Wednesday, December 31, 2008

Tire/rim installed!

The outer tire pops easily in place thanks to the spring setup on the upper suspension, the idler wheels also maintain a tight grip on the inner rim while allowing the drive wheel to rotate quite smoothly!

A shot showing the twin suspension viewed from below, here you can see the spring supports. They are glued to the right side of the crescent and attached to the left side via two bolts.

The frame is completed!!! Now all that is left to do is make the battery/rider support and install the electronics!

Upper Twin Suspension

The Zero will also sport two upper idler wheels to hold the whole inner frame in place. Above you can see the assembled setup.

Springs are also added to help counter the tension exerted by the front suspension, this also cushions the vehicle against vibrations while keeping the inner frame (and rider) in place when going through a bumpy road.

Above shows the upper suspension installed, the springs rest on extra supports fixed to the crescent frame.

Front suspension done!

Extra bracing has been added around the suspension arms. Also, aluminum tubing was also threaded through the suspension rods to help strengthen the whole setup.

Sunday, December 28, 2008

Front suspension in the works...

Here are the parts to the front suspension, you can see the idler gear, washers, suspension rod and spring, and finally, the suspension support made from wood and a smaller metal bushing. The top left shows one of the assembled suspension arms.
Suspension fully assembled!

Drive Train Assembled

From left to right: Drive gear (black), clutch ring, spindle and spur gear (yellow).

The whole drive train close-up, the clutch ring and the drive gear are fixed on the shaft, whereas the yellow spur gear and the spindle rotate freely on the drive shaft.

The whole thing now assembled onto the frame. You can see the small pinion gear on the motor and the auxiliary spur gear (black). The only torque applied to the yellow spur gear comes from the motor via the auxiliary gear, which also rotates freely on a fixed shaft and bearings. Because of the centrifugal clutch, the transmission can only be engaged by the spur gear moving forward. So, when the motor is stopped, the drive gear is still rotating, since the clutch ring only allows it to rotate forwards. With the frictional forces present around the drive shaft, this should bring the vehicle to a smooth stop.

Centrifugal Clutch

At the heart of the drive train is the centrifugal clutch. Since monowheels suffer from the effects of "gerbling" under breaking, that is, when sudden deceleration is applied, the inner hub, along with the rider will have a tendency to roll backwards along the inner wheel. The worse case scenario occurs when the entire inner hub simply starts rotating around the inner wheel as the vehicle slows down, which is potentially (very) dangerous!

In an attempt to solve this problem, we've installed a clutch system which consists of an outer "clutch ring" and an inner spindle attached to the main drive gear:

Clutch ring (above) and spindle non-assembled (below):

Part of the spindle is fixed to the drive gear (yellow). Below is the spindle completely assembled:

Close up of the spindle, when the drive gear turns, the grey swing arms (made of strong ABS plastic) will swing outwards due to the centrifugal force applied. In turn, they will catch onto the inner teeth of the clutch ring, engaging the transmission and moving the vehicle forwards. Below you can see the clutch ring, now fully sanded:

Sunday, December 21, 2008

Frame 90% complete

Update: The frame is almost complete, all that is left to do is install the braces that will hold them in place, dill holes for the gear train, and installing the idlers.

The steering is provided by a single servo located at the front. The battery will be placed on a holder which will be then fixed on the servo arm.