Gearing can make a huge difference to a cyclist, enabling even the least fit rider to climb a steep hill, albeit slowly. [Berm Peak Express] took that to the next level, creating a super-low geared bicycle capable of actually towing seriously heavy loads.
The build consists of a custom 74-tooth sprocket for the rear wheel, paired with a 24-tooth chain ring for the pedals. The custom sprocket doesn’t have any holes drilled or other lightening measures taken, but given the slow speeds involved, the extra rotating mass probably isn’t much of an issue. With that gearing, 3.08 turns of the pedals will result in just one turn of the rear wheel, with the aim to provide tractor-like torque with the trade-off being incredibly low forward speed.
Installing the giant rear cog required using a 3D-printed guide to keep the chain tensioned, and the rear brakes are entirely absent, but it all came together. Bikes aren’t built for towing, and some issues are faced with dragging a Jeep as the bike struggles with balance and traction. However, with some effort, a grown adult can be towed in a child carriage up a hill, no problems.
The bike proves difficult to ride as the forward speed is so slow that balance is problematic. However, it was interesting to see the experiment run, and the wear marks on the hub from the huge loads put through the rear wheel. If you’re digging the weird bikes, though, check out this hubless design as well. Video after the break.