Design

No-Tip Clip

The No-Tip-Clip is a device the clamps onto the bottom frame of a wheelchair via two 3D-printed caps that sandwich the frame in between, held together with screws, as seen in figure 10. The main bolt is connected to a durable rubber caster wheel, and turns to the desired height. 

1. Nut-Bolt System

The most important aspect of a device that prevents tipping is that it must be in contact with the ground, otherwise, there is still room for movement. Since the device may be connected to wheelchairs with frames of varying heights from the ground, it must be able to be adjustable in height with very fine margins, leaving no gaps between the support's wheel and the ground, as referenced by the testing explained in Mockuptesting and feedback.

Therefore, a Nut-Bolt system was chosen since it allows for extremely precise height adjustments. The user simply turns the wheel, which is connected to a 7/8" bolt to the desired height and hand-tightens the nuts to prevent further rotation, as demonstrated in the videos below. The system allows for the device to have a height ranging from 3.5 " all the way to 8".

2. Oval Cutout Clamp

The clamp that connects the device to wheelchairs features 2 pieces that fit over each other, sandwiching the frame in between. Another important aspect of the No-Tip-Clip, as requested by our in client from the Project Partner Interview, is that it must be firmly connected to the wheelchair, and able to support the weight of a person when leaning back, all while not adding significant weight to the wheelchair. 

Therefore, the clamp that attaches the support wheel to the wheelchair's bottom frame is 3D-printed, which offers adequate strength and prevents the device from exceeding 3 lbs, which was the preferred limit as requested by Ms. Michelle Urban. 

A key feature of the cutout that fits around the frame is its oval shape. This cutout's radius -3 "- is larger than most wheelchairs' frames' of around 1.5", ensuring that the device can fit around various models of wheelchairs. Additionally, the inside of the cutout is filled with hot glue as shown in figure 13, prototyping for a rubber coating, that adds significant friction between the clamp and the wheelchair, ensuring that the device doesn't rotate around the wheelchair's frame.

3. Lengenthed screws

Similar to the oval-shaped cutouts, the bolts used in the device were specifically chosen to have a larger room for adjustment. The main 7/8" bolt allows the device's height to range from 4" - 8.5". Likewise, the 1/4 " bolts can fit around frames ranging from 1" - 3" in diameter.