if possible.
Remember those slots are as deep as the UHMW is thick. The depth of this receiving slot is how much the steel is going to dig into and compress the UHMW. You only want a little. The strength of the mesh comes from a precise fit of the cutouts in the gears, not the clamping action of the steel tubes.
Step 4: Slot the Gear
AFTER you are completely done with fitting the metal pieces together, center the bottom tube on one of the gears and lightly spray paint it to mark where the teeth will land. Grind this area out with a Dremel tool. Be patient. A sharp bit can go too far pretty quickly and we want the best fit we can get.
Repeat the process with the handlebar gooseneck. In the end, you should have two goosenecks with a gear mounted on each. You can mount the one without the handlebar on the bicycle fork and lock it into place for now.
Step 5: Prep Your Donor Fork and Head Tube
Cut the fork from the bottom of the stem taking care to leave the bottom bearing race in place (on the extra fork, not the one we're leaving on the bike).
Cut the head tube from the extra frame and install the stem, bearings and handlebar (with gear). Tighten it all up as if you were installing it for use.
Slowly and in several steps, trim the extra head tube to fit it to the bike frame. First trim it so the gears don't touch, then little by little grind more away to make a nice tight fit of the two head tubes together with a tight mesh of the gears. When you're satisfied with the fit, take it all apart and weld or braze the extra head tube onto the frame.
Step 6: Paint It and Put It Together
To keep it from rusting, throw a coat of paint on it.
Clean and lube the bearings and assemble it. If you did it right, you'll have a bicycle that will be a huge challenge to learn to ride!
Here's the YouTube video of my first attempt.
Step 7: UPDATE!
The UHMW gears didn't hold up very well, so we ended up re-making them from aluminum and that is covered in this video.