Gotta go to the shop...

We have been spending the bulk of our free time in the machine shop the past few weeks. Learning a lot, working on the assembly and hopefully having time to test.

Update

We have decided to revisit the centrifugal force application concept. It was ruled out months ago because its need for fine tuning, but at this point we needed a way to harness the centrifugal forces instead of fighting it.

We have been very busy redesigning, haven't had time for detailed posts. We have a good design now, we think we can get it together in time and we're feeling good about it now. We have about a month to build and test. It is going to be very busy. Here are some Creo models.

Central stationary shaft, with 2 bearings (red) in a bearing housing attached to a timing belt pulley. A steel channel is attached to the bearing housing and hangs out on both sides. The holes are a pivot point for the force applicator.

Force applicator operates when the centrifugal forces on the bottom mass (nut on thread) out weight the centrifugal forces on the roller (top). They pivot about the steel pin held by black collars.

This is the full functional assembly. The cylindrical bearing housing rotates the steel channel and pivoting force applicator around the stationary composite disc.

Big Design problem

We have been working on getting our design together to start ordering and fabrication in the past few days. Unfortunately, we have run into a problem in our concept that, embarrassingly enough, we overlooked while designing this concept.

The problem is overcoming the centrifugal force that will act on the roller as it spins around the composite disc. Because of the small radius and extremely fast rotation, even 5000 rpm, and 1lb weight estimation will cause approx 3000 lbf of centrifugal force. With our design that would require the spring to overcome that 3000 lbf to apply any force to the disc. I attached a quick sketch for clarity. 

We need to make drastic design changes, this will set us back enormously because we are suppose to be fabricating in a few weeks.

Winter Presentation Elevator Pitch

We made a video elevator pitch for our winter term presentation.

Quick Update Controls

In addition to solidifying detailed design, we are looking into the sensory equipment and controls we will need to implement. We will need a proximity sensor, strain gagues, signal amplifiers and a micro-controller at the very least. These are being spec'd out.

Spring Locking Mechanism Detail Design

We've worked on designing the locking spring force applicator and started a parts list and mapping out what materials we need to buy. detailed design is the first image and the second is the conceptual assembly.

Detailed design shows a large roller on an inclined linear slide. The roller slide assembly is pushed by the spring. This spring force will be adjusted by a screw in the back of the block.

This is a conceptual assembly. The detailed assembly design including motor, frame, bearings, and counter weight is next.

Piezo-electric concept will not work

We spent the last few weeks looking into what we need to build the piezo-electric concept. It turns out that our understanding of the actuators that we were hoping to use isn't near what we would need.

The actuators have a stopping force of 300lbs, but that is at 0.00" displacement.
The controller alone for what we are theorizing would cost up toward $30,000 and the actuators would be $2000 each. Way over our $3000 budget.

This means we will be falling back on our secondary design, the locking spring force applicator. This change late in the semester will set us back a bit.