Adjustable Ratchet Mechanism and Other Mechanisms

Fig 1 Fig 2

Fig 3 Fig 4

Fig 5

I needed a way of regulating speed by applying pressure to the drills trigger so I needed a mechanism that can apply pressure and be manually adjusted. So I thought of a bike helmet. How does that mechanism apply pressure and not move? I couldn’t get hold of a bike helmet but I did have a face shield that I took apart. (Fig 1 and 5)

It consists of 4 major parts: the knob with 4 pins on the back (Fig 2), the front piece with ratchet teeth (Fig 3), 2 arms with teeth (Fig 4) and a clip that sits inside the front piece. (Fig 6 and 7)

Fig 6 Fig 7

It works because of the pins on the back of the knob engaging and disengaging with the clip. So in (Fig 6) the clip is turning clockwise meaning it can flow round not getting stuck in the ratchet teeth of the front piece, pushing the arms up. Without the knob it would get stuck when it turns back the other way, but because of the four pins when it is turned counterclockwise the pins engage with the clip bending the arms of the clip in disengaging them from the ratchet teeth on the front piece pushing the arms down (Fig 7) .

So I took this concept and designed it in order to be wrapped around a drill and support it. I put a ratchet on both sides so it is more sturdy and adds more power pushing down on the drill.

Fig 8: Showing the inside of the mechanism

Fig 9 Showing the mechanism working

Fig 10

Improvements to be made

On the 3d printed version of the knobs the four pegs on the back kept on breaking so I have to use the actual version of the knob for model. So I need to improve the the strength of the pegs or a new way of attaching them like small pieces of down poking through. (Fig 10)
Experiment with just one side of the mechanism.

Other Mechanisms:

U Joint

The joint that was meant to be on the pottery wheel was the U joint that would sit over the top of the drill and allow for on the fly adjustments.

Fig 11 Assembly Fig 12 In context

The pieces were printed but I forgot to apply a tolerance meaning the pieces didn’t fit together so I wasn’t able to test it. (Fig 13)

Fig 13

Linear actuator

I tried using a linear actuator which works by having a screw thread locked in place so when it spins it pulls down the top piece. It worked but because of where the grip had to be it would have to be attached to the side of the wheel or machine. (Fig 14) This meant that the user would have to stretch really far to use it, as well as the top pieces arm being very long to engage the trigger being more area for it to break

Fig 14